Initial v1.0.0 commit

vendor/golang.org/x/tools/AUTHORS

@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.

vendor/golang.org/x/tools/CONTRIBUTORS

@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.

vendor/golang.org/x/tools/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/tools/PATENTS

@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the Go project.
+
+Google hereby grants to You a perpetual, worldwide, non-exclusive,
+no-charge, royalty-free, irrevocable (except as stated in this section)
+patent license to make, have made, use, offer to sell, sell, import,
+transfer and otherwise run, modify and propagate the contents of this
+implementation of Go, where such license applies only to those patent
+claims, both currently owned or controlled by Google and acquired in
+the future, licensable by Google that are necessarily infringed by this
+implementation of Go.  This grant does not include claims that would be
+infringed only as a consequence of further modification of this
+implementation.  If you or your agent or exclusive licensee institute or
+order or agree to the institution of patent litigation against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of Go or any code incorporated within this
+implementation of Go constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of Go
+shall terminate as of the date such litigation is filed.

vendor/golang.org/x/tools/go/ast/astutil/enclosing.go

@@ -0,0 +1,627 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+// This file defines utilities for working with source positions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"sort"
+)
+
+// PathEnclosingInterval returns the node that encloses the source
+// interval [start, end), and all its ancestors up to the AST root.
+//
+// The definition of "enclosing" used by this function considers
+// additional whitespace abutting a node to be enclosed by it.
+// In this example:
+//
+//              z := x + y // add them
+//                   <-A->
+//                  <----B----->
+//
+// the ast.BinaryExpr(+) node is considered to enclose interval B
+// even though its [Pos()..End()) is actually only interval A.
+// This behaviour makes user interfaces more tolerant of imperfect
+// input.
+//
+// This function treats tokens as nodes, though they are not included
+// in the result. e.g. PathEnclosingInterval("+") returns the
+// enclosing ast.BinaryExpr("x + y").
+//
+// If start==end, the 1-char interval following start is used instead.
+//
+// The 'exact' result is true if the interval contains only path[0]
+// and perhaps some adjacent whitespace.  It is false if the interval
+// overlaps multiple children of path[0], or if it contains only
+// interior whitespace of path[0].
+// In this example:
+//
+//              z := x + y // add them
+//                <--C-->     <---E-->
+//                  ^
+//                  D
+//
+// intervals C, D and E are inexact.  C is contained by the
+// z-assignment statement, because it spans three of its children (:=,
+// x, +).  So too is the 1-char interval D, because it contains only
+// interior whitespace of the assignment.  E is considered interior
+// whitespace of the BlockStmt containing the assignment.
+//
+// Precondition: [start, end) both lie within the same file as root.
+// TODO(adonovan): return (nil, false) in this case and remove precond.
+// Requires FileSet; see loader.tokenFileContainsPos.
+//
+// Postcondition: path is never nil; it always contains at least 'root'.
+//
+func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Node, exact bool) {
+	// fmt.Printf("EnclosingInterval %d %d\n", start, end) // debugging
+
+	// Precondition: node.[Pos..End) and adjoining whitespace contain [start, end).
+	var visit func(node ast.Node) bool
+	visit = func(node ast.Node) bool {
+		path = append(path, node)
+
+		nodePos := node.Pos()
+		nodeEnd := node.End()
+
+		// fmt.Printf("visit(%T, %d, %d)\n", node, nodePos, nodeEnd) // debugging
+
+		// Intersect [start, end) with interval of node.
+		if start < nodePos {
+			start = nodePos
+		}
+		if end > nodeEnd {
+			end = nodeEnd
+		}
+
+		// Find sole child that contains [start, end).
+		children := childrenOf(node)
+		l := len(children)
+		for i, child := range children {
+			// [childPos, childEnd) is unaugmented interval of child.
+			childPos := child.Pos()
+			childEnd := child.End()
+
+			// [augPos, augEnd) is whitespace-augmented interval of child.
+			augPos := childPos
+			augEnd := childEnd
+			if i > 0 {
+				augPos = children[i-1].End() // start of preceding whitespace
+			}
+			if i < l-1 {
+				nextChildPos := children[i+1].Pos()
+				// Does [start, end) lie between child and next child?
+				if start >= augEnd && end <= nextChildPos {
+					return false // inexact match
+				}
+				augEnd = nextChildPos // end of following whitespace
+			}
+
+			// fmt.Printf("\tchild %d: [%d..%d)\tcontains interval [%d..%d)?\n",
+			// 	i, augPos, augEnd, start, end) // debugging
+
+			// Does augmented child strictly contain [start, end)?
+			if augPos <= start && end <= augEnd {
+				_, isToken := child.(tokenNode)
+				return isToken || visit(child)
+			}
+
+			// Does [start, end) overlap multiple children?
+			// i.e. left-augmented child contains start
+			// but LR-augmented child does not contain end.
+			if start < childEnd && end > augEnd {
+				break
+			}
+		}
+
+		// No single child contained [start, end),
+		// so node is the result.  Is it exact?
+
+		// (It's tempting to put this condition before the
+		// child loop, but it gives the wrong result in the
+		// case where a node (e.g. ExprStmt) and its sole
+		// child have equal intervals.)
+		if start == nodePos && end == nodeEnd {
+			return true // exact match
+		}
+
+		return false // inexact: overlaps multiple children
+	}
+
+	if start > end {
+		start, end = end, start
+	}
+
+	if start < root.End() && end > root.Pos() {
+		if start == end {
+			end = start + 1 // empty interval => interval of size 1
+		}
+		exact = visit(root)
+
+		// Reverse the path:
+		for i, l := 0, len(path); i < l/2; i++ {
+			path[i], path[l-1-i] = path[l-1-i], path[i]
+		}
+	} else {
+		// Selection lies within whitespace preceding the
+		// first (or following the last) declaration in the file.
+		// The result nonetheless always includes the ast.File.
+		path = append(path, root)
+	}
+
+	return
+}
+
+// tokenNode is a dummy implementation of ast.Node for a single token.
+// They are used transiently by PathEnclosingInterval but never escape
+// this package.
+//
+type tokenNode struct {
+	pos token.Pos
+	end token.Pos
+}
+
+func (n tokenNode) Pos() token.Pos {
+	return n.pos
+}
+
+func (n tokenNode) End() token.Pos {
+	return n.end
+}
+
+func tok(pos token.Pos, len int) ast.Node {
+	return tokenNode{pos, pos + token.Pos(len)}
+}
+
+// childrenOf returns the direct non-nil children of ast.Node n.
+// It may include fake ast.Node implementations for bare tokens.
+// it is not safe to call (e.g.) ast.Walk on such nodes.
+//
+func childrenOf(n ast.Node) []ast.Node {
+	var children []ast.Node
+
+	// First add nodes for all true subtrees.
+	ast.Inspect(n, func(node ast.Node) bool {
+		if node == n { // push n
+			return true // recur
+		}
+		if node != nil { // push child
+			children = append(children, node)
+		}
+		return false // no recursion
+	})
+
+	// Then add fake Nodes for bare tokens.
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Elt.End(), len("]")))
+
+	case *ast.AssignStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.BasicLit:
+		children = append(children,
+			tok(n.ValuePos, len(n.Value)))
+
+	case *ast.BinaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.BlockStmt:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("}")))
+
+	case *ast.BranchStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.CallExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+		if n.Ellipsis != 0 {
+			children = append(children, tok(n.Ellipsis, len("...")))
+		}
+
+	case *ast.CaseClause:
+		if n.List == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.ChanType:
+		switch n.Dir {
+		case ast.RECV:
+			children = append(children, tok(n.Begin, len("<-chan")))
+		case ast.SEND:
+			children = append(children, tok(n.Begin, len("chan<-")))
+		case ast.RECV | ast.SEND:
+			children = append(children, tok(n.Begin, len("chan")))
+		}
+
+	case *ast.CommClause:
+		if n.Comm == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.Comment:
+		// nop
+
+	case *ast.CommentGroup:
+		// nop
+
+	case *ast.CompositeLit:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("{")))
+
+	case *ast.DeclStmt:
+		// nop
+
+	case *ast.DeferStmt:
+		children = append(children,
+			tok(n.Defer, len("defer")))
+
+	case *ast.Ellipsis:
+		children = append(children,
+			tok(n.Ellipsis, len("...")))
+
+	case *ast.EmptyStmt:
+		// nop
+
+	case *ast.ExprStmt:
+		// nop
+
+	case *ast.Field:
+		// TODO(adonovan): Field.{Doc,Comment,Tag}?
+
+	case *ast.FieldList:
+		children = append(children,
+			tok(n.Opening, len("(")),
+			tok(n.Closing, len(")")))
+
+	case *ast.File:
+		// TODO test: Doc
+		children = append(children,
+			tok(n.Package, len("package")))
+
+	case *ast.ForStmt:
+		children = append(children,
+			tok(n.For, len("for")))
+
+	case *ast.FuncDecl:
+		// TODO(adonovan): FuncDecl.Comment?
+
+		// Uniquely, FuncDecl breaks the invariant that
+		// preorder traversal yields tokens in lexical order:
+		// in fact, FuncDecl.Recv precedes FuncDecl.Type.Func.
+		//
+		// As a workaround, we inline the case for FuncType
+		// here and order things correctly.
+		//
+		children = nil // discard ast.Walk(FuncDecl) info subtrees
+		children = append(children, tok(n.Type.Func, len("func")))
+		if n.Recv != nil {
+			children = append(children, n.Recv)
+		}
+		children = append(children, n.Name)
+		if n.Type.Params != nil {
+			children = append(children, n.Type.Params)
+		}
+		if n.Type.Results != nil {
+			children = append(children, n.Type.Results)
+		}
+		if n.Body != nil {
+			children = append(children, n.Body)
+		}
+
+	case *ast.FuncLit:
+		// nop
+
+	case *ast.FuncType:
+		if n.Func != 0 {
+			children = append(children,
+				tok(n.Func, len("func")))
+		}
+
+	case *ast.GenDecl:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+		if n.Lparen != 0 {
+			children = append(children,
+				tok(n.Lparen, len("(")),
+				tok(n.Rparen, len(")")))
+		}
+
+	case *ast.GoStmt:
+		children = append(children,
+			tok(n.Go, len("go")))
+
+	case *ast.Ident:
+		children = append(children,
+			tok(n.NamePos, len(n.Name)))
+
+	case *ast.IfStmt:
+		children = append(children,
+			tok(n.If, len("if")))
+
+	case *ast.ImportSpec:
+		// TODO(adonovan): ImportSpec.{Doc,EndPos}?
+
+	case *ast.IncDecStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.IndexExpr:
+		children = append(children,
+			tok(n.Lbrack, len("{")),
+			tok(n.Rbrack, len("}")))
+
+	case *ast.InterfaceType:
+		children = append(children,
+			tok(n.Interface, len("interface")))
+
+	case *ast.KeyValueExpr:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.LabeledStmt:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.MapType:
+		children = append(children,
+			tok(n.Map, len("map")))
+
+	case *ast.ParenExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.RangeStmt:
+		children = append(children,
+			tok(n.For, len("for")),
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.ReturnStmt:
+		children = append(children,
+			tok(n.Return, len("return")))
+
+	case *ast.SelectStmt:
+		children = append(children,
+			tok(n.Select, len("select")))
+
+	case *ast.SelectorExpr:
+		// nop
+
+	case *ast.SendStmt:
+		children = append(children,
+			tok(n.Arrow, len("<-")))
+
+	case *ast.SliceExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *ast.StarExpr:
+		children = append(children, tok(n.Star, len("*")))
+
+	case *ast.StructType:
+		children = append(children, tok(n.Struct, len("struct")))
+
+	case *ast.SwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.TypeAssertExpr:
+		children = append(children,
+			tok(n.Lparen-1, len(".")),
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.TypeSpec:
+		// TODO(adonovan): TypeSpec.{Doc,Comment}?
+
+	case *ast.TypeSwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.UnaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.ValueSpec:
+		// TODO(adonovan): ValueSpec.{Doc,Comment}?
+
+	case *ast.BadDecl, *ast.BadExpr, *ast.BadStmt:
+		// nop
+	}
+
+	// TODO(adonovan): opt: merge the logic of ast.Inspect() into
+	// the switch above so we can make interleaved callbacks for
+	// both Nodes and Tokens in the right order and avoid the need
+	// to sort.
+	sort.Sort(byPos(children))
+
+	return children
+}
+
+type byPos []ast.Node
+
+func (sl byPos) Len() int {
+	return len(sl)
+}
+func (sl byPos) Less(i, j int) bool {
+	return sl[i].Pos() < sl[j].Pos()
+}
+func (sl byPos) Swap(i, j int) {
+	sl[i], sl[j] = sl[j], sl[i]
+}
+
+// NodeDescription returns a description of the concrete type of n suitable
+// for a user interface.
+//
+// TODO(adonovan): in some cases (e.g. Field, FieldList, Ident,
+// StarExpr) we could be much more specific given the path to the AST
+// root.  Perhaps we should do that.
+//
+func NodeDescription(n ast.Node) string {
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		return "array type"
+	case *ast.AssignStmt:
+		return "assignment"
+	case *ast.BadDecl:
+		return "bad declaration"
+	case *ast.BadExpr:
+		return "bad expression"
+	case *ast.BadStmt:
+		return "bad statement"
+	case *ast.BasicLit:
+		return "basic literal"
+	case *ast.BinaryExpr:
+		return fmt.Sprintf("binary %s operation", n.Op)
+	case *ast.BlockStmt:
+		return "block"
+	case *ast.BranchStmt:
+		switch n.Tok {
+		case token.BREAK:
+			return "break statement"
+		case token.CONTINUE:
+			return "continue statement"
+		case token.GOTO:
+			return "goto statement"
+		case token.FALLTHROUGH:
+			return "fall-through statement"
+		}
+	case *ast.CallExpr:
+		if len(n.Args) == 1 && !n.Ellipsis.IsValid() {
+			return "function call (or conversion)"
+		}
+		return "function call"
+	case *ast.CaseClause:
+		return "case clause"
+	case *ast.ChanType:
+		return "channel type"
+	case *ast.CommClause:
+		return "communication clause"
+	case *ast.Comment:
+		return "comment"
+	case *ast.CommentGroup:
+		return "comment group"
+	case *ast.CompositeLit:
+		return "composite literal"
+	case *ast.DeclStmt:
+		return NodeDescription(n.Decl) + " statement"
+	case *ast.DeferStmt:
+		return "defer statement"
+	case *ast.Ellipsis:
+		return "ellipsis"
+	case *ast.EmptyStmt:
+		return "empty statement"
+	case *ast.ExprStmt:
+		return "expression statement"
+	case *ast.Field:
+		// Can be any of these:
+		// struct {x, y int}  -- struct field(s)
+		// struct {T}         -- anon struct field
+		// interface {I}      -- interface embedding
+		// interface {f()}    -- interface method
+		// func (A) func(B) C -- receiver, param(s), result(s)
+		return "field/method/parameter"
+	case *ast.FieldList:
+		return "field/method/parameter list"
+	case *ast.File:
+		return "source file"
+	case *ast.ForStmt:
+		return "for loop"
+	case *ast.FuncDecl:
+		return "function declaration"
+	case *ast.FuncLit:
+		return "function literal"
+	case *ast.FuncType:
+		return "function type"
+	case *ast.GenDecl:
+		switch n.Tok {
+		case token.IMPORT:
+			return "import declaration"
+		case token.CONST:
+			return "constant declaration"
+		case token.TYPE:
+			return "type declaration"
+		case token.VAR:
+			return "variable declaration"
+		}
+	case *ast.GoStmt:
+		return "go statement"
+	case *ast.Ident:
+		return "identifier"
+	case *ast.IfStmt:
+		return "if statement"
+	case *ast.ImportSpec:
+		return "import specification"
+	case *ast.IncDecStmt:
+		if n.Tok == token.INC {
+			return "increment statement"
+		}
+		return "decrement statement"
+	case *ast.IndexExpr:
+		return "index expression"
+	case *ast.InterfaceType:
+		return "interface type"
+	case *ast.KeyValueExpr:
+		return "key/value association"
+	case *ast.LabeledStmt:
+		return "statement label"
+	case *ast.MapType:
+		return "map type"
+	case *ast.Package:
+		return "package"
+	case *ast.ParenExpr:
+		return "parenthesized " + NodeDescription(n.X)
+	case *ast.RangeStmt:
+		return "range loop"
+	case *ast.ReturnStmt:
+		return "return statement"
+	case *ast.SelectStmt:
+		return "select statement"
+	case *ast.SelectorExpr:
+		return "selector"
+	case *ast.SendStmt:
+		return "channel send"
+	case *ast.SliceExpr:
+		return "slice expression"
+	case *ast.StarExpr:
+		return "*-operation" // load/store expr or pointer type
+	case *ast.StructType:
+		return "struct type"
+	case *ast.SwitchStmt:
+		return "switch statement"
+	case *ast.TypeAssertExpr:
+		return "type assertion"
+	case *ast.TypeSpec:
+		return "type specification"
+	case *ast.TypeSwitchStmt:
+		return "type switch"
+	case *ast.UnaryExpr:
+		return fmt.Sprintf("unary %s operation", n.Op)
+	case *ast.ValueSpec:
+		return "value specification"
+
+	}
+	panic(fmt.Sprintf("unexpected node type: %T", n))
+}

vendor/golang.org/x/tools/go/ast/astutil/imports.go

@@ -0,0 +1,482 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package astutil contains common utilities for working with the Go AST.
+package astutil // import "golang.org/x/tools/go/ast/astutil"
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"strconv"
+	"strings"
+)
+
+// AddImport adds the import path to the file f, if absent.
+func AddImport(fset *token.FileSet, f *ast.File, path string) (added bool) {
+	return AddNamedImport(fset, f, "", path)
+}
+
+// AddNamedImport adds the import with the given name and path to the file f, if absent.
+// If name is not empty, it is used to rename the import.
+//
+// For example, calling
+//	AddNamedImport(fset, f, "pathpkg", "path")
+// adds
+//	import pathpkg "path"
+func AddNamedImport(fset *token.FileSet, f *ast.File, name, path string) (added bool) {
+	if imports(f, name, path) {
+		return false
+	}
+
+	newImport := &ast.ImportSpec{
+		Path: &ast.BasicLit{
+			Kind:  token.STRING,
+			Value: strconv.Quote(path),
+		},
+	}
+	if name != "" {
+		newImport.Name = &ast.Ident{Name: name}
+	}
+
+	// Find an import decl to add to.
+	// The goal is to find an existing import
+	// whose import path has the longest shared
+	// prefix with path.
+	var (
+		bestMatch  = -1         // length of longest shared prefix
+		lastImport = -1         // index in f.Decls of the file's final import decl
+		impDecl    *ast.GenDecl // import decl containing the best match
+		impIndex   = -1         // spec index in impDecl containing the best match
+
+		isThirdPartyPath = isThirdParty(path)
+	)
+	for i, decl := range f.Decls {
+		gen, ok := decl.(*ast.GenDecl)
+		if ok && gen.Tok == token.IMPORT {
+			lastImport = i
+			// Do not add to import "C", to avoid disrupting the
+			// association with its doc comment, breaking cgo.
+			if declImports(gen, "C") {
+				continue
+			}
+
+			// Match an empty import decl if that's all that is available.
+			if len(gen.Specs) == 0 && bestMatch == -1 {
+				impDecl = gen
+			}
+
+			// Compute longest shared prefix with imports in this group and find best
+			// matched import spec.
+			// 1. Always prefer import spec with longest shared prefix.
+			// 2. While match length is 0,
+			// - for stdlib package: prefer first import spec.
+			// - for third party package: prefer first third party import spec.
+			// We cannot use last import spec as best match for third party package
+			// because grouped imports are usually placed last by goimports -local
+			// flag.
+			// See issue #19190.
+			seenAnyThirdParty := false
+			for j, spec := range gen.Specs {
+				impspec := spec.(*ast.ImportSpec)
+				p := importPath(impspec)
+				n := matchLen(p, path)
+				if n > bestMatch || (bestMatch == 0 && !seenAnyThirdParty && isThirdPartyPath) {
+					bestMatch = n
+					impDecl = gen
+					impIndex = j
+				}
+				seenAnyThirdParty = seenAnyThirdParty || isThirdParty(p)
+			}
+		}
+	}
+
+	// If no import decl found, add one after the last import.
+	if impDecl == nil {
+		impDecl = &ast.GenDecl{
+			Tok: token.IMPORT,
+		}
+		if lastImport >= 0 {
+			impDecl.TokPos = f.Decls[lastImport].End()
+		} else {
+			// There are no existing imports.
+			// Our new import, preceded by a blank line,  goes after the package declaration
+			// and after the comment, if any, that starts on the same line as the
+			// package declaration.
+			impDecl.TokPos = f.Package
+
+			file := fset.File(f.Package)
+			pkgLine := file.Line(f.Package)
+			for _, c := range f.Comments {
+				if file.Line(c.Pos()) > pkgLine {
+					break
+				}
+				// +2 for a blank line
+				impDecl.TokPos = c.End() + 2
+			}
+		}
+		f.Decls = append(f.Decls, nil)
+		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
+		f.Decls[lastImport+1] = impDecl
+	}
+
+	// Insert new import at insertAt.
+	insertAt := 0
+	if impIndex >= 0 {
+		// insert after the found import
+		insertAt = impIndex + 1
+	}
+	impDecl.Specs = append(impDecl.Specs, nil)
+	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
+	impDecl.Specs[insertAt] = newImport
+	pos := impDecl.Pos()
+	if insertAt > 0 {
+		// If there is a comment after an existing import, preserve the comment
+		// position by adding the new import after the comment.
+		if spec, ok := impDecl.Specs[insertAt-1].(*ast.ImportSpec); ok && spec.Comment != nil {
+			pos = spec.Comment.End()
+		} else {
+			// Assign same position as the previous import,
+			// so that the sorter sees it as being in the same block.
+			pos = impDecl.Specs[insertAt-1].Pos()
+		}
+	}
+	if newImport.Name != nil {
+		newImport.Name.NamePos = pos
+	}
+	newImport.Path.ValuePos = pos
+	newImport.EndPos = pos
+
+	// Clean up parens. impDecl contains at least one spec.
+	if len(impDecl.Specs) == 1 {
+		// Remove unneeded parens.
+		impDecl.Lparen = token.NoPos
+	} else if !impDecl.Lparen.IsValid() {
+		// impDecl needs parens added.
+		impDecl.Lparen = impDecl.Specs[0].Pos()
+	}
+
+	f.Imports = append(f.Imports, newImport)
+
+	if len(f.Decls) <= 1 {
+		return true
+	}
+
+	// Merge all the import declarations into the first one.
+	var first *ast.GenDecl
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
+			continue
+		}
+		if first == nil {
+			first = gen
+			continue // Don't touch the first one.
+		}
+		// We now know there is more than one package in this import
+		// declaration. Ensure that it ends up parenthesized.
+		first.Lparen = first.Pos()
+		// Move the imports of the other import declaration to the first one.
+		for _, spec := range gen.Specs {
+			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
+			first.Specs = append(first.Specs, spec)
+		}
+		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		i--
+	}
+
+	return true
+}
+
+func isThirdParty(importPath string) bool {
+	// Third party package import path usually contains "." (".com", ".org", ...)
+	// This logic is taken from golang.org/x/tools/imports package.
+	return strings.Contains(importPath, ".")
+}
+
+// DeleteImport deletes the import path from the file f, if present.
+// If there are duplicate import declarations, all matching ones are deleted.
+func DeleteImport(fset *token.FileSet, f *ast.File, path string) (deleted bool) {
+	return DeleteNamedImport(fset, f, "", path)
+}
+
+// DeleteNamedImport deletes the import with the given name and path from the file f, if present.
+// If there are duplicate import declarations, all matching ones are deleted.
+func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (deleted bool) {
+	var delspecs []*ast.ImportSpec
+	var delcomments []*ast.CommentGroup
+
+	// Find the import nodes that import path, if any.
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT {
+			continue
+		}
+		for j := 0; j < len(gen.Specs); j++ {
+			spec := gen.Specs[j]
+			impspec := spec.(*ast.ImportSpec)
+			if importName(impspec) != name || importPath(impspec) != path {
+				continue
+			}
+
+			// We found an import spec that imports path.
+			// Delete it.
+			delspecs = append(delspecs, impspec)
+			deleted = true
+			copy(gen.Specs[j:], gen.Specs[j+1:])
+			gen.Specs = gen.Specs[:len(gen.Specs)-1]
+
+			// If this was the last import spec in this decl,
+			// delete the decl, too.
+			if len(gen.Specs) == 0 {
+				copy(f.Decls[i:], f.Decls[i+1:])
+				f.Decls = f.Decls[:len(f.Decls)-1]
+				i--
+				break
+			} else if len(gen.Specs) == 1 {
+				if impspec.Doc != nil {
+					delcomments = append(delcomments, impspec.Doc)
+				}
+				if impspec.Comment != nil {
+					delcomments = append(delcomments, impspec.Comment)
+				}
+				for _, cg := range f.Comments {
+					// Found comment on the same line as the import spec.
+					if cg.End() < impspec.Pos() && fset.Position(cg.End()).Line == fset.Position(impspec.Pos()).Line {
+						delcomments = append(delcomments, cg)
+						break
+					}
+				}
+
+				spec := gen.Specs[0].(*ast.ImportSpec)
+
+				// Move the documentation right after the import decl.
+				if spec.Doc != nil {
+					for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
+						fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+					}
+				}
+				for _, cg := range f.Comments {
+					if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
+						for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
+							fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+						}
+						break
+					}
+				}
+			}
+			if j > 0 {
+				lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
+				lastLine := fset.Position(lastImpspec.Path.ValuePos).Line
+				line := fset.Position(impspec.Path.ValuePos).Line
+
+				// We deleted an entry but now there may be
+				// a blank line-sized hole where the import was.
+				if line-lastLine > 1 || !gen.Rparen.IsValid() {
+					// There was a blank line immediately preceding the deleted import,
+					// so there's no need to close the hole. The right parenthesis is
+					// invalid after AddImport to an import statement without parenthesis.
+					// Do nothing.
+				} else if line != fset.File(gen.Rparen).LineCount() {
+					// There was no blank line. Close the hole.
+					fset.File(gen.Rparen).MergeLine(line)
+				}
+			}
+			j--
+		}
+	}
+
+	// Delete imports from f.Imports.
+	for i := 0; i < len(f.Imports); i++ {
+		imp := f.Imports[i]
+		for j, del := range delspecs {
+			if imp == del {
+				copy(f.Imports[i:], f.Imports[i+1:])
+				f.Imports = f.Imports[:len(f.Imports)-1]
+				copy(delspecs[j:], delspecs[j+1:])
+				delspecs = delspecs[:len(delspecs)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	// Delete comments from f.Comments.
+	for i := 0; i < len(f.Comments); i++ {
+		cg := f.Comments[i]
+		for j, del := range delcomments {
+			if cg == del {
+				copy(f.Comments[i:], f.Comments[i+1:])
+				f.Comments = f.Comments[:len(f.Comments)-1]
+				copy(delcomments[j:], delcomments[j+1:])
+				delcomments = delcomments[:len(delcomments)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	if len(delspecs) > 0 {
+		panic(fmt.Sprintf("deleted specs from Decls but not Imports: %v", delspecs))
+	}
+
+	return
+}
+
+// RewriteImport rewrites any import of path oldPath to path newPath.
+func RewriteImport(fset *token.FileSet, f *ast.File, oldPath, newPath string) (rewrote bool) {
+	for _, imp := range f.Imports {
+		if importPath(imp) == oldPath {
+			rewrote = true
+			// record old End, because the default is to compute
+			// it using the length of imp.Path.Value.
+			imp.EndPos = imp.End()
+			imp.Path.Value = strconv.Quote(newPath)
+		}
+	}
+	return
+}
+
+// UsesImport reports whether a given import is used.
+func UsesImport(f *ast.File, path string) (used bool) {
+	spec := importSpec(f, path)
+	if spec == nil {
+		return
+	}
+
+	name := spec.Name.String()
+	switch name {
+	case "<nil>":
+		// If the package name is not explicitly specified,
+		// make an educated guess. This is not guaranteed to be correct.
+		lastSlash := strings.LastIndex(path, "/")
+		if lastSlash == -1 {
+			name = path
+		} else {
+			name = path[lastSlash+1:]
+		}
+	case "_", ".":
+		// Not sure if this import is used - err on the side of caution.
+		return true
+	}
+
+	ast.Walk(visitFn(func(n ast.Node) {
+		sel, ok := n.(*ast.SelectorExpr)
+		if ok && isTopName(sel.X, name) {
+			used = true
+		}
+	}), f)
+
+	return
+}
+
+type visitFn func(node ast.Node)
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	fn(node)
+	return fn
+}
+
+// imports reports whether f has an import with the specified name and path.
+func imports(f *ast.File, name, path string) bool {
+	for _, s := range f.Imports {
+		if importName(s) == name && importPath(s) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// importSpec returns the import spec if f imports path,
+// or nil otherwise.
+func importSpec(f *ast.File, path string) *ast.ImportSpec {
+	for _, s := range f.Imports {
+		if importPath(s) == path {
+			return s
+		}
+	}
+	return nil
+}
+
+// importName returns the name of s,
+// or "" if the import is not named.
+func importName(s *ast.ImportSpec) string {
+	if s.Name == nil {
+		return ""
+	}
+	return s.Name.Name
+}
+
+// importPath returns the unquoted import path of s,
+// or "" if the path is not properly quoted.
+func importPath(s *ast.ImportSpec) string {
+	t, err := strconv.Unquote(s.Path.Value)
+	if err != nil {
+		return ""
+	}
+	return t
+}
+
+// declImports reports whether gen contains an import of path.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// matchLen returns the length of the longest path segment prefix shared by x and y.
+func matchLen(x, y string) int {
+	n := 0
+	for i := 0; i < len(x) && i < len(y) && x[i] == y[i]; i++ {
+		if x[i] == '/' {
+			n++
+		}
+	}
+	return n
+}
+
+// isTopName returns true if n is a top-level unresolved identifier with the given name.
+func isTopName(n ast.Expr, name string) bool {
+	id, ok := n.(*ast.Ident)
+	return ok && id.Name == name && id.Obj == nil
+}
+
+// Imports returns the file imports grouped by paragraph.
+func Imports(fset *token.FileSet, f *ast.File) [][]*ast.ImportSpec {
+	var groups [][]*ast.ImportSpec
+
+	for _, decl := range f.Decls {
+		genDecl, ok := decl.(*ast.GenDecl)
+		if !ok || genDecl.Tok != token.IMPORT {
+			break
+		}
+
+		group := []*ast.ImportSpec{}
+
+		var lastLine int
+		for _, spec := range genDecl.Specs {
+			importSpec := spec.(*ast.ImportSpec)
+			pos := importSpec.Path.ValuePos
+			line := fset.Position(pos).Line
+			if lastLine > 0 && pos > 0 && line-lastLine > 1 {
+				groups = append(groups, group)
+				group = []*ast.ImportSpec{}
+			}
+			group = append(group, importSpec)
+			lastLine = line
+		}
+		groups = append(groups, group)
+	}
+
+	return groups
+}

vendor/golang.org/x/tools/go/ast/astutil/rewrite.go

@@ -0,0 +1,477 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+import (
+	"fmt"
+	"go/ast"
+	"reflect"
+	"sort"
+)
+
+// An ApplyFunc is invoked by Apply for each node n, even if n is nil,
+// before and/or after the node's children, using a Cursor describing
+// the current node and providing operations on it.
+//
+// The return value of ApplyFunc controls the syntax tree traversal.
+// See Apply for details.
+type ApplyFunc func(*Cursor) bool
+
+// Apply traverses a syntax tree recursively, starting with root,
+// and calling pre and post for each node as described below.
+// Apply returns the syntax tree, possibly modified.
+//
+// If pre is not nil, it is called for each node before the node's
+// children are traversed (pre-order). If pre returns false, no
+// children are traversed, and post is not called for that node.
+//
+// If post is not nil, and a prior call of pre didn't return false,
+// post is called for each node after its children are traversed
+// (post-order). If post returns false, traversal is terminated and
+// Apply returns immediately.
+//
+// Only fields that refer to AST nodes are considered children;
+// i.e., token.Pos, Scopes, Objects, and fields of basic types
+// (strings, etc.) are ignored.
+//
+// Children are traversed in the order in which they appear in the
+// respective node's struct definition. A package's files are
+// traversed in the filenames' alphabetical order.
+//
+func Apply(root ast.Node, pre, post ApplyFunc) (result ast.Node) {
+	parent := &struct{ ast.Node }{root}
+	defer func() {
+		if r := recover(); r != nil && r != abort {
+			panic(r)
+		}
+		result = parent.Node
+	}()
+	a := &application{pre: pre, post: post}
+	a.apply(parent, "Node", nil, root)
+	return
+}
+
+var abort = new(int) // singleton, to signal termination of Apply
+
+// A Cursor describes a node encountered during Apply.
+// Information about the node and its parent is available
+// from the Node, Parent, Name, and Index methods.
+//
+// If p is a variable of type and value of the current parent node
+// c.Parent(), and f is the field identifier with name c.Name(),
+// the following invariants hold:
+//
+//   p.f            == c.Node()  if c.Index() <  0
+//   p.f[c.Index()] == c.Node()  if c.Index() >= 0
+//
+// The methods Replace, Delete, InsertBefore, and InsertAfter
+// can be used to change the AST without disrupting Apply.
+type Cursor struct {
+	parent ast.Node
+	name   string
+	iter   *iterator // valid if non-nil
+	node   ast.Node
+}
+
+// Node returns the current Node.
+func (c *Cursor) Node() ast.Node { return c.node }
+
+// Parent returns the parent of the current Node.
+func (c *Cursor) Parent() ast.Node { return c.parent }
+
+// Name returns the name of the parent Node field that contains the current Node.
+// If the parent is a *ast.Package and the current Node is a *ast.File, Name returns
+// the filename for the current Node.
+func (c *Cursor) Name() string { return c.name }
+
+// Index reports the index >= 0 of the current Node in the slice of Nodes that
+// contains it, or a value < 0 if the current Node is not part of a slice.
+// The index of the current node changes if InsertBefore is called while
+// processing the current node.
+func (c *Cursor) Index() int {
+	if c.iter != nil {
+		return c.iter.index
+	}
+	return -1
+}
+
+// field returns the current node's parent field value.
+func (c *Cursor) field() reflect.Value {
+	return reflect.Indirect(reflect.ValueOf(c.parent)).FieldByName(c.name)
+}
+
+// Replace replaces the current Node with n.
+// The replacement node is not walked by Apply.
+func (c *Cursor) Replace(n ast.Node) {
+	if _, ok := c.node.(*ast.File); ok {
+		file, ok := n.(*ast.File)
+		if !ok {
+			panic("attempt to replace *ast.File with non-*ast.File")
+		}
+		c.parent.(*ast.Package).Files[c.name] = file
+		return
+	}
+
+	v := c.field()
+	if i := c.Index(); i >= 0 {
+		v = v.Index(i)
+	}
+	v.Set(reflect.ValueOf(n))
+}
+
+// Delete deletes the current Node from its containing slice.
+// If the current Node is not part of a slice, Delete panics.
+// As a special case, if the current node is a package file,
+// Delete removes it from the package's Files map.
+func (c *Cursor) Delete() {
+	if _, ok := c.node.(*ast.File); ok {
+		delete(c.parent.(*ast.Package).Files, c.name)
+		return
+	}
+
+	i := c.Index()
+	if i < 0 {
+		panic("Delete node not contained in slice")
+	}
+	v := c.field()
+	l := v.Len()
+	reflect.Copy(v.Slice(i, l), v.Slice(i+1, l))
+	v.Index(l - 1).Set(reflect.Zero(v.Type().Elem()))
+	v.SetLen(l - 1)
+	c.iter.step--
+}
+
+// InsertAfter inserts n after the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertAfter panics.
+// Apply does not walk n.
+func (c *Cursor) InsertAfter(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertAfter node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+2, l), v.Slice(i+1, l))
+	v.Index(i + 1).Set(reflect.ValueOf(n))
+	c.iter.step++
+}
+
+// InsertBefore inserts n before the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertBefore panics.
+// Apply will not walk n.
+func (c *Cursor) InsertBefore(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertBefore node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+1, l), v.Slice(i, l))
+	v.Index(i).Set(reflect.ValueOf(n))
+	c.iter.index++
+}
+
+// application carries all the shared data so we can pass it around cheaply.
+type application struct {
+	pre, post ApplyFunc
+	cursor    Cursor
+	iter      iterator
+}
+
+func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.Node) {
+	// convert typed nil into untyped nil
+	if v := reflect.ValueOf(n); v.Kind() == reflect.Ptr && v.IsNil() {
+		n = nil
+	}
+
+	// avoid heap-allocating a new cursor for each apply call; reuse a.cursor instead
+	saved := a.cursor
+	a.cursor.parent = parent
+	a.cursor.name = name
+	a.cursor.iter = iter
+	a.cursor.node = n
+
+	if a.pre != nil && !a.pre(&a.cursor) {
+		a.cursor = saved
+		return
+	}
+
+	// walk children
+	// (the order of the cases matches the order of the corresponding node types in go/ast)
+	switch n := n.(type) {
+	case nil:
+		// nothing to do
+
+	// Comments and fields
+	case *ast.Comment:
+		// nothing to do
+
+	case *ast.CommentGroup:
+		if n != nil {
+			a.applyList(n, "List")
+		}
+
+	case *ast.Field:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.FieldList:
+		a.applyList(n, "List")
+
+	// Expressions
+	case *ast.BadExpr, *ast.Ident, *ast.BasicLit:
+		// nothing to do
+
+	case *ast.Ellipsis:
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.FuncLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CompositeLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Elts")
+
+	case *ast.ParenExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SelectorExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Sel", nil, n.Sel)
+
+	case *ast.IndexExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Index", nil, n.Index)
+
+	case *ast.SliceExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Low", nil, n.Low)
+		a.apply(n, "High", nil, n.High)
+		a.apply(n, "Max", nil, n.Max)
+
+	case *ast.TypeAssertExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Type", nil, n.Type)
+
+	case *ast.CallExpr:
+		a.apply(n, "Fun", nil, n.Fun)
+		a.applyList(n, "Args")
+
+	case *ast.StarExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.UnaryExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.BinaryExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Y", nil, n.Y)
+
+	case *ast.KeyValueExpr:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	// Types
+	case *ast.ArrayType:
+		a.apply(n, "Len", nil, n.Len)
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.StructType:
+		a.apply(n, "Fields", nil, n.Fields)
+
+	case *ast.FuncType:
+		a.apply(n, "Params", nil, n.Params)
+		a.apply(n, "Results", nil, n.Results)
+
+	case *ast.InterfaceType:
+		a.apply(n, "Methods", nil, n.Methods)
+
+	case *ast.MapType:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.ChanType:
+		a.apply(n, "Value", nil, n.Value)
+
+	// Statements
+	case *ast.BadStmt:
+		// nothing to do
+
+	case *ast.DeclStmt:
+		a.apply(n, "Decl", nil, n.Decl)
+
+	case *ast.EmptyStmt:
+		// nothing to do
+
+	case *ast.LabeledStmt:
+		a.apply(n, "Label", nil, n.Label)
+		a.apply(n, "Stmt", nil, n.Stmt)
+
+	case *ast.ExprStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SendStmt:
+		a.apply(n, "Chan", nil, n.Chan)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.IncDecStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.AssignStmt:
+		a.applyList(n, "Lhs")
+		a.applyList(n, "Rhs")
+
+	case *ast.GoStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.DeferStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.ReturnStmt:
+		a.applyList(n, "Results")
+
+	case *ast.BranchStmt:
+		a.apply(n, "Label", nil, n.Label)
+
+	case *ast.BlockStmt:
+		a.applyList(n, "List")
+
+	case *ast.IfStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Body", nil, n.Body)
+		a.apply(n, "Else", nil, n.Else)
+
+	case *ast.CaseClause:
+		a.applyList(n, "List")
+		a.applyList(n, "Body")
+
+	case *ast.SwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.TypeSwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Assign", nil, n.Assign)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CommClause:
+		a.apply(n, "Comm", nil, n.Comm)
+		a.applyList(n, "Body")
+
+	case *ast.SelectStmt:
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.ForStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Post", nil, n.Post)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.RangeStmt:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Declarations
+	case *ast.ImportSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Path", nil, n.Path)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.ValueSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Values")
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.TypeSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.BadDecl:
+		// nothing to do
+
+	case *ast.GenDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Specs")
+
+	case *ast.FuncDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Recv", nil, n.Recv)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Files and packages
+	case *ast.File:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.applyList(n, "Decls")
+		// Don't walk n.Comments; they have either been walked already if
+		// they are Doc comments, or they can be easily walked explicitly.
+
+	case *ast.Package:
+		// collect and sort names for reproducible behavior
+		var names []string
+		for name := range n.Files {
+			names = append(names, name)
+		}
+		sort.Strings(names)
+		for _, name := range names {
+			a.apply(n, name, nil, n.Files[name])
+		}
+
+	default:
+		panic(fmt.Sprintf("Apply: unexpected node type %T", n))
+	}
+
+	if a.post != nil && !a.post(&a.cursor) {
+		panic(abort)
+	}
+
+	a.cursor = saved
+}
+
+// An iterator controls iteration over a slice of nodes.
+type iterator struct {
+	index, step int
+}
+
+func (a *application) applyList(parent ast.Node, name string) {
+	// avoid heap-allocating a new iterator for each applyList call; reuse a.iter instead
+	saved := a.iter
+	a.iter.index = 0
+	for {
+		// must reload parent.name each time, since cursor modifications might change it
+		v := reflect.Indirect(reflect.ValueOf(parent)).FieldByName(name)
+		if a.iter.index >= v.Len() {
+			break
+		}
+
+		// element x may be nil in a bad AST - be cautious
+		var x ast.Node
+		if e := v.Index(a.iter.index); e.IsValid() {
+			x = e.Interface().(ast.Node)
+		}
+
+		a.iter.step = 1
+		a.apply(parent, name, &a.iter, x)
+		a.iter.index += a.iter.step
+	}
+	a.iter = saved
+}

vendor/golang.org/x/tools/go/ast/astutil/util.go

@@ -0,0 +1,18 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+import "go/ast"
+
+// Unparen returns e with any enclosing parentheses stripped.
+func Unparen(e ast.Expr) ast.Expr {
+	for {
+		p, ok := e.(*ast.ParenExpr)
+		if !ok {
+			return e
+		}
+		e = p.X
+	}
+}

vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go

@@ -0,0 +1,109 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gcexportdata provides functions for locating, reading, and
+// writing export data files containing type information produced by the
+// gc compiler.  This package supports go1.7 export data format and all
+// later versions.
+//
+// Although it might seem convenient for this package to live alongside
+// go/types in the standard library, this would cause version skew
+// problems for developer tools that use it, since they must be able to
+// consume the outputs of the gc compiler both before and after a Go
+// update such as from Go 1.7 to Go 1.8.  Because this package lives in
+// golang.org/x/tools, sites can update their version of this repo some
+// time before the Go 1.8 release and rebuild and redeploy their
+// developer tools, which will then be able to consume both Go 1.7 and
+// Go 1.8 export data files, so they will work before and after the
+// Go update. (See discussion at https://golang.org/issue/15651.)
+//
+package gcexportdata // import "golang.org/x/tools/go/gcexportdata"
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/token"
+	"go/types"
+	"io"
+	"io/ioutil"
+
+	"golang.org/x/tools/go/internal/gcimporter"
+)
+
+// Find returns the name of an object (.o) or archive (.a) file
+// containing type information for the specified import path,
+// using the workspace layout conventions of go/build.
+// If no file was found, an empty filename is returned.
+//
+// A relative srcDir is interpreted relative to the current working directory.
+//
+// Find also returns the package's resolved (canonical) import path,
+// reflecting the effects of srcDir and vendoring on importPath.
+func Find(importPath, srcDir string) (filename, path string) {
+	return gcimporter.FindPkg(importPath, srcDir)
+}
+
+// NewReader returns a reader for the export data section of an object
+// (.o) or archive (.a) file read from r.  The new reader may provide
+// additional trailing data beyond the end of the export data.
+func NewReader(r io.Reader) (io.Reader, error) {
+	buf := bufio.NewReader(r)
+	_, err := gcimporter.FindExportData(buf)
+	// If we ever switch to a zip-like archive format with the ToC
+	// at the end, we can return the correct portion of export data,
+	// but for now we must return the entire rest of the file.
+	return buf, err
+}
+
+// Read reads export data from in, decodes it, and returns type
+// information for the package.
+// The package name is specified by path.
+// File position information is added to fset.
+//
+// Read may inspect and add to the imports map to ensure that references
+// within the export data to other packages are consistent.  The caller
+// must ensure that imports[path] does not exist, or exists but is
+// incomplete (see types.Package.Complete), and Read inserts the
+// resulting package into this map entry.
+//
+// On return, the state of the reader is undefined.
+func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) {
+	data, err := ioutil.ReadAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("reading export data for %q: %v", path, err)
+	}
+
+	if bytes.HasPrefix(data, []byte("!<arch>")) {
+		return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path)
+	}
+
+	// The App Engine Go runtime v1.6 uses the old export data format.
+	// TODO(adonovan): delete once v1.7 has been around for a while.
+	if bytes.HasPrefix(data, []byte("package ")) {
+		return gcimporter.ImportData(imports, path, path, bytes.NewReader(data))
+	}
+
+	// The indexed export format starts with an 'i'; the older
+	// binary export format starts with a 'c', 'd', or 'v'
+	// (from "version"). Select appropriate importer.
+	if len(data) > 0 && data[0] == 'i' {
+		_, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
+		return pkg, err
+	}
+
+	_, pkg, err := gcimporter.BImportData(fset, imports, data, path)
+	return pkg, err
+}
+
+// Write writes encoded type information for the specified package to out.
+// The FileSet provides file position information for named objects.
+func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
+	b, err := gcimporter.IExportData(fset, pkg)
+	if err != nil {
+		return err
+	}
+	_, err = out.Write(b)
+	return err
+}

vendor/golang.org/x/tools/go/gcexportdata/importer.go

@@ -0,0 +1,73 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gcexportdata
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"os"
+)
+
+// NewImporter returns a new instance of the types.Importer interface
+// that reads type information from export data files written by gc.
+// The Importer also satisfies types.ImporterFrom.
+//
+// Export data files are located using "go build" workspace conventions
+// and the build.Default context.
+//
+// Use this importer instead of go/importer.For("gc", ...) to avoid the
+// version-skew problems described in the documentation of this package,
+// or to control the FileSet or access the imports map populated during
+// package loading.
+//
+func NewImporter(fset *token.FileSet, imports map[string]*types.Package) types.ImporterFrom {
+	return importer{fset, imports}
+}
+
+type importer struct {
+	fset    *token.FileSet
+	imports map[string]*types.Package
+}
+
+func (imp importer) Import(importPath string) (*types.Package, error) {
+	return imp.ImportFrom(importPath, "", 0)
+}
+
+func (imp importer) ImportFrom(importPath, srcDir string, mode types.ImportMode) (_ *types.Package, err error) {
+	filename, path := Find(importPath, srcDir)
+	if filename == "" {
+		if importPath == "unsafe" {
+			// Even for unsafe, call Find first in case
+			// the package was vendored.
+			return types.Unsafe, nil
+		}
+		return nil, fmt.Errorf("can't find import: %s", importPath)
+	}
+
+	if pkg, ok := imp.imports[path]; ok && pkg.Complete() {
+		return pkg, nil // cache hit
+	}
+
+	// open file
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		f.Close()
+		if err != nil {
+			// add file name to error
+			err = fmt.Errorf("reading export data: %s: %v", filename, err)
+		}
+	}()
+
+	r, err := NewReader(f)
+	if err != nil {
+		return nil, err
+	}
+
+	return Read(r, imp.fset, imp.imports, path)
+}

vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go

@@ -0,0 +1,852 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Binary package export.
+// This file was derived from $GOROOT/src/cmd/compile/internal/gc/bexport.go;
+// see that file for specification of the format.
+
+package gcimporter
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"math"
+	"math/big"
+	"sort"
+	"strings"
+)
+
+// If debugFormat is set, each integer and string value is preceded by a marker
+// and position information in the encoding. This mechanism permits an importer
+// to recognize immediately when it is out of sync. The importer recognizes this
+// mode automatically (i.e., it can import export data produced with debugging
+// support even if debugFormat is not set at the time of import). This mode will
+// lead to massively larger export data (by a factor of 2 to 3) and should only
+// be enabled during development and debugging.
+//
+// NOTE: This flag is the first flag to enable if importing dies because of
+// (suspected) format errors, and whenever a change is made to the format.
+const debugFormat = false // default: false
+
+// If trace is set, debugging output is printed to std out.
+const trace = false // default: false
+
+// Current export format version. Increase with each format change.
+// Note: The latest binary (non-indexed) export format is at version 6.
+//       This exporter is still at level 4, but it doesn't matter since
+//       the binary importer can handle older versions just fine.
+// 6: package height (CL 105038) -- NOT IMPLEMENTED HERE
+// 5: improved position encoding efficiency (issue 20080, CL 41619) -- NOT IMPLEMEMTED HERE
+// 4: type name objects support type aliases, uses aliasTag
+// 3: Go1.8 encoding (same as version 2, aliasTag defined but never used)
+// 2: removed unused bool in ODCL export (compiler only)
+// 1: header format change (more regular), export package for _ struct fields
+// 0: Go1.7 encoding
+const exportVersion = 4
+
+// trackAllTypes enables cycle tracking for all types, not just named
+// types. The existing compiler invariants assume that unnamed types
+// that are not completely set up are not used, or else there are spurious
+// errors.
+// If disabled, only named types are tracked, possibly leading to slightly
+// less efficient encoding in rare cases. It also prevents the export of
+// some corner-case type declarations (but those are not handled correctly
+// with with the textual export format either).
+// TODO(gri) enable and remove once issues caused by it are fixed
+const trackAllTypes = false
+
+type exporter struct {
+	fset *token.FileSet
+	out  bytes.Buffer
+
+	// object -> index maps, indexed in order of serialization
+	strIndex map[string]int
+	pkgIndex map[*types.Package]int
+	typIndex map[types.Type]int
+
+	// position encoding
+	posInfoFormat bool
+	prevFile      string
+	prevLine      int
+
+	// debugging support
+	written int // bytes written
+	indent  int // for trace
+}
+
+// internalError represents an error generated inside this package.
+type internalError string
+
+func (e internalError) Error() string { return "gcimporter: " + string(e) }
+
+func internalErrorf(format string, args ...interface{}) error {
+	return internalError(fmt.Sprintf(format, args...))
+}
+
+// BExportData returns binary export data for pkg.
+// If no file set is provided, position info will be missing.
+func BExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
+	defer func() {
+		if e := recover(); e != nil {
+			if ierr, ok := e.(internalError); ok {
+				err = ierr
+				return
+			}
+			// Not an internal error; panic again.
+			panic(e)
+		}
+	}()
+
+	p := exporter{
+		fset:          fset,
+		strIndex:      map[string]int{"": 0}, // empty string is mapped to 0
+		pkgIndex:      make(map[*types.Package]int),
+		typIndex:      make(map[types.Type]int),
+		posInfoFormat: true, // TODO(gri) might become a flag, eventually
+	}
+
+	// write version info
+	// The version string must start with "version %d" where %d is the version
+	// number. Additional debugging information may follow after a blank; that
+	// text is ignored by the importer.
+	p.rawStringln(fmt.Sprintf("version %d", exportVersion))
+	var debug string
+	if debugFormat {
+		debug = "debug"
+	}
+	p.rawStringln(debug) // cannot use p.bool since it's affected by debugFormat; also want to see this clearly
+	p.bool(trackAllTypes)
+	p.bool(p.posInfoFormat)
+
+	// --- generic export data ---
+
+	// populate type map with predeclared "known" types
+	for index, typ := range predeclared() {
+		p.typIndex[typ] = index
+	}
+	if len(p.typIndex) != len(predeclared()) {
+		return nil, internalError("duplicate entries in type map?")
+	}
+
+	// write package data
+	p.pkg(pkg, true)
+	if trace {
+		p.tracef("\n")
+	}
+
+	// write objects
+	objcount := 0
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		if !ast.IsExported(name) {
+			continue
+		}
+		if trace {
+			p.tracef("\n")
+		}
+		p.obj(scope.Lookup(name))
+		objcount++
+	}
+
+	// indicate end of list
+	if trace {
+		p.tracef("\n")
+	}
+	p.tag(endTag)
+
+	// for self-verification only (redundant)
+	p.int(objcount)
+
+	if trace {
+		p.tracef("\n")
+	}
+
+	// --- end of export data ---
+
+	return p.out.Bytes(), nil
+}
+
+func (p *exporter) pkg(pkg *types.Package, emptypath bool) {
+	if pkg == nil {
+		panic(internalError("unexpected nil pkg"))
+	}
+
+	// if we saw the package before, write its index (>= 0)
+	if i, ok := p.pkgIndex[pkg]; ok {
+		p.index('P', i)
+		return
+	}
+
+	// otherwise, remember the package, write the package tag (< 0) and package data
+	if trace {
+		p.tracef("P%d = { ", len(p.pkgIndex))
+		defer p.tracef("} ")
+	}
+	p.pkgIndex[pkg] = len(p.pkgIndex)
+
+	p.tag(packageTag)
+	p.string(pkg.Name())
+	if emptypath {
+		p.string("")
+	} else {
+		p.string(pkg.Path())
+	}
+}
+
+func (p *exporter) obj(obj types.Object) {
+	switch obj := obj.(type) {
+	case *types.Const:
+		p.tag(constTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		p.typ(obj.Type())
+		p.value(obj.Val())
+
+	case *types.TypeName:
+		if obj.IsAlias() {
+			p.tag(aliasTag)
+			p.pos(obj)
+			p.qualifiedName(obj)
+		} else {
+			p.tag(typeTag)
+		}
+		p.typ(obj.Type())
+
+	case *types.Var:
+		p.tag(varTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		p.typ(obj.Type())
+
+	case *types.Func:
+		p.tag(funcTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		sig := obj.Type().(*types.Signature)
+		p.paramList(sig.Params(), sig.Variadic())
+		p.paramList(sig.Results(), false)
+
+	default:
+		panic(internalErrorf("unexpected object %v (%T)", obj, obj))
+	}
+}
+
+func (p *exporter) pos(obj types.Object) {
+	if !p.posInfoFormat {
+		return
+	}
+
+	file, line := p.fileLine(obj)
+	if file == p.prevFile {
+		// common case: write line delta
+		// delta == 0 means different file or no line change
+		delta := line - p.prevLine
+		p.int(delta)
+		if delta == 0 {
+			p.int(-1) // -1 means no file change
+		}
+	} else {
+		// different file
+		p.int(0)
+		// Encode filename as length of common prefix with previous
+		// filename, followed by (possibly empty) suffix. Filenames
+		// frequently share path prefixes, so this can save a lot
+		// of space and make export data size less dependent on file
+		// path length. The suffix is unlikely to be empty because
+		// file names tend to end in ".go".
+		n := commonPrefixLen(p.prevFile, file)
+		p.int(n)           // n >= 0
+		p.string(file[n:]) // write suffix only
+		p.prevFile = file
+		p.int(line)
+	}
+	p.prevLine = line
+}
+
+func (p *exporter) fileLine(obj types.Object) (file string, line int) {
+	if p.fset != nil {
+		pos := p.fset.Position(obj.Pos())
+		file = pos.Filename
+		line = pos.Line
+	}
+	return
+}
+
+func commonPrefixLen(a, b string) int {
+	if len(a) > len(b) {
+		a, b = b, a
+	}
+	// len(a) <= len(b)
+	i := 0
+	for i < len(a) && a[i] == b[i] {
+		i++
+	}
+	return i
+}
+
+func (p *exporter) qualifiedName(obj types.Object) {
+	p.string(obj.Name())
+	p.pkg(obj.Pkg(), false)
+}
+
+func (p *exporter) typ(t types.Type) {
+	if t == nil {
+		panic(internalError("nil type"))
+	}
+
+	// Possible optimization: Anonymous pointer types *T where
+	// T is a named type are common. We could canonicalize all
+	// such types *T to a single type PT = *T. This would lead
+	// to at most one *T entry in typIndex, and all future *T's
+	// would be encoded as the respective index directly. Would
+	// save 1 byte (pointerTag) per *T and reduce the typIndex
+	// size (at the cost of a canonicalization map). We can do
+	// this later, without encoding format change.
+
+	// if we saw the type before, write its index (>= 0)
+	if i, ok := p.typIndex[t]; ok {
+		p.index('T', i)
+		return
+	}
+
+	// otherwise, remember the type, write the type tag (< 0) and type data
+	if trackAllTypes {
+		if trace {
+			p.tracef("T%d = {>\n", len(p.typIndex))
+			defer p.tracef("<\n} ")
+		}
+		p.typIndex[t] = len(p.typIndex)
+	}
+
+	switch t := t.(type) {
+	case *types.Named:
+		if !trackAllTypes {
+			// if we don't track all types, track named types now
+			p.typIndex[t] = len(p.typIndex)
+		}
+
+		p.tag(namedTag)
+		p.pos(t.Obj())
+		p.qualifiedName(t.Obj())
+		p.typ(t.Underlying())
+		if !types.IsInterface(t) {
+			p.assocMethods(t)
+		}
+
+	case *types.Array:
+		p.tag(arrayTag)
+		p.int64(t.Len())
+		p.typ(t.Elem())
+
+	case *types.Slice:
+		p.tag(sliceTag)
+		p.typ(t.Elem())
+
+	case *dddSlice:
+		p.tag(dddTag)
+		p.typ(t.elem)
+
+	case *types.Struct:
+		p.tag(structTag)
+		p.fieldList(t)
+
+	case *types.Pointer:
+		p.tag(pointerTag)
+		p.typ(t.Elem())
+
+	case *types.Signature:
+		p.tag(signatureTag)
+		p.paramList(t.Params(), t.Variadic())
+		p.paramList(t.Results(), false)
+
+	case *types.Interface:
+		p.tag(interfaceTag)
+		p.iface(t)
+
+	case *types.Map:
+		p.tag(mapTag)
+		p.typ(t.Key())
+		p.typ(t.Elem())
+
+	case *types.Chan:
+		p.tag(chanTag)
+		p.int(int(3 - t.Dir())) // hack
+		p.typ(t.Elem())
+
+	default:
+		panic(internalErrorf("unexpected type %T: %s", t, t))
+	}
+}
+
+func (p *exporter) assocMethods(named *types.Named) {
+	// Sort methods (for determinism).
+	var methods []*types.Func
+	for i := 0; i < named.NumMethods(); i++ {
+		methods = append(methods, named.Method(i))
+	}
+	sort.Sort(methodsByName(methods))
+
+	p.int(len(methods))
+
+	if trace && methods != nil {
+		p.tracef("associated methods {>\n")
+	}
+
+	for i, m := range methods {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+
+		p.pos(m)
+		name := m.Name()
+		p.string(name)
+		if !exported(name) {
+			p.pkg(m.Pkg(), false)
+		}
+
+		sig := m.Type().(*types.Signature)
+		p.paramList(types.NewTuple(sig.Recv()), false)
+		p.paramList(sig.Params(), sig.Variadic())
+		p.paramList(sig.Results(), false)
+		p.int(0) // dummy value for go:nointerface pragma - ignored by importer
+	}
+
+	if trace && methods != nil {
+		p.tracef("<\n} ")
+	}
+}
+
+type methodsByName []*types.Func
+
+func (x methodsByName) Len() int           { return len(x) }
+func (x methodsByName) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x methodsByName) Less(i, j int) bool { return x[i].Name() < x[j].Name() }
+
+func (p *exporter) fieldList(t *types.Struct) {
+	if trace && t.NumFields() > 0 {
+		p.tracef("fields {>\n")
+		defer p.tracef("<\n} ")
+	}
+
+	p.int(t.NumFields())
+	for i := 0; i < t.NumFields(); i++ {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+		p.field(t.Field(i))
+		p.string(t.Tag(i))
+	}
+}
+
+func (p *exporter) field(f *types.Var) {
+	if !f.IsField() {
+		panic(internalError("field expected"))
+	}
+
+	p.pos(f)
+	p.fieldName(f)
+	p.typ(f.Type())
+}
+
+func (p *exporter) iface(t *types.Interface) {
+	// TODO(gri): enable importer to load embedded interfaces,
+	// then emit Embeddeds and ExplicitMethods separately here.
+	p.int(0)
+
+	n := t.NumMethods()
+	if trace && n > 0 {
+		p.tracef("methods {>\n")
+		defer p.tracef("<\n} ")
+	}
+	p.int(n)
+	for i := 0; i < n; i++ {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+		p.method(t.Method(i))
+	}
+}
+
+func (p *exporter) method(m *types.Func) {
+	sig := m.Type().(*types.Signature)
+	if sig.Recv() == nil {
+		panic(internalError("method expected"))
+	}
+
+	p.pos(m)
+	p.string(m.Name())
+	if m.Name() != "_" && !ast.IsExported(m.Name()) {
+		p.pkg(m.Pkg(), false)
+	}
+
+	// interface method; no need to encode receiver.
+	p.paramList(sig.Params(), sig.Variadic())
+	p.paramList(sig.Results(), false)
+}
+
+func (p *exporter) fieldName(f *types.Var) {
+	name := f.Name()
+
+	if f.Anonymous() {
+		// anonymous field - we distinguish between 3 cases:
+		// 1) field name matches base type name and is exported
+		// 2) field name matches base type name and is not exported
+		// 3) field name doesn't match base type name (alias name)
+		bname := basetypeName(f.Type())
+		if name == bname {
+			if ast.IsExported(name) {
+				name = "" // 1) we don't need to know the field name or package
+			} else {
+				name = "?" // 2) use unexported name "?" to force package export
+			}
+		} else {
+			// 3) indicate alias and export name as is
+			// (this requires an extra "@" but this is a rare case)
+			p.string("@")
+		}
+	}
+
+	p.string(name)
+	if name != "" && !ast.IsExported(name) {
+		p.pkg(f.Pkg(), false)
+	}
+}
+
+func basetypeName(typ types.Type) string {
+	switch typ := deref(typ).(type) {
+	case *types.Basic:
+		return typ.Name()
+	case *types.Named:
+		return typ.Obj().Name()
+	default:
+		return "" // unnamed type
+	}
+}
+
+func (p *exporter) paramList(params *types.Tuple, variadic bool) {
+	// use negative length to indicate unnamed parameters
+	// (look at the first parameter only since either all
+	// names are present or all are absent)
+	n := params.Len()
+	if n > 0 && params.At(0).Name() == "" {
+		n = -n
+	}
+	p.int(n)
+	for i := 0; i < params.Len(); i++ {
+		q := params.At(i)
+		t := q.Type()
+		if variadic && i == params.Len()-1 {
+			t = &dddSlice{t.(*types.Slice).Elem()}
+		}
+		p.typ(t)
+		if n > 0 {
+			name := q.Name()
+			p.string(name)
+			if name != "_" {
+				p.pkg(q.Pkg(), false)
+			}
+		}
+		p.string("") // no compiler-specific info
+	}
+}
+
+func (p *exporter) value(x constant.Value) {
+	if trace {
+		p.tracef("= ")
+	}
+
+	switch x.Kind() {
+	case constant.Bool:
+		tag := falseTag
+		if constant.BoolVal(x) {
+			tag = trueTag
+		}
+		p.tag(tag)
+
+	case constant.Int:
+		if v, exact := constant.Int64Val(x); exact {
+			// common case: x fits into an int64 - use compact encoding
+			p.tag(int64Tag)
+			p.int64(v)
+			return
+		}
+		// uncommon case: large x - use float encoding
+		// (powers of 2 will be encoded efficiently with exponent)
+		p.tag(floatTag)
+		p.float(constant.ToFloat(x))
+
+	case constant.Float:
+		p.tag(floatTag)
+		p.float(x)
+
+	case constant.Complex:
+		p.tag(complexTag)
+		p.float(constant.Real(x))
+		p.float(constant.Imag(x))
+
+	case constant.String:
+		p.tag(stringTag)
+		p.string(constant.StringVal(x))
+
+	case constant.Unknown:
+		// package contains type errors
+		p.tag(unknownTag)
+
+	default:
+		panic(internalErrorf("unexpected value %v (%T)", x, x))
+	}
+}
+
+func (p *exporter) float(x constant.Value) {
+	if x.Kind() != constant.Float {
+		panic(internalErrorf("unexpected constant %v, want float", x))
+	}
+	// extract sign (there is no -0)
+	sign := constant.Sign(x)
+	if sign == 0 {
+		// x == 0
+		p.int(0)
+		return
+	}
+	// x != 0
+
+	var f big.Float
+	if v, exact := constant.Float64Val(x); exact {
+		// float64
+		f.SetFloat64(v)
+	} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
+		// TODO(gri): add big.Rat accessor to constant.Value.
+		r := valueToRat(num)
+		f.SetRat(r.Quo(r, valueToRat(denom)))
+	} else {
+		// Value too large to represent as a fraction => inaccessible.
+		// TODO(gri): add big.Float accessor to constant.Value.
+		f.SetFloat64(math.MaxFloat64) // FIXME
+	}
+
+	// extract exponent such that 0.5 <= m < 1.0
+	var m big.Float
+	exp := f.MantExp(&m)
+
+	// extract mantissa as *big.Int
+	// - set exponent large enough so mant satisfies mant.IsInt()
+	// - get *big.Int from mant
+	m.SetMantExp(&m, int(m.MinPrec()))
+	mant, acc := m.Int(nil)
+	if acc != big.Exact {
+		panic(internalError("internal error"))
+	}
+
+	p.int(sign)
+	p.int(exp)
+	p.string(string(mant.Bytes()))
+}
+
+func valueToRat(x constant.Value) *big.Rat {
+	// Convert little-endian to big-endian.
+	// I can't believe this is necessary.
+	bytes := constant.Bytes(x)
+	for i := 0; i < len(bytes)/2; i++ {
+		bytes[i], bytes[len(bytes)-1-i] = bytes[len(bytes)-1-i], bytes[i]
+	}
+	return new(big.Rat).SetInt(new(big.Int).SetBytes(bytes))
+}
+
+func (p *exporter) bool(b bool) bool {
+	if trace {
+		p.tracef("[")
+		defer p.tracef("= %v] ", b)
+	}
+
+	x := 0
+	if b {
+		x = 1
+	}
+	p.int(x)
+	return b
+}
+
+// ----------------------------------------------------------------------------
+// Low-level encoders
+
+func (p *exporter) index(marker byte, index int) {
+	if index < 0 {
+		panic(internalError("invalid index < 0"))
+	}
+	if debugFormat {
+		p.marker('t')
+	}
+	if trace {
+		p.tracef("%c%d ", marker, index)
+	}
+	p.rawInt64(int64(index))
+}
+
+func (p *exporter) tag(tag int) {
+	if tag >= 0 {
+		panic(internalError("invalid tag >= 0"))
+	}
+	if debugFormat {
+		p.marker('t')
+	}
+	if trace {
+		p.tracef("%s ", tagString[-tag])
+	}
+	p.rawInt64(int64(tag))
+}
+
+func (p *exporter) int(x int) {
+	p.int64(int64(x))
+}
+
+func (p *exporter) int64(x int64) {
+	if debugFormat {
+		p.marker('i')
+	}
+	if trace {
+		p.tracef("%d ", x)
+	}
+	p.rawInt64(x)
+}
+
+func (p *exporter) string(s string) {
+	if debugFormat {
+		p.marker('s')
+	}
+	if trace {
+		p.tracef("%q ", s)
+	}
+	// if we saw the string before, write its index (>= 0)
+	// (the empty string is mapped to 0)
+	if i, ok := p.strIndex[s]; ok {
+		p.rawInt64(int64(i))
+		return
+	}
+	// otherwise, remember string and write its negative length and bytes
+	p.strIndex[s] = len(p.strIndex)
+	p.rawInt64(-int64(len(s)))
+	for i := 0; i < len(s); i++ {
+		p.rawByte(s[i])
+	}
+}
+
+// marker emits a marker byte and position information which makes
+// it easy for a reader to detect if it is "out of sync". Used for
+// debugFormat format only.
+func (p *exporter) marker(m byte) {
+	p.rawByte(m)
+	// Enable this for help tracking down the location
+	// of an incorrect marker when running in debugFormat.
+	if false && trace {
+		p.tracef("#%d ", p.written)
+	}
+	p.rawInt64(int64(p.written))
+}
+
+// rawInt64 should only be used by low-level encoders.
+func (p *exporter) rawInt64(x int64) {
+	var tmp [binary.MaxVarintLen64]byte
+	n := binary.PutVarint(tmp[:], x)
+	for i := 0; i < n; i++ {
+		p.rawByte(tmp[i])
+	}
+}
+
+// rawStringln should only be used to emit the initial version string.
+func (p *exporter) rawStringln(s string) {
+	for i := 0; i < len(s); i++ {
+		p.rawByte(s[i])
+	}
+	p.rawByte('\n')
+}
+
+// rawByte is the bottleneck interface to write to p.out.
+// rawByte escapes b as follows (any encoding does that
+// hides '$'):
+//
+//	'$'  => '|' 'S'
+//	'|'  => '|' '|'
+//
+// Necessary so other tools can find the end of the
+// export data by searching for "$$".
+// rawByte should only be used by low-level encoders.
+func (p *exporter) rawByte(b byte) {
+	switch b {
+	case '$':
+		// write '$' as '|' 'S'
+		b = 'S'
+		fallthrough
+	case '|':
+		// write '|' as '|' '|'
+		p.out.WriteByte('|')
+		p.written++
+	}
+	p.out.WriteByte(b)
+	p.written++
+}
+
+// tracef is like fmt.Printf but it rewrites the format string
+// to take care of indentation.
+func (p *exporter) tracef(format string, args ...interface{}) {
+	if strings.ContainsAny(format, "<>\n") {
+		var buf bytes.Buffer
+		for i := 0; i < len(format); i++ {
+			// no need to deal with runes
+			ch := format[i]
+			switch ch {
+			case '>':
+				p.indent++
+				continue
+			case '<':
+				p.indent--
+				continue
+			}
+			buf.WriteByte(ch)
+			if ch == '\n' {
+				for j := p.indent; j > 0; j-- {
+					buf.WriteString(".  ")
+				}
+			}
+		}
+		format = buf.String()
+	}
+	fmt.Printf(format, args...)
+}
+
+// Debugging support.
+// (tagString is only used when tracing is enabled)
+var tagString = [...]string{
+	// Packages
+	-packageTag: "package",
+
+	// Types
+	-namedTag:     "named type",
+	-arrayTag:     "array",
+	-sliceTag:     "slice",
+	-dddTag:       "ddd",
+	-structTag:    "struct",
+	-pointerTag:   "pointer",
+	-signatureTag: "signature",
+	-interfaceTag: "interface",
+	-mapTag:       "map",
+	-chanTag:      "chan",
+
+	// Values
+	-falseTag:    "false",
+	-trueTag:     "true",
+	-int64Tag:    "int64",
+	-floatTag:    "float",
+	-fractionTag: "fraction",
+	-complexTag:  "complex",
+	-stringTag:   "string",
+	-unknownTag:  "unknown",
+
+	// Type aliases
+	-aliasTag: "alias",
+}

vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go

@@ -0,0 +1,93 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is a copy of $GOROOT/src/go/internal/gcimporter/exportdata.go.
+
+// This file implements FindExportData.
+
+package gcimporter
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
+	// See $GOROOT/include/ar.h.
+	hdr := make([]byte, 16+12+6+6+8+10+2)
+	_, err = io.ReadFull(r, hdr)
+	if err != nil {
+		return
+	}
+	// leave for debugging
+	if false {
+		fmt.Printf("header: %s", hdr)
+	}
+	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
+	size, err = strconv.Atoi(s)
+	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
+		err = fmt.Errorf("invalid archive header")
+		return
+	}
+	name = strings.TrimSpace(string(hdr[:16]))
+	return
+}
+
+// FindExportData positions the reader r at the beginning of the
+// export data section of an underlying GC-created object/archive
+// file by reading from it. The reader must be positioned at the
+// start of the file before calling this function. The hdr result
+// is the string before the export data, either "$$" or "$$B".
+//
+func FindExportData(r *bufio.Reader) (hdr string, err error) {
+	// Read first line to make sure this is an object file.
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		err = fmt.Errorf("can't find export data (%v)", err)
+		return
+	}
+
+	if string(line) == "!<arch>\n" {
+		// Archive file. Scan to __.PKGDEF.
+		var name string
+		if name, _, err = readGopackHeader(r); err != nil {
+			return
+		}
+
+		// First entry should be __.PKGDEF.
+		if name != "__.PKGDEF" {
+			err = fmt.Errorf("go archive is missing __.PKGDEF")
+			return
+		}
+
+		// Read first line of __.PKGDEF data, so that line
+		// is once again the first line of the input.
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+
+	// Now at __.PKGDEF in archive or still at beginning of file.
+	// Either way, line should begin with "go object ".
+	if !strings.HasPrefix(string(line), "go object ") {
+		err = fmt.Errorf("not a Go object file")
+		return
+	}
+
+	// Skip over object header to export data.
+	// Begins after first line starting with $$.
+	for line[0] != '$' {
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+	hdr = string(line)
+
+	return
+}

vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go

@@ -0,0 +1,739 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Indexed binary package export.
+// This file was derived from $GOROOT/src/cmd/compile/internal/gc/iexport.go;
+// see that file for specification of the format.
+
+package gcimporter
+
+import (
+	"bytes"
+	"encoding/binary"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"io"
+	"math/big"
+	"reflect"
+	"sort"
+)
+
+// Current indexed export format version. Increase with each format change.
+// 0: Go1.11 encoding
+const iexportVersion = 0
+
+// IExportData returns the binary export data for pkg.
+//
+// If no file set is provided, position info will be missing.
+// The package path of the top-level package will not be recorded,
+// so that calls to IImportData can override with a provided package path.
+func IExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
+	defer func() {
+		if e := recover(); e != nil {
+			if ierr, ok := e.(internalError); ok {
+				err = ierr
+				return
+			}
+			// Not an internal error; panic again.
+			panic(e)
+		}
+	}()
+
+	p := iexporter{
+		out:         bytes.NewBuffer(nil),
+		fset:        fset,
+		allPkgs:     map[*types.Package]bool{},
+		stringIndex: map[string]uint64{},
+		declIndex:   map[types.Object]uint64{},
+		typIndex:    map[types.Type]uint64{},
+		localpkg:    pkg,
+	}
+
+	for i, pt := range predeclared() {
+		p.typIndex[pt] = uint64(i)
+	}
+	if len(p.typIndex) > predeclReserved {
+		panic(internalErrorf("too many predeclared types: %d > %d", len(p.typIndex), predeclReserved))
+	}
+
+	// Initialize work queue with exported declarations.
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		if ast.IsExported(name) {
+			p.pushDecl(scope.Lookup(name))
+		}
+	}
+
+	// Loop until no more work.
+	for !p.declTodo.empty() {
+		p.doDecl(p.declTodo.popHead())
+	}
+
+	// Append indices to data0 section.
+	dataLen := uint64(p.data0.Len())
+	w := p.newWriter()
+	w.writeIndex(p.declIndex)
+	w.flush()
+
+	// Assemble header.
+	var hdr intWriter
+	hdr.WriteByte('i')
+	hdr.uint64(iexportVersion)
+	hdr.uint64(uint64(p.strings.Len()))
+	hdr.uint64(dataLen)
+
+	// Flush output.
+	io.Copy(p.out, &hdr)
+	io.Copy(p.out, &p.strings)
+	io.Copy(p.out, &p.data0)
+
+	return p.out.Bytes(), nil
+}
+
+// writeIndex writes out an object index. mainIndex indicates whether
+// we're writing out the main index, which is also read by
+// non-compiler tools and includes a complete package description
+// (i.e., name and height).
+func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
+	// Build a map from packages to objects from that package.
+	pkgObjs := map[*types.Package][]types.Object{}
+
+	// For the main index, make sure to include every package that
+	// we reference, even if we're not exporting (or reexporting)
+	// any symbols from it.
+	pkgObjs[w.p.localpkg] = nil
+	for pkg := range w.p.allPkgs {
+		pkgObjs[pkg] = nil
+	}
+
+	for obj := range index {
+		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], obj)
+	}
+
+	var pkgs []*types.Package
+	for pkg, objs := range pkgObjs {
+		pkgs = append(pkgs, pkg)
+
+		sort.Slice(objs, func(i, j int) bool {
+			return objs[i].Name() < objs[j].Name()
+		})
+	}
+
+	sort.Slice(pkgs, func(i, j int) bool {
+		return w.exportPath(pkgs[i]) < w.exportPath(pkgs[j])
+	})
+
+	w.uint64(uint64(len(pkgs)))
+	for _, pkg := range pkgs {
+		w.string(w.exportPath(pkg))
+		w.string(pkg.Name())
+		w.uint64(uint64(0)) // package height is not needed for go/types
+
+		objs := pkgObjs[pkg]
+		w.uint64(uint64(len(objs)))
+		for _, obj := range objs {
+			w.string(obj.Name())
+			w.uint64(index[obj])
+		}
+	}
+}
+
+type iexporter struct {
+	fset *token.FileSet
+	out  *bytes.Buffer
+
+	localpkg *types.Package
+
+	// allPkgs tracks all packages that have been referenced by
+	// the export data, so we can ensure to include them in the
+	// main index.
+	allPkgs map[*types.Package]bool
+
+	declTodo objQueue
+
+	strings     intWriter
+	stringIndex map[string]uint64
+
+	data0     intWriter
+	declIndex map[types.Object]uint64
+	typIndex  map[types.Type]uint64
+}
+
+// stringOff returns the offset of s within the string section.
+// If not already present, it's added to the end.
+func (p *iexporter) stringOff(s string) uint64 {
+	off, ok := p.stringIndex[s]
+	if !ok {
+		off = uint64(p.strings.Len())
+		p.stringIndex[s] = off
+
+		p.strings.uint64(uint64(len(s)))
+		p.strings.WriteString(s)
+	}
+	return off
+}
+
+// pushDecl adds n to the declaration work queue, if not already present.
+func (p *iexporter) pushDecl(obj types.Object) {
+	// Package unsafe is known to the compiler and predeclared.
+	assert(obj.Pkg() != types.Unsafe)
+
+	if _, ok := p.declIndex[obj]; ok {
+		return
+	}
+
+	p.declIndex[obj] = ^uint64(0) // mark n present in work queue
+	p.declTodo.pushTail(obj)
+}
+
+// exportWriter handles writing out individual data section chunks.
+type exportWriter struct {
+	p *iexporter
+
+	data     intWriter
+	currPkg  *types.Package
+	prevFile string
+	prevLine int64
+}
+
+func (w *exportWriter) exportPath(pkg *types.Package) string {
+	if pkg == w.p.localpkg {
+		return ""
+	}
+	return pkg.Path()
+}
+
+func (p *iexporter) doDecl(obj types.Object) {
+	w := p.newWriter()
+	w.setPkg(obj.Pkg(), false)
+
+	switch obj := obj.(type) {
+	case *types.Var:
+		w.tag('V')
+		w.pos(obj.Pos())
+		w.typ(obj.Type(), obj.Pkg())
+
+	case *types.Func:
+		sig, _ := obj.Type().(*types.Signature)
+		if sig.Recv() != nil {
+			panic(internalErrorf("unexpected method: %v", sig))
+		}
+		w.tag('F')
+		w.pos(obj.Pos())
+		w.signature(sig)
+
+	case *types.Const:
+		w.tag('C')
+		w.pos(obj.Pos())
+		w.value(obj.Type(), obj.Val())
+
+	case *types.TypeName:
+		if obj.IsAlias() {
+			w.tag('A')
+			w.pos(obj.Pos())
+			w.typ(obj.Type(), obj.Pkg())
+			break
+		}
+
+		// Defined type.
+		w.tag('T')
+		w.pos(obj.Pos())
+
+		underlying := obj.Type().Underlying()
+		w.typ(underlying, obj.Pkg())
+
+		t := obj.Type()
+		if types.IsInterface(t) {
+			break
+		}
+
+		named, ok := t.(*types.Named)
+		if !ok {
+			panic(internalErrorf("%s is not a defined type", t))
+		}
+
+		n := named.NumMethods()
+		w.uint64(uint64(n))
+		for i := 0; i < n; i++ {
+			m := named.Method(i)
+			w.pos(m.Pos())
+			w.string(m.Name())
+			sig, _ := m.Type().(*types.Signature)
+			w.param(sig.Recv())
+			w.signature(sig)
+		}
+
+	default:
+		panic(internalErrorf("unexpected object: %v", obj))
+	}
+
+	p.declIndex[obj] = w.flush()
+}
+
+func (w *exportWriter) tag(tag byte) {
+	w.data.WriteByte(tag)
+}
+
+func (w *exportWriter) pos(pos token.Pos) {
+	if w.p.fset == nil {
+		w.int64(0)
+		return
+	}
+
+	p := w.p.fset.Position(pos)
+	file := p.Filename
+	line := int64(p.Line)
+
+	// When file is the same as the last position (common case),
+	// we can save a few bytes by delta encoding just the line
+	// number.
+	//
+	// Note: Because data objects may be read out of order (or not
+	// at all), we can only apply delta encoding within a single
+	// object. This is handled implicitly by tracking prevFile and
+	// prevLine as fields of exportWriter.
+
+	if file == w.prevFile {
+		delta := line - w.prevLine
+		w.int64(delta)
+		if delta == deltaNewFile {
+			w.int64(-1)
+		}
+	} else {
+		w.int64(deltaNewFile)
+		w.int64(line) // line >= 0
+		w.string(file)
+		w.prevFile = file
+	}
+	w.prevLine = line
+}
+
+func (w *exportWriter) pkg(pkg *types.Package) {
+	// Ensure any referenced packages are declared in the main index.
+	w.p.allPkgs[pkg] = true
+
+	w.string(w.exportPath(pkg))
+}
+
+func (w *exportWriter) qualifiedIdent(obj types.Object) {
+	// Ensure any referenced declarations are written out too.
+	w.p.pushDecl(obj)
+
+	w.string(obj.Name())
+	w.pkg(obj.Pkg())
+}
+
+func (w *exportWriter) typ(t types.Type, pkg *types.Package) {
+	w.data.uint64(w.p.typOff(t, pkg))
+}
+
+func (p *iexporter) newWriter() *exportWriter {
+	return &exportWriter{p: p}
+}
+
+func (w *exportWriter) flush() uint64 {
+	off := uint64(w.p.data0.Len())
+	io.Copy(&w.p.data0, &w.data)
+	return off
+}
+
+func (p *iexporter) typOff(t types.Type, pkg *types.Package) uint64 {
+	off, ok := p.typIndex[t]
+	if !ok {
+		w := p.newWriter()
+		w.doTyp(t, pkg)
+		off = predeclReserved + w.flush()
+		p.typIndex[t] = off
+	}
+	return off
+}
+
+func (w *exportWriter) startType(k itag) {
+	w.data.uint64(uint64(k))
+}
+
+func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
+	switch t := t.(type) {
+	case *types.Named:
+		w.startType(definedType)
+		w.qualifiedIdent(t.Obj())
+
+	case *types.Pointer:
+		w.startType(pointerType)
+		w.typ(t.Elem(), pkg)
+
+	case *types.Slice:
+		w.startType(sliceType)
+		w.typ(t.Elem(), pkg)
+
+	case *types.Array:
+		w.startType(arrayType)
+		w.uint64(uint64(t.Len()))
+		w.typ(t.Elem(), pkg)
+
+	case *types.Chan:
+		w.startType(chanType)
+		// 1 RecvOnly; 2 SendOnly; 3 SendRecv
+		var dir uint64
+		switch t.Dir() {
+		case types.RecvOnly:
+			dir = 1
+		case types.SendOnly:
+			dir = 2
+		case types.SendRecv:
+			dir = 3
+		}
+		w.uint64(dir)
+		w.typ(t.Elem(), pkg)
+
+	case *types.Map:
+		w.startType(mapType)
+		w.typ(t.Key(), pkg)
+		w.typ(t.Elem(), pkg)
+
+	case *types.Signature:
+		w.startType(signatureType)
+		w.setPkg(pkg, true)
+		w.signature(t)
+
+	case *types.Struct:
+		w.startType(structType)
+		w.setPkg(pkg, true)
+
+		n := t.NumFields()
+		w.uint64(uint64(n))
+		for i := 0; i < n; i++ {
+			f := t.Field(i)
+			w.pos(f.Pos())
+			w.string(f.Name())
+			w.typ(f.Type(), pkg)
+			w.bool(f.Anonymous())
+			w.string(t.Tag(i)) // note (or tag)
+		}
+
+	case *types.Interface:
+		w.startType(interfaceType)
+		w.setPkg(pkg, true)
+
+		n := t.NumEmbeddeds()
+		w.uint64(uint64(n))
+		for i := 0; i < n; i++ {
+			f := t.Embedded(i)
+			w.pos(f.Obj().Pos())
+			w.typ(f.Obj().Type(), f.Obj().Pkg())
+		}
+
+		n = t.NumExplicitMethods()
+		w.uint64(uint64(n))
+		for i := 0; i < n; i++ {
+			m := t.ExplicitMethod(i)
+			w.pos(m.Pos())
+			w.string(m.Name())
+			sig, _ := m.Type().(*types.Signature)
+			w.signature(sig)
+		}
+
+	default:
+		panic(internalErrorf("unexpected type: %v, %v", t, reflect.TypeOf(t)))
+	}
+}
+
+func (w *exportWriter) setPkg(pkg *types.Package, write bool) {
+	if write {
+		w.pkg(pkg)
+	}
+
+	w.currPkg = pkg
+}
+
+func (w *exportWriter) signature(sig *types.Signature) {
+	w.paramList(sig.Params())
+	w.paramList(sig.Results())
+	if sig.Params().Len() > 0 {
+		w.bool(sig.Variadic())
+	}
+}
+
+func (w *exportWriter) paramList(tup *types.Tuple) {
+	n := tup.Len()
+	w.uint64(uint64(n))
+	for i := 0; i < n; i++ {
+		w.param(tup.At(i))
+	}
+}
+
+func (w *exportWriter) param(obj types.Object) {
+	w.pos(obj.Pos())
+	w.localIdent(obj)
+	w.typ(obj.Type(), obj.Pkg())
+}
+
+func (w *exportWriter) value(typ types.Type, v constant.Value) {
+	w.typ(typ, nil)
+
+	switch v.Kind() {
+	case constant.Bool:
+		w.bool(constant.BoolVal(v))
+	case constant.Int:
+		var i big.Int
+		if i64, exact := constant.Int64Val(v); exact {
+			i.SetInt64(i64)
+		} else if ui64, exact := constant.Uint64Val(v); exact {
+			i.SetUint64(ui64)
+		} else {
+			i.SetString(v.ExactString(), 10)
+		}
+		w.mpint(&i, typ)
+	case constant.Float:
+		f := constantToFloat(v)
+		w.mpfloat(f, typ)
+	case constant.Complex:
+		w.mpfloat(constantToFloat(constant.Real(v)), typ)
+		w.mpfloat(constantToFloat(constant.Imag(v)), typ)
+	case constant.String:
+		w.string(constant.StringVal(v))
+	case constant.Unknown:
+		// package contains type errors
+	default:
+		panic(internalErrorf("unexpected value %v (%T)", v, v))
+	}
+}
+
+// constantToFloat converts a constant.Value with kind constant.Float to a
+// big.Float.
+func constantToFloat(x constant.Value) *big.Float {
+	assert(x.Kind() == constant.Float)
+	// Use the same floating-point precision (512) as cmd/compile
+	// (see Mpprec in cmd/compile/internal/gc/mpfloat.go).
+	const mpprec = 512
+	var f big.Float
+	f.SetPrec(mpprec)
+	if v, exact := constant.Float64Val(x); exact {
+		// float64
+		f.SetFloat64(v)
+	} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
+		// TODO(gri): add big.Rat accessor to constant.Value.
+		n := valueToRat(num)
+		d := valueToRat(denom)
+		f.SetRat(n.Quo(n, d))
+	} else {
+		// Value too large to represent as a fraction => inaccessible.
+		// TODO(gri): add big.Float accessor to constant.Value.
+		_, ok := f.SetString(x.ExactString())
+		assert(ok)
+	}
+	return &f
+}
+
+// mpint exports a multi-precision integer.
+//
+// For unsigned types, small values are written out as a single
+// byte. Larger values are written out as a length-prefixed big-endian
+// byte string, where the length prefix is encoded as its complement.
+// For example, bytes 0, 1, and 2 directly represent the integer
+// values 0, 1, and 2; while bytes 255, 254, and 253 indicate a 1-,
+// 2-, and 3-byte big-endian string follow.
+//
+// Encoding for signed types use the same general approach as for
+// unsigned types, except small values use zig-zag encoding and the
+// bottom bit of length prefix byte for large values is reserved as a
+// sign bit.
+//
+// The exact boundary between small and large encodings varies
+// according to the maximum number of bytes needed to encode a value
+// of type typ. As a special case, 8-bit types are always encoded as a
+// single byte.
+//
+// TODO(mdempsky): Is this level of complexity really worthwhile?
+func (w *exportWriter) mpint(x *big.Int, typ types.Type) {
+	basic, ok := typ.Underlying().(*types.Basic)
+	if !ok {
+		panic(internalErrorf("unexpected type %v (%T)", typ.Underlying(), typ.Underlying()))
+	}
+
+	signed, maxBytes := intSize(basic)
+
+	negative := x.Sign() < 0
+	if !signed && negative {
+		panic(internalErrorf("negative unsigned integer; type %v, value %v", typ, x))
+	}
+
+	b := x.Bytes()
+	if len(b) > 0 && b[0] == 0 {
+		panic(internalErrorf("leading zeros"))
+	}
+	if uint(len(b)) > maxBytes {
+		panic(internalErrorf("bad mpint length: %d > %d (type %v, value %v)", len(b), maxBytes, typ, x))
+	}
+
+	maxSmall := 256 - maxBytes
+	if signed {
+		maxSmall = 256 - 2*maxBytes
+	}
+	if maxBytes == 1 {
+		maxSmall = 256
+	}
+
+	// Check if x can use small value encoding.
+	if len(b) <= 1 {
+		var ux uint
+		if len(b) == 1 {
+			ux = uint(b[0])
+		}
+		if signed {
+			ux <<= 1
+			if negative {
+				ux--
+			}
+		}
+		if ux < maxSmall {
+			w.data.WriteByte(byte(ux))
+			return
+		}
+	}
+
+	n := 256 - uint(len(b))
+	if signed {
+		n = 256 - 2*uint(len(b))
+		if negative {
+			n |= 1
+		}
+	}
+	if n < maxSmall || n >= 256 {
+		panic(internalErrorf("encoding mistake: %d, %v, %v => %d", len(b), signed, negative, n))
+	}
+
+	w.data.WriteByte(byte(n))
+	w.data.Write(b)
+}
+
+// mpfloat exports a multi-precision floating point number.
+//
+// The number's value is decomposed into mantissa × 2**exponent, where
+// mantissa is an integer. The value is written out as mantissa (as a
+// multi-precision integer) and then the exponent, except exponent is
+// omitted if mantissa is zero.
+func (w *exportWriter) mpfloat(f *big.Float, typ types.Type) {
+	if f.IsInf() {
+		panic("infinite constant")
+	}
+
+	// Break into f = mant × 2**exp, with 0.5 <= mant < 1.
+	var mant big.Float
+	exp := int64(f.MantExp(&mant))
+
+	// Scale so that mant is an integer.
+	prec := mant.MinPrec()
+	mant.SetMantExp(&mant, int(prec))
+	exp -= int64(prec)
+
+	manti, acc := mant.Int(nil)
+	if acc != big.Exact {
+		panic(internalErrorf("mantissa scaling failed for %f (%s)", f, acc))
+	}
+	w.mpint(manti, typ)
+	if manti.Sign() != 0 {
+		w.int64(exp)
+	}
+}
+
+func (w *exportWriter) bool(b bool) bool {
+	var x uint64
+	if b {
+		x = 1
+	}
+	w.uint64(x)
+	return b
+}
+
+func (w *exportWriter) int64(x int64)   { w.data.int64(x) }
+func (w *exportWriter) uint64(x uint64) { w.data.uint64(x) }
+func (w *exportWriter) string(s string) { w.uint64(w.p.stringOff(s)) }
+
+func (w *exportWriter) localIdent(obj types.Object) {
+	// Anonymous parameters.
+	if obj == nil {
+		w.string("")
+		return
+	}
+
+	name := obj.Name()
+	if name == "_" {
+		w.string("_")
+		return
+	}
+
+	w.string(name)
+}
+
+type intWriter struct {
+	bytes.Buffer
+}
+
+func (w *intWriter) int64(x int64) {
+	var buf [binary.MaxVarintLen64]byte
+	n := binary.PutVarint(buf[:], x)
+	w.Write(buf[:n])
+}
+
+func (w *intWriter) uint64(x uint64) {
+	var buf [binary.MaxVarintLen64]byte
+	n := binary.PutUvarint(buf[:], x)
+	w.Write(buf[:n])
+}
+
+func assert(cond bool) {
+	if !cond {
+		panic("internal error: assertion failed")
+	}
+}
+
+// The below is copied from go/src/cmd/compile/internal/gc/syntax.go.
+
+// objQueue is a FIFO queue of types.Object. The zero value of objQueue is
+// a ready-to-use empty queue.
+type objQueue struct {
+	ring       []types.Object
+	head, tail int
+}
+
+// empty returns true if q contains no Nodes.
+func (q *objQueue) empty() bool {
+	return q.head == q.tail
+}
+
+// pushTail appends n to the tail of the queue.
+func (q *objQueue) pushTail(obj types.Object) {
+	if len(q.ring) == 0 {
+		q.ring = make([]types.Object, 16)
+	} else if q.head+len(q.ring) == q.tail {
+		// Grow the ring.
+		nring := make([]types.Object, len(q.ring)*2)
+		// Copy the old elements.
+		part := q.ring[q.head%len(q.ring):]
+		if q.tail-q.head <= len(part) {
+			part = part[:q.tail-q.head]
+			copy(nring, part)
+		} else {
+			pos := copy(nring, part)
+			copy(nring[pos:], q.ring[:q.tail%len(q.ring)])
+		}
+		q.ring, q.head, q.tail = nring, 0, q.tail-q.head
+	}
+
+	q.ring[q.tail%len(q.ring)] = obj
+	q.tail++
+}
+
+// popHead pops a node from the head of the queue. It panics if q is empty.
+func (q *objQueue) popHead() types.Object {
+	if q.empty() {
+		panic("dequeue empty")
+	}
+	obj := q.ring[q.head%len(q.ring)]
+	q.head++
+	return obj
+}

vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go

@@ -0,0 +1,630 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Indexed package import.
+// See cmd/compile/internal/gc/iexport.go for the export data format.
+
+// This file is a copy of $GOROOT/src/go/internal/gcimporter/iimport.go.
+
+package gcimporter
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"io"
+	"sort"
+)
+
+type intReader struct {
+	*bytes.Reader
+	path string
+}
+
+func (r *intReader) int64() int64 {
+	i, err := binary.ReadVarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+func (r *intReader) uint64() uint64 {
+	i, err := binary.ReadUvarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+const predeclReserved = 32
+
+type itag uint64
+
+const (
+	// Types
+	definedType itag = iota
+	pointerType
+	sliceType
+	arrayType
+	chanType
+	mapType
+	signatureType
+	structType
+	interfaceType
+)
+
+// IImportData imports a package from the serialized package data
+// and returns the number of bytes consumed and a reference to the package.
+// If the export data version is not recognized or the format is otherwise
+// compromised, an error is returned.
+func IImportData(fset *token.FileSet, imports map[string]*types.Package, data []byte, path string) (_ int, pkg *types.Package, err error) {
+	const currentVersion = 1
+	version := int64(-1)
+	defer func() {
+		if e := recover(); e != nil {
+			if version > currentVersion {
+				err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
+			} else {
+				err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
+			}
+		}
+	}()
+
+	r := &intReader{bytes.NewReader(data), path}
+
+	version = int64(r.uint64())
+	switch version {
+	case currentVersion, 0:
+	default:
+		errorf("unknown iexport format version %d", version)
+	}
+
+	sLen := int64(r.uint64())
+	dLen := int64(r.uint64())
+
+	whence, _ := r.Seek(0, io.SeekCurrent)
+	stringData := data[whence : whence+sLen]
+	declData := data[whence+sLen : whence+sLen+dLen]
+	r.Seek(sLen+dLen, io.SeekCurrent)
+
+	p := iimporter{
+		ipath:   path,
+		version: int(version),
+
+		stringData:  stringData,
+		stringCache: make(map[uint64]string),
+		pkgCache:    make(map[uint64]*types.Package),
+
+		declData: declData,
+		pkgIndex: make(map[*types.Package]map[string]uint64),
+		typCache: make(map[uint64]types.Type),
+
+		fake: fakeFileSet{
+			fset:  fset,
+			files: make(map[string]*token.File),
+		},
+	}
+
+	for i, pt := range predeclared() {
+		p.typCache[uint64(i)] = pt
+	}
+
+	pkgList := make([]*types.Package, r.uint64())
+	for i := range pkgList {
+		pkgPathOff := r.uint64()
+		pkgPath := p.stringAt(pkgPathOff)
+		pkgName := p.stringAt(r.uint64())
+		_ = r.uint64() // package height; unused by go/types
+
+		if pkgPath == "" {
+			pkgPath = path
+		}
+		pkg := imports[pkgPath]
+		if pkg == nil {
+			pkg = types.NewPackage(pkgPath, pkgName)
+			imports[pkgPath] = pkg
+		} else if pkg.Name() != pkgName {
+			errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
+		}
+
+		p.pkgCache[pkgPathOff] = pkg
+
+		nameIndex := make(map[string]uint64)
+		for nSyms := r.uint64(); nSyms > 0; nSyms-- {
+			name := p.stringAt(r.uint64())
+			nameIndex[name] = r.uint64()
+		}
+
+		p.pkgIndex[pkg] = nameIndex
+		pkgList[i] = pkg
+	}
+	if len(pkgList) == 0 {
+		errorf("no packages found for %s", path)
+		panic("unreachable")
+	}
+	p.ipkg = pkgList[0]
+	names := make([]string, 0, len(p.pkgIndex[p.ipkg]))
+	for name := range p.pkgIndex[p.ipkg] {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	for _, name := range names {
+		p.doDecl(p.ipkg, name)
+	}
+
+	for _, typ := range p.interfaceList {
+		typ.Complete()
+	}
+
+	// record all referenced packages as imports
+	list := append(([]*types.Package)(nil), pkgList[1:]...)
+	sort.Sort(byPath(list))
+	p.ipkg.SetImports(list)
+
+	// package was imported completely and without errors
+	p.ipkg.MarkComplete()
+
+	consumed, _ := r.Seek(0, io.SeekCurrent)
+	return int(consumed), p.ipkg, nil
+}
+
+type iimporter struct {
+	ipath   string
+	ipkg    *types.Package
+	version int
+
+	stringData  []byte
+	stringCache map[uint64]string
+	pkgCache    map[uint64]*types.Package
+
+	declData []byte
+	pkgIndex map[*types.Package]map[string]uint64
+	typCache map[uint64]types.Type
+
+	fake          fakeFileSet
+	interfaceList []*types.Interface
+}
+
+func (p *iimporter) doDecl(pkg *types.Package, name string) {
+	// See if we've already imported this declaration.
+	if obj := pkg.Scope().Lookup(name); obj != nil {
+		return
+	}
+
+	off, ok := p.pkgIndex[pkg][name]
+	if !ok {
+		errorf("%v.%v not in index", pkg, name)
+	}
+
+	r := &importReader{p: p, currPkg: pkg}
+	r.declReader.Reset(p.declData[off:])
+
+	r.obj(name)
+}
+
+func (p *iimporter) stringAt(off uint64) string {
+	if s, ok := p.stringCache[off]; ok {
+		return s
+	}
+
+	slen, n := binary.Uvarint(p.stringData[off:])
+	if n <= 0 {
+		errorf("varint failed")
+	}
+	spos := off + uint64(n)
+	s := string(p.stringData[spos : spos+slen])
+	p.stringCache[off] = s
+	return s
+}
+
+func (p *iimporter) pkgAt(off uint64) *types.Package {
+	if pkg, ok := p.pkgCache[off]; ok {
+		return pkg
+	}
+	path := p.stringAt(off)
+	if path == p.ipath {
+		return p.ipkg
+	}
+	errorf("missing package %q in %q", path, p.ipath)
+	return nil
+}
+
+func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
+	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
+		return t
+	}
+
+	if off < predeclReserved {
+		errorf("predeclared type missing from cache: %v", off)
+	}
+
+	r := &importReader{p: p}
+	r.declReader.Reset(p.declData[off-predeclReserved:])
+	t := r.doType(base)
+
+	if base == nil || !isInterface(t) {
+		p.typCache[off] = t
+	}
+	return t
+}
+
+type importReader struct {
+	p          *iimporter
+	declReader bytes.Reader
+	currPkg    *types.Package
+	prevFile   string
+	prevLine   int64
+	prevColumn int64
+}
+
+func (r *importReader) obj(name string) {
+	tag := r.byte()
+	pos := r.pos()
+
+	switch tag {
+	case 'A':
+		typ := r.typ()
+
+		r.declare(types.NewTypeName(pos, r.currPkg, name, typ))
+
+	case 'C':
+		typ, val := r.value()
+
+		r.declare(types.NewConst(pos, r.currPkg, name, typ, val))
+
+	case 'F':
+		sig := r.signature(nil)
+
+		r.declare(types.NewFunc(pos, r.currPkg, name, sig))
+
+	case 'T':
+		// Types can be recursive. We need to setup a stub
+		// declaration before recursing.
+		obj := types.NewTypeName(pos, r.currPkg, name, nil)
+		named := types.NewNamed(obj, nil, nil)
+		r.declare(obj)
+
+		underlying := r.p.typAt(r.uint64(), named).Underlying()
+		named.SetUnderlying(underlying)
+
+		if !isInterface(underlying) {
+			for n := r.uint64(); n > 0; n-- {
+				mpos := r.pos()
+				mname := r.ident()
+				recv := r.param()
+				msig := r.signature(recv)
+
+				named.AddMethod(types.NewFunc(mpos, r.currPkg, mname, msig))
+			}
+		}
+
+	case 'V':
+		typ := r.typ()
+
+		r.declare(types.NewVar(pos, r.currPkg, name, typ))
+
+	default:
+		errorf("unexpected tag: %v", tag)
+	}
+}
+
+func (r *importReader) declare(obj types.Object) {
+	obj.Pkg().Scope().Insert(obj)
+}
+
+func (r *importReader) value() (typ types.Type, val constant.Value) {
+	typ = r.typ()
+
+	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
+	case types.IsBoolean:
+		val = constant.MakeBool(r.bool())
+
+	case types.IsString:
+		val = constant.MakeString(r.string())
+
+	case types.IsInteger:
+		val = r.mpint(b)
+
+	case types.IsFloat:
+		val = r.mpfloat(b)
+
+	case types.IsComplex:
+		re := r.mpfloat(b)
+		im := r.mpfloat(b)
+		val = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
+
+	default:
+		if b.Kind() == types.Invalid {
+			val = constant.MakeUnknown()
+			return
+		}
+		errorf("unexpected type %v", typ) // panics
+		panic("unreachable")
+	}
+
+	return
+}
+
+func intSize(b *types.Basic) (signed bool, maxBytes uint) {
+	if (b.Info() & types.IsUntyped) != 0 {
+		return true, 64
+	}
+
+	switch b.Kind() {
+	case types.Float32, types.Complex64:
+		return true, 3
+	case types.Float64, types.Complex128:
+		return true, 7
+	}
+
+	signed = (b.Info() & types.IsUnsigned) == 0
+	switch b.Kind() {
+	case types.Int8, types.Uint8:
+		maxBytes = 1
+	case types.Int16, types.Uint16:
+		maxBytes = 2
+	case types.Int32, types.Uint32:
+		maxBytes = 4
+	default:
+		maxBytes = 8
+	}
+
+	return
+}
+
+func (r *importReader) mpint(b *types.Basic) constant.Value {
+	signed, maxBytes := intSize(b)
+
+	maxSmall := 256 - maxBytes
+	if signed {
+		maxSmall = 256 - 2*maxBytes
+	}
+	if maxBytes == 1 {
+		maxSmall = 256
+	}
+
+	n, _ := r.declReader.ReadByte()
+	if uint(n) < maxSmall {
+		v := int64(n)
+		if signed {
+			v >>= 1
+			if n&1 != 0 {
+				v = ^v
+			}
+		}
+		return constant.MakeInt64(v)
+	}
+
+	v := -n
+	if signed {
+		v = -(n &^ 1) >> 1
+	}
+	if v < 1 || uint(v) > maxBytes {
+		errorf("weird decoding: %v, %v => %v", n, signed, v)
+	}
+
+	buf := make([]byte, v)
+	io.ReadFull(&r.declReader, buf)
+
+	// convert to little endian
+	// TODO(gri) go/constant should have a more direct conversion function
+	//           (e.g., once it supports a big.Float based implementation)
+	for i, j := 0, len(buf)-1; i < j; i, j = i+1, j-1 {
+		buf[i], buf[j] = buf[j], buf[i]
+	}
+
+	x := constant.MakeFromBytes(buf)
+	if signed && n&1 != 0 {
+		x = constant.UnaryOp(token.SUB, x, 0)
+	}
+	return x
+}
+
+func (r *importReader) mpfloat(b *types.Basic) constant.Value {
+	x := r.mpint(b)
+	if constant.Sign(x) == 0 {
+		return x
+	}
+
+	exp := r.int64()
+	switch {
+	case exp > 0:
+		x = constant.Shift(x, token.SHL, uint(exp))
+	case exp < 0:
+		d := constant.Shift(constant.MakeInt64(1), token.SHL, uint(-exp))
+		x = constant.BinaryOp(x, token.QUO, d)
+	}
+	return x
+}
+
+func (r *importReader) ident() string {
+	return r.string()
+}
+
+func (r *importReader) qualifiedIdent() (*types.Package, string) {
+	name := r.string()
+	pkg := r.pkg()
+	return pkg, name
+}
+
+func (r *importReader) pos() token.Pos {
+	if r.p.version >= 1 {
+		r.posv1()
+	} else {
+		r.posv0()
+	}
+
+	if r.prevFile == "" && r.prevLine == 0 && r.prevColumn == 0 {
+		return token.NoPos
+	}
+	return r.p.fake.pos(r.prevFile, int(r.prevLine), int(r.prevColumn))
+}
+
+func (r *importReader) posv0() {
+	delta := r.int64()
+	if delta != deltaNewFile {
+		r.prevLine += delta
+	} else if l := r.int64(); l == -1 {
+		r.prevLine += deltaNewFile
+	} else {
+		r.prevFile = r.string()
+		r.prevLine = l
+	}
+}
+
+func (r *importReader) posv1() {
+	delta := r.int64()
+	r.prevColumn += delta >> 1
+	if delta&1 != 0 {
+		delta = r.int64()
+		r.prevLine += delta >> 1
+		if delta&1 != 0 {
+			r.prevFile = r.string()
+		}
+	}
+}
+
+func (r *importReader) typ() types.Type {
+	return r.p.typAt(r.uint64(), nil)
+}
+
+func isInterface(t types.Type) bool {
+	_, ok := t.(*types.Interface)
+	return ok
+}
+
+func (r *importReader) pkg() *types.Package { return r.p.pkgAt(r.uint64()) }
+func (r *importReader) string() string      { return r.p.stringAt(r.uint64()) }
+
+func (r *importReader) doType(base *types.Named) types.Type {
+	switch k := r.kind(); k {
+	default:
+		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
+		return nil
+
+	case definedType:
+		pkg, name := r.qualifiedIdent()
+		r.p.doDecl(pkg, name)
+		return pkg.Scope().Lookup(name).(*types.TypeName).Type()
+	case pointerType:
+		return types.NewPointer(r.typ())
+	case sliceType:
+		return types.NewSlice(r.typ())
+	case arrayType:
+		n := r.uint64()
+		return types.NewArray(r.typ(), int64(n))
+	case chanType:
+		dir := chanDir(int(r.uint64()))
+		return types.NewChan(dir, r.typ())
+	case mapType:
+		return types.NewMap(r.typ(), r.typ())
+	case signatureType:
+		r.currPkg = r.pkg()
+		return r.signature(nil)
+
+	case structType:
+		r.currPkg = r.pkg()
+
+		fields := make([]*types.Var, r.uint64())
+		tags := make([]string, len(fields))
+		for i := range fields {
+			fpos := r.pos()
+			fname := r.ident()
+			ftyp := r.typ()
+			emb := r.bool()
+			tag := r.string()
+
+			fields[i] = types.NewField(fpos, r.currPkg, fname, ftyp, emb)
+			tags[i] = tag
+		}
+		return types.NewStruct(fields, tags)
+
+	case interfaceType:
+		r.currPkg = r.pkg()
+
+		embeddeds := make([]types.Type, r.uint64())
+		for i := range embeddeds {
+			_ = r.pos()
+			embeddeds[i] = r.typ()
+		}
+
+		methods := make([]*types.Func, r.uint64())
+		for i := range methods {
+			mpos := r.pos()
+			mname := r.ident()
+
+			// TODO(mdempsky): Matches bimport.go, but I
+			// don't agree with this.
+			var recv *types.Var
+			if base != nil {
+				recv = types.NewVar(token.NoPos, r.currPkg, "", base)
+			}
+
+			msig := r.signature(recv)
+			methods[i] = types.NewFunc(mpos, r.currPkg, mname, msig)
+		}
+
+		typ := newInterface(methods, embeddeds)
+		r.p.interfaceList = append(r.p.interfaceList, typ)
+		return typ
+	}
+}
+
+func (r *importReader) kind() itag {
+	return itag(r.uint64())
+}
+
+func (r *importReader) signature(recv *types.Var) *types.Signature {
+	params := r.paramList()
+	results := r.paramList()
+	variadic := params.Len() > 0 && r.bool()
+	return types.NewSignature(recv, params, results, variadic)
+}
+
+func (r *importReader) paramList() *types.Tuple {
+	xs := make([]*types.Var, r.uint64())
+	for i := range xs {
+		xs[i] = r.param()
+	}
+	return types.NewTuple(xs...)
+}
+
+func (r *importReader) param() *types.Var {
+	pos := r.pos()
+	name := r.ident()
+	typ := r.typ()
+	return types.NewParam(pos, r.currPkg, name, typ)
+}
+
+func (r *importReader) bool() bool {
+	return r.uint64() != 0
+}
+
+func (r *importReader) int64() int64 {
+	n, err := binary.ReadVarint(&r.declReader)
+	if err != nil {
+		errorf("readVarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) uint64() uint64 {
+	n, err := binary.ReadUvarint(&r.declReader)
+	if err != nil {
+		errorf("readUvarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) byte() byte {
+	x, err := r.declReader.ReadByte()
+	if err != nil {
+		errorf("declReader.ReadByte: %v", err)
+	}
+	return x
+}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface10.go

@@ -0,0 +1,21 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.11
+
+package gcimporter
+
+import "go/types"
+
+func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
+	named := make([]*types.Named, len(embeddeds))
+	for i, e := range embeddeds {
+		var ok bool
+		named[i], ok = e.(*types.Named)
+		if !ok {
+			panic("embedding of non-defined interfaces in interfaces is not supported before Go 1.11")
+		}
+	}
+	return types.NewInterface(methods, named)
+}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface11.go

@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.11
+
+package gcimporter
+
+import "go/types"
+
+func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
+	return types.NewInterfaceType(methods, embeddeds)
+}

vendor/golang.org/x/tools/go/internal/packagesdriver/sizes.go

@@ -0,0 +1,49 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package packagesdriver fetches type sizes for go/packages and go/analysis.
+package packagesdriver
+
+import (
+	"context"
+	"fmt"
+	"go/types"
+	"strings"
+
+	"golang.org/x/tools/internal/gocommand"
+)
+
+var debug = false
+
+func GetSizesGolist(ctx context.Context, inv gocommand.Invocation, gocmdRunner *gocommand.Runner) (types.Sizes, error) {
+	inv.Verb = "list"
+	inv.Args = []string{"-f", "{{context.GOARCH}} {{context.Compiler}}", "--", "unsafe"}
+	stdout, stderr, friendlyErr, rawErr := gocmdRunner.RunRaw(ctx, inv)
+	var goarch, compiler string
+	if rawErr != nil {
+		if strings.Contains(rawErr.Error(), "cannot find main module") {
+			// User's running outside of a module. All bets are off. Get GOARCH and guess compiler is gc.
+			// TODO(matloob): Is this a problem in practice?
+			inv.Verb = "env"
+			inv.Args = []string{"GOARCH"}
+			envout, enverr := gocmdRunner.Run(ctx, inv)
+			if enverr != nil {
+				return nil, enverr
+			}
+			goarch = strings.TrimSpace(envout.String())
+			compiler = "gc"
+		} else {
+			return nil, friendlyErr
+		}
+	} else {
+		fields := strings.Fields(stdout.String())
+		if len(fields) < 2 {
+			return nil, fmt.Errorf("could not parse GOARCH and Go compiler in format \"<GOARCH> <compiler>\":\nstdout: <<%s>>\nstderr: <<%s>>",
+				stdout.String(), stderr.String())
+		}
+		goarch = fields[0]
+		compiler = fields[1]
+	}
+	return types.SizesFor(compiler, goarch), nil
+}

vendor/golang.org/x/tools/go/packages/doc.go

@@ -0,0 +1,221 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package packages loads Go packages for inspection and analysis.
+
+The Load function takes as input a list of patterns and return a list of Package
+structs describing individual packages matched by those patterns.
+The LoadMode controls the amount of detail in the loaded packages.
+
+Load passes most patterns directly to the underlying build tool,
+but all patterns with the prefix "query=", where query is a
+non-empty string of letters from [a-z], are reserved and may be
+interpreted as query operators.
+
+Two query operators are currently supported: "file" and "pattern".
+
+The query "file=path/to/file.go" matches the package or packages enclosing
+the Go source file path/to/file.go.  For example "file=~/go/src/fmt/print.go"
+might return the packages "fmt" and "fmt [fmt.test]".
+
+The query "pattern=string" causes "string" to be passed directly to
+the underlying build tool. In most cases this is unnecessary,
+but an application can use Load("pattern=" + x) as an escaping mechanism
+to ensure that x is not interpreted as a query operator if it contains '='.
+
+All other query operators are reserved for future use and currently
+cause Load to report an error.
+
+The Package struct provides basic information about the package, including
+
+  - ID, a unique identifier for the package in the returned set;
+  - GoFiles, the names of the package's Go source files;
+  - Imports, a map from source import strings to the Packages they name;
+  - Types, the type information for the package's exported symbols;
+  - Syntax, the parsed syntax trees for the package's source code; and
+  - TypeInfo, the result of a complete type-check of the package syntax trees.
+
+(See the documentation for type Package for the complete list of fields
+and more detailed descriptions.)
+
+For example,
+
+	Load(nil, "bytes", "unicode...")
+
+returns four Package structs describing the standard library packages
+bytes, unicode, unicode/utf16, and unicode/utf8. Note that one pattern
+can match multiple packages and that a package might be matched by
+multiple patterns: in general it is not possible to determine which
+packages correspond to which patterns.
+
+Note that the list returned by Load contains only the packages matched
+by the patterns. Their dependencies can be found by walking the import
+graph using the Imports fields.
+
+The Load function can be configured by passing a pointer to a Config as
+the first argument. A nil Config is equivalent to the zero Config, which
+causes Load to run in LoadFiles mode, collecting minimal information.
+See the documentation for type Config for details.
+
+As noted earlier, the Config.Mode controls the amount of detail
+reported about the loaded packages. See the documentation for type LoadMode
+for details.
+
+Most tools should pass their command-line arguments (after any flags)
+uninterpreted to the loader, so that the loader can interpret them
+according to the conventions of the underlying build system.
+See the Example function for typical usage.
+
+*/
+package packages // import "golang.org/x/tools/go/packages"
+
+/*
+
+Motivation and design considerations
+
+The new package's design solves problems addressed by two existing
+packages: go/build, which locates and describes packages, and
+golang.org/x/tools/go/loader, which loads, parses and type-checks them.
+The go/build.Package structure encodes too much of the 'go build' way
+of organizing projects, leaving us in need of a data type that describes a
+package of Go source code independent of the underlying build system.
+We wanted something that works equally well with go build and vgo, and
+also other build systems such as Bazel and Blaze, making it possible to
+construct analysis tools that work in all these environments.
+Tools such as errcheck and staticcheck were essentially unavailable to
+the Go community at Google, and some of Google's internal tools for Go
+are unavailable externally.
+This new package provides a uniform way to obtain package metadata by
+querying each of these build systems, optionally supporting their
+preferred command-line notations for packages, so that tools integrate
+neatly with users' build environments. The Metadata query function
+executes an external query tool appropriate to the current workspace.
+
+Loading packages always returns the complete import graph "all the way down",
+even if all you want is information about a single package, because the query
+mechanisms of all the build systems we currently support ({go,vgo} list, and
+blaze/bazel aspect-based query) cannot provide detailed information
+about one package without visiting all its dependencies too, so there is
+no additional asymptotic cost to providing transitive information.
+(This property might not be true of a hypothetical 5th build system.)
+
+In calls to TypeCheck, all initial packages, and any package that
+transitively depends on one of them, must be loaded from source.
+Consider A->B->C->D->E: if A,C are initial, A,B,C must be loaded from
+source; D may be loaded from export data, and E may not be loaded at all
+(though it's possible that D's export data mentions it, so a
+types.Package may be created for it and exposed.)
+
+The old loader had a feature to suppress type-checking of function
+bodies on a per-package basis, primarily intended to reduce the work of
+obtaining type information for imported packages. Now that imports are
+satisfied by export data, the optimization no longer seems necessary.
+
+Despite some early attempts, the old loader did not exploit export data,
+instead always using the equivalent of WholeProgram mode. This was due
+to the complexity of mixing source and export data packages (now
+resolved by the upward traversal mentioned above), and because export data
+files were nearly always missing or stale. Now that 'go build' supports
+caching, all the underlying build systems can guarantee to produce
+export data in a reasonable (amortized) time.
+
+Test "main" packages synthesized by the build system are now reported as
+first-class packages, avoiding the need for clients (such as go/ssa) to
+reinvent this generation logic.
+
+One way in which go/packages is simpler than the old loader is in its
+treatment of in-package tests. In-package tests are packages that
+consist of all the files of the library under test, plus the test files.
+The old loader constructed in-package tests by a two-phase process of
+mutation called "augmentation": first it would construct and type check
+all the ordinary library packages and type-check the packages that
+depend on them; then it would add more (test) files to the package and
+type-check again. This two-phase approach had four major problems:
+1) in processing the tests, the loader modified the library package,
+   leaving no way for a client application to see both the test
+   package and the library package; one would mutate into the other.
+2) because test files can declare additional methods on types defined in
+   the library portion of the package, the dispatch of method calls in
+   the library portion was affected by the presence of the test files.
+   This should have been a clue that the packages were logically
+   different.
+3) this model of "augmentation" assumed at most one in-package test
+   per library package, which is true of projects using 'go build',
+   but not other build systems.
+4) because of the two-phase nature of test processing, all packages that
+   import the library package had to be processed before augmentation,
+   forcing a "one-shot" API and preventing the client from calling Load
+   in several times in sequence as is now possible in WholeProgram mode.
+   (TypeCheck mode has a similar one-shot restriction for a different reason.)
+
+Early drafts of this package supported "multi-shot" operation.
+Although it allowed clients to make a sequence of calls (or concurrent
+calls) to Load, building up the graph of Packages incrementally,
+it was of marginal value: it complicated the API
+(since it allowed some options to vary across calls but not others),
+it complicated the implementation,
+it cannot be made to work in Types mode, as explained above,
+and it was less efficient than making one combined call (when this is possible).
+Among the clients we have inspected, none made multiple calls to load
+but could not be easily and satisfactorily modified to make only a single call.
+However, applications changes may be required.
+For example, the ssadump command loads the user-specified packages
+and in addition the runtime package.  It is tempting to simply append
+"runtime" to the user-provided list, but that does not work if the user
+specified an ad-hoc package such as [a.go b.go].
+Instead, ssadump no longer requests the runtime package,
+but seeks it among the dependencies of the user-specified packages,
+and emits an error if it is not found.
+
+Overlays: The Overlay field in the Config allows providing alternate contents
+for Go source files, by providing a mapping from file path to contents.
+go/packages will pull in new imports added in overlay files when go/packages
+is run in LoadImports mode or greater.
+Overlay support for the go list driver isn't complete yet: if the file doesn't
+exist on disk, it will only be recognized in an overlay if it is a non-test file
+and the package would be reported even without the overlay.
+
+Questions & Tasks
+
+- Add GOARCH/GOOS?
+  They are not portable concepts, but could be made portable.
+  Our goal has been to allow users to express themselves using the conventions
+  of the underlying build system: if the build system honors GOARCH
+  during a build and during a metadata query, then so should
+  applications built atop that query mechanism.
+  Conversely, if the target architecture of the build is determined by
+  command-line flags, the application can pass the relevant
+  flags through to the build system using a command such as:
+    myapp -query_flag="--cpu=amd64" -query_flag="--os=darwin"
+  However, this approach is low-level, unwieldy, and non-portable.
+  GOOS and GOARCH seem important enough to warrant a dedicated option.
+
+- How should we handle partial failures such as a mixture of good and
+  malformed patterns, existing and non-existent packages, successful and
+  failed builds, import failures, import cycles, and so on, in a call to
+  Load?
+
+- Support bazel, blaze, and go1.10 list, not just go1.11 list.
+
+- Handle (and test) various partial success cases, e.g.
+  a mixture of good packages and:
+  invalid patterns
+  nonexistent packages
+  empty packages
+  packages with malformed package or import declarations
+  unreadable files
+  import cycles
+  other parse errors
+  type errors
+  Make sure we record errors at the correct place in the graph.
+
+- Missing packages among initial arguments are not reported.
+  Return bogus packages for them, like golist does.
+
+- "undeclared name" errors (for example) are reported out of source file
+  order. I suspect this is due to the breadth-first resolution now used
+  by go/types. Is that a bug? Discuss with gri.
+
+*/

vendor/golang.org/x/tools/go/packages/external.go

@@ -0,0 +1,101 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file enables an external tool to intercept package requests.
+// If the tool is present then its results are used in preference to
+// the go list command.
+
+package packages
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	exec "golang.org/x/sys/execabs"
+	"os"
+	"strings"
+)
+
+// The Driver Protocol
+//
+// The driver, given the inputs to a call to Load, returns metadata about the packages specified.
+// This allows for different build systems to support go/packages by telling go/packages how the
+// packages' source is organized.
+// The driver is a binary, either specified by the GOPACKAGESDRIVER environment variable or in
+// the path as gopackagesdriver. It's given the inputs to load in its argv. See the package
+// documentation in doc.go for the full description of the patterns that need to be supported.
+// A driver receives as a JSON-serialized driverRequest struct in standard input and will
+// produce a JSON-serialized driverResponse (see definition in packages.go) in its standard output.
+
+// driverRequest is used to provide the portion of Load's Config that is needed by a driver.
+type driverRequest struct {
+	Mode LoadMode `json:"mode"`
+	// Env specifies the environment the underlying build system should be run in.
+	Env []string `json:"env"`
+	// BuildFlags are flags that should be passed to the underlying build system.
+	BuildFlags []string `json:"build_flags"`
+	// Tests specifies whether the patterns should also return test packages.
+	Tests bool `json:"tests"`
+	// Overlay maps file paths (relative to the driver's working directory) to the byte contents
+	// of overlay files.
+	Overlay map[string][]byte `json:"overlay"`
+}
+
+// findExternalDriver returns the file path of a tool that supplies
+// the build system package structure, or "" if not found."
+// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
+// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
+func findExternalDriver(cfg *Config) driver {
+	const toolPrefix = "GOPACKAGESDRIVER="
+	tool := ""
+	for _, env := range cfg.Env {
+		if val := strings.TrimPrefix(env, toolPrefix); val != env {
+			tool = val
+		}
+	}
+	if tool != "" && tool == "off" {
+		return nil
+	}
+	if tool == "" {
+		var err error
+		tool, err = exec.LookPath("gopackagesdriver")
+		if err != nil {
+			return nil
+		}
+	}
+	return func(cfg *Config, words ...string) (*driverResponse, error) {
+		req, err := json.Marshal(driverRequest{
+			Mode:       cfg.Mode,
+			Env:        cfg.Env,
+			BuildFlags: cfg.BuildFlags,
+			Tests:      cfg.Tests,
+			Overlay:    cfg.Overlay,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
+		}
+
+		buf := new(bytes.Buffer)
+		stderr := new(bytes.Buffer)
+		cmd := exec.CommandContext(cfg.Context, tool, words...)
+		cmd.Dir = cfg.Dir
+		cmd.Env = cfg.Env
+		cmd.Stdin = bytes.NewReader(req)
+		cmd.Stdout = buf
+		cmd.Stderr = stderr
+
+		if err := cmd.Run(); err != nil {
+			return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
+		}
+		if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
+			fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd), stderr)
+		}
+
+		var response driverResponse
+		if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
+			return nil, err
+		}
+		return &response, nil
+	}
+}

vendor/golang.org/x/tools/go/packages/golist_overlay.go

@@ -0,0 +1,575 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"encoding/json"
+	"fmt"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/internal/gocommand"
+)
+
+// processGolistOverlay provides rudimentary support for adding
+// files that don't exist on disk to an overlay. The results can be
+// sometimes incorrect.
+// TODO(matloob): Handle unsupported cases, including the following:
+// - determining the correct package to add given a new import path
+func (state *golistState) processGolistOverlay(response *responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
+	havePkgs := make(map[string]string) // importPath -> non-test package ID
+	needPkgsSet := make(map[string]bool)
+	modifiedPkgsSet := make(map[string]bool)
+
+	pkgOfDir := make(map[string][]*Package)
+	for _, pkg := range response.dr.Packages {
+		// This is an approximation of import path to id. This can be
+		// wrong for tests, vendored packages, and a number of other cases.
+		havePkgs[pkg.PkgPath] = pkg.ID
+		dir, err := commonDir(pkg.GoFiles)
+		if err != nil {
+			return nil, nil, err
+		}
+		if dir != "" {
+			pkgOfDir[dir] = append(pkgOfDir[dir], pkg)
+		}
+	}
+
+	// If no new imports are added, it is safe to avoid loading any needPkgs.
+	// Otherwise, it's hard to tell which package is actually being loaded
+	// (due to vendoring) and whether any modified package will show up
+	// in the transitive set of dependencies (because new imports are added,
+	// potentially modifying the transitive set of dependencies).
+	var overlayAddsImports bool
+
+	// If both a package and its test package are created by the overlay, we
+	// need the real package first. Process all non-test files before test
+	// files, and make the whole process deterministic while we're at it.
+	var overlayFiles []string
+	for opath := range state.cfg.Overlay {
+		overlayFiles = append(overlayFiles, opath)
+	}
+	sort.Slice(overlayFiles, func(i, j int) bool {
+		iTest := strings.HasSuffix(overlayFiles[i], "_test.go")
+		jTest := strings.HasSuffix(overlayFiles[j], "_test.go")
+		if iTest != jTest {
+			return !iTest // non-tests are before tests.
+		}
+		return overlayFiles[i] < overlayFiles[j]
+	})
+	for _, opath := range overlayFiles {
+		contents := state.cfg.Overlay[opath]
+		base := filepath.Base(opath)
+		dir := filepath.Dir(opath)
+		var pkg *Package           // if opath belongs to both a package and its test variant, this will be the test variant
+		var testVariantOf *Package // if opath is a test file, this is the package it is testing
+		var fileExists bool
+		isTestFile := strings.HasSuffix(opath, "_test.go")
+		pkgName, ok := extractPackageName(opath, contents)
+		if !ok {
+			// Don't bother adding a file that doesn't even have a parsable package statement
+			// to the overlay.
+			continue
+		}
+		// If all the overlay files belong to a different package, change the
+		// package name to that package.
+		maybeFixPackageName(pkgName, isTestFile, pkgOfDir[dir])
+	nextPackage:
+		for _, p := range response.dr.Packages {
+			if pkgName != p.Name && p.ID != "command-line-arguments" {
+				continue
+			}
+			for _, f := range p.GoFiles {
+				if !sameFile(filepath.Dir(f), dir) {
+					continue
+				}
+				// Make sure to capture information on the package's test variant, if needed.
+				if isTestFile && !hasTestFiles(p) {
+					// TODO(matloob): Are there packages other than the 'production' variant
+					// of a package that this can match? This shouldn't match the test main package
+					// because the file is generated in another directory.
+					testVariantOf = p
+					continue nextPackage
+				} else if !isTestFile && hasTestFiles(p) {
+					// We're examining a test variant, but the overlaid file is
+					// a non-test file. Because the overlay implementation
+					// (currently) only adds a file to one package, skip this
+					// package, so that we can add the file to the production
+					// variant of the package. (https://golang.org/issue/36857
+					// tracks handling overlays on both the production and test
+					// variant of a package).
+					continue nextPackage
+				}
+				if pkg != nil && p != pkg && pkg.PkgPath == p.PkgPath {
+					// We have already seen the production version of the
+					// for which p is a test variant.
+					if hasTestFiles(p) {
+						testVariantOf = pkg
+					}
+				}
+				pkg = p
+				if filepath.Base(f) == base {
+					fileExists = true
+				}
+			}
+		}
+		// The overlay could have included an entirely new package or an
+		// ad-hoc package. An ad-hoc package is one that we have manually
+		// constructed from inadequate `go list` results for a file= query.
+		// It will have the ID command-line-arguments.
+		if pkg == nil || pkg.ID == "command-line-arguments" {
+			// Try to find the module or gopath dir the file is contained in.
+			// Then for modules, add the module opath to the beginning.
+			pkgPath, ok, err := state.getPkgPath(dir)
+			if err != nil {
+				return nil, nil, err
+			}
+			if !ok {
+				break
+			}
+			var forTest string // only set for x tests
+			isXTest := strings.HasSuffix(pkgName, "_test")
+			if isXTest {
+				forTest = pkgPath
+				pkgPath += "_test"
+			}
+			id := pkgPath
+			if isTestFile {
+				if isXTest {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, forTest)
+				} else {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
+				}
+			}
+			if pkg != nil {
+				// TODO(rstambler): We should change the package's path and ID
+				// here. The only issue is that this messes with the roots.
+			} else {
+				// Try to reclaim a package with the same ID, if it exists in the response.
+				for _, p := range response.dr.Packages {
+					if reclaimPackage(p, id, opath, contents) {
+						pkg = p
+						break
+					}
+				}
+				// Otherwise, create a new package.
+				if pkg == nil {
+					pkg = &Package{
+						PkgPath: pkgPath,
+						ID:      id,
+						Name:    pkgName,
+						Imports: make(map[string]*Package),
+					}
+					response.addPackage(pkg)
+					havePkgs[pkg.PkgPath] = id
+					// Add the production package's sources for a test variant.
+					if isTestFile && !isXTest && testVariantOf != nil {
+						pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
+						pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
+						// Add the package under test and its imports to the test variant.
+						pkg.forTest = testVariantOf.PkgPath
+						for k, v := range testVariantOf.Imports {
+							pkg.Imports[k] = &Package{ID: v.ID}
+						}
+					}
+					if isXTest {
+						pkg.forTest = forTest
+					}
+				}
+			}
+		}
+		if !fileExists {
+			pkg.GoFiles = append(pkg.GoFiles, opath)
+			// TODO(matloob): Adding the file to CompiledGoFiles can exhibit the wrong behavior
+			// if the file will be ignored due to its build tags.
+			pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, opath)
+			modifiedPkgsSet[pkg.ID] = true
+		}
+		imports, err := extractImports(opath, contents)
+		if err != nil {
+			// Let the parser or type checker report errors later.
+			continue
+		}
+		for _, imp := range imports {
+			// TODO(rstambler): If the package is an x test and the import has
+			// a test variant, make sure to replace it.
+			if _, found := pkg.Imports[imp]; found {
+				continue
+			}
+			overlayAddsImports = true
+			id, ok := havePkgs[imp]
+			if !ok {
+				var err error
+				id, err = state.resolveImport(dir, imp)
+				if err != nil {
+					return nil, nil, err
+				}
+			}
+			pkg.Imports[imp] = &Package{ID: id}
+			// Add dependencies to the non-test variant version of this package as well.
+			if testVariantOf != nil {
+				testVariantOf.Imports[imp] = &Package{ID: id}
+			}
+		}
+	}
+
+	// toPkgPath guesses the package path given the id.
+	toPkgPath := func(sourceDir, id string) (string, error) {
+		if i := strings.IndexByte(id, ' '); i >= 0 {
+			return state.resolveImport(sourceDir, id[:i])
+		}
+		return state.resolveImport(sourceDir, id)
+	}
+
+	// Now that new packages have been created, do another pass to determine
+	// the new set of missing packages.
+	for _, pkg := range response.dr.Packages {
+		for _, imp := range pkg.Imports {
+			if len(pkg.GoFiles) == 0 {
+				return nil, nil, fmt.Errorf("cannot resolve imports for package %q with no Go files", pkg.PkgPath)
+			}
+			pkgPath, err := toPkgPath(filepath.Dir(pkg.GoFiles[0]), imp.ID)
+			if err != nil {
+				return nil, nil, err
+			}
+			if _, ok := havePkgs[pkgPath]; !ok {
+				needPkgsSet[pkgPath] = true
+			}
+		}
+	}
+
+	if overlayAddsImports {
+		needPkgs = make([]string, 0, len(needPkgsSet))
+		for pkg := range needPkgsSet {
+			needPkgs = append(needPkgs, pkg)
+		}
+	}
+	modifiedPkgs = make([]string, 0, len(modifiedPkgsSet))
+	for pkg := range modifiedPkgsSet {
+		modifiedPkgs = append(modifiedPkgs, pkg)
+	}
+	return modifiedPkgs, needPkgs, err
+}
+
+// resolveImport finds the ID of a package given its import path.
+// In particular, it will find the right vendored copy when in GOPATH mode.
+func (state *golistState) resolveImport(sourceDir, importPath string) (string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return "", err
+	}
+	if env["GOMOD"] != "" {
+		return importPath, nil
+	}
+
+	searchDir := sourceDir
+	for {
+		vendorDir := filepath.Join(searchDir, "vendor")
+		exists, ok := state.vendorDirs[vendorDir]
+		if !ok {
+			info, err := os.Stat(vendorDir)
+			exists = err == nil && info.IsDir()
+			state.vendorDirs[vendorDir] = exists
+		}
+
+		if exists {
+			vendoredPath := filepath.Join(vendorDir, importPath)
+			if info, err := os.Stat(vendoredPath); err == nil && info.IsDir() {
+				// We should probably check for .go files here, but shame on anyone who fools us.
+				path, ok, err := state.getPkgPath(vendoredPath)
+				if err != nil {
+					return "", err
+				}
+				if ok {
+					return path, nil
+				}
+			}
+		}
+
+		// We know we've hit the top of the filesystem when we Dir / and get /,
+		// or C:\ and get C:\, etc.
+		next := filepath.Dir(searchDir)
+		if next == searchDir {
+			break
+		}
+		searchDir = next
+	}
+	return importPath, nil
+}
+
+func hasTestFiles(p *Package) bool {
+	for _, f := range p.GoFiles {
+		if strings.HasSuffix(f, "_test.go") {
+			return true
+		}
+	}
+	return false
+}
+
+// determineRootDirs returns a mapping from absolute directories that could
+// contain code to their corresponding import path prefixes.
+func (state *golistState) determineRootDirs() (map[string]string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return nil, err
+	}
+	if env["GOMOD"] != "" {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
+		})
+	} else {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
+		})
+	}
+	return state.rootDirs, state.rootDirsError
+}
+
+func (state *golistState) determineRootDirsModules() (map[string]string, error) {
+	// List all of the modules--the first will be the directory for the main
+	// module. Any replaced modules will also need to be treated as roots.
+	// Editing files in the module cache isn't a great idea, so we don't
+	// plan to ever support that.
+	out, err := state.invokeGo("list", "-m", "-json", "all")
+	if err != nil {
+		// 'go list all' will fail if we're outside of a module and
+		// GO111MODULE=on. Try falling back without 'all'.
+		var innerErr error
+		out, innerErr = state.invokeGo("list", "-m", "-json")
+		if innerErr != nil {
+			return nil, err
+		}
+	}
+	roots := map[string]string{}
+	modules := map[string]string{}
+	var i int
+	for dec := json.NewDecoder(out); dec.More(); {
+		mod := new(gocommand.ModuleJSON)
+		if err := dec.Decode(mod); err != nil {
+			return nil, err
+		}
+		if mod.Dir != "" && mod.Path != "" {
+			// This is a valid module; add it to the map.
+			absDir, err := filepath.Abs(mod.Dir)
+			if err != nil {
+				return nil, err
+			}
+			modules[absDir] = mod.Path
+			// The first result is the main module.
+			if i == 0 || mod.Replace != nil && mod.Replace.Path != "" {
+				roots[absDir] = mod.Path
+			}
+		}
+		i++
+	}
+	return roots, nil
+}
+
+func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
+	m := map[string]string{}
+	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
+		absDir, err := filepath.Abs(dir)
+		if err != nil {
+			return nil, err
+		}
+		m[filepath.Join(absDir, "src")] = ""
+	}
+	return m, nil
+}
+
+func extractImports(filename string, contents []byte) ([]string, error) {
+	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.ImportsOnly) // TODO(matloob): reuse fileset?
+	if err != nil {
+		return nil, err
+	}
+	var res []string
+	for _, imp := range f.Imports {
+		quotedPath := imp.Path.Value
+		path, err := strconv.Unquote(quotedPath)
+		if err != nil {
+			return nil, err
+		}
+		res = append(res, path)
+	}
+	return res, nil
+}
+
+// reclaimPackage attempts to reuse a package that failed to load in an overlay.
+//
+// If the package has errors and has no Name, GoFiles, or Imports,
+// then it's possible that it doesn't yet exist on disk.
+func reclaimPackage(pkg *Package, id string, filename string, contents []byte) bool {
+	// TODO(rstambler): Check the message of the actual error?
+	// It differs between $GOPATH and module mode.
+	if pkg.ID != id {
+		return false
+	}
+	if len(pkg.Errors) != 1 {
+		return false
+	}
+	if pkg.Name != "" || pkg.ExportFile != "" {
+		return false
+	}
+	if len(pkg.GoFiles) > 0 || len(pkg.CompiledGoFiles) > 0 || len(pkg.OtherFiles) > 0 {
+		return false
+	}
+	if len(pkg.Imports) > 0 {
+		return false
+	}
+	pkgName, ok := extractPackageName(filename, contents)
+	if !ok {
+		return false
+	}
+	pkg.Name = pkgName
+	pkg.Errors = nil
+	return true
+}
+
+func extractPackageName(filename string, contents []byte) (string, bool) {
+	// TODO(rstambler): Check the message of the actual error?
+	// It differs between $GOPATH and module mode.
+	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.PackageClauseOnly) // TODO(matloob): reuse fileset?
+	if err != nil {
+		return "", false
+	}
+	return f.Name.Name, true
+}
+
+// commonDir returns the directory that all files are in, "" if files is empty,
+// or an error if they aren't in the same directory.
+func commonDir(files []string) (string, error) {
+	seen := make(map[string]bool)
+	for _, f := range files {
+		seen[filepath.Dir(f)] = true
+	}
+	if len(seen) > 1 {
+		return "", fmt.Errorf("files (%v) are in more than one directory: %v", files, seen)
+	}
+	for k := range seen {
+		// seen has only one element; return it.
+		return k, nil
+	}
+	return "", nil // no files
+}
+
+// It is possible that the files in the disk directory dir have a different package
+// name from newName, which is deduced from the overlays. If they all have a different
+// package name, and they all have the same package name, then that name becomes
+// the package name.
+// It returns true if it changes the package name, false otherwise.
+func maybeFixPackageName(newName string, isTestFile bool, pkgsOfDir []*Package) {
+	names := make(map[string]int)
+	for _, p := range pkgsOfDir {
+		names[p.Name]++
+	}
+	if len(names) != 1 {
+		// some files are in different packages
+		return
+	}
+	var oldName string
+	for k := range names {
+		oldName = k
+	}
+	if newName == oldName {
+		return
+	}
+	// We might have a case where all of the package names in the directory are
+	// the same, but the overlay file is for an x test, which belongs to its
+	// own package. If the x test does not yet exist on disk, we may not yet
+	// have its package name on disk, but we should not rename the packages.
+	//
+	// We use a heuristic to determine if this file belongs to an x test:
+	// The test file should have a package name whose package name has a _test
+	// suffix or looks like "newName_test".
+	maybeXTest := strings.HasPrefix(oldName+"_test", newName) || strings.HasSuffix(newName, "_test")
+	if isTestFile && maybeXTest {
+		return
+	}
+	for _, p := range pkgsOfDir {
+		p.Name = newName
+	}
+}
+
+// This function is copy-pasted from
+// https://github.com/golang/go/blob/9706f510a5e2754595d716bd64be8375997311fb/src/cmd/go/internal/search/search.go#L360.
+// It should be deleted when we remove support for overlays from go/packages.
+//
+// NOTE: This does not handle any ./... or ./ style queries, as this function
+// doesn't know the working directory.
+//
+// matchPattern(pattern)(name) reports whether
+// name matches pattern. Pattern is a limited glob
+// pattern in which '...' means 'any string' and there
+// is no other special syntax.
+// Unfortunately, there are two special cases. Quoting "go help packages":
+//
+// First, /... at the end of the pattern can match an empty string,
+// so that net/... matches both net and packages in its subdirectories, like net/http.
+// Second, any slash-separated pattern element containing a wildcard never
+// participates in a match of the "vendor" element in the path of a vendored
+// package, so that ./... does not match packages in subdirectories of
+// ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
+// Note, however, that a directory named vendor that itself contains code
+// is not a vendored package: cmd/vendor would be a command named vendor,
+// and the pattern cmd/... matches it.
+func matchPattern(pattern string) func(name string) bool {
+	// Convert pattern to regular expression.
+	// The strategy for the trailing /... is to nest it in an explicit ? expression.
+	// The strategy for the vendor exclusion is to change the unmatchable
+	// vendor strings to a disallowed code point (vendorChar) and to use
+	// "(anything but that codepoint)*" as the implementation of the ... wildcard.
+	// This is a bit complicated but the obvious alternative,
+	// namely a hand-written search like in most shell glob matchers,
+	// is too easy to make accidentally exponential.
+	// Using package regexp guarantees linear-time matching.
+
+	const vendorChar = "\x00"
+
+	if strings.Contains(pattern, vendorChar) {
+		return func(name string) bool { return false }
+	}
+
+	re := regexp.QuoteMeta(pattern)
+	re = replaceVendor(re, vendorChar)
+	switch {
+	case strings.HasSuffix(re, `/`+vendorChar+`/\.\.\.`):
+		re = strings.TrimSuffix(re, `/`+vendorChar+`/\.\.\.`) + `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case re == vendorChar+`/\.\.\.`:
+		re = `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case strings.HasSuffix(re, `/\.\.\.`):
+		re = strings.TrimSuffix(re, `/\.\.\.`) + `(/\.\.\.)?`
+	}
+	re = strings.ReplaceAll(re, `\.\.\.`, `[^`+vendorChar+`]*`)
+
+	reg := regexp.MustCompile(`^` + re + `$`)
+
+	return func(name string) bool {
+		if strings.Contains(name, vendorChar) {
+			return false
+		}
+		return reg.MatchString(replaceVendor(name, vendorChar))
+	}
+}
+
+// replaceVendor returns the result of replacing
+// non-trailing vendor path elements in x with repl.
+func replaceVendor(x, repl string) string {
+	if !strings.Contains(x, "vendor") {
+		return x
+	}
+	elem := strings.Split(x, "/")
+	for i := 0; i < len(elem)-1; i++ {
+		if elem[i] == "vendor" {
+			elem[i] = repl
+		}
+	}
+	return strings.Join(elem, "/")
+}

vendor/golang.org/x/tools/go/packages/loadmode_string.go

@@ -0,0 +1,57 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"strings"
+)
+
+var allModes = []LoadMode{
+	NeedName,
+	NeedFiles,
+	NeedCompiledGoFiles,
+	NeedImports,
+	NeedDeps,
+	NeedExportsFile,
+	NeedTypes,
+	NeedSyntax,
+	NeedTypesInfo,
+	NeedTypesSizes,
+}
+
+var modeStrings = []string{
+	"NeedName",
+	"NeedFiles",
+	"NeedCompiledGoFiles",
+	"NeedImports",
+	"NeedDeps",
+	"NeedExportsFile",
+	"NeedTypes",
+	"NeedSyntax",
+	"NeedTypesInfo",
+	"NeedTypesSizes",
+}
+
+func (mod LoadMode) String() string {
+	m := mod
+	if m == 0 {
+		return "LoadMode(0)"
+	}
+	var out []string
+	for i, x := range allModes {
+		if x > m {
+			break
+		}
+		if (m & x) != 0 {
+			out = append(out, modeStrings[i])
+			m = m ^ x
+		}
+	}
+	if m != 0 {
+		out = append(out, "Unknown")
+	}
+	return fmt.Sprintf("LoadMode(%s)", strings.Join(out, "|"))
+}

vendor/golang.org/x/tools/go/packages/visit.go

@@ -0,0 +1,59 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"os"
+	"sort"
+)
+
+// Visit visits all the packages in the import graph whose roots are
+// pkgs, calling the optional pre function the first time each package
+// is encountered (preorder), and the optional post function after a
+// package's dependencies have been visited (postorder).
+// The boolean result of pre(pkg) determines whether
+// the imports of package pkg are visited.
+func Visit(pkgs []*Package, pre func(*Package) bool, post func(*Package)) {
+	seen := make(map[*Package]bool)
+	var visit func(*Package)
+	visit = func(pkg *Package) {
+		if !seen[pkg] {
+			seen[pkg] = true
+
+			if pre == nil || pre(pkg) {
+				paths := make([]string, 0, len(pkg.Imports))
+				for path := range pkg.Imports {
+					paths = append(paths, path)
+				}
+				sort.Strings(paths) // Imports is a map, this makes visit stable
+				for _, path := range paths {
+					visit(pkg.Imports[path])
+				}
+			}
+
+			if post != nil {
+				post(pkg)
+			}
+		}
+	}
+	for _, pkg := range pkgs {
+		visit(pkg)
+	}
+}
+
+// PrintErrors prints to os.Stderr the accumulated errors of all
+// packages in the import graph rooted at pkgs, dependencies first.
+// PrintErrors returns the number of errors printed.
+func PrintErrors(pkgs []*Package) int {
+	var n int
+	Visit(pkgs, nil, func(pkg *Package) {
+		for _, err := range pkg.Errors {
+			fmt.Fprintln(os.Stderr, err)
+			n++
+		}
+	})
+	return n
+}

vendor/golang.org/x/tools/imports/forward.go

@@ -0,0 +1,77 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package imports implements a Go pretty-printer (like package "go/format")
+// that also adds or removes import statements as necessary.
+package imports // import "golang.org/x/tools/imports"
+
+import (
+	"io/ioutil"
+	"log"
+
+	"golang.org/x/tools/internal/gocommand"
+	intimp "golang.org/x/tools/internal/imports"
+)
+
+// Options specifies options for processing files.
+type Options struct {
+	Fragment  bool // Accept fragment of a source file (no package statement)
+	AllErrors bool // Report all errors (not just the first 10 on different lines)
+
+	Comments  bool // Print comments (true if nil *Options provided)
+	TabIndent bool // Use tabs for indent (true if nil *Options provided)
+	TabWidth  int  // Tab width (8 if nil *Options provided)
+
+	FormatOnly bool // Disable the insertion and deletion of imports
+}
+
+// Debug controls verbose logging.
+var Debug = false
+
+// LocalPrefix is a comma-separated string of import path prefixes, which, if
+// set, instructs Process to sort the import paths with the given prefixes
+// into another group after 3rd-party packages.
+var LocalPrefix string
+
+// Process formats and adjusts imports for the provided file.
+// If opt is nil the defaults are used, and if src is nil the source
+// is read from the filesystem.
+//
+// Note that filename's directory influences which imports can be chosen,
+// so it is important that filename be accurate.
+// To process data ``as if'' it were in filename, pass the data as a non-nil src.
+func Process(filename string, src []byte, opt *Options) ([]byte, error) {
+	var err error
+	if src == nil {
+		src, err = ioutil.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
+	}
+	if opt == nil {
+		opt = &Options{Comments: true, TabIndent: true, TabWidth: 8}
+	}
+	intopt := &intimp.Options{
+		Env: &intimp.ProcessEnv{
+			GocmdRunner: &gocommand.Runner{},
+		},
+		LocalPrefix: LocalPrefix,
+		AllErrors:   opt.AllErrors,
+		Comments:    opt.Comments,
+		FormatOnly:  opt.FormatOnly,
+		Fragment:    opt.Fragment,
+		TabIndent:   opt.TabIndent,
+		TabWidth:    opt.TabWidth,
+	}
+	if Debug {
+		intopt.Env.Logf = log.Printf
+	}
+	return intimp.Process(filename, src, intopt)
+}
+
+// VendorlessPath returns the devendorized version of the import path ipath.
+// For example, VendorlessPath("foo/bar/vendor/a/b") returns "a/b".
+func VendorlessPath(ipath string) string {
+	return intimp.VendorlessPath(ipath)
+}

vendor/golang.org/x/tools/internal/event/core/event.go

@@ -0,0 +1,85 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package core provides support for event based telemetry.
+package core
+
+import (
+	"fmt"
+	"time"
+
+	"golang.org/x/tools/internal/event/label"
+)
+
+// Event holds the information about an event of note that occurred.
+type Event struct {
+	at time.Time
+
+	// As events are often on the stack, storing the first few labels directly
+	// in the event can avoid an allocation at all for the very common cases of
+	// simple events.
+	// The length needs to be large enough to cope with the majority of events
+	// but no so large as to cause undue stack pressure.
+	// A log message with two values will use 3 labels (one for each value and
+	// one for the message itself).
+
+	static  [3]label.Label // inline storage for the first few labels
+	dynamic []label.Label  // dynamically sized storage for remaining labels
+}
+
+// eventLabelMap implements label.Map for a the labels of an Event.
+type eventLabelMap struct {
+	event Event
+}
+
+func (ev Event) At() time.Time { return ev.at }
+
+func (ev Event) Format(f fmt.State, r rune) {
+	if !ev.at.IsZero() {
+		fmt.Fprint(f, ev.at.Format("2006/01/02 15:04:05 "))
+	}
+	for index := 0; ev.Valid(index); index++ {
+		if l := ev.Label(index); l.Valid() {
+			fmt.Fprintf(f, "\n\t%v", l)
+		}
+	}
+}
+
+func (ev Event) Valid(index int) bool {
+	return index >= 0 && index < len(ev.static)+len(ev.dynamic)
+}
+
+func (ev Event) Label(index int) label.Label {
+	if index < len(ev.static) {
+		return ev.static[index]
+	}
+	return ev.dynamic[index-len(ev.static)]
+}
+
+func (ev Event) Find(key label.Key) label.Label {
+	for _, l := range ev.static {
+		if l.Key() == key {
+			return l
+		}
+	}
+	for _, l := range ev.dynamic {
+		if l.Key() == key {
+			return l
+		}
+	}
+	return label.Label{}
+}
+
+func MakeEvent(static [3]label.Label, labels []label.Label) Event {
+	return Event{
+		static:  static,
+		dynamic: labels,
+	}
+}
+
+// CloneEvent event returns a copy of the event with the time adjusted to at.
+func CloneEvent(ev Event, at time.Time) Event {
+	ev.at = at
+	return ev
+}

vendor/golang.org/x/tools/internal/event/core/export.go

@@ -0,0 +1,70 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package core
+
+import (
+	"context"
+	"sync/atomic"
+	"time"
+	"unsafe"
+
+	"golang.org/x/tools/internal/event/label"
+)
+
+// Exporter is a function that handles events.
+// It may return a modified context and event.
+type Exporter func(context.Context, Event, label.Map) context.Context
+
+var (
+	exporter unsafe.Pointer
+)
+
+// SetExporter sets the global exporter function that handles all events.
+// The exporter is called synchronously from the event call site, so it should
+// return quickly so as not to hold up user code.
+func SetExporter(e Exporter) {
+	p := unsafe.Pointer(&e)
+	if e == nil {
+		// &e is always valid, and so p is always valid, but for the early abort
+		// of ProcessEvent to be efficient it needs to make the nil check on the
+		// pointer without having to dereference it, so we make the nil function
+		// also a nil pointer
+		p = nil
+	}
+	atomic.StorePointer(&exporter, p)
+}
+
+// deliver is called to deliver an event to the supplied exporter.
+// it will fill in the time.
+func deliver(ctx context.Context, exporter Exporter, ev Event) context.Context {
+	// add the current time to the event
+	ev.at = time.Now()
+	// hand the event off to the current exporter
+	return exporter(ctx, ev, ev)
+}
+
+// Export is called to deliver an event to the global exporter if set.
+func Export(ctx context.Context, ev Event) context.Context {
+	// get the global exporter and abort early if there is not one
+	exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
+	if exporterPtr == nil {
+		return ctx
+	}
+	return deliver(ctx, *exporterPtr, ev)
+}
+
+// ExportPair is called to deliver a start event to the supplied exporter.
+// It also returns a function that will deliver the end event to the same
+// exporter.
+// It will fill in the time.
+func ExportPair(ctx context.Context, begin, end Event) (context.Context, func()) {
+	// get the global exporter and abort early if there is not one
+	exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
+	if exporterPtr == nil {
+		return ctx, func() {}
+	}
+	ctx = deliver(ctx, *exporterPtr, begin)
+	return ctx, func() { deliver(ctx, *exporterPtr, end) }
+}

vendor/golang.org/x/tools/internal/event/core/fast.go

@@ -0,0 +1,77 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package core
+
+import (
+	"context"
+
+	"golang.org/x/tools/internal/event/keys"
+	"golang.org/x/tools/internal/event/label"
+)
+
+// Log1 takes a message and one label delivers a log event to the exporter.
+// It is a customized version of Print that is faster and does no allocation.
+func Log1(ctx context.Context, message string, t1 label.Label) {
+	Export(ctx, MakeEvent([3]label.Label{
+		keys.Msg.Of(message),
+		t1,
+	}, nil))
+}
+
+// Log2 takes a message and two labels and delivers a log event to the exporter.
+// It is a customized version of Print that is faster and does no allocation.
+func Log2(ctx context.Context, message string, t1 label.Label, t2 label.Label) {
+	Export(ctx, MakeEvent([3]label.Label{
+		keys.Msg.Of(message),
+		t1,
+		t2,
+	}, nil))
+}
+
+// Metric1 sends a label event to the exporter with the supplied labels.
+func Metric1(ctx context.Context, t1 label.Label) context.Context {
+	return Export(ctx, MakeEvent([3]label.Label{
+		keys.Metric.New(),
+		t1,
+	}, nil))
+}
+
+// Metric2 sends a label event to the exporter with the supplied labels.
+func Metric2(ctx context.Context, t1, t2 label.Label) context.Context {
+	return Export(ctx, MakeEvent([3]label.Label{
+		keys.Metric.New(),
+		t1,
+		t2,
+	}, nil))
+}
+
+// Start1 sends a span start event with the supplied label list to the exporter.
+// It also returns a function that will end the span, which should normally be
+// deferred.
+func Start1(ctx context.Context, name string, t1 label.Label) (context.Context, func()) {
+	return ExportPair(ctx,
+		MakeEvent([3]label.Label{
+			keys.Start.Of(name),
+			t1,
+		}, nil),
+		MakeEvent([3]label.Label{
+			keys.End.New(),
+		}, nil))
+}
+
+// Start2 sends a span start event with the supplied label list to the exporter.
+// It also returns a function that will end the span, which should normally be
+// deferred.
+func Start2(ctx context.Context, name string, t1, t2 label.Label) (context.Context, func()) {
+	return ExportPair(ctx,
+		MakeEvent([3]label.Label{
+			keys.Start.Of(name),
+			t1,
+			t2,
+		}, nil),
+		MakeEvent([3]label.Label{
+			keys.End.New(),
+		}, nil))
+}

vendor/golang.org/x/tools/internal/event/doc.go

@@ -0,0 +1,7 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package event provides a set of packages that cover the main
+// concepts of telemetry in an implementation agnostic way.
+package event

vendor/golang.org/x/tools/internal/event/event.go

@@ -0,0 +1,127 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package event
+
+import (
+	"context"
+
+	"golang.org/x/tools/internal/event/core"
+	"golang.org/x/tools/internal/event/keys"
+	"golang.org/x/tools/internal/event/label"
+)
+
+// Exporter is a function that handles events.
+// It may return a modified context and event.
+type Exporter func(context.Context, core.Event, label.Map) context.Context
+
+// SetExporter sets the global exporter function that handles all events.
+// The exporter is called synchronously from the event call site, so it should
+// return quickly so as not to hold up user code.
+func SetExporter(e Exporter) {
+	core.SetExporter(core.Exporter(e))
+}
+
+// Log takes a message and a label list and combines them into a single event
+// before delivering them to the exporter.
+func Log(ctx context.Context, message string, labels ...label.Label) {
+	core.Export(ctx, core.MakeEvent([3]label.Label{
+		keys.Msg.Of(message),
+	}, labels))
+}
+
+// IsLog returns true if the event was built by the Log function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsLog(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Msg
+}
+
+// Error takes a message and a label list and combines them into a single event
+// before delivering them to the exporter. It captures the error in the
+// delivered event.
+func Error(ctx context.Context, message string, err error, labels ...label.Label) {
+	core.Export(ctx, core.MakeEvent([3]label.Label{
+		keys.Msg.Of(message),
+		keys.Err.Of(err),
+	}, labels))
+}
+
+// IsError returns true if the event was built by the Error function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsError(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Msg &&
+		ev.Label(1).Key() == keys.Err
+}
+
+// Metric sends a label event to the exporter with the supplied labels.
+func Metric(ctx context.Context, labels ...label.Label) {
+	core.Export(ctx, core.MakeEvent([3]label.Label{
+		keys.Metric.New(),
+	}, labels))
+}
+
+// IsMetric returns true if the event was built by the Metric function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsMetric(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Metric
+}
+
+// Label sends a label event to the exporter with the supplied labels.
+func Label(ctx context.Context, labels ...label.Label) context.Context {
+	return core.Export(ctx, core.MakeEvent([3]label.Label{
+		keys.Label.New(),
+	}, labels))
+}
+
+// IsLabel returns true if the event was built by the Label function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsLabel(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Label
+}
+
+// Start sends a span start event with the supplied label list to the exporter.
+// It also returns a function that will end the span, which should normally be
+// deferred.
+func Start(ctx context.Context, name string, labels ...label.Label) (context.Context, func()) {
+	return core.ExportPair(ctx,
+		core.MakeEvent([3]label.Label{
+			keys.Start.Of(name),
+		}, labels),
+		core.MakeEvent([3]label.Label{
+			keys.End.New(),
+		}, nil))
+}
+
+// IsStart returns true if the event was built by the Start function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsStart(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Start
+}
+
+// IsEnd returns true if the event was built by the End function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsEnd(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.End
+}
+
+// Detach returns a context without an associated span.
+// This allows the creation of spans that are not children of the current span.
+func Detach(ctx context.Context) context.Context {
+	return core.Export(ctx, core.MakeEvent([3]label.Label{
+		keys.Detach.New(),
+	}, nil))
+}
+
+// IsDetach returns true if the event was built by the Detach function.
+// It is intended to be used in exporters to identify the semantics of the
+// event when deciding what to do with it.
+func IsDetach(ev core.Event) bool {
+	return ev.Label(0).Key() == keys.Detach
+}

vendor/golang.org/x/tools/internal/event/keys/keys.go

@@ -0,0 +1,564 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package keys
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"strconv"
+
+	"golang.org/x/tools/internal/event/label"
+)
+
+// Value represents a key for untyped values.
+type Value struct {
+	name        string
+	description string
+}
+
+// New creates a new Key for untyped values.
+func New(name, description string) *Value {
+	return &Value{name: name, description: description}
+}
+
+func (k *Value) Name() string        { return k.name }
+func (k *Value) Description() string { return k.description }
+
+func (k *Value) Format(w io.Writer, buf []byte, l label.Label) {
+	fmt.Fprint(w, k.From(l))
+}
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Value) Get(lm label.Map) interface{} {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return nil
+}
+
+// From can be used to get a value from a Label.
+func (k *Value) From(t label.Label) interface{} { return t.UnpackValue() }
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Value) Of(value interface{}) label.Label { return label.OfValue(k, value) }
+
+// Tag represents a key for tagging labels that have no value.
+// These are used when the existence of the label is the entire information it
+// carries, such as marking events to be of a specific kind, or from a specific
+// package.
+type Tag struct {
+	name        string
+	description string
+}
+
+// NewTag creates a new Key for tagging labels.
+func NewTag(name, description string) *Tag {
+	return &Tag{name: name, description: description}
+}
+
+func (k *Tag) Name() string        { return k.name }
+func (k *Tag) Description() string { return k.description }
+
+func (k *Tag) Format(w io.Writer, buf []byte, l label.Label) {}
+
+// New creates a new Label with this key.
+func (k *Tag) New() label.Label { return label.OfValue(k, nil) }
+
+// Int represents a key
+type Int struct {
+	name        string
+	description string
+}
+
+// NewInt creates a new Key for int values.
+func NewInt(name, description string) *Int {
+	return &Int{name: name, description: description}
+}
+
+func (k *Int) Name() string        { return k.name }
+func (k *Int) Description() string { return k.description }
+
+func (k *Int) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendInt(buf, int64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Int) Of(v int) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Int) Get(lm label.Map) int {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Int) From(t label.Label) int { return int(t.Unpack64()) }
+
+// Int8 represents a key
+type Int8 struct {
+	name        string
+	description string
+}
+
+// NewInt8 creates a new Key for int8 values.
+func NewInt8(name, description string) *Int8 {
+	return &Int8{name: name, description: description}
+}
+
+func (k *Int8) Name() string        { return k.name }
+func (k *Int8) Description() string { return k.description }
+
+func (k *Int8) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendInt(buf, int64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Int8) Of(v int8) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Int8) Get(lm label.Map) int8 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Int8) From(t label.Label) int8 { return int8(t.Unpack64()) }
+
+// Int16 represents a key
+type Int16 struct {
+	name        string
+	description string
+}
+
+// NewInt16 creates a new Key for int16 values.
+func NewInt16(name, description string) *Int16 {
+	return &Int16{name: name, description: description}
+}
+
+func (k *Int16) Name() string        { return k.name }
+func (k *Int16) Description() string { return k.description }
+
+func (k *Int16) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendInt(buf, int64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Int16) Of(v int16) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Int16) Get(lm label.Map) int16 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Int16) From(t label.Label) int16 { return int16(t.Unpack64()) }
+
+// Int32 represents a key
+type Int32 struct {
+	name        string
+	description string
+}
+
+// NewInt32 creates a new Key for int32 values.
+func NewInt32(name, description string) *Int32 {
+	return &Int32{name: name, description: description}
+}
+
+func (k *Int32) Name() string        { return k.name }
+func (k *Int32) Description() string { return k.description }
+
+func (k *Int32) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendInt(buf, int64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Int32) Of(v int32) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Int32) Get(lm label.Map) int32 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Int32) From(t label.Label) int32 { return int32(t.Unpack64()) }
+
+// Int64 represents a key
+type Int64 struct {
+	name        string
+	description string
+}
+
+// NewInt64 creates a new Key for int64 values.
+func NewInt64(name, description string) *Int64 {
+	return &Int64{name: name, description: description}
+}
+
+func (k *Int64) Name() string        { return k.name }
+func (k *Int64) Description() string { return k.description }
+
+func (k *Int64) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendInt(buf, k.From(l), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Int64) Of(v int64) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Int64) Get(lm label.Map) int64 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Int64) From(t label.Label) int64 { return int64(t.Unpack64()) }
+
+// UInt represents a key
+type UInt struct {
+	name        string
+	description string
+}
+
+// NewUInt creates a new Key for uint values.
+func NewUInt(name, description string) *UInt {
+	return &UInt{name: name, description: description}
+}
+
+func (k *UInt) Name() string        { return k.name }
+func (k *UInt) Description() string { return k.description }
+
+func (k *UInt) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendUint(buf, uint64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *UInt) Of(v uint) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *UInt) Get(lm label.Map) uint {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *UInt) From(t label.Label) uint { return uint(t.Unpack64()) }
+
+// UInt8 represents a key
+type UInt8 struct {
+	name        string
+	description string
+}
+
+// NewUInt8 creates a new Key for uint8 values.
+func NewUInt8(name, description string) *UInt8 {
+	return &UInt8{name: name, description: description}
+}
+
+func (k *UInt8) Name() string        { return k.name }
+func (k *UInt8) Description() string { return k.description }
+
+func (k *UInt8) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendUint(buf, uint64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *UInt8) Of(v uint8) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *UInt8) Get(lm label.Map) uint8 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *UInt8) From(t label.Label) uint8 { return uint8(t.Unpack64()) }
+
+// UInt16 represents a key
+type UInt16 struct {
+	name        string
+	description string
+}
+
+// NewUInt16 creates a new Key for uint16 values.
+func NewUInt16(name, description string) *UInt16 {
+	return &UInt16{name: name, description: description}
+}
+
+func (k *UInt16) Name() string        { return k.name }
+func (k *UInt16) Description() string { return k.description }
+
+func (k *UInt16) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendUint(buf, uint64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *UInt16) Of(v uint16) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *UInt16) Get(lm label.Map) uint16 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *UInt16) From(t label.Label) uint16 { return uint16(t.Unpack64()) }
+
+// UInt32 represents a key
+type UInt32 struct {
+	name        string
+	description string
+}
+
+// NewUInt32 creates a new Key for uint32 values.
+func NewUInt32(name, description string) *UInt32 {
+	return &UInt32{name: name, description: description}
+}
+
+func (k *UInt32) Name() string        { return k.name }
+func (k *UInt32) Description() string { return k.description }
+
+func (k *UInt32) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendUint(buf, uint64(k.From(l)), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *UInt32) Of(v uint32) label.Label { return label.Of64(k, uint64(v)) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *UInt32) Get(lm label.Map) uint32 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *UInt32) From(t label.Label) uint32 { return uint32(t.Unpack64()) }
+
+// UInt64 represents a key
+type UInt64 struct {
+	name        string
+	description string
+}
+
+// NewUInt64 creates a new Key for uint64 values.
+func NewUInt64(name, description string) *UInt64 {
+	return &UInt64{name: name, description: description}
+}
+
+func (k *UInt64) Name() string        { return k.name }
+func (k *UInt64) Description() string { return k.description }
+
+func (k *UInt64) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendUint(buf, k.From(l), 10))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *UInt64) Of(v uint64) label.Label { return label.Of64(k, v) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *UInt64) Get(lm label.Map) uint64 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *UInt64) From(t label.Label) uint64 { return t.Unpack64() }
+
+// Float32 represents a key
+type Float32 struct {
+	name        string
+	description string
+}
+
+// NewFloat32 creates a new Key for float32 values.
+func NewFloat32(name, description string) *Float32 {
+	return &Float32{name: name, description: description}
+}
+
+func (k *Float32) Name() string        { return k.name }
+func (k *Float32) Description() string { return k.description }
+
+func (k *Float32) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendFloat(buf, float64(k.From(l)), 'E', -1, 32))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Float32) Of(v float32) label.Label {
+	return label.Of64(k, uint64(math.Float32bits(v)))
+}
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Float32) Get(lm label.Map) float32 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Float32) From(t label.Label) float32 {
+	return math.Float32frombits(uint32(t.Unpack64()))
+}
+
+// Float64 represents a key
+type Float64 struct {
+	name        string
+	description string
+}
+
+// NewFloat64 creates a new Key for int64 values.
+func NewFloat64(name, description string) *Float64 {
+	return &Float64{name: name, description: description}
+}
+
+func (k *Float64) Name() string        { return k.name }
+func (k *Float64) Description() string { return k.description }
+
+func (k *Float64) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendFloat(buf, k.From(l), 'E', -1, 64))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Float64) Of(v float64) label.Label {
+	return label.Of64(k, math.Float64bits(v))
+}
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Float64) Get(lm label.Map) float64 {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return 0
+}
+
+// From can be used to get a value from a Label.
+func (k *Float64) From(t label.Label) float64 {
+	return math.Float64frombits(t.Unpack64())
+}
+
+// String represents a key
+type String struct {
+	name        string
+	description string
+}
+
+// NewString creates a new Key for int64 values.
+func NewString(name, description string) *String {
+	return &String{name: name, description: description}
+}
+
+func (k *String) Name() string        { return k.name }
+func (k *String) Description() string { return k.description }
+
+func (k *String) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendQuote(buf, k.From(l)))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *String) Of(v string) label.Label { return label.OfString(k, v) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *String) Get(lm label.Map) string {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return ""
+}
+
+// From can be used to get a value from a Label.
+func (k *String) From(t label.Label) string { return t.UnpackString() }
+
+// Boolean represents a key
+type Boolean struct {
+	name        string
+	description string
+}
+
+// NewBoolean creates a new Key for bool values.
+func NewBoolean(name, description string) *Boolean {
+	return &Boolean{name: name, description: description}
+}
+
+func (k *Boolean) Name() string        { return k.name }
+func (k *Boolean) Description() string { return k.description }
+
+func (k *Boolean) Format(w io.Writer, buf []byte, l label.Label) {
+	w.Write(strconv.AppendBool(buf, k.From(l)))
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Boolean) Of(v bool) label.Label {
+	if v {
+		return label.Of64(k, 1)
+	}
+	return label.Of64(k, 0)
+}
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Boolean) Get(lm label.Map) bool {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return false
+}
+
+// From can be used to get a value from a Label.
+func (k *Boolean) From(t label.Label) bool { return t.Unpack64() > 0 }
+
+// Error represents a key
+type Error struct {
+	name        string
+	description string
+}
+
+// NewError creates a new Key for int64 values.
+func NewError(name, description string) *Error {
+	return &Error{name: name, description: description}
+}
+
+func (k *Error) Name() string        { return k.name }
+func (k *Error) Description() string { return k.description }
+
+func (k *Error) Format(w io.Writer, buf []byte, l label.Label) {
+	io.WriteString(w, k.From(l).Error())
+}
+
+// Of creates a new Label with this key and the supplied value.
+func (k *Error) Of(v error) label.Label { return label.OfValue(k, v) }
+
+// Get can be used to get a label for the key from a label.Map.
+func (k *Error) Get(lm label.Map) error {
+	if t := lm.Find(k); t.Valid() {
+		return k.From(t)
+	}
+	return nil
+}
+
+// From can be used to get a value from a Label.
+func (k *Error) From(t label.Label) error {
+	err, _ := t.UnpackValue().(error)
+	return err
+}

vendor/golang.org/x/tools/internal/event/keys/standard.go

@@ -0,0 +1,22 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package keys
+
+var (
+	// Msg is a key used to add message strings to label lists.
+	Msg = NewString("message", "a readable message")
+	// Label is a key used to indicate an event adds labels to the context.
+	Label = NewTag("label", "a label context marker")
+	// Start is used for things like traces that have a name.
+	Start = NewString("start", "span start")
+	// Metric is a key used to indicate an event records metrics.
+	End = NewTag("end", "a span end marker")
+	// Metric is a key used to indicate an event records metrics.
+	Detach = NewTag("detach", "a span detach marker")
+	// Err is a key used to add error values to label lists.
+	Err = NewError("error", "an error that occurred")
+	// Metric is a key used to indicate an event records metrics.
+	Metric = NewTag("metric", "a metric event marker")
+)

vendor/golang.org/x/tools/internal/event/label/label.go

@@ -0,0 +1,213 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package label
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"unsafe"
+)
+
+// Key is used as the identity of a Label.
+// Keys are intended to be compared by pointer only, the name should be unique
+// for communicating with external systems, but it is not required or enforced.
+type Key interface {
+	// Name returns the key name.
+	Name() string
+	// Description returns a string that can be used to describe the value.
+	Description() string
+
+	// Format is used in formatting to append the value of the label to the
+	// supplied buffer.
+	// The formatter may use the supplied buf as a scratch area to avoid
+	// allocations.
+	Format(w io.Writer, buf []byte, l Label)
+}
+
+// Label holds a key and value pair.
+// It is normally used when passing around lists of labels.
+type Label struct {
+	key     Key
+	packed  uint64
+	untyped interface{}
+}
+
+// Map is the interface to a collection of Labels indexed by key.
+type Map interface {
+	// Find returns the label that matches the supplied key.
+	Find(key Key) Label
+}
+
+// List is the interface to something that provides an iterable
+// list of labels.
+// Iteration should start from 0 and continue until Valid returns false.
+type List interface {
+	// Valid returns true if the index is within range for the list.
+	// It does not imply the label at that index will itself be valid.
+	Valid(index int) bool
+	// Label returns the label at the given index.
+	Label(index int) Label
+}
+
+// list implements LabelList for a list of Labels.
+type list struct {
+	labels []Label
+}
+
+// filter wraps a LabelList filtering out specific labels.
+type filter struct {
+	keys       []Key
+	underlying List
+}
+
+// listMap implements LabelMap for a simple list of labels.
+type listMap struct {
+	labels []Label
+}
+
+// mapChain implements LabelMap for a list of underlying LabelMap.
+type mapChain struct {
+	maps []Map
+}
+
+// OfValue creates a new label from the key and value.
+// This method is for implementing new key types, label creation should
+// normally be done with the Of method of the key.
+func OfValue(k Key, value interface{}) Label { return Label{key: k, untyped: value} }
+
+// UnpackValue assumes the label was built using LabelOfValue and returns the value
+// that was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Label) UnpackValue() interface{} { return t.untyped }
+
+// Of64 creates a new label from a key and a uint64. This is often
+// used for non uint64 values that can be packed into a uint64.
+// This method is for implementing new key types, label creation should
+// normally be done with the Of method of the key.
+func Of64(k Key, v uint64) Label { return Label{key: k, packed: v} }
+
+// Unpack64 assumes the label was built using LabelOf64 and returns the value that
+// was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Label) Unpack64() uint64 { return t.packed }
+
+// OfString creates a new label from a key and a string.
+// This method is for implementing new key types, label creation should
+// normally be done with the Of method of the key.
+func OfString(k Key, v string) Label {
+	hdr := (*reflect.StringHeader)(unsafe.Pointer(&v))
+	return Label{
+		key:     k,
+		packed:  uint64(hdr.Len),
+		untyped: unsafe.Pointer(hdr.Data),
+	}
+}
+
+// UnpackString assumes the label was built using LabelOfString and returns the
+// value that was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Label) UnpackString() string {
+	var v string
+	hdr := (*reflect.StringHeader)(unsafe.Pointer(&v))
+	hdr.Data = uintptr(t.untyped.(unsafe.Pointer))
+	hdr.Len = int(t.packed)
+	return *(*string)(unsafe.Pointer(hdr))
+}
+
+// Valid returns true if the Label is a valid one (it has a key).
+func (t Label) Valid() bool { return t.key != nil }
+
+// Key returns the key of this Label.
+func (t Label) Key() Key { return t.key }
+
+// Format is used for debug printing of labels.
+func (t Label) Format(f fmt.State, r rune) {
+	if !t.Valid() {
+		io.WriteString(f, `nil`)
+		return
+	}
+	io.WriteString(f, t.Key().Name())
+	io.WriteString(f, "=")
+	var buf [128]byte
+	t.Key().Format(f, buf[:0], t)
+}
+
+func (l *list) Valid(index int) bool {
+	return index >= 0 && index < len(l.labels)
+}
+
+func (l *list) Label(index int) Label {
+	return l.labels[index]
+}
+
+func (f *filter) Valid(index int) bool {
+	return f.underlying.Valid(index)
+}
+
+func (f *filter) Label(index int) Label {
+	l := f.underlying.Label(index)
+	for _, f := range f.keys {
+		if l.Key() == f {
+			return Label{}
+		}
+	}
+	return l
+}
+
+func (lm listMap) Find(key Key) Label {
+	for _, l := range lm.labels {
+		if l.Key() == key {
+			return l
+		}
+	}
+	return Label{}
+}
+
+func (c mapChain) Find(key Key) Label {
+	for _, src := range c.maps {
+		l := src.Find(key)
+		if l.Valid() {
+			return l
+		}
+	}
+	return Label{}
+}
+
+var emptyList = &list{}
+
+func NewList(labels ...Label) List {
+	if len(labels) == 0 {
+		return emptyList
+	}
+	return &list{labels: labels}
+}
+
+func Filter(l List, keys ...Key) List {
+	if len(keys) == 0 {
+		return l
+	}
+	return &filter{keys: keys, underlying: l}
+}
+
+func NewMap(labels ...Label) Map {
+	return listMap{labels: labels}
+}
+
+func MergeMaps(srcs ...Map) Map {
+	var nonNil []Map
+	for _, src := range srcs {
+		if src != nil {
+			nonNil = append(nonNil, src)
+		}
+	}
+	if len(nonNil) == 1 {
+		return nonNil[0]
+	}
+	return mapChain{maps: nonNil}
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk.go

@@ -0,0 +1,196 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package fastwalk provides a faster version of filepath.Walk for file system
+// scanning tools.
+package fastwalk
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sync"
+)
+
+// ErrTraverseLink is used as a return value from WalkFuncs to indicate that the
+// symlink named in the call may be traversed.
+var ErrTraverseLink = errors.New("fastwalk: traverse symlink, assuming target is a directory")
+
+// ErrSkipFiles is a used as a return value from WalkFuncs to indicate that the
+// callback should not be called for any other files in the current directory.
+// Child directories will still be traversed.
+var ErrSkipFiles = errors.New("fastwalk: skip remaining files in directory")
+
+// Walk is a faster implementation of filepath.Walk.
+//
+// filepath.Walk's design necessarily calls os.Lstat on each file,
+// even if the caller needs less info.
+// Many tools need only the type of each file.
+// On some platforms, this information is provided directly by the readdir
+// system call, avoiding the need to stat each file individually.
+// fastwalk_unix.go contains a fork of the syscall routines.
+//
+// See golang.org/issue/16399
+//
+// Walk walks the file tree rooted at root, calling walkFn for
+// each file or directory in the tree, including root.
+//
+// If fastWalk returns filepath.SkipDir, the directory is skipped.
+//
+// Unlike filepath.Walk:
+//   * file stat calls must be done by the user.
+//     The only provided metadata is the file type, which does not include
+//     any permission bits.
+//   * multiple goroutines stat the filesystem concurrently. The provided
+//     walkFn must be safe for concurrent use.
+//   * fastWalk can follow symlinks if walkFn returns the TraverseLink
+//     sentinel error. It is the walkFn's responsibility to prevent
+//     fastWalk from going into symlink cycles.
+func Walk(root string, walkFn func(path string, typ os.FileMode) error) error {
+	// TODO(bradfitz): make numWorkers configurable? We used a
+	// minimum of 4 to give the kernel more info about multiple
+	// things we want, in hopes its I/O scheduling can take
+	// advantage of that. Hopefully most are in cache. Maybe 4 is
+	// even too low of a minimum. Profile more.
+	numWorkers := 4
+	if n := runtime.NumCPU(); n > numWorkers {
+		numWorkers = n
+	}
+
+	// Make sure to wait for all workers to finish, otherwise
+	// walkFn could still be called after returning. This Wait call
+	// runs after close(e.donec) below.
+	var wg sync.WaitGroup
+	defer wg.Wait()
+
+	w := &walker{
+		fn:       walkFn,
+		enqueuec: make(chan walkItem, numWorkers), // buffered for performance
+		workc:    make(chan walkItem, numWorkers), // buffered for performance
+		donec:    make(chan struct{}),
+
+		// buffered for correctness & not leaking goroutines:
+		resc: make(chan error, numWorkers),
+	}
+	defer close(w.donec)
+
+	for i := 0; i < numWorkers; i++ {
+		wg.Add(1)
+		go w.doWork(&wg)
+	}
+	todo := []walkItem{{dir: root}}
+	out := 0
+	for {
+		workc := w.workc
+		var workItem walkItem
+		if len(todo) == 0 {
+			workc = nil
+		} else {
+			workItem = todo[len(todo)-1]
+		}
+		select {
+		case workc <- workItem:
+			todo = todo[:len(todo)-1]
+			out++
+		case it := <-w.enqueuec:
+			todo = append(todo, it)
+		case err := <-w.resc:
+			out--
+			if err != nil {
+				return err
+			}
+			if out == 0 && len(todo) == 0 {
+				// It's safe to quit here, as long as the buffered
+				// enqueue channel isn't also readable, which might
+				// happen if the worker sends both another unit of
+				// work and its result before the other select was
+				// scheduled and both w.resc and w.enqueuec were
+				// readable.
+				select {
+				case it := <-w.enqueuec:
+					todo = append(todo, it)
+				default:
+					return nil
+				}
+			}
+		}
+	}
+}
+
+// doWork reads directories as instructed (via workc) and runs the
+// user's callback function.
+func (w *walker) doWork(wg *sync.WaitGroup) {
+	defer wg.Done()
+	for {
+		select {
+		case <-w.donec:
+			return
+		case it := <-w.workc:
+			select {
+			case <-w.donec:
+				return
+			case w.resc <- w.walk(it.dir, !it.callbackDone):
+			}
+		}
+	}
+}
+
+type walker struct {
+	fn func(path string, typ os.FileMode) error
+
+	donec    chan struct{} // closed on fastWalk's return
+	workc    chan walkItem // to workers
+	enqueuec chan walkItem // from workers
+	resc     chan error    // from workers
+}
+
+type walkItem struct {
+	dir          string
+	callbackDone bool // callback already called; don't do it again
+}
+
+func (w *walker) enqueue(it walkItem) {
+	select {
+	case w.enqueuec <- it:
+	case <-w.donec:
+	}
+}
+
+func (w *walker) onDirEnt(dirName, baseName string, typ os.FileMode) error {
+	joined := dirName + string(os.PathSeparator) + baseName
+	if typ == os.ModeDir {
+		w.enqueue(walkItem{dir: joined})
+		return nil
+	}
+
+	err := w.fn(joined, typ)
+	if typ == os.ModeSymlink {
+		if err == ErrTraverseLink {
+			// Set callbackDone so we don't call it twice for both the
+			// symlink-as-symlink and the symlink-as-directory later:
+			w.enqueue(walkItem{dir: joined, callbackDone: true})
+			return nil
+		}
+		if err == filepath.SkipDir {
+			// Permit SkipDir on symlinks too.
+			return nil
+		}
+	}
+	return err
+}
+
+func (w *walker) walk(root string, runUserCallback bool) error {
+	if runUserCallback {
+		err := w.fn(root, os.ModeDir)
+		if err == filepath.SkipDir {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+	}
+
+	return readDir(root, w.onDirEnt)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_fileno.go

@@ -0,0 +1,13 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build freebsd openbsd netbsd
+
+package fastwalk
+
+import "syscall"
+
+func direntInode(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Fileno)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_ino.go

@@ -0,0 +1,14 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux darwin
+// +build !appengine
+
+package fastwalk
+
+import "syscall"
+
+func direntInode(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Ino)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_namlen_bsd.go

@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin freebsd openbsd netbsd
+
+package fastwalk
+
+import "syscall"
+
+func direntNamlen(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Namlen)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_namlen_linux.go

@@ -0,0 +1,29 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+// +build !appengine
+
+package fastwalk
+
+import (
+	"bytes"
+	"syscall"
+	"unsafe"
+)
+
+func direntNamlen(dirent *syscall.Dirent) uint64 {
+	const fixedHdr = uint16(unsafe.Offsetof(syscall.Dirent{}.Name))
+	nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
+	const nameBufLen = uint16(len(nameBuf))
+	limit := dirent.Reclen - fixedHdr
+	if limit > nameBufLen {
+		limit = nameBufLen
+	}
+	nameLen := bytes.IndexByte(nameBuf[:limit], 0)
+	if nameLen < 0 {
+		panic("failed to find terminating 0 byte in dirent")
+	}
+	return uint64(nameLen)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_portable.go

@@ -0,0 +1,37 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine !linux,!darwin,!freebsd,!openbsd,!netbsd
+
+package fastwalk
+
+import (
+	"io/ioutil"
+	"os"
+)
+
+// readDir calls fn for each directory entry in dirName.
+// It does not descend into directories or follow symlinks.
+// If fn returns a non-nil error, readDir returns with that error
+// immediately.
+func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
+	fis, err := ioutil.ReadDir(dirName)
+	if err != nil {
+		return err
+	}
+	skipFiles := false
+	for _, fi := range fis {
+		if fi.Mode().IsRegular() && skipFiles {
+			continue
+		}
+		if err := fn(dirName, fi.Name(), fi.Mode()&os.ModeType); err != nil {
+			if err == ErrSkipFiles {
+				skipFiles = true
+				continue
+			}
+			return err
+		}
+	}
+	return nil
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_unix.go

@@ -0,0 +1,128 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux darwin freebsd openbsd netbsd
+// +build !appengine
+
+package fastwalk
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+const blockSize = 8 << 10
+
+// unknownFileMode is a sentinel (and bogus) os.FileMode
+// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
+const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
+
+func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
+	fd, err := syscall.Open(dirName, 0, 0)
+	if err != nil {
+		return &os.PathError{Op: "open", Path: dirName, Err: err}
+	}
+	defer syscall.Close(fd)
+
+	// The buffer must be at least a block long.
+	buf := make([]byte, blockSize) // stack-allocated; doesn't escape
+	bufp := 0                      // starting read position in buf
+	nbuf := 0                      // end valid data in buf
+	skipFiles := false
+	for {
+		if bufp >= nbuf {
+			bufp = 0
+			nbuf, err = syscall.ReadDirent(fd, buf)
+			if err != nil {
+				return os.NewSyscallError("readdirent", err)
+			}
+			if nbuf <= 0 {
+				return nil
+			}
+		}
+		consumed, name, typ := parseDirEnt(buf[bufp:nbuf])
+		bufp += consumed
+		if name == "" || name == "." || name == ".." {
+			continue
+		}
+		// Fallback for filesystems (like old XFS) that don't
+		// support Dirent.Type and have DT_UNKNOWN (0) there
+		// instead.
+		if typ == unknownFileMode {
+			fi, err := os.Lstat(dirName + "/" + name)
+			if err != nil {
+				// It got deleted in the meantime.
+				if os.IsNotExist(err) {
+					continue
+				}
+				return err
+			}
+			typ = fi.Mode() & os.ModeType
+		}
+		if skipFiles && typ.IsRegular() {
+			continue
+		}
+		if err := fn(dirName, name, typ); err != nil {
+			if err == ErrSkipFiles {
+				skipFiles = true
+				continue
+			}
+			return err
+		}
+	}
+}
+
+func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) {
+	// golang.org/issue/37269
+	dirent := &syscall.Dirent{}
+	copy((*[unsafe.Sizeof(syscall.Dirent{})]byte)(unsafe.Pointer(dirent))[:], buf)
+	if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
+		panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v))
+	}
+	if len(buf) < int(dirent.Reclen) {
+		panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen))
+	}
+	consumed = int(dirent.Reclen)
+	if direntInode(dirent) == 0 { // File absent in directory.
+		return
+	}
+	switch dirent.Type {
+	case syscall.DT_REG:
+		typ = 0
+	case syscall.DT_DIR:
+		typ = os.ModeDir
+	case syscall.DT_LNK:
+		typ = os.ModeSymlink
+	case syscall.DT_BLK:
+		typ = os.ModeDevice
+	case syscall.DT_FIFO:
+		typ = os.ModeNamedPipe
+	case syscall.DT_SOCK:
+		typ = os.ModeSocket
+	case syscall.DT_UNKNOWN:
+		typ = unknownFileMode
+	default:
+		// Skip weird things.
+		// It's probably a DT_WHT (http://lwn.net/Articles/325369/)
+		// or something. Revisit if/when this package is moved outside
+		// of goimports. goimports only cares about regular files,
+		// symlinks, and directories.
+		return
+	}
+
+	nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
+	nameLen := direntNamlen(dirent)
+
+	// Special cases for common things:
+	if nameLen == 1 && nameBuf[0] == '.' {
+		name = "."
+	} else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' {
+		name = ".."
+	} else {
+		name = string(nameBuf[:nameLen])
+	}
+	return
+}

vendor/golang.org/x/tools/internal/gocommand/invoke.go

@@ -0,0 +1,273 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gocommand is a helper for calling the go command.
+package gocommand
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	exec "golang.org/x/sys/execabs"
+	"io"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/tools/internal/event"
+)
+
+// An Runner will run go command invocations and serialize
+// them if it sees a concurrency error.
+type Runner struct {
+	// once guards the runner initialization.
+	once sync.Once
+
+	// inFlight tracks available workers.
+	inFlight chan struct{}
+
+	// serialized guards the ability to run a go command serially,
+	// to avoid deadlocks when claiming workers.
+	serialized chan struct{}
+}
+
+const maxInFlight = 10
+
+func (runner *Runner) initialize() {
+	runner.once.Do(func() {
+		runner.inFlight = make(chan struct{}, maxInFlight)
+		runner.serialized = make(chan struct{}, 1)
+	})
+}
+
+// 1.13: go: updates to go.mod needed, but contents have changed
+// 1.14: go: updating go.mod: existing contents have changed since last read
+var modConcurrencyError = regexp.MustCompile(`go:.*go.mod.*contents have changed`)
+
+// Run is a convenience wrapper around RunRaw.
+// It returns only stdout and a "friendly" error.
+func (runner *Runner) Run(ctx context.Context, inv Invocation) (*bytes.Buffer, error) {
+	stdout, _, friendly, _ := runner.RunRaw(ctx, inv)
+	return stdout, friendly
+}
+
+// RunPiped runs the invocation serially, always waiting for any concurrent
+// invocations to complete first.
+func (runner *Runner) RunPiped(ctx context.Context, inv Invocation, stdout, stderr io.Writer) error {
+	_, err := runner.runPiped(ctx, inv, stdout, stderr)
+	return err
+}
+
+// RunRaw runs the invocation, serializing requests only if they fight over
+// go.mod changes.
+func (runner *Runner) RunRaw(ctx context.Context, inv Invocation) (*bytes.Buffer, *bytes.Buffer, error, error) {
+	// Make sure the runner is always initialized.
+	runner.initialize()
+
+	// First, try to run the go command concurrently.
+	stdout, stderr, friendlyErr, err := runner.runConcurrent(ctx, inv)
+
+	// If we encounter a load concurrency error, we need to retry serially.
+	if friendlyErr == nil || !modConcurrencyError.MatchString(friendlyErr.Error()) {
+		return stdout, stderr, friendlyErr, err
+	}
+	event.Error(ctx, "Load concurrency error, will retry serially", err)
+
+	// Run serially by calling runPiped.
+	stdout.Reset()
+	stderr.Reset()
+	friendlyErr, err = runner.runPiped(ctx, inv, stdout, stderr)
+	return stdout, stderr, friendlyErr, err
+}
+
+func (runner *Runner) runConcurrent(ctx context.Context, inv Invocation) (*bytes.Buffer, *bytes.Buffer, error, error) {
+	// Wait for 1 worker to become available.
+	select {
+	case <-ctx.Done():
+		return nil, nil, nil, ctx.Err()
+	case runner.inFlight <- struct{}{}:
+		defer func() { <-runner.inFlight }()
+	}
+
+	stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
+	friendlyErr, err := inv.runWithFriendlyError(ctx, stdout, stderr)
+	return stdout, stderr, friendlyErr, err
+}
+
+func (runner *Runner) runPiped(ctx context.Context, inv Invocation, stdout, stderr io.Writer) (error, error) {
+	// Make sure the runner is always initialized.
+	runner.initialize()
+
+	// Acquire the serialization lock. This avoids deadlocks between two
+	// runPiped commands.
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case runner.serialized <- struct{}{}:
+		defer func() { <-runner.serialized }()
+	}
+
+	// Wait for all in-progress go commands to return before proceeding,
+	// to avoid load concurrency errors.
+	for i := 0; i < maxInFlight; i++ {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case runner.inFlight <- struct{}{}:
+			// Make sure we always "return" any workers we took.
+			defer func() { <-runner.inFlight }()
+		}
+	}
+
+	return inv.runWithFriendlyError(ctx, stdout, stderr)
+}
+
+// An Invocation represents a call to the go command.
+type Invocation struct {
+	Verb       string
+	Args       []string
+	BuildFlags []string
+	ModFlag    string
+	ModFile    string
+	Overlay    string
+	// If CleanEnv is set, the invocation will run only with the environment
+	// in Env, not starting with os.Environ.
+	CleanEnv   bool
+	Env        []string
+	WorkingDir string
+	Logf       func(format string, args ...interface{})
+}
+
+func (i *Invocation) runWithFriendlyError(ctx context.Context, stdout, stderr io.Writer) (friendlyError error, rawError error) {
+	rawError = i.run(ctx, stdout, stderr)
+	if rawError != nil {
+		friendlyError = rawError
+		// Check for 'go' executable not being found.
+		if ee, ok := rawError.(*exec.Error); ok && ee.Err == exec.ErrNotFound {
+			friendlyError = fmt.Errorf("go command required, not found: %v", ee)
+		}
+		if ctx.Err() != nil {
+			friendlyError = ctx.Err()
+		}
+		friendlyError = fmt.Errorf("err: %v: stderr: %s", friendlyError, stderr)
+	}
+	return
+}
+
+func (i *Invocation) run(ctx context.Context, stdout, stderr io.Writer) error {
+	log := i.Logf
+	if log == nil {
+		log = func(string, ...interface{}) {}
+	}
+
+	goArgs := []string{i.Verb}
+
+	appendModFile := func() {
+		if i.ModFile != "" {
+			goArgs = append(goArgs, "-modfile="+i.ModFile)
+		}
+	}
+	appendModFlag := func() {
+		if i.ModFlag != "" {
+			goArgs = append(goArgs, "-mod="+i.ModFlag)
+		}
+	}
+	appendOverlayFlag := func() {
+		if i.Overlay != "" {
+			goArgs = append(goArgs, "-overlay="+i.Overlay)
+		}
+	}
+
+	switch i.Verb {
+	case "env", "version":
+		goArgs = append(goArgs, i.Args...)
+	case "mod":
+		// mod needs the sub-verb before flags.
+		goArgs = append(goArgs, i.Args[0])
+		appendModFile()
+		goArgs = append(goArgs, i.Args[1:]...)
+	case "get":
+		goArgs = append(goArgs, i.BuildFlags...)
+		appendModFile()
+		goArgs = append(goArgs, i.Args...)
+
+	default: // notably list and build.
+		goArgs = append(goArgs, i.BuildFlags...)
+		appendModFile()
+		appendModFlag()
+		appendOverlayFlag()
+		goArgs = append(goArgs, i.Args...)
+	}
+	cmd := exec.Command("go", goArgs...)
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
+	// On darwin the cwd gets resolved to the real path, which breaks anything that
+	// expects the working directory to keep the original path, including the
+	// go command when dealing with modules.
+	// The Go stdlib has a special feature where if the cwd and the PWD are the
+	// same node then it trusts the PWD, so by setting it in the env for the child
+	// process we fix up all the paths returned by the go command.
+	if !i.CleanEnv {
+		cmd.Env = os.Environ()
+	}
+	cmd.Env = append(cmd.Env, i.Env...)
+	if i.WorkingDir != "" {
+		cmd.Env = append(cmd.Env, "PWD="+i.WorkingDir)
+		cmd.Dir = i.WorkingDir
+	}
+	defer func(start time.Time) { log("%s for %v", time.Since(start), cmdDebugStr(cmd)) }(time.Now())
+
+	return runCmdContext(ctx, cmd)
+}
+
+// runCmdContext is like exec.CommandContext except it sends os.Interrupt
+// before os.Kill.
+func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+	resChan := make(chan error, 1)
+	go func() {
+		resChan <- cmd.Wait()
+	}()
+
+	select {
+	case err := <-resChan:
+		return err
+	case <-ctx.Done():
+	}
+	// Cancelled. Interrupt and see if it ends voluntarily.
+	cmd.Process.Signal(os.Interrupt)
+	select {
+	case err := <-resChan:
+		return err
+	case <-time.After(time.Second):
+	}
+	// Didn't shut down in response to interrupt. Kill it hard.
+	cmd.Process.Kill()
+	return <-resChan
+}
+
+func cmdDebugStr(cmd *exec.Cmd) string {
+	env := make(map[string]string)
+	for _, kv := range cmd.Env {
+		split := strings.SplitN(kv, "=", 2)
+		k, v := split[0], split[1]
+		env[k] = v
+	}
+
+	var args []string
+	for _, arg := range cmd.Args {
+		quoted := strconv.Quote(arg)
+		if quoted[1:len(quoted)-1] != arg || strings.Contains(arg, " ") {
+			args = append(args, quoted)
+		} else {
+			args = append(args, arg)
+		}
+	}
+	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], strings.Join(args, " "))
+}

vendor/golang.org/x/tools/internal/gocommand/vendor.go

@@ -0,0 +1,102 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gocommand
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"golang.org/x/mod/semver"
+)
+
+// ModuleJSON holds information about a module.
+type ModuleJSON struct {
+	Path      string      // module path
+	Replace   *ModuleJSON // replaced by this module
+	Main      bool        // is this the main module?
+	Indirect  bool        // is this module only an indirect dependency of main module?
+	Dir       string      // directory holding files for this module, if any
+	GoMod     string      // path to go.mod file for this module, if any
+	GoVersion string      // go version used in module
+}
+
+var modFlagRegexp = regexp.MustCompile(`-mod[ =](\w+)`)
+
+// VendorEnabled reports whether vendoring is enabled. It takes a *Runner to execute Go commands
+// with the supplied context.Context and Invocation. The Invocation can contain pre-defined fields,
+// of which only Verb and Args are modified to run the appropriate Go command.
+// Inspired by setDefaultBuildMod in modload/init.go
+func VendorEnabled(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON, bool, error) {
+	mainMod, go114, err := getMainModuleAnd114(ctx, inv, r)
+	if err != nil {
+		return nil, false, err
+	}
+
+	// We check the GOFLAGS to see if there is anything overridden or not.
+	inv.Verb = "env"
+	inv.Args = []string{"GOFLAGS"}
+	stdout, err := r.Run(ctx, inv)
+	if err != nil {
+		return nil, false, err
+	}
+	goflags := string(bytes.TrimSpace(stdout.Bytes()))
+	matches := modFlagRegexp.FindStringSubmatch(goflags)
+	var modFlag string
+	if len(matches) != 0 {
+		modFlag = matches[1]
+	}
+	if modFlag != "" {
+		// Don't override an explicit '-mod=' argument.
+		return mainMod, modFlag == "vendor", nil
+	}
+	if mainMod == nil || !go114 {
+		return mainMod, false, nil
+	}
+	// Check 1.14's automatic vendor mode.
+	if fi, err := os.Stat(filepath.Join(mainMod.Dir, "vendor")); err == nil && fi.IsDir() {
+		if mainMod.GoVersion != "" && semver.Compare("v"+mainMod.GoVersion, "v1.14") >= 0 {
+			// The Go version is at least 1.14, and a vendor directory exists.
+			// Set -mod=vendor by default.
+			return mainMod, true, nil
+		}
+	}
+	return mainMod, false, nil
+}
+
+// getMainModuleAnd114 gets the main module's information and whether the
+// go command in use is 1.14+. This is the information needed to figure out
+// if vendoring should be enabled.
+func getMainModuleAnd114(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON, bool, error) {
+	const format = `{{.Path}}
+{{.Dir}}
+{{.GoMod}}
+{{.GoVersion}}
+{{range context.ReleaseTags}}{{if eq . "go1.14"}}{{.}}{{end}}{{end}}
+`
+	inv.Verb = "list"
+	inv.Args = []string{"-m", "-f", format}
+	stdout, err := r.Run(ctx, inv)
+	if err != nil {
+		return nil, false, err
+	}
+
+	lines := strings.Split(stdout.String(), "\n")
+	if len(lines) < 5 {
+		return nil, false, fmt.Errorf("unexpected stdout: %q", stdout.String())
+	}
+	mod := &ModuleJSON{
+		Path:      lines[0],
+		Dir:       lines[1],
+		GoMod:     lines[2],
+		GoVersion: lines[3],
+		Main:      true,
+	}
+	return mod, lines[4] == "go1.14", nil
+}

vendor/golang.org/x/tools/internal/gocommand/version.go

@@ -0,0 +1,51 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gocommand
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+// GoVersion checks the go version by running "go list" with modules off.
+// It returns the X in Go 1.X.
+func GoVersion(ctx context.Context, inv Invocation, r *Runner) (int, error) {
+	inv.Verb = "list"
+	inv.Args = []string{"-e", "-f", `{{context.ReleaseTags}}`}
+	inv.Env = append(append([]string{}, inv.Env...), "GO111MODULE=off")
+	// Unset any unneeded flags, and remove them from BuildFlags, if they're
+	// present.
+	inv.ModFile = ""
+	inv.ModFlag = ""
+	var buildFlags []string
+	for _, flag := range inv.BuildFlags {
+		// Flags can be prefixed by one or two dashes.
+		f := strings.TrimPrefix(strings.TrimPrefix(flag, "-"), "-")
+		if strings.HasPrefix(f, "mod=") || strings.HasPrefix(f, "modfile=") {
+			continue
+		}
+		buildFlags = append(buildFlags, flag)
+	}
+	inv.BuildFlags = buildFlags
+	stdoutBytes, err := r.Run(ctx, inv)
+	if err != nil {
+		return 0, err
+	}
+	stdout := stdoutBytes.String()
+	if len(stdout) < 3 {
+		return 0, fmt.Errorf("bad ReleaseTags output: %q", stdout)
+	}
+	// Split up "[go1.1 go1.15]"
+	tags := strings.Fields(stdout[1 : len(stdout)-2])
+	for i := len(tags) - 1; i >= 0; i-- {
+		var version int
+		if _, err := fmt.Sscanf(tags[i], "go1.%d", &version); err != nil {
+			continue
+		}
+		return version, nil
+	}
+	return 0, fmt.Errorf("no parseable ReleaseTags in %v", tags)
+}

vendor/golang.org/x/tools/internal/gopathwalk/walk.go

@@ -0,0 +1,264 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gopathwalk is like filepath.Walk but specialized for finding Go
+// packages, particularly in $GOPATH and $GOROOT.
+package gopathwalk
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/tools/internal/fastwalk"
+)
+
+// Options controls the behavior of a Walk call.
+type Options struct {
+	// If Logf is non-nil, debug logging is enabled through this function.
+	Logf func(format string, args ...interface{})
+	// Search module caches. Also disables legacy goimports ignore rules.
+	ModulesEnabled bool
+}
+
+// RootType indicates the type of a Root.
+type RootType int
+
+const (
+	RootUnknown RootType = iota
+	RootGOROOT
+	RootGOPATH
+	RootCurrentModule
+	RootModuleCache
+	RootOther
+)
+
+// A Root is a starting point for a Walk.
+type Root struct {
+	Path string
+	Type RootType
+}
+
+// Walk walks Go source directories ($GOROOT, $GOPATH, etc) to find packages.
+// For each package found, add will be called (concurrently) with the absolute
+// paths of the containing source directory and the package directory.
+// add will be called concurrently.
+func Walk(roots []Root, add func(root Root, dir string), opts Options) {
+	WalkSkip(roots, add, func(Root, string) bool { return false }, opts)
+}
+
+// WalkSkip walks Go source directories ($GOROOT, $GOPATH, etc) to find packages.
+// For each package found, add will be called (concurrently) with the absolute
+// paths of the containing source directory and the package directory.
+// For each directory that will be scanned, skip will be called (concurrently)
+// with the absolute paths of the containing source directory and the directory.
+// If skip returns false on a directory it will be processed.
+// add will be called concurrently.
+// skip will be called concurrently.
+func WalkSkip(roots []Root, add func(root Root, dir string), skip func(root Root, dir string) bool, opts Options) {
+	for _, root := range roots {
+		walkDir(root, add, skip, opts)
+	}
+}
+
+// walkDir creates a walker and starts fastwalk with this walker.
+func walkDir(root Root, add func(Root, string), skip func(root Root, dir string) bool, opts Options) {
+	if _, err := os.Stat(root.Path); os.IsNotExist(err) {
+		if opts.Logf != nil {
+			opts.Logf("skipping nonexistent directory: %v", root.Path)
+		}
+		return
+	}
+	start := time.Now()
+	if opts.Logf != nil {
+		opts.Logf("gopathwalk: scanning %s", root.Path)
+	}
+	w := &walker{
+		root: root,
+		add:  add,
+		skip: skip,
+		opts: opts,
+	}
+	w.init()
+	if err := fastwalk.Walk(root.Path, w.walk); err != nil {
+		log.Printf("gopathwalk: scanning directory %v: %v", root.Path, err)
+	}
+
+	if opts.Logf != nil {
+		opts.Logf("gopathwalk: scanned %s in %v", root.Path, time.Since(start))
+	}
+}
+
+// walker is the callback for fastwalk.Walk.
+type walker struct {
+	root Root                    // The source directory to scan.
+	add  func(Root, string)      // The callback that will be invoked for every possible Go package dir.
+	skip func(Root, string) bool // The callback that will be invoked for every dir. dir is skipped if it returns true.
+	opts Options                 // Options passed to Walk by the user.
+
+	ignoredDirs []os.FileInfo // The ignored directories, loaded from .goimportsignore files.
+}
+
+// init initializes the walker based on its Options
+func (w *walker) init() {
+	var ignoredPaths []string
+	if w.root.Type == RootModuleCache {
+		ignoredPaths = []string{"cache"}
+	}
+	if !w.opts.ModulesEnabled && w.root.Type == RootGOPATH {
+		ignoredPaths = w.getIgnoredDirs(w.root.Path)
+		ignoredPaths = append(ignoredPaths, "v", "mod")
+	}
+
+	for _, p := range ignoredPaths {
+		full := filepath.Join(w.root.Path, p)
+		if fi, err := os.Stat(full); err == nil {
+			w.ignoredDirs = append(w.ignoredDirs, fi)
+			if w.opts.Logf != nil {
+				w.opts.Logf("Directory added to ignore list: %s", full)
+			}
+		} else if w.opts.Logf != nil {
+			w.opts.Logf("Error statting ignored directory: %v", err)
+		}
+	}
+}
+
+// getIgnoredDirs reads an optional config file at <path>/.goimportsignore
+// of relative directories to ignore when scanning for go files.
+// The provided path is one of the $GOPATH entries with "src" appended.
+func (w *walker) getIgnoredDirs(path string) []string {
+	file := filepath.Join(path, ".goimportsignore")
+	slurp, err := ioutil.ReadFile(file)
+	if w.opts.Logf != nil {
+		if err != nil {
+			w.opts.Logf("%v", err)
+		} else {
+			w.opts.Logf("Read %s", file)
+		}
+	}
+	if err != nil {
+		return nil
+	}
+
+	var ignoredDirs []string
+	bs := bufio.NewScanner(bytes.NewReader(slurp))
+	for bs.Scan() {
+		line := strings.TrimSpace(bs.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		ignoredDirs = append(ignoredDirs, line)
+	}
+	return ignoredDirs
+}
+
+// shouldSkipDir reports whether the file should be skipped or not.
+func (w *walker) shouldSkipDir(fi os.FileInfo, dir string) bool {
+	for _, ignoredDir := range w.ignoredDirs {
+		if os.SameFile(fi, ignoredDir) {
+			return true
+		}
+	}
+	if w.skip != nil {
+		// Check with the user specified callback.
+		return w.skip(w.root, dir)
+	}
+	return false
+}
+
+// walk walks through the given path.
+func (w *walker) walk(path string, typ os.FileMode) error {
+	dir := filepath.Dir(path)
+	if typ.IsRegular() {
+		if dir == w.root.Path && (w.root.Type == RootGOROOT || w.root.Type == RootGOPATH) {
+			// Doesn't make sense to have regular files
+			// directly in your $GOPATH/src or $GOROOT/src.
+			return fastwalk.ErrSkipFiles
+		}
+		if !strings.HasSuffix(path, ".go") {
+			return nil
+		}
+
+		w.add(w.root, dir)
+		return fastwalk.ErrSkipFiles
+	}
+	if typ == os.ModeDir {
+		base := filepath.Base(path)
+		if base == "" || base[0] == '.' || base[0] == '_' ||
+			base == "testdata" ||
+			(w.root.Type == RootGOROOT && w.opts.ModulesEnabled && base == "vendor") ||
+			(!w.opts.ModulesEnabled && base == "node_modules") {
+			return filepath.SkipDir
+		}
+		fi, err := os.Lstat(path)
+		if err == nil && w.shouldSkipDir(fi, path) {
+			return filepath.SkipDir
+		}
+		return nil
+	}
+	if typ == os.ModeSymlink {
+		base := filepath.Base(path)
+		if strings.HasPrefix(base, ".#") {
+			// Emacs noise.
+			return nil
+		}
+		fi, err := os.Lstat(path)
+		if err != nil {
+			// Just ignore it.
+			return nil
+		}
+		if w.shouldTraverse(dir, fi) {
+			return fastwalk.ErrTraverseLink
+		}
+	}
+	return nil
+}
+
+// shouldTraverse reports whether the symlink fi, found in dir,
+// should be followed.  It makes sure symlinks were never visited
+// before to avoid symlink loops.
+func (w *walker) shouldTraverse(dir string, fi os.FileInfo) bool {
+	path := filepath.Join(dir, fi.Name())
+	target, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		return false
+	}
+	ts, err := os.Stat(target)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return false
+	}
+	if !ts.IsDir() {
+		return false
+	}
+	if w.shouldSkipDir(ts, dir) {
+		return false
+	}
+	// Check for symlink loops by statting each directory component
+	// and seeing if any are the same file as ts.
+	for {
+		parent := filepath.Dir(path)
+		if parent == path {
+			// Made it to the root without seeing a cycle.
+			// Use this symlink.
+			return true
+		}
+		parentInfo, err := os.Stat(parent)
+		if err != nil {
+			return false
+		}
+		if os.SameFile(ts, parentInfo) {
+			// Cycle. Don't traverse.
+			return false
+		}
+		path = parent
+	}
+
+}

vendor/golang.org/x/tools/internal/imports/imports.go

@@ -0,0 +1,346 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run mkstdlib.go
+
+// Package imports implements a Go pretty-printer (like package "go/format")
+// that also adds or removes import statements as necessary.
+package imports
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/go/ast/astutil"
+)
+
+// Options is golang.org/x/tools/imports.Options with extra internal-only options.
+type Options struct {
+	Env *ProcessEnv // The environment to use. Note: this contains the cached module and filesystem state.
+
+	// LocalPrefix is a comma-separated string of import path prefixes, which, if
+	// set, instructs Process to sort the import paths with the given prefixes
+	// into another group after 3rd-party packages.
+	LocalPrefix string
+
+	Fragment  bool // Accept fragment of a source file (no package statement)
+	AllErrors bool // Report all errors (not just the first 10 on different lines)
+
+	Comments  bool // Print comments (true if nil *Options provided)
+	TabIndent bool // Use tabs for indent (true if nil *Options provided)
+	TabWidth  int  // Tab width (8 if nil *Options provided)
+
+	FormatOnly bool // Disable the insertion and deletion of imports
+}
+
+// Process implements golang.org/x/tools/imports.Process with explicit context in opt.Env.
+func Process(filename string, src []byte, opt *Options) (formatted []byte, err error) {
+	fileSet := token.NewFileSet()
+	file, adjust, err := parse(fileSet, filename, src, opt)
+	if err != nil {
+		return nil, err
+	}
+
+	if !opt.FormatOnly {
+		if err := fixImports(fileSet, file, filename, opt.Env); err != nil {
+			return nil, err
+		}
+	}
+	return formatFile(fileSet, file, src, adjust, opt)
+}
+
+// FixImports returns a list of fixes to the imports that, when applied,
+// will leave the imports in the same state as Process. src and opt must
+// be specified.
+//
+// Note that filename's directory influences which imports can be chosen,
+// so it is important that filename be accurate.
+func FixImports(filename string, src []byte, opt *Options) (fixes []*ImportFix, err error) {
+	fileSet := token.NewFileSet()
+	file, _, err := parse(fileSet, filename, src, opt)
+	if err != nil {
+		return nil, err
+	}
+
+	return getFixes(fileSet, file, filename, opt.Env)
+}
+
+// ApplyFixes applies all of the fixes to the file and formats it. extraMode
+// is added in when parsing the file. src and opts must be specified, but no
+// env is needed.
+func ApplyFixes(fixes []*ImportFix, filename string, src []byte, opt *Options, extraMode parser.Mode) (formatted []byte, err error) {
+	// Don't use parse() -- we don't care about fragments or statement lists
+	// here, and we need to work with unparseable files.
+	fileSet := token.NewFileSet()
+	parserMode := parser.Mode(0)
+	if opt.Comments {
+		parserMode |= parser.ParseComments
+	}
+	if opt.AllErrors {
+		parserMode |= parser.AllErrors
+	}
+	parserMode |= extraMode
+
+	file, err := parser.ParseFile(fileSet, filename, src, parserMode)
+	if file == nil {
+		return nil, err
+	}
+
+	// Apply the fixes to the file.
+	apply(fileSet, file, fixes)
+
+	return formatFile(fileSet, file, src, nil, opt)
+}
+
+func formatFile(fileSet *token.FileSet, file *ast.File, src []byte, adjust func(orig []byte, src []byte) []byte, opt *Options) ([]byte, error) {
+	mergeImports(fileSet, file)
+	sortImports(opt.LocalPrefix, fileSet, file)
+	imps := astutil.Imports(fileSet, file)
+	var spacesBefore []string // import paths we need spaces before
+	for _, impSection := range imps {
+		// Within each block of contiguous imports, see if any
+		// import lines are in different group numbers. If so,
+		// we'll need to put a space between them so it's
+		// compatible with gofmt.
+		lastGroup := -1
+		for _, importSpec := range impSection {
+			importPath, _ := strconv.Unquote(importSpec.Path.Value)
+			groupNum := importGroup(opt.LocalPrefix, importPath)
+			if groupNum != lastGroup && lastGroup != -1 {
+				spacesBefore = append(spacesBefore, importPath)
+			}
+			lastGroup = groupNum
+		}
+
+	}
+
+	printerMode := printer.UseSpaces
+	if opt.TabIndent {
+		printerMode |= printer.TabIndent
+	}
+	printConfig := &printer.Config{Mode: printerMode, Tabwidth: opt.TabWidth}
+
+	var buf bytes.Buffer
+	err := printConfig.Fprint(&buf, fileSet, file)
+	if err != nil {
+		return nil, err
+	}
+	out := buf.Bytes()
+	if adjust != nil {
+		out = adjust(src, out)
+	}
+	if len(spacesBefore) > 0 {
+		out, err = addImportSpaces(bytes.NewReader(out), spacesBefore)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	out, err = format.Source(out)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// parse parses src, which was read from filename,
+// as a Go source file or statement list.
+func parse(fset *token.FileSet, filename string, src []byte, opt *Options) (*ast.File, func(orig, src []byte) []byte, error) {
+	parserMode := parser.Mode(0)
+	if opt.Comments {
+		parserMode |= parser.ParseComments
+	}
+	if opt.AllErrors {
+		parserMode |= parser.AllErrors
+	}
+
+	// Try as whole source file.
+	file, err := parser.ParseFile(fset, filename, src, parserMode)
+	if err == nil {
+		return file, nil, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// package line and we accept fragmented input, fall through to
+	// try as a source fragment.  Stop and return on any other error.
+	if !opt.Fragment || !strings.Contains(err.Error(), "expected 'package'") {
+		return nil, nil, err
+	}
+
+	// If this is a declaration list, make it a source file
+	// by inserting a package clause.
+	// Insert using a ;, not a newline, so that parse errors are on
+	// the correct line.
+	const prefix = "package main;"
+	psrc := append([]byte(prefix), src...)
+	file, err = parser.ParseFile(fset, filename, psrc, parserMode)
+	if err == nil {
+		// Gofmt will turn the ; into a \n.
+		// Do that ourselves now and update the file contents,
+		// so that positions and line numbers are correct going forward.
+		psrc[len(prefix)-1] = '\n'
+		fset.File(file.Package).SetLinesForContent(psrc)
+
+		// If a main function exists, we will assume this is a main
+		// package and leave the file.
+		if containsMainFunc(file) {
+			return file, nil, nil
+		}
+
+		adjust := func(orig, src []byte) []byte {
+			// Remove the package clause.
+			src = src[len(prefix):]
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// declaration, fall through to try as a statement list.
+	// Stop and return on any other error.
+	if !strings.Contains(err.Error(), "expected declaration") {
+		return nil, nil, err
+	}
+
+	// If this is a statement list, make it a source file
+	// by inserting a package clause and turning the list
+	// into a function body.  This handles expressions too.
+	// Insert using a ;, not a newline, so that the line numbers
+	// in fsrc match the ones in src.
+	fsrc := append(append([]byte("package p; func _() {"), src...), '}')
+	file, err = parser.ParseFile(fset, filename, fsrc, parserMode)
+	if err == nil {
+		adjust := func(orig, src []byte) []byte {
+			// Remove the wrapping.
+			// Gofmt has turned the ; into a \n\n.
+			src = src[len("package p\n\nfunc _() {"):]
+			src = src[:len(src)-len("}\n")]
+			// Gofmt has also indented the function body one level.
+			// Remove that indent.
+			src = bytes.Replace(src, []byte("\n\t"), []byte("\n"), -1)
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+
+	// Failed, and out of options.
+	return nil, nil, err
+}
+
+// containsMainFunc checks if a file contains a function declaration with the
+// function signature 'func main()'
+func containsMainFunc(file *ast.File) bool {
+	for _, decl := range file.Decls {
+		if f, ok := decl.(*ast.FuncDecl); ok {
+			if f.Name.Name != "main" {
+				continue
+			}
+
+			if len(f.Type.Params.List) != 0 {
+				continue
+			}
+
+			if f.Type.Results != nil && len(f.Type.Results.List) != 0 {
+				continue
+			}
+
+			return true
+		}
+	}
+
+	return false
+}
+
+func cutSpace(b []byte) (before, middle, after []byte) {
+	i := 0
+	for i < len(b) && (b[i] == ' ' || b[i] == '\t' || b[i] == '\n') {
+		i++
+	}
+	j := len(b)
+	for j > 0 && (b[j-1] == ' ' || b[j-1] == '\t' || b[j-1] == '\n') {
+		j--
+	}
+	if i <= j {
+		return b[:i], b[i:j], b[j:]
+	}
+	return nil, nil, b[j:]
+}
+
+// matchSpace reformats src to use the same space context as orig.
+// 1) If orig begins with blank lines, matchSpace inserts them at the beginning of src.
+// 2) matchSpace copies the indentation of the first non-blank line in orig
+//    to every non-blank line in src.
+// 3) matchSpace copies the trailing space from orig and uses it in place
+//   of src's trailing space.
+func matchSpace(orig []byte, src []byte) []byte {
+	before, _, after := cutSpace(orig)
+	i := bytes.LastIndex(before, []byte{'\n'})
+	before, indent := before[:i+1], before[i+1:]
+
+	_, src, _ = cutSpace(src)
+
+	var b bytes.Buffer
+	b.Write(before)
+	for len(src) > 0 {
+		line := src
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, src = line[:i+1], line[i+1:]
+		} else {
+			src = nil
+		}
+		if len(line) > 0 && line[0] != '\n' { // not blank
+			b.Write(indent)
+		}
+		b.Write(line)
+	}
+	b.Write(after)
+	return b.Bytes()
+}
+
+var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+)"`)
+
+func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
+	var out bytes.Buffer
+	in := bufio.NewReader(r)
+	inImports := false
+	done := false
+	for {
+		s, err := in.ReadString('\n')
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+
+		if !inImports && !done && strings.HasPrefix(s, "import") {
+			inImports = true
+		}
+		if inImports && (strings.HasPrefix(s, "var") ||
+			strings.HasPrefix(s, "func") ||
+			strings.HasPrefix(s, "const") ||
+			strings.HasPrefix(s, "type")) {
+			done = true
+			inImports = false
+		}
+		if inImports && len(breaks) > 0 {
+			if m := impLine.FindStringSubmatch(s); m != nil {
+				if m[1] == breaks[0] {
+					out.WriteByte('\n')
+					breaks = breaks[1:]
+				}
+			}
+		}
+
+		fmt.Fprint(&out, s)
+	}
+	return out.Bytes(), nil
+}

vendor/golang.org/x/tools/internal/imports/mod.go

@@ -0,0 +1,693 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package imports
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+
+	"golang.org/x/mod/module"
+	"golang.org/x/tools/internal/gocommand"
+	"golang.org/x/tools/internal/gopathwalk"
+)
+
+// ModuleResolver implements resolver for modules using the go command as little
+// as feasible.
+type ModuleResolver struct {
+	env            *ProcessEnv
+	moduleCacheDir string
+	dummyVendorMod *gocommand.ModuleJSON // If vendoring is enabled, the pseudo-module that represents the /vendor directory.
+	roots          []gopathwalk.Root
+	scanSema       chan struct{} // scanSema prevents concurrent scans and guards scannedRoots.
+	scannedRoots   map[gopathwalk.Root]bool
+
+	initialized   bool
+	main          *gocommand.ModuleJSON
+	modsByModPath []*gocommand.ModuleJSON // All modules, ordered by # of path components in module Path...
+	modsByDir     []*gocommand.ModuleJSON // ...or Dir.
+
+	// moduleCacheCache stores information about the module cache.
+	moduleCacheCache *dirInfoCache
+	otherCache       *dirInfoCache
+}
+
+func newModuleResolver(e *ProcessEnv) *ModuleResolver {
+	r := &ModuleResolver{
+		env:      e,
+		scanSema: make(chan struct{}, 1),
+	}
+	r.scanSema <- struct{}{}
+	return r
+}
+
+func (r *ModuleResolver) init() error {
+	if r.initialized {
+		return nil
+	}
+
+	goenv, err := r.env.goEnv()
+	if err != nil {
+		return err
+	}
+	inv := gocommand.Invocation{
+		BuildFlags: r.env.BuildFlags,
+		ModFlag:    r.env.ModFlag,
+		ModFile:    r.env.ModFile,
+		Env:        r.env.env(),
+		Logf:       r.env.Logf,
+		WorkingDir: r.env.WorkingDir,
+	}
+	mainMod, vendorEnabled, err := gocommand.VendorEnabled(context.TODO(), inv, r.env.GocmdRunner)
+	if err != nil {
+		return err
+	}
+
+	if mainMod != nil && vendorEnabled {
+		// Vendor mode is on, so all the non-Main modules are irrelevant,
+		// and we need to search /vendor for everything.
+		r.main = mainMod
+		r.dummyVendorMod = &gocommand.ModuleJSON{
+			Path: "",
+			Dir:  filepath.Join(mainMod.Dir, "vendor"),
+		}
+		r.modsByModPath = []*gocommand.ModuleJSON{mainMod, r.dummyVendorMod}
+		r.modsByDir = []*gocommand.ModuleJSON{mainMod, r.dummyVendorMod}
+	} else {
+		// Vendor mode is off, so run go list -m ... to find everything.
+		err := r.initAllMods()
+		// We expect an error when running outside of a module with
+		// GO111MODULE=on. Other errors are fatal.
+		if err != nil && !strings.Contains(err.Error(), "working directory is not part of a module") {
+			return err
+		}
+	}
+
+	if gmc := r.env.Env["GOMODCACHE"]; gmc != "" {
+		r.moduleCacheDir = gmc
+	} else {
+		gopaths := filepath.SplitList(goenv["GOPATH"])
+		if len(gopaths) == 0 {
+			return fmt.Errorf("empty GOPATH")
+		}
+		r.moduleCacheDir = filepath.Join(gopaths[0], "/pkg/mod")
+	}
+
+	sort.Slice(r.modsByModPath, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.modsByModPath[x].Path, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+	sort.Slice(r.modsByDir, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.modsByDir[x].Dir, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+
+	r.roots = []gopathwalk.Root{
+		{filepath.Join(goenv["GOROOT"], "/src"), gopathwalk.RootGOROOT},
+	}
+	if r.main != nil {
+		r.roots = append(r.roots, gopathwalk.Root{r.main.Dir, gopathwalk.RootCurrentModule})
+	}
+	if vendorEnabled {
+		r.roots = append(r.roots, gopathwalk.Root{r.dummyVendorMod.Dir, gopathwalk.RootOther})
+	} else {
+		addDep := func(mod *gocommand.ModuleJSON) {
+			if mod.Replace == nil {
+				// This is redundant with the cache, but we'll skip it cheaply enough.
+				r.roots = append(r.roots, gopathwalk.Root{mod.Dir, gopathwalk.RootModuleCache})
+			} else {
+				r.roots = append(r.roots, gopathwalk.Root{mod.Dir, gopathwalk.RootOther})
+			}
+		}
+		// Walk dependent modules before scanning the full mod cache, direct deps first.
+		for _, mod := range r.modsByModPath {
+			if !mod.Indirect && !mod.Main {
+				addDep(mod)
+			}
+		}
+		for _, mod := range r.modsByModPath {
+			if mod.Indirect && !mod.Main {
+				addDep(mod)
+			}
+		}
+		r.roots = append(r.roots, gopathwalk.Root{r.moduleCacheDir, gopathwalk.RootModuleCache})
+	}
+
+	r.scannedRoots = map[gopathwalk.Root]bool{}
+	if r.moduleCacheCache == nil {
+		r.moduleCacheCache = &dirInfoCache{
+			dirs:      map[string]*directoryPackageInfo{},
+			listeners: map[*int]cacheListener{},
+		}
+	}
+	if r.otherCache == nil {
+		r.otherCache = &dirInfoCache{
+			dirs:      map[string]*directoryPackageInfo{},
+			listeners: map[*int]cacheListener{},
+		}
+	}
+	r.initialized = true
+	return nil
+}
+
+func (r *ModuleResolver) initAllMods() error {
+	stdout, err := r.env.invokeGo(context.TODO(), "list", "-m", "-e", "-json", "...")
+	if err != nil {
+		return err
+	}
+	for dec := json.NewDecoder(stdout); dec.More(); {
+		mod := &gocommand.ModuleJSON{}
+		if err := dec.Decode(mod); err != nil {
+			return err
+		}
+		if mod.Dir == "" {
+			if r.env.Logf != nil {
+				r.env.Logf("module %v has not been downloaded and will be ignored", mod.Path)
+			}
+			// Can't do anything with a module that's not downloaded.
+			continue
+		}
+		// golang/go#36193: the go command doesn't always clean paths.
+		mod.Dir = filepath.Clean(mod.Dir)
+		r.modsByModPath = append(r.modsByModPath, mod)
+		r.modsByDir = append(r.modsByDir, mod)
+		if mod.Main {
+			r.main = mod
+		}
+	}
+	return nil
+}
+
+func (r *ModuleResolver) ClearForNewScan() {
+	<-r.scanSema
+	r.scannedRoots = map[gopathwalk.Root]bool{}
+	r.otherCache = &dirInfoCache{
+		dirs:      map[string]*directoryPackageInfo{},
+		listeners: map[*int]cacheListener{},
+	}
+	r.scanSema <- struct{}{}
+}
+
+func (r *ModuleResolver) ClearForNewMod() {
+	<-r.scanSema
+	*r = ModuleResolver{
+		env:              r.env,
+		moduleCacheCache: r.moduleCacheCache,
+		otherCache:       r.otherCache,
+		scanSema:         r.scanSema,
+	}
+	r.init()
+	r.scanSema <- struct{}{}
+}
+
+// findPackage returns the module and directory that contains the package at
+// the given import path, or returns nil, "" if no module is in scope.
+func (r *ModuleResolver) findPackage(importPath string) (*gocommand.ModuleJSON, string) {
+	// This can't find packages in the stdlib, but that's harmless for all
+	// the existing code paths.
+	for _, m := range r.modsByModPath {
+		if !strings.HasPrefix(importPath, m.Path) {
+			continue
+		}
+		pathInModule := importPath[len(m.Path):]
+		pkgDir := filepath.Join(m.Dir, pathInModule)
+		if r.dirIsNestedModule(pkgDir, m) {
+			continue
+		}
+
+		if info, ok := r.cacheLoad(pkgDir); ok {
+			if loaded, err := info.reachedStatus(nameLoaded); loaded {
+				if err != nil {
+					continue // No package in this dir.
+				}
+				return m, pkgDir
+			}
+			if scanned, err := info.reachedStatus(directoryScanned); scanned && err != nil {
+				continue // Dir is unreadable, etc.
+			}
+			// This is slightly wrong: a directory doesn't have to have an
+			// importable package to count as a package for package-to-module
+			// resolution. package main or _test files should count but
+			// don't.
+			// TODO(heschi): fix this.
+			if _, err := r.cachePackageName(info); err == nil {
+				return m, pkgDir
+			}
+		}
+
+		// Not cached. Read the filesystem.
+		pkgFiles, err := ioutil.ReadDir(pkgDir)
+		if err != nil {
+			continue
+		}
+		// A module only contains a package if it has buildable go
+		// files in that directory. If not, it could be provided by an
+		// outer module. See #29736.
+		for _, fi := range pkgFiles {
+			if ok, _ := r.env.matchFile(pkgDir, fi.Name()); ok {
+				return m, pkgDir
+			}
+		}
+	}
+	return nil, ""
+}
+
+func (r *ModuleResolver) cacheLoad(dir string) (directoryPackageInfo, bool) {
+	if info, ok := r.moduleCacheCache.Load(dir); ok {
+		return info, ok
+	}
+	return r.otherCache.Load(dir)
+}
+
+func (r *ModuleResolver) cacheStore(info directoryPackageInfo) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		r.moduleCacheCache.Store(info.dir, info)
+	} else {
+		r.otherCache.Store(info.dir, info)
+	}
+}
+
+func (r *ModuleResolver) cacheKeys() []string {
+	return append(r.moduleCacheCache.Keys(), r.otherCache.Keys()...)
+}
+
+// cachePackageName caches the package name for a dir already in the cache.
+func (r *ModuleResolver) cachePackageName(info directoryPackageInfo) (string, error) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		return r.moduleCacheCache.CachePackageName(info)
+	}
+	return r.otherCache.CachePackageName(info)
+}
+
+func (r *ModuleResolver) cacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		return r.moduleCacheCache.CacheExports(ctx, env, info)
+	}
+	return r.otherCache.CacheExports(ctx, env, info)
+}
+
+// findModuleByDir returns the module that contains dir, or nil if no such
+// module is in scope.
+func (r *ModuleResolver) findModuleByDir(dir string) *gocommand.ModuleJSON {
+	// This is quite tricky and may not be correct. dir could be:
+	// - a package in the main module.
+	// - a replace target underneath the main module's directory.
+	//    - a nested module in the above.
+	// - a replace target somewhere totally random.
+	//    - a nested module in the above.
+	// - in the mod cache.
+	// - in /vendor/ in -mod=vendor mode.
+	//    - nested module? Dunno.
+	// Rumor has it that replace targets cannot contain other replace targets.
+	for _, m := range r.modsByDir {
+		if !strings.HasPrefix(dir, m.Dir) {
+			continue
+		}
+
+		if r.dirIsNestedModule(dir, m) {
+			continue
+		}
+
+		return m
+	}
+	return nil
+}
+
+// dirIsNestedModule reports if dir is contained in a nested module underneath
+// mod, not actually in mod.
+func (r *ModuleResolver) dirIsNestedModule(dir string, mod *gocommand.ModuleJSON) bool {
+	if !strings.HasPrefix(dir, mod.Dir) {
+		return false
+	}
+	if r.dirInModuleCache(dir) {
+		// Nested modules in the module cache are pruned,
+		// so it cannot be a nested module.
+		return false
+	}
+	if mod != nil && mod == r.dummyVendorMod {
+		// The /vendor pseudomodule is flattened and doesn't actually count.
+		return false
+	}
+	modDir, _ := r.modInfo(dir)
+	if modDir == "" {
+		return false
+	}
+	return modDir != mod.Dir
+}
+
+func (r *ModuleResolver) modInfo(dir string) (modDir string, modName string) {
+	readModName := func(modFile string) string {
+		modBytes, err := ioutil.ReadFile(modFile)
+		if err != nil {
+			return ""
+		}
+		return modulePath(modBytes)
+	}
+
+	if r.dirInModuleCache(dir) {
+		if matches := modCacheRegexp.FindStringSubmatch(dir); len(matches) == 3 {
+			index := strings.Index(dir, matches[1]+"@"+matches[2])
+			modDir := filepath.Join(dir[:index], matches[1]+"@"+matches[2])
+			return modDir, readModName(filepath.Join(modDir, "go.mod"))
+		}
+	}
+	for {
+		if info, ok := r.cacheLoad(dir); ok {
+			return info.moduleDir, info.moduleName
+		}
+		f := filepath.Join(dir, "go.mod")
+		info, err := os.Stat(f)
+		if err == nil && !info.IsDir() {
+			return dir, readModName(f)
+		}
+
+		d := filepath.Dir(dir)
+		if len(d) >= len(dir) {
+			return "", "" // reached top of file system, no go.mod
+		}
+		dir = d
+	}
+}
+
+func (r *ModuleResolver) dirInModuleCache(dir string) bool {
+	if r.moduleCacheDir == "" {
+		return false
+	}
+	return strings.HasPrefix(dir, r.moduleCacheDir)
+}
+
+func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
+	if err := r.init(); err != nil {
+		return nil, err
+	}
+	names := map[string]string{}
+	for _, path := range importPaths {
+		_, packageDir := r.findPackage(path)
+		if packageDir == "" {
+			continue
+		}
+		name, err := packageDirToName(packageDir)
+		if err != nil {
+			continue
+		}
+		names[path] = name
+	}
+	return names, nil
+}
+
+func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error {
+	if err := r.init(); err != nil {
+		return err
+	}
+
+	processDir := func(info directoryPackageInfo) {
+		// Skip this directory if we were not able to get the package information successfully.
+		if scanned, err := info.reachedStatus(directoryScanned); !scanned || err != nil {
+			return
+		}
+		pkg, err := r.canonicalize(info)
+		if err != nil {
+			return
+		}
+
+		if !callback.dirFound(pkg) {
+			return
+		}
+		pkg.packageName, err = r.cachePackageName(info)
+		if err != nil {
+			return
+		}
+
+		if !callback.packageNameLoaded(pkg) {
+			return
+		}
+		_, exports, err := r.loadExports(ctx, pkg, false)
+		if err != nil {
+			return
+		}
+		callback.exportsLoaded(pkg, exports)
+	}
+
+	// Start processing everything in the cache, and listen for the new stuff
+	// we discover in the walk below.
+	stop1 := r.moduleCacheCache.ScanAndListen(ctx, processDir)
+	defer stop1()
+	stop2 := r.otherCache.ScanAndListen(ctx, processDir)
+	defer stop2()
+
+	// We assume cached directories are fully cached, including all their
+	// children, and have not changed. We can skip them.
+	skip := func(root gopathwalk.Root, dir string) bool {
+		info, ok := r.cacheLoad(dir)
+		if !ok {
+			return false
+		}
+		// This directory can be skipped as long as we have already scanned it.
+		// Packages with errors will continue to have errors, so there is no need
+		// to rescan them.
+		packageScanned, _ := info.reachedStatus(directoryScanned)
+		return packageScanned
+	}
+
+	// Add anything new to the cache, and process it if we're still listening.
+	add := func(root gopathwalk.Root, dir string) {
+		r.cacheStore(r.scanDirForPackage(root, dir))
+	}
+
+	// r.roots and the callback are not necessarily safe to use in the
+	// goroutine below. Process them eagerly.
+	roots := filterRoots(r.roots, callback.rootFound)
+	// We can't cancel walks, because we need them to finish to have a usable
+	// cache. Instead, run them in a separate goroutine and detach.
+	scanDone := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			return
+		case <-r.scanSema:
+		}
+		defer func() { r.scanSema <- struct{}{} }()
+		// We have the lock on r.scannedRoots, and no other scans can run.
+		for _, root := range roots {
+			if ctx.Err() != nil {
+				return
+			}
+
+			if r.scannedRoots[root] {
+				continue
+			}
+			gopathwalk.WalkSkip([]gopathwalk.Root{root}, add, skip, gopathwalk.Options{Logf: r.env.Logf, ModulesEnabled: true})
+			r.scannedRoots[root] = true
+		}
+		close(scanDone)
+	}()
+	select {
+	case <-ctx.Done():
+	case <-scanDone:
+	}
+	return nil
+}
+
+func (r *ModuleResolver) scoreImportPath(ctx context.Context, path string) float64 {
+	if _, ok := stdlib[path]; ok {
+		return MaxRelevance
+	}
+	mod, _ := r.findPackage(path)
+	return modRelevance(mod)
+}
+
+func modRelevance(mod *gocommand.ModuleJSON) float64 {
+	var relevance float64
+	switch {
+	case mod == nil: // out of scope
+		return MaxRelevance - 4
+	case mod.Indirect:
+		relevance = MaxRelevance - 3
+	case !mod.Main:
+		relevance = MaxRelevance - 2
+	default:
+		relevance = MaxRelevance - 1 // main module ties with stdlib
+	}
+
+	_, versionString, ok := module.SplitPathVersion(mod.Path)
+	if ok {
+		index := strings.Index(versionString, "v")
+		if index == -1 {
+			return relevance
+		}
+		if versionNumber, err := strconv.ParseFloat(versionString[index+1:], 64); err == nil {
+			relevance += versionNumber / 1000
+		}
+	}
+
+	return relevance
+}
+
+// canonicalize gets the result of canonicalizing the packages using the results
+// of initializing the resolver from 'go list -m'.
+func (r *ModuleResolver) canonicalize(info directoryPackageInfo) (*pkg, error) {
+	// Packages in GOROOT are already canonical, regardless of the std/cmd modules.
+	if info.rootType == gopathwalk.RootGOROOT {
+		return &pkg{
+			importPathShort: info.nonCanonicalImportPath,
+			dir:             info.dir,
+			packageName:     path.Base(info.nonCanonicalImportPath),
+			relevance:       MaxRelevance,
+		}, nil
+	}
+
+	importPath := info.nonCanonicalImportPath
+	mod := r.findModuleByDir(info.dir)
+	// Check if the directory is underneath a module that's in scope.
+	if mod != nil {
+		// It is. If dir is the target of a replace directive,
+		// our guessed import path is wrong. Use the real one.
+		if mod.Dir == info.dir {
+			importPath = mod.Path
+		} else {
+			dirInMod := info.dir[len(mod.Dir)+len("/"):]
+			importPath = path.Join(mod.Path, filepath.ToSlash(dirInMod))
+		}
+	} else if !strings.HasPrefix(importPath, info.moduleName) {
+		// The module's name doesn't match the package's import path. It
+		// probably needs a replace directive we don't have.
+		return nil, fmt.Errorf("package in %q is not valid without a replace statement", info.dir)
+	}
+
+	res := &pkg{
+		importPathShort: importPath,
+		dir:             info.dir,
+		relevance:       modRelevance(mod),
+	}
+	// We may have discovered a package that has a different version
+	// in scope already. Canonicalize to that one if possible.
+	if _, canonicalDir := r.findPackage(importPath); canonicalDir != "" {
+		res.dir = canonicalDir
+	}
+	return res, nil
+}
+
+func (r *ModuleResolver) loadExports(ctx context.Context, pkg *pkg, includeTest bool) (string, []string, error) {
+	if err := r.init(); err != nil {
+		return "", nil, err
+	}
+	if info, ok := r.cacheLoad(pkg.dir); ok && !includeTest {
+		return r.cacheExports(ctx, r.env, info)
+	}
+	return loadExportsFromFiles(ctx, r.env, pkg.dir, includeTest)
+}
+
+func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) directoryPackageInfo {
+	subdir := ""
+	if dir != root.Path {
+		subdir = dir[len(root.Path)+len("/"):]
+	}
+	importPath := filepath.ToSlash(subdir)
+	if strings.HasPrefix(importPath, "vendor/") {
+		// Only enter vendor directories if they're explicitly requested as a root.
+		return directoryPackageInfo{
+			status: directoryScanned,
+			err:    fmt.Errorf("unwanted vendor directory"),
+		}
+	}
+	switch root.Type {
+	case gopathwalk.RootCurrentModule:
+		importPath = path.Join(r.main.Path, filepath.ToSlash(subdir))
+	case gopathwalk.RootModuleCache:
+		matches := modCacheRegexp.FindStringSubmatch(subdir)
+		if len(matches) == 0 {
+			return directoryPackageInfo{
+				status: directoryScanned,
+				err:    fmt.Errorf("invalid module cache path: %v", subdir),
+			}
+		}
+		modPath, err := module.UnescapePath(filepath.ToSlash(matches[1]))
+		if err != nil {
+			if r.env.Logf != nil {
+				r.env.Logf("decoding module cache path %q: %v", subdir, err)
+			}
+			return directoryPackageInfo{
+				status: directoryScanned,
+				err:    fmt.Errorf("decoding module cache path %q: %v", subdir, err),
+			}
+		}
+		importPath = path.Join(modPath, filepath.ToSlash(matches[3]))
+	}
+
+	modDir, modName := r.modInfo(dir)
+	result := directoryPackageInfo{
+		status:                 directoryScanned,
+		dir:                    dir,
+		rootType:               root.Type,
+		nonCanonicalImportPath: importPath,
+		moduleDir:              modDir,
+		moduleName:             modName,
+	}
+	if root.Type == gopathwalk.RootGOROOT {
+		// stdlib packages are always in scope, despite the confusing go.mod
+		return result
+	}
+	return result
+}
+
+// modCacheRegexp splits a path in a module cache into module, module version, and package.
+var modCacheRegexp = regexp.MustCompile(`(.*)@([^/\\]*)(.*)`)
+
+var (
+	slashSlash = []byte("//")
+	moduleStr  = []byte("module")
+)
+
+// modulePath returns the module path from the gomod file text.
+// If it cannot find a module path, it returns an empty string.
+// It is tolerant of unrelated problems in the go.mod file.
+//
+// Copied from cmd/go/internal/modfile.
+func modulePath(mod []byte) string {
+	for len(mod) > 0 {
+		line := mod
+		mod = nil
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, mod = line[:i], line[i+1:]
+		}
+		if i := bytes.Index(line, slashSlash); i >= 0 {
+			line = line[:i]
+		}
+		line = bytes.TrimSpace(line)
+		if !bytes.HasPrefix(line, moduleStr) {
+			continue
+		}
+		line = line[len(moduleStr):]
+		n := len(line)
+		line = bytes.TrimSpace(line)
+		if len(line) == n || len(line) == 0 {
+			continue
+		}
+
+		if line[0] == '"' || line[0] == '`' {
+			p, err := strconv.Unquote(string(line))
+			if err != nil {
+				return "" // malformed quoted string or multiline module path
+			}
+			return p
+		}
+
+		return string(line)
+	}
+	return "" // missing module path
+}

vendor/golang.org/x/tools/internal/imports/mod_cache.go

@@ -0,0 +1,236 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package imports
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"golang.org/x/tools/internal/gopathwalk"
+)
+
+// To find packages to import, the resolver needs to know about all of the
+// the packages that could be imported. This includes packages that are
+// already in modules that are in (1) the current module, (2) replace targets,
+// and (3) packages in the module cache. Packages in (1) and (2) may change over
+// time, as the client may edit the current module and locally replaced modules.
+// The module cache (which includes all of the packages in (3)) can only
+// ever be added to.
+//
+// The resolver can thus save state about packages in the module cache
+// and guarantee that this will not change over time. To obtain information
+// about new modules added to the module cache, the module cache should be
+// rescanned.
+//
+// It is OK to serve information about modules that have been deleted,
+// as they do still exist.
+// TODO(suzmue): can we share information with the caller about
+// what module needs to be downloaded to import this package?
+
+type directoryPackageStatus int
+
+const (
+	_ directoryPackageStatus = iota
+	directoryScanned
+	nameLoaded
+	exportsLoaded
+)
+
+type directoryPackageInfo struct {
+	// status indicates the extent to which this struct has been filled in.
+	status directoryPackageStatus
+	// err is non-nil when there was an error trying to reach status.
+	err error
+
+	// Set when status >= directoryScanned.
+
+	// dir is the absolute directory of this package.
+	dir      string
+	rootType gopathwalk.RootType
+	// nonCanonicalImportPath is the package's expected import path. It may
+	// not actually be importable at that path.
+	nonCanonicalImportPath string
+
+	// Module-related information.
+	moduleDir  string // The directory that is the module root of this dir.
+	moduleName string // The module name that contains this dir.
+
+	// Set when status >= nameLoaded.
+
+	packageName string // the package name, as declared in the source.
+
+	// Set when status >= exportsLoaded.
+
+	exports []string
+}
+
+// reachedStatus returns true when info has a status at least target and any error associated with
+// an attempt to reach target.
+func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (bool, error) {
+	if info.err == nil {
+		return info.status >= target, nil
+	}
+	if info.status == target {
+		return true, info.err
+	}
+	return true, nil
+}
+
+// dirInfoCache is a concurrency safe map for storing information about
+// directories that may contain packages.
+//
+// The information in this cache is built incrementally. Entries are initialized in scan.
+// No new keys should be added in any other functions, as all directories containing
+// packages are identified in scan.
+//
+// Other functions, including loadExports and findPackage, may update entries in this cache
+// as they discover new things about the directory.
+//
+// The information in the cache is not expected to change for the cache's
+// lifetime, so there is no protection against competing writes. Users should
+// take care not to hold the cache across changes to the underlying files.
+//
+// TODO(suzmue): consider other concurrency strategies and data structures (RWLocks, sync.Map, etc)
+type dirInfoCache struct {
+	mu sync.Mutex
+	// dirs stores information about packages in directories, keyed by absolute path.
+	dirs      map[string]*directoryPackageInfo
+	listeners map[*int]cacheListener
+}
+
+type cacheListener func(directoryPackageInfo)
+
+// ScanAndListen calls listener on all the items in the cache, and on anything
+// newly added. The returned stop function waits for all in-flight callbacks to
+// finish and blocks new ones.
+func (d *dirInfoCache) ScanAndListen(ctx context.Context, listener cacheListener) func() {
+	ctx, cancel := context.WithCancel(ctx)
+
+	// Flushing out all the callbacks is tricky without knowing how many there
+	// are going to be. Setting an arbitrary limit makes it much easier.
+	const maxInFlight = 10
+	sema := make(chan struct{}, maxInFlight)
+	for i := 0; i < maxInFlight; i++ {
+		sema <- struct{}{}
+	}
+
+	cookie := new(int) // A unique ID we can use for the listener.
+
+	// We can't hold mu while calling the listener.
+	d.mu.Lock()
+	var keys []string
+	for key := range d.dirs {
+		keys = append(keys, key)
+	}
+	d.listeners[cookie] = func(info directoryPackageInfo) {
+		select {
+		case <-ctx.Done():
+			return
+		case <-sema:
+		}
+		listener(info)
+		sema <- struct{}{}
+	}
+	d.mu.Unlock()
+
+	stop := func() {
+		cancel()
+		d.mu.Lock()
+		delete(d.listeners, cookie)
+		d.mu.Unlock()
+		for i := 0; i < maxInFlight; i++ {
+			<-sema
+		}
+	}
+
+	// Process the pre-existing keys.
+	for _, k := range keys {
+		select {
+		case <-ctx.Done():
+			return stop
+		default:
+		}
+		if v, ok := d.Load(k); ok {
+			listener(v)
+		}
+	}
+
+	return stop
+}
+
+// Store stores the package info for dir.
+func (d *dirInfoCache) Store(dir string, info directoryPackageInfo) {
+	d.mu.Lock()
+	_, old := d.dirs[dir]
+	d.dirs[dir] = &info
+	var listeners []cacheListener
+	for _, l := range d.listeners {
+		listeners = append(listeners, l)
+	}
+	d.mu.Unlock()
+
+	if !old {
+		for _, l := range listeners {
+			l(info)
+		}
+	}
+}
+
+// Load returns a copy of the directoryPackageInfo for absolute directory dir.
+func (d *dirInfoCache) Load(dir string) (directoryPackageInfo, bool) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	info, ok := d.dirs[dir]
+	if !ok {
+		return directoryPackageInfo{}, false
+	}
+	return *info, true
+}
+
+// Keys returns the keys currently present in d.
+func (d *dirInfoCache) Keys() (keys []string) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	for key := range d.dirs {
+		keys = append(keys, key)
+	}
+	return keys
+}
+
+func (d *dirInfoCache) CachePackageName(info directoryPackageInfo) (string, error) {
+	if loaded, err := info.reachedStatus(nameLoaded); loaded {
+		return info.packageName, err
+	}
+	if scanned, err := info.reachedStatus(directoryScanned); !scanned || err != nil {
+		return "", fmt.Errorf("cannot read package name, scan error: %v", err)
+	}
+	info.packageName, info.err = packageDirToName(info.dir)
+	info.status = nameLoaded
+	d.Store(info.dir, info)
+	return info.packageName, info.err
+}
+
+func (d *dirInfoCache) CacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+	if reached, _ := info.reachedStatus(exportsLoaded); reached {
+		return info.packageName, info.exports, info.err
+	}
+	if reached, err := info.reachedStatus(nameLoaded); reached && err != nil {
+		return "", nil, err
+	}
+	info.packageName, info.exports, info.err = loadExportsFromFiles(ctx, env, info.dir, false)
+	if info.err == context.Canceled || info.err == context.DeadlineExceeded {
+		return info.packageName, info.exports, info.err
+	}
+	// The cache structure wants things to proceed linearly. We can skip a
+	// step here, but only if we succeed.
+	if info.status == nameLoaded || info.err == nil {
+		info.status = exportsLoaded
+	} else {
+		info.status = nameLoaded
+	}
+	d.Store(info.dir, info)
+	return info.packageName, info.exports, info.err
+}

vendor/golang.org/x/tools/internal/imports/sortimports.go

@@ -0,0 +1,280 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Hacked up copy of go/ast/import.go
+
+package imports
+
+import (
+	"go/ast"
+	"go/token"
+	"sort"
+	"strconv"
+)
+
+// sortImports sorts runs of consecutive import lines in import blocks in f.
+// It also removes duplicate imports when it is possible to do so without data loss.
+func sortImports(localPrefix string, fset *token.FileSet, f *ast.File) {
+	for i, d := range f.Decls {
+		d, ok := d.(*ast.GenDecl)
+		if !ok || d.Tok != token.IMPORT {
+			// Not an import declaration, so we're done.
+			// Imports are always first.
+			break
+		}
+
+		if len(d.Specs) == 0 {
+			// Empty import block, remove it.
+			f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		}
+
+		if !d.Lparen.IsValid() {
+			// Not a block: sorted by default.
+			continue
+		}
+
+		// Identify and sort runs of specs on successive lines.
+		i := 0
+		specs := d.Specs[:0]
+		for j, s := range d.Specs {
+			if j > i && fset.Position(s.Pos()).Line > 1+fset.Position(d.Specs[j-1].End()).Line {
+				// j begins a new run.  End this one.
+				specs = append(specs, sortSpecs(localPrefix, fset, f, d.Specs[i:j])...)
+				i = j
+			}
+		}
+		specs = append(specs, sortSpecs(localPrefix, fset, f, d.Specs[i:])...)
+		d.Specs = specs
+
+		// Deduping can leave a blank line before the rparen; clean that up.
+		if len(d.Specs) > 0 {
+			lastSpec := d.Specs[len(d.Specs)-1]
+			lastLine := fset.Position(lastSpec.Pos()).Line
+			if rParenLine := fset.Position(d.Rparen).Line; rParenLine > lastLine+1 {
+				fset.File(d.Rparen).MergeLine(rParenLine - 1)
+			}
+		}
+	}
+}
+
+// mergeImports merges all the import declarations into the first one.
+// Taken from golang.org/x/tools/ast/astutil.
+func mergeImports(fset *token.FileSet, f *ast.File) {
+	if len(f.Decls) <= 1 {
+		return
+	}
+
+	// Merge all the import declarations into the first one.
+	var first *ast.GenDecl
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
+			continue
+		}
+		if first == nil {
+			first = gen
+			continue // Don't touch the first one.
+		}
+		// We now know there is more than one package in this import
+		// declaration. Ensure that it ends up parenthesized.
+		first.Lparen = first.Pos()
+		// Move the imports of the other import declaration to the first one.
+		for _, spec := range gen.Specs {
+			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
+			first.Specs = append(first.Specs, spec)
+		}
+		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		i--
+	}
+}
+
+// declImports reports whether gen contains an import of path.
+// Taken from golang.org/x/tools/ast/astutil.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+func importPath(s ast.Spec) string {
+	t, err := strconv.Unquote(s.(*ast.ImportSpec).Path.Value)
+	if err == nil {
+		return t
+	}
+	return ""
+}
+
+func importName(s ast.Spec) string {
+	n := s.(*ast.ImportSpec).Name
+	if n == nil {
+		return ""
+	}
+	return n.Name
+}
+
+func importComment(s ast.Spec) string {
+	c := s.(*ast.ImportSpec).Comment
+	if c == nil {
+		return ""
+	}
+	return c.Text()
+}
+
+// collapse indicates whether prev may be removed, leaving only next.
+func collapse(prev, next ast.Spec) bool {
+	if importPath(next) != importPath(prev) || importName(next) != importName(prev) {
+		return false
+	}
+	return prev.(*ast.ImportSpec).Comment == nil
+}
+
+type posSpan struct {
+	Start token.Pos
+	End   token.Pos
+}
+
+func sortSpecs(localPrefix string, fset *token.FileSet, f *ast.File, specs []ast.Spec) []ast.Spec {
+	// Can't short-circuit here even if specs are already sorted,
+	// since they might yet need deduplication.
+	// A lone import, however, may be safely ignored.
+	if len(specs) <= 1 {
+		return specs
+	}
+
+	// Record positions for specs.
+	pos := make([]posSpan, len(specs))
+	for i, s := range specs {
+		pos[i] = posSpan{s.Pos(), s.End()}
+	}
+
+	// Identify comments in this range.
+	// Any comment from pos[0].Start to the final line counts.
+	lastLine := fset.Position(pos[len(pos)-1].End).Line
+	cstart := len(f.Comments)
+	cend := len(f.Comments)
+	for i, g := range f.Comments {
+		if g.Pos() < pos[0].Start {
+			continue
+		}
+		if i < cstart {
+			cstart = i
+		}
+		if fset.Position(g.End()).Line > lastLine {
+			cend = i
+			break
+		}
+	}
+	comments := f.Comments[cstart:cend]
+
+	// Assign each comment to the import spec preceding it.
+	importComment := map[*ast.ImportSpec][]*ast.CommentGroup{}
+	specIndex := 0
+	for _, g := range comments {
+		for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() {
+			specIndex++
+		}
+		s := specs[specIndex].(*ast.ImportSpec)
+		importComment[s] = append(importComment[s], g)
+	}
+
+	// Sort the import specs by import path.
+	// Remove duplicates, when possible without data loss.
+	// Reassign the import paths to have the same position sequence.
+	// Reassign each comment to abut the end of its spec.
+	// Sort the comments by new position.
+	sort.Sort(byImportSpec{localPrefix, specs})
+
+	// Dedup. Thanks to our sorting, we can just consider
+	// adjacent pairs of imports.
+	deduped := specs[:0]
+	for i, s := range specs {
+		if i == len(specs)-1 || !collapse(s, specs[i+1]) {
+			deduped = append(deduped, s)
+		} else {
+			p := s.Pos()
+			fset.File(p).MergeLine(fset.Position(p).Line)
+		}
+	}
+	specs = deduped
+
+	// Fix up comment positions
+	for i, s := range specs {
+		s := s.(*ast.ImportSpec)
+		if s.Name != nil {
+			s.Name.NamePos = pos[i].Start
+		}
+		s.Path.ValuePos = pos[i].Start
+		s.EndPos = pos[i].End
+		nextSpecPos := pos[i].End
+
+		for _, g := range importComment[s] {
+			for _, c := range g.List {
+				c.Slash = pos[i].End
+				nextSpecPos = c.End()
+			}
+		}
+		if i < len(specs)-1 {
+			pos[i+1].Start = nextSpecPos
+			pos[i+1].End = nextSpecPos
+		}
+	}
+
+	sort.Sort(byCommentPos(comments))
+
+	// Fixup comments can insert blank lines, because import specs are on different lines.
+	// We remove those blank lines here by merging import spec to the first import spec line.
+	firstSpecLine := fset.Position(specs[0].Pos()).Line
+	for _, s := range specs[1:] {
+		p := s.Pos()
+		line := fset.File(p).Line(p)
+		for previousLine := line - 1; previousLine >= firstSpecLine; {
+			fset.File(p).MergeLine(previousLine)
+			previousLine--
+		}
+	}
+	return specs
+}
+
+type byImportSpec struct {
+	localPrefix string
+	specs       []ast.Spec // slice of *ast.ImportSpec
+}
+
+func (x byImportSpec) Len() int      { return len(x.specs) }
+func (x byImportSpec) Swap(i, j int) { x.specs[i], x.specs[j] = x.specs[j], x.specs[i] }
+func (x byImportSpec) Less(i, j int) bool {
+	ipath := importPath(x.specs[i])
+	jpath := importPath(x.specs[j])
+
+	igroup := importGroup(x.localPrefix, ipath)
+	jgroup := importGroup(x.localPrefix, jpath)
+	if igroup != jgroup {
+		return igroup < jgroup
+	}
+
+	if ipath != jpath {
+		return ipath < jpath
+	}
+	iname := importName(x.specs[i])
+	jname := importName(x.specs[j])
+
+	if iname != jname {
+		return iname < jname
+	}
+	return importComment(x.specs[i]) < importComment(x.specs[j])
+}
+
+type byCommentPos []*ast.CommentGroup
+
+func (x byCommentPos) Len() int           { return len(x) }
+func (x byCommentPos) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x byCommentPos) Less(i, j int) bool { return x[i].Pos() < x[j].Pos() }

vendor/golang.org/x/tools/internal/packagesinternal/packages.go

@@ -0,0 +1,21 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package packagesinternal exposes internal-only fields from go/packages.
+package packagesinternal
+
+import (
+	"golang.org/x/tools/internal/gocommand"
+)
+
+var GetForTest = func(p interface{}) string { return "" }
+
+var GetGoCmdRunner = func(config interface{}) *gocommand.Runner { return nil }
+
+var SetGoCmdRunner = func(config interface{}, runner *gocommand.Runner) {}
+
+var TypecheckCgo int
+
+var SetModFlag = func(config interface{}, value string) {}
+var SetModFile = func(config interface{}, value string) {}

vendor/golang.org/x/tools/internal/typesinternal/errorcode_string.go

@@ -0,0 +1,152 @@
+// Code generated by "stringer -type=ErrorCode"; DO NOT EDIT.
+
+package typesinternal
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Test-1]
+	_ = x[BlankPkgName-2]
+	_ = x[MismatchedPkgName-3]
+	_ = x[InvalidPkgUse-4]
+	_ = x[BadImportPath-5]
+	_ = x[BrokenImport-6]
+	_ = x[ImportCRenamed-7]
+	_ = x[UnusedImport-8]
+	_ = x[InvalidInitCycle-9]
+	_ = x[DuplicateDecl-10]
+	_ = x[InvalidDeclCycle-11]
+	_ = x[InvalidTypeCycle-12]
+	_ = x[InvalidConstInit-13]
+	_ = x[InvalidConstVal-14]
+	_ = x[InvalidConstType-15]
+	_ = x[UntypedNil-16]
+	_ = x[WrongAssignCount-17]
+	_ = x[UnassignableOperand-18]
+	_ = x[NoNewVar-19]
+	_ = x[MultiValAssignOp-20]
+	_ = x[InvalidIfaceAssign-21]
+	_ = x[InvalidChanAssign-22]
+	_ = x[IncompatibleAssign-23]
+	_ = x[UnaddressableFieldAssign-24]
+	_ = x[NotAType-25]
+	_ = x[InvalidArrayLen-26]
+	_ = x[BlankIfaceMethod-27]
+	_ = x[IncomparableMapKey-28]
+	_ = x[InvalidIfaceEmbed-29]
+	_ = x[InvalidPtrEmbed-30]
+	_ = x[BadRecv-31]
+	_ = x[InvalidRecv-32]
+	_ = x[DuplicateFieldAndMethod-33]
+	_ = x[DuplicateMethod-34]
+	_ = x[InvalidBlank-35]
+	_ = x[InvalidIota-36]
+	_ = x[MissingInitBody-37]
+	_ = x[InvalidInitSig-38]
+	_ = x[InvalidInitDecl-39]
+	_ = x[InvalidMainDecl-40]
+	_ = x[TooManyValues-41]
+	_ = x[NotAnExpr-42]
+	_ = x[TruncatedFloat-43]
+	_ = x[NumericOverflow-44]
+	_ = x[UndefinedOp-45]
+	_ = x[MismatchedTypes-46]
+	_ = x[DivByZero-47]
+	_ = x[NonNumericIncDec-48]
+	_ = x[UnaddressableOperand-49]
+	_ = x[InvalidIndirection-50]
+	_ = x[NonIndexableOperand-51]
+	_ = x[InvalidIndex-52]
+	_ = x[SwappedSliceIndices-53]
+	_ = x[NonSliceableOperand-54]
+	_ = x[InvalidSliceExpr-55]
+	_ = x[InvalidShiftCount-56]
+	_ = x[InvalidShiftOperand-57]
+	_ = x[InvalidReceive-58]
+	_ = x[InvalidSend-59]
+	_ = x[DuplicateLitKey-60]
+	_ = x[MissingLitKey-61]
+	_ = x[InvalidLitIndex-62]
+	_ = x[OversizeArrayLit-63]
+	_ = x[MixedStructLit-64]
+	_ = x[InvalidStructLit-65]
+	_ = x[MissingLitField-66]
+	_ = x[DuplicateLitField-67]
+	_ = x[UnexportedLitField-68]
+	_ = x[InvalidLitField-69]
+	_ = x[UntypedLit-70]
+	_ = x[InvalidLit-71]
+	_ = x[AmbiguousSelector-72]
+	_ = x[UndeclaredImportedName-73]
+	_ = x[UnexportedName-74]
+	_ = x[UndeclaredName-75]
+	_ = x[MissingFieldOrMethod-76]
+	_ = x[BadDotDotDotSyntax-77]
+	_ = x[NonVariadicDotDotDot-78]
+	_ = x[MisplacedDotDotDot-79]
+	_ = x[InvalidDotDotDotOperand-80]
+	_ = x[InvalidDotDotDot-81]
+	_ = x[UncalledBuiltin-82]
+	_ = x[InvalidAppend-83]
+	_ = x[InvalidCap-84]
+	_ = x[InvalidClose-85]
+	_ = x[InvalidCopy-86]
+	_ = x[InvalidComplex-87]
+	_ = x[InvalidDelete-88]
+	_ = x[InvalidImag-89]
+	_ = x[InvalidLen-90]
+	_ = x[SwappedMakeArgs-91]
+	_ = x[InvalidMake-92]
+	_ = x[InvalidReal-93]
+	_ = x[InvalidAssert-94]
+	_ = x[ImpossibleAssert-95]
+	_ = x[InvalidConversion-96]
+	_ = x[InvalidUntypedConversion-97]
+	_ = x[BadOffsetofSyntax-98]
+	_ = x[InvalidOffsetof-99]
+	_ = x[UnusedExpr-100]
+	_ = x[UnusedVar-101]
+	_ = x[MissingReturn-102]
+	_ = x[WrongResultCount-103]
+	_ = x[OutOfScopeResult-104]
+	_ = x[InvalidCond-105]
+	_ = x[InvalidPostDecl-106]
+	_ = x[InvalidChanRange-107]
+	_ = x[InvalidIterVar-108]
+	_ = x[InvalidRangeExpr-109]
+	_ = x[MisplacedBreak-110]
+	_ = x[MisplacedContinue-111]
+	_ = x[MisplacedFallthrough-112]
+	_ = x[DuplicateCase-113]
+	_ = x[DuplicateDefault-114]
+	_ = x[BadTypeKeyword-115]
+	_ = x[InvalidTypeSwitch-116]
+	_ = x[InvalidSelectCase-117]
+	_ = x[UndeclaredLabel-118]
+	_ = x[DuplicateLabel-119]
+	_ = x[MisplacedLabel-120]
+	_ = x[UnusedLabel-121]
+	_ = x[JumpOverDecl-122]
+	_ = x[JumpIntoBlock-123]
+	_ = x[InvalidMethodExpr-124]
+	_ = x[WrongArgCount-125]
+	_ = x[InvalidCall-126]
+	_ = x[UnusedResults-127]
+	_ = x[InvalidDefer-128]
+	_ = x[InvalidGo-129]
+}
+
+const _ErrorCode_name = "TestBlankPkgNameMismatchedPkgNameInvalidPkgUseBadImportPathBrokenImportImportCRenamedUnusedImportInvalidInitCycleDuplicateDeclInvalidDeclCycleInvalidTypeCycleInvalidConstInitInvalidConstValInvalidConstTypeUntypedNilWrongAssignCountUnassignableOperandNoNewVarMultiValAssignOpInvalidIfaceAssignInvalidChanAssignIncompatibleAssignUnaddressableFieldAssignNotATypeInvalidArrayLenBlankIfaceMethodIncomparableMapKeyInvalidIfaceEmbedInvalidPtrEmbedBadRecvInvalidRecvDuplicateFieldAndMethodDuplicateMethodInvalidBlankInvalidIotaMissingInitBodyInvalidInitSigInvalidInitDeclInvalidMainDeclTooManyValuesNotAnExprTruncatedFloatNumericOverflowUndefinedOpMismatchedTypesDivByZeroNonNumericIncDecUnaddressableOperandInvalidIndirectionNonIndexableOperandInvalidIndexSwappedSliceIndicesNonSliceableOperandInvalidSliceExprInvalidShiftCountInvalidShiftOperandInvalidReceiveInvalidSendDuplicateLitKeyMissingLitKeyInvalidLitIndexOversizeArrayLitMixedStructLitInvalidStructLitMissingLitFieldDuplicateLitFieldUnexportedLitFieldInvalidLitFieldUntypedLitInvalidLitAmbiguousSelectorUndeclaredImportedNameUnexportedNameUndeclaredNameMissingFieldOrMethodBadDotDotDotSyntaxNonVariadicDotDotDotMisplacedDotDotDotInvalidDotDotDotOperandInvalidDotDotDotUncalledBuiltinInvalidAppendInvalidCapInvalidCloseInvalidCopyInvalidComplexInvalidDeleteInvalidImagInvalidLenSwappedMakeArgsInvalidMakeInvalidRealInvalidAssertImpossibleAssertInvalidConversionInvalidUntypedConversionBadOffsetofSyntaxInvalidOffsetofUnusedExprUnusedVarMissingReturnWrongResultCountOutOfScopeResultInvalidCondInvalidPostDeclInvalidChanRangeInvalidIterVarInvalidRangeExprMisplacedBreakMisplacedContinueMisplacedFallthroughDuplicateCaseDuplicateDefaultBadTypeKeywordInvalidTypeSwitchInvalidSelectCaseUndeclaredLabelDuplicateLabelMisplacedLabelUnusedLabelJumpOverDeclJumpIntoBlockInvalidMethodExprWrongArgCountInvalidCallUnusedResultsInvalidDeferInvalidGo"
+
+var _ErrorCode_index = [...]uint16{0, 4, 16, 33, 46, 59, 71, 85, 97, 113, 126, 142, 158, 174, 189, 205, 215, 231, 250, 258, 274, 292, 309, 327, 351, 359, 374, 390, 408, 425, 440, 447, 458, 481, 496, 508, 519, 534, 548, 563, 578, 591, 600, 614, 629, 640, 655, 664, 680, 700, 718, 737, 749, 768, 787, 803, 820, 839, 853, 864, 879, 892, 907, 923, 937, 953, 968, 985, 1003, 1018, 1028, 1038, 1055, 1077, 1091, 1105, 1125, 1143, 1163, 1181, 1204, 1220, 1235, 1248, 1258, 1270, 1281, 1295, 1308, 1319, 1329, 1344, 1355, 1366, 1379, 1395, 1412, 1436, 1453, 1468, 1478, 1487, 1500, 1516, 1532, 1543, 1558, 1574, 1588, 1604, 1618, 1635, 1655, 1668, 1684, 1698, 1715, 1732, 1747, 1761, 1775, 1786, 1798, 1811, 1828, 1841, 1852, 1865, 1877, 1886}
+
+func (i ErrorCode) String() string {
+	i -= 1
+	if i < 0 || i >= ErrorCode(len(_ErrorCode_index)-1) {
+		return "ErrorCode(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _ErrorCode_name[_ErrorCode_index[i]:_ErrorCode_index[i+1]]
+}

vendor/golang.org/x/tools/internal/typesinternal/types.go

@@ -0,0 +1,45 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typesinternal provides access to internal go/types APIs that are not
+// yet exported.
+package typesinternal
+
+import (
+	"go/token"
+	"go/types"
+	"reflect"
+	"unsafe"
+)
+
+func SetUsesCgo(conf *types.Config) bool {
+	v := reflect.ValueOf(conf).Elem()
+
+	f := v.FieldByName("go115UsesCgo")
+	if !f.IsValid() {
+		f = v.FieldByName("UsesCgo")
+		if !f.IsValid() {
+			return false
+		}
+	}
+
+	addr := unsafe.Pointer(f.UnsafeAddr())
+	*(*bool)(addr) = true
+
+	return true
+}
+
+func ReadGo116ErrorData(terr types.Error) (ErrorCode, token.Pos, token.Pos, bool) {
+	var data [3]int
+	// By coincidence all of these fields are ints, which simplifies things.
+	v := reflect.ValueOf(terr)
+	for i, name := range []string{"go116code", "go116start", "go116end"} {
+		f := v.FieldByName(name)
+		if !f.IsValid() {
+			return 0, 0, 0, false
+		}
+		data[i] = int(f.Int())
+	}
+	return ErrorCode(data[0]), token.Pos(data[1]), token.Pos(data[2]), true
+}