Fix name resolution in typealias with constraint (#144)

The body of a typealias gets inlined into wherever the typealias
is used. This fixes a bug where the references in the typealias body can
resolve to the wrong value.

pkl-core/src/main/java/org/pkl/core/ast/member/TypeAliasNode.java

@@ -82,7 +82,8 @@ public final class TypeAliasNode extends ExpressionNode {
             simpleName,
             module,
             qualifiedName,
-            typeParameters);
+            typeParameters,
+            frame.materialize());
 
     VmUtils.evaluateAnnotations(frame, annotationNodes, annotations);
     cachedTypeAlias.initTypeCheckNode(typeAnnotationNode.execute(frame));

pkl-core/src/main/java/org/pkl/core/ast/type/TypeNode.java

@@ -1614,13 +1614,36 @@ public abstract class TypeNode extends PklNode {
       return getMirrors(typeArgumentNodes);
     }
 
+    /**
+     * A typealias body is effectively inlined into the type node, and not executed in its own
+     * frame.
+     *
+     * <p>Before executing the typealias body, use the owner and receiver of the original frame
+     * where the typealias was declared, so that we preserve its original scope.
+     */
     public void execute(VirtualFrame frame, Object value) {
+      var prevOwner = VmUtils.getOwner(frame);
+      var prevReceiver = VmUtils.getReceiver(frame);
+      VmUtils.setOwner(frame, VmUtils.getOwner(typeAlias.getEnclosingFrame()));
+      VmUtils.setReceiver(frame, VmUtils.getReceiver(typeAlias.getEnclosingFrame()));
+
       aliasedTypeNode.execute(frame, value);
+      VmUtils.setOwner(frame, prevOwner);
+      VmUtils.setReceiver(frame, prevReceiver);
     }
 
+    /** See docstring on {@link TypeAliasTypeNode#execute}. */
     @Override
     public void executeAndSet(VirtualFrame frame, Object value) {
+      var prevOwner = VmUtils.getOwner(frame);
+      var prevReceiver = VmUtils.getReceiver(frame);
+      VmUtils.setOwner(frame, VmUtils.getOwner(typeAlias.getEnclosingFrame()));
+      VmUtils.setReceiver(frame, VmUtils.getReceiver(typeAlias.getEnclosingFrame()));
+
       aliasedTypeNode.executeAndSet(frame, value);
+
+      VmUtils.setOwner(frame, prevOwner);
+      VmUtils.setReceiver(frame, prevReceiver);
     }
 
     @Override

pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java

@@ -16,6 +16,8 @@
 package org.pkl.core.runtime;
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
+import com.oracle.truffle.api.frame.Frame;
+import com.oracle.truffle.api.frame.MaterializedFrame;
 import com.oracle.truffle.api.source.SourceSection;
 import java.util.ArrayList;
 import java.util.List;
@@ -42,6 +44,7 @@ public final class VmTypeAlias extends VmValue {
   private final VmTyped module;
   private final String qualifiedName;
   private final List<TypeParameter> typeParameters;
+  private final MaterializedFrame enclosingFrame;
 
   @LateInit private TypeNode typeNode;
 
@@ -66,7 +69,8 @@ public final class VmTypeAlias extends VmValue {
       String simpleName,
       VmTyped module,
       String qualifiedName,
-      List<TypeParameter> typeParameters) {
+      List<TypeParameter> typeParameters,
+      MaterializedFrame enclosingFrame) {
     this.sourceSection = sourceSection;
     this.headerSection = headerSection;
     this.docComment = docComment;
@@ -76,6 +80,7 @@ public final class VmTypeAlias extends VmValue {
     this.module = module;
     this.qualifiedName = qualifiedName;
     this.typeParameters = typeParameters;
+    this.enclosingFrame = enclosingFrame;
   }
 
   public void initTypeCheckNode(TypeNode typeNode) {
@@ -155,6 +160,10 @@ public final class VmTypeAlias extends VmValue {
     return typeNode;
   }
 
+  public Frame getEnclosingFrame() {
+    return enclosingFrame;
+  }
+
   @TruffleBoundary
   public TypeNode instantiate(TypeNode[] typeArgumentNodes) {
     // Cloning the type node means that the entire type check remains within a single root node,

pkl-core/src/main/java/org/pkl/core/runtime/VmUtils.java

@@ -136,6 +136,10 @@ public final class VmUtils {
     return result;
   }
 
+  public static void setReceiver(Frame frame, Object receiver) {
+    frame.getArguments()[0] = receiver;
+  }
+
   public static VmObjectLike getObjectReceiver(Frame frame) {
     return (VmObjectLike) getReceiver(frame);
   }
@@ -156,6 +160,10 @@ public final class VmUtils {
     return result;
   }
 
+  public static void setOwner(Frame frame, VmObjectLike owner) {
+    frame.getArguments()[1] = owner;
+  }
+
   /** Returns a `ObjectMember`'s key while executing the corresponding `MemberNode`. */
   public static Object getMemberKey(Frame frame) {
     return frame.getArguments()[2];

pkl-core/src/test/files/LanguageSnippetTests/input-helper/types/typeAliasConstraint2.pkl

@@ -0,0 +1,3 @@
+class MyClass
+
+typealias MyTypeAlias = MyClass(getClass() == MyClass)

pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint1.pkl

@@ -0,0 +1,12 @@
+// length should bind to `String#length` instead of `ClassWithLengthProperty#length`
+local typealias OneCharacterString = String(length == 1)
+
+local class ClassWithLengthProperty {
+  length: Int = 99
+  
+  // length constraint binds to ClassWithLengthProperty.length here
+  characters: List<OneCharacterString> = List("a", "b")
+}
+
+res1: OneCharacterString = "a"
+res2 = let (c = new ClassWithLengthProperty {}) c.characters

pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint2.pkl

@@ -0,0 +1,8 @@
+import ".../input-helper/types/typeAliasConstraint2.pkl" as helper
+
+foo: Int = 1
+bar: helper.MyTypeAlias(foo == 1) = new helper.MyClass {}
+
+function qux(bar: helper.MyTypeAlias(foo == 1)) = (bar) {}
+
+qux = qux(new helper.MyTypeAlias {})

pkl-core/src/test/files/LanguageSnippetTests/output/api/string.pcf

@@ -341,8 +341,8 @@ examples {
     "abcdefg"
     "abcdefg"
     "   abcdefg"
-    "Type constraint `this.length == 1` violated. Value: \"\""
-    "Type constraint `this.length == 1` violated. Value: \"aa\""
+    "Type constraint `length == 1` violated. Value: \"\""
+    "Type constraint `length == 1` violated. Value: \"aa\""
   }
   ["padEnd()"] {
     ""
@@ -351,8 +351,8 @@ examples {
     "abcdefg"
     "abcdefg"
     "abcdefg   "
-    "Type constraint `this.length == 1` violated. Value: \"\""
-    "Type constraint `this.length == 1` violated. Value: \"aa\""
+    "Type constraint `length == 1` violated. Value: \"\""
+    "Type constraint `length == 1` violated. Value: \"aa\""
   }
   ["toBooleanOrNull()"] {
     true

pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint1.pcf

@@ -0,0 +1,2 @@
+res1 = "a"
+res2 = List("a", "b")

pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint2.pcf

@@ -0,0 +1,3 @@
+foo = 1
+bar {}
+qux {}

stdlib/base.pkl

@@ -1058,7 +1058,7 @@ external class Boolean extends Any {
 }
 
 /// A Unicode character (code point).
-typealias Char = String(this.length == 1) // `this.` works around rdar://75074742
+typealias Char = String(length == 1)
 
 /// A sequence of Unicode characters (code points).
 ///