Prepare 0.27.1 release (#839)

Motivation:
- simplify implementation of lazy type checking
- fix correctness issues of lazy type checking (#785)

Changes:
- implement listing/mapping type cast via amendment (`parent`) instead of delegation (`delegate`)
- handle type checking of *computed* elements/entries in the same way as type checking of computed properties
  - ElementOrEntryNode is the equivalent of TypeCheckedPropertyNode
- remove fields VmListingOrMapping.delegate/typeNodeFrame/cachedMembers/checkedMembers
- fix #785 by executing all type casts between a member's owner and receiver
- fix #823 by storing owner and receiver directly
  instead of storing the mutable frame containing them (typeNodeFrame)
- remove overrides of VmObject methods that are no longer required
  - good for Truffle partial evaluation and JVM inlining
- revert a85a173faa except for added tests
- move `VmUtils.setOwner` and `VmUtils.setReceiver` and make them private
  - these methods aren't generally safe to use

Result:
- simpler code with greater optimization potential
  - VmListingOrMapping can now have both a type node and new members
- fewer changes to surrounding code
- smaller memory footprint
- better performance in some cases
- fixes https://github.com/apple/pkl/issues/785
- fixes https://github.com/apple/pkl/issues/823

Potential future optimizations:
- avoid lazy type checking overhead for untyped listings/mappings
- improve efficiency of forcing a typed listing/mapping
  - currently, lazy type checking will traverse the parent chain once per member,
    reducing the performance benefit of shallow-forcing
	  a listing/mapping over evaluating each member individually
- avoid creating an intermediate untyped listing/mapping in the following cases:
  - `new Listing<X> {...}`
  - amendment of `property: Listing<X>`

docs/antora.yml

@@ -1,6 +1,6 @@
 name: main
 title: Main Project
-version: 0.27.0-dev
-prerelease: true
+version: 0.27.1
+prerelease: false
 nav:
 - nav.adoc

docs/modules/ROOT/partials/component-attributes.adoc

@@ -3,10 +3,10 @@
 // the following attributes must be updated immediately before a release
 
 // pkl version corresponding to current git commit without -dev suffix or git hash
-:pkl-version-no-suffix: 0.27.0
+:pkl-version-no-suffix: 0.27.1
 // tells whether pkl version corresponding to current git commit
 // is a release version (:is-release-version: '') or dev version (:!is-release-version:)
-:!is-release-version:
+:is-release-version: ''
 
 // the remaining attributes do not need to be updated regularly
 

docs/modules/release-notes/pages/0.27.adoc

@@ -1,6 +1,6 @@
 = Pkl 0.27 Release Notes
 :version: 0.27
-:version-minor: 0.27.0
+:version-minor: 0.27.1
 :release-date: November 5th, 2024
 
 include::ROOT:partial$component-attributes.adoc[]
@@ -377,7 +377,7 @@ These are:
 
 The `String` to `Number` converter methods, for example,  {uri-stdlib-StringToInt}[`String.toInt()`], can now handle underscore separators (https://github.com/apple/pkl/pull/578[#578], https://github.com/apple/pkl/pull/580[#580]).
 
-This better aligns with the source code representation of file:///Users/danielchao/code/apple/pkl-lang.org/build/local/main/current/language-reference/index.html#integers[number literals].
+This better aligns with the source code representation of xref:language-reference:index.adoc#integers[number literals].
 
 [source,pkl]
 ----

docs/modules/release-notes/pages/changelog.adoc

@@ -1,6 +1,28 @@
 = Changelog
 include::ROOT:partial$component-attributes.adoc[]
 
+[[release-0.27.1]]
+== 0.27.1 (2024-12-06)
+
+=== Fixes
+
+- Fixes a broken "number literals" link in the 0.27 release notes (https://github.com/apple/pkl/pull/784[#784]).
+- Fixes a possible deadlock during external reader process close (https://github.com/apple/pkl/pull/786[#786]).
+- Fixes counting elements with computed indices multiple times in length computation of listings (https://github.com/apple/pkl/pull/797[#797]).
+- Fixes non Pkl modules being reported in GatherImports task, leading to plugin failures (https://github.com/apple/pkl/pull/821[#821]).
+- Fixes a problem where the delegate chain of type casts for Listing/Mapping get unreasonably big, even though the type nodes are the same, which may lead to a stack overflow or performance degradation (https://github.com/apple/pkl/pull/826[#826]).
+- Fixes incorrect scoping of type variables in lazy Listing/Mapping type checking in cross-module typealiases (https://github.com/apple/pkl/pull/789[#789]).
+- Fixes regression in type checking logic for Listing/Mapping (https://github.com/apple/pkl/pull/789[#789]).
+
+=== Contributors ❤️
+
+Thank you to all the contributors for this release!
+
+* link:https://github.com/GUI[@GUI]
+* link:https://github.com/HT154[@HT154]
+* link:https://github.com/odenix[@odenix] (formerly @translatenix)
+
+
 [[release-0.27.0]]
 == 0.27.0 (2024-11-05)
 

gradle.properties

@@ -1,7 +1,7 @@
 # suppress inspection "UnusedProperty" for whole file
 
 group=org.pkl-lang
-version=0.27.0
+version=0.27.1
 
 # google-java-format requires jdk.compiler exports
 org.gradle.jvmargs= \

jbang-catalog.json

@@ -2,17 +2,17 @@
   "catalogs": {},
   "aliases": {
     "pkl": {
-      "script-ref": "org.pkl-lang:pkl-cli-java:0.26.3",
+      "script-ref": "org.pkl-lang:pkl-cli-java:0.27.1",
       "java-agents": []
     },
     "pkl-codegen-java": {
-      "script-ref": "org.pkl-lang:pkl-codegen-java:0.26.3",
+      "script-ref": "org.pkl-lang:pkl-codegen-java:0.27.1",
       "java-agents": []
     },
     "pkl-codegen-kotlin": {
-      "script-ref": "org.pkl-lang:pkl-codegen-kotlin:0.26.3",
+      "script-ref": "org.pkl-lang:pkl-codegen-kotlin:0.27.1",
       "java-agents": []
     }
   },
   "templates": {}
-}
+}

pkl-commons-test/src/main/kotlin/org/pkl/commons/test/FileTestUtils.kt

@@ -19,6 +19,7 @@ import java.nio.file.Path
 import java.util.stream.Collectors
 import kotlin.io.path.*
 import org.assertj.core.api.Assertions.fail
+import org.opentest4j.AssertionFailedError
 import org.pkl.commons.*
 
 object FileTestUtils {
@@ -110,5 +111,11 @@ data class SnippetOutcome(val expectedOutFile: Path, val actual: String, val suc
   }
 
   private fun failWithDiff(message: String): Nothing =
-    throw PklAssertionFailedError(message, expected, actual)
+    if (System.getProperty("sun.java.command", "").contains("intellij")) {
+      // IntelliJ only shows diffs for AssertionFailedError
+      throw AssertionFailedError(message, expected, actual)
+    } else {
+      // Gradle test logging/report only shows diffs for PklAssertionFailedError
+      throw PklAssertionFailedError(message, expected, actual)
+    }
 }

pkl-core/src/main/java/org/pkl/core/ast/builder/AstBuilder.java

@@ -1221,7 +1221,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
             member.initConstantValue(constantNode);
           } else {
             member.initMemberNode(
-                new UntypedObjectMemberNode(
+                ElementOrEntryNodeGen.create(
                     language, scope.buildFrameDescriptor(), member, elementNode));
           }
 
@@ -1278,7 +1278,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
           member.initConstantValue(constantNode);
         } else {
           member.initMemberNode(
-              new UntypedObjectMemberNode(
+              ElementOrEntryNodeGen.create(
                   language, scope.buildFrameDescriptor(), member, valueNode));
         }
       } else { // ["key"] { ... }
@@ -1287,7 +1287,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
                 objectBodyCtxs,
                 new ReadSuperEntryNode(unavailableSourceSection(), new GetMemberKeyNode()));
         member.initMemberNode(
-            new UntypedObjectMemberNode(
+            ElementOrEntryNodeGen.create(
                 language, scope.buildFrameDescriptor(), member, objectBody));
       }
 
@@ -2446,6 +2446,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
     return new UnresolvedTypeNode.Parameterized(
         createSourceSection(ctx),
+        language,
         doVisitTypeName(idCtx),
         argCtx.ts.stream().map(this::visitType).toArray(UnresolvedTypeNode[]::new));
   }

pkl-core/src/main/java/org/pkl/core/ast/expression/generator/GeneratorPredicateMemberNode.java

@@ -103,7 +103,7 @@ public abstract class GeneratorPredicateMemberNode extends GeneratorMemberNode {
             var callTarget = member.getCallTarget();
             value = callTarget.call(parent, owner, key);
           }
-          owner.setCachedValue(key, value, member);
+          owner.setCachedValue(key, value);
         }
 
         frame.setAuxiliarySlot(customThisSlot, value);

pkl-core/src/main/java/org/pkl/core/ast/expression/literal/EntriesLiteralNode.java

@@ -43,15 +43,15 @@ public abstract class EntriesLiteralNode extends SpecializedObjectLiteralNode {
   @Children private final ExpressionNode[] keyNodes;
   private final ObjectMember[] values;
 
-  public EntriesLiteralNode(
+  protected EntriesLiteralNode(
       SourceSection sourceSection,
       VmLanguage language,
-      // contains local properties and default property (if present)
-      // does *not* contain entries with constant keys to maintain definition order of entries
       String qualifiedScopeName,
       boolean isCustomThisScope,
       @Nullable FrameDescriptor parametersDescriptor,
       UnresolvedTypeNode[] parameterTypes,
+      // contains local properties and default property (if present)
+      // does *not* contain entries with constant keys to maintain definition order of entries
       UnmodifiableEconomicMap<Object, ObjectMember> members,
       ExpressionNode[] keyNodes,
       ObjectMember[] values) {
@@ -103,7 +103,8 @@ public abstract class EntriesLiteralNode extends SpecializedObjectLiteralNode {
         frame.materialize(),
         parent,
         createListMembers(frame, parent.getLength()),
-        parent.getLength() + keyNodes.length);
+        // `[x] = y` overrides existing element and doesn't increase length
+        parent.getLength());
   }
 
   @Specialization

pkl-core/src/main/java/org/pkl/core/ast/expression/member/ReadLocalPropertyNode.java

@@ -71,7 +71,7 @@ public final class ReadLocalPropertyNode extends ExpressionNode {
 
     if (result == null) {
       result = callNode.call(objReceiver, owner, property.getName());
-      objReceiver.setCachedValue(property, result, property);
+      objReceiver.setCachedValue(property, result);
     }
 
     return result;

pkl-core/src/main/java/org/pkl/core/ast/expression/primary/ResolveVariableNode.java

@@ -184,12 +184,12 @@ public final class ResolveVariableNode extends ExpressionNode {
       if (member != null) {
         var constantValue = member.getConstantValue();
         if (constantValue != null) {
-          baseModule.setCachedValue(variableName, constantValue, member);
+          baseModule.setCachedValue(variableName, constantValue);
           return new ConstantValueNode(sourceSection, constantValue);
         }
 
         var computedValue = member.getCallTarget().call(baseModule, baseModule);
-        baseModule.setCachedValue(variableName, computedValue, member);
+        baseModule.setCachedValue(variableName, computedValue);
         return new ConstantValueNode(sourceSection, computedValue);
       }
     }

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

@@ -0,0 +1,73 @@
+/*
+ * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.core.ast.member;
+
+import com.oracle.truffle.api.dsl.Cached;
+import com.oracle.truffle.api.dsl.Cached.Shared;
+import com.oracle.truffle.api.dsl.Executed;
+import com.oracle.truffle.api.dsl.Specialization;
+import com.oracle.truffle.api.frame.FrameDescriptor;
+import com.oracle.truffle.api.frame.VirtualFrame;
+import com.oracle.truffle.api.nodes.IndirectCallNode;
+import org.pkl.core.ast.ExpressionNode;
+import org.pkl.core.ast.expression.primary.GetReceiverNode;
+import org.pkl.core.runtime.VmDynamic;
+import org.pkl.core.runtime.VmLanguage;
+import org.pkl.core.runtime.VmListing;
+import org.pkl.core.runtime.VmMapping;
+import org.pkl.core.runtime.VmUtils;
+import org.pkl.core.util.Nullable;
+
+/** Equivalent of {@link TypedPropertyNode} for elements/entries. */
+public abstract class ElementOrEntryNode extends RegularMemberNode {
+  @Child @Executed protected ExpressionNode receiverNode = new GetReceiverNode();
+
+  protected ElementOrEntryNode(
+      @Nullable VmLanguage language,
+      FrameDescriptor descriptor,
+      ObjectMember member,
+      ExpressionNode bodyNode) {
+
+    super(language, descriptor, member, bodyNode);
+  }
+
+  @Specialization
+  protected Object evalListing(
+      VirtualFrame frame,
+      VmListing receiver,
+      @Cached("create()") @Shared("callNode") IndirectCallNode callNode) {
+    var result = executeBody(frame);
+    return VmUtils.shouldRunTypeCheck(frame)
+        ? receiver.executeTypeCasts(result, VmUtils.getOwner(frame), callNode, null, null)
+        : result;
+  }
+
+  @Specialization
+  protected Object evalMapping(
+      VirtualFrame frame,
+      VmMapping receiver,
+      @Cached("create()") @Shared("callNode") IndirectCallNode callNode) {
+    var result = executeBody(frame);
+    return VmUtils.shouldRunTypeCheck(frame)
+        ? receiver.executeTypeCasts(result, VmUtils.getOwner(frame), callNode, null, null)
+        : result;
+  }
+
+  @Specialization
+  protected Object evalDynamic(VirtualFrame frame, VmDynamic ignored) {
+    return executeBody(frame);
+  }
+}

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

@@ -26,7 +26,7 @@ import org.pkl.core.runtime.VmLanguage;
 import org.pkl.core.util.Nullable;
 
 /** Performs a typecast on a Mapping entry value, or a Listing element. */
-public class ListingOrMappingTypeCastNode extends PklRootNode {
+public final class ListingOrMappingTypeCastNode extends PklRootNode {
 
   @Child private TypeNode typeNode;
   private final String qualifiedName;

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

@@ -73,7 +73,7 @@ public abstract class ResolveDeclaredTypeNode extends ExpressionNode {
     var result = module.getCachedValue(importName);
     if (result == null) {
       result = callNode.call(member.getCallTarget(), module, module, importName);
-      module.setCachedValue(importName, result, member);
+      module.setCachedValue(importName, result);
     }
     return (VmTyped) result;
   }
@@ -94,7 +94,7 @@ public abstract class ResolveDeclaredTypeNode extends ExpressionNode {
     var result = module.getCachedValue(typeName);
     if (result == null) {
       result = callNode.call(member.getCallTarget(), module, module, typeName);
-      module.setCachedValue(typeName, result, member);
+      module.setCachedValue(typeName, result);
     }
     return result;
   }

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

@@ -21,6 +21,7 @@ import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.dsl.Cached;
 import com.oracle.truffle.api.dsl.Fallback;
 import com.oracle.truffle.api.dsl.Specialization;
+import com.oracle.truffle.api.frame.Frame;
 import com.oracle.truffle.api.frame.FrameDescriptor;
 import com.oracle.truffle.api.frame.FrameSlotKind;
 import com.oracle.truffle.api.frame.VirtualFrame;
@@ -161,7 +162,11 @@ public abstract class TypeNode extends PklNode {
   }
 
   /** Tells if this typenode is the same typecheck as the other typenode. */
-  public abstract boolean isEquivalentTo(TypeNode other);
+  public boolean isEquivalentTo(TypeNode other) {
+    return this == other || doIsEquivalentTo(other);
+  }
+
+  protected abstract boolean doIsEquivalentTo(TypeNode other);
 
   public @Nullable VmClass getVmClass() {
     return null;
@@ -304,7 +309,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof UnknownTypeNode;
     }
 
@@ -371,7 +376,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof NothingTypeNode;
     }
 
@@ -408,7 +413,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof FinalModuleTypeNode finalModuleTypeNode)) {
         return false;
       }
@@ -460,7 +465,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof NonFinalModuleTypeNode nonFinalModuleTypeNode)) {
         return false;
       }
@@ -496,7 +501,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof StringLiteralTypeNode stringLiteralTypeNode)) {
         return false;
       }
@@ -551,7 +556,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof TypedTypeNode;
     }
 
@@ -586,7 +591,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof DynamicTypeNode;
     }
 
@@ -636,7 +641,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof FinalClassTypeNode finalClassTypeNode)) {
         return false;
       }
@@ -705,7 +710,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof NonFinalClassTypeNode nonFinalClassTypeNode)) {
         return false;
       }
@@ -772,7 +777,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof NullableTypeNode nullableTypeNode)) {
         return false;
       }
@@ -842,7 +847,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     @ExplodeLoop
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof UnionTypeNode unionTypeNode)) {
         return false;
       }
@@ -1016,7 +1021,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     @TruffleBoundary
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof UnionOfStringLiteralsTypeNode unionOfStringLiteralsTypeNode)) {
         return false;
       }
@@ -1092,7 +1097,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return false;
     }
 
@@ -1223,7 +1228,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof ListTypeNode listTypeNode)) {
         return false;
       }
@@ -1268,7 +1273,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof SetTypeNode setTypeNode)) {
         return false;
       }
@@ -1360,7 +1365,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof MapTypeNode mapTypeNode)) {
         return false;
       }
@@ -1414,8 +1419,9 @@ public abstract class TypeNode extends PklNode {
   }
 
   public static final class ListingTypeNode extends ListingOrMappingTypeNode {
-    public ListingTypeNode(SourceSection sourceSection, TypeNode valueTypeNode) {
-      super(sourceSection, null, valueTypeNode);
+    public ListingTypeNode(
+        SourceSection sourceSection, VmLanguage language, TypeNode valueTypeNode) {
+      super(sourceSection, language, null, valueTypeNode);
     }
 
     @Override
@@ -1423,7 +1429,17 @@ public abstract class TypeNode extends PklNode {
       if (!(value instanceof VmListing vmListing)) {
         throw typeMismatch(value, BaseModule.getListingClass());
       }
-      return doTypeCast(frame, vmListing);
+      if (vmListing.isValueTypeKnownSubtypeOf(valueTypeNode)) {
+        return vmListing;
+      }
+      return new VmListing(
+          vmListing.getEnclosingFrame(),
+          vmListing,
+          EconomicMaps.emptyMap(),
+          vmListing.getLength(),
+          getValueTypeCastNode(),
+          VmUtils.getReceiver(frame),
+          VmUtils.getOwner(frame));
     }
 
     @Override
@@ -1451,7 +1467,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof ListingTypeNode listingTypeNode)) {
         return false;
       }
@@ -1466,9 +1482,12 @@ public abstract class TypeNode extends PklNode {
 
   public static final class MappingTypeNode extends ListingOrMappingTypeNode {
     public MappingTypeNode(
-        SourceSection sourceSection, TypeNode keyTypeNode, TypeNode valueTypeNode) {
+        SourceSection sourceSection,
+        VmLanguage language,
+        TypeNode keyTypeNode,
+        TypeNode valueTypeNode) {
 
-      super(sourceSection, keyTypeNode, valueTypeNode);
+      super(sourceSection, language, keyTypeNode, valueTypeNode);
     }
 
     @Override
@@ -1478,7 +1497,16 @@ public abstract class TypeNode extends PklNode {
       }
       // execute type checks on mapping keys
       doEagerCheck(frame, vmMapping, false, true);
-      return doTypeCast(frame, vmMapping);
+      if (vmMapping.isValueTypeKnownSubtypeOf(valueTypeNode)) {
+        return vmMapping;
+      }
+      return new VmMapping(
+          vmMapping.getEnclosingFrame(),
+          vmMapping,
+          EconomicMaps.emptyMap(),
+          getValueTypeCastNode(),
+          VmUtils.getReceiver(frame),
+          VmUtils.getOwner(frame));
     }
 
     @Override
@@ -1509,7 +1537,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof MappingTypeNode mappingTypeNode)) {
         return false;
       }
@@ -1526,17 +1554,22 @@ public abstract class TypeNode extends PklNode {
   }
 
   public abstract static class ListingOrMappingTypeNode extends ObjectSlotTypeNode {
+    private final VmLanguage language;
     @Child protected @Nullable TypeNode keyTypeNode;
     @Child protected TypeNode valueTypeNode;
-    @Child @Nullable protected ListingOrMappingTypeCastNode listingOrMappingTypeCastNode;
+    @Child @Nullable protected ListingOrMappingTypeCastNode valueTypeCastNode;
 
     private final boolean skipKeyTypeChecks;
     private final boolean skipValueTypeChecks;
 
     protected ListingOrMappingTypeNode(
-        SourceSection sourceSection, @Nullable TypeNode keyTypeNode, TypeNode valueTypeNode) {
+        SourceSection sourceSection,
+        VmLanguage language,
+        @Nullable TypeNode keyTypeNode,
+        TypeNode valueTypeNode) {
 
       super(sourceSection);
+      this.language = language;
       this.keyTypeNode = keyTypeNode;
       this.valueTypeNode = valueTypeNode;
 
@@ -1556,17 +1589,14 @@ public abstract class TypeNode extends PklNode {
       return valueTypeNode;
     }
 
-    protected ListingOrMappingTypeCastNode getListingOrMappingTypeCastNode() {
-      if (listingOrMappingTypeCastNode == null) {
+    protected ListingOrMappingTypeCastNode getValueTypeCastNode() {
+      if (valueTypeCastNode == null) {
         CompilerDirectives.transferToInterpreterAndInvalidate();
-        listingOrMappingTypeCastNode =
+        valueTypeCastNode =
             new ListingOrMappingTypeCastNode(
-                VmLanguage.get(this),
-                getRootNode().getFrameDescriptor(),
-                valueTypeNode,
-                getRootNode().getName());
+                language, new FrameDescriptor(), valueTypeNode, getRootNode().getName());
       }
-      return listingOrMappingTypeCastNode;
+      return valueTypeCastNode;
     }
 
     // either (if defaultMemberValue != null):
@@ -1647,15 +1677,6 @@ public abstract class TypeNode extends PklNode {
           EconomicMaps.of(Identifier.DEFAULT, defaultMember));
     }
 
-    protected <T extends VmListingOrMapping<T>> T doTypeCast(VirtualFrame frame, T original) {
-      // optimization: don't create new object if the original already has the same typecheck, or if
-      // this typecheck is a no-op.
-      if (isNoopTypeCheck() || original.hasSameChecksAs(valueTypeNode)) {
-        return original;
-      }
-      return original.withCheckedMembers(getListingOrMappingTypeCastNode(), frame.materialize());
-    }
-
     protected void doEagerCheck(VirtualFrame frame, VmObject object) {
       doEagerCheck(frame, object, skipKeyTypeChecks, skipValueTypeChecks);
     }
@@ -1700,7 +1721,7 @@ public abstract class TypeNode extends PklNode {
                 var callTarget = member.getCallTarget();
                 memberValue = callTarget.call(object, owner, memberKey);
               }
-              object.setCachedValue(memberKey, memberValue, member);
+              object.setCachedValue(memberKey, memberValue);
             }
             valueTypeNode.executeEagerly(frame, memberValue);
           }
@@ -1748,7 +1769,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     @ExplodeLoop
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof FunctionTypeNode functionTypeNode)) {
         return false;
       }
@@ -1845,7 +1866,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof FunctionClassTypeNode functionClassTypeNode)) {
         return false;
       }
@@ -1883,7 +1904,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     @ExplodeLoop
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof FunctionNClassTypeNode functionNClassTypeNode)) {
         return false;
       }
@@ -1986,7 +2007,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof PairTypeNode pairTypeNode)) {
         return false;
       }
@@ -2043,7 +2064,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if (!(other instanceof VarArgsTypeNode varArgsTypeNode)) {
         return false;
       }
@@ -2095,7 +2116,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof TypeVariableNode;
     }
 
@@ -2135,7 +2156,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof NonNullTypeAliasTypeNode;
     }
 
@@ -2184,7 +2205,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof UIntTypeAliasTypeNode aliasTypeNode && mask == aliasTypeNode.mask;
     }
 
@@ -2228,7 +2249,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof Int8TypeAliasTypeNode;
     }
 
@@ -2272,7 +2293,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof Int16TypeAliasTypeNode;
     }
 
@@ -2316,7 +2337,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof Int32TypeAliasTypeNode;
     }
 
@@ -2387,14 +2408,14 @@ public abstract class TypeNode extends PklNode {
     public Object 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()));
+      setOwner(frame, VmUtils.getOwner(typeAlias.getEnclosingFrame()));
+      setReceiver(frame, VmUtils.getReceiver(typeAlias.getEnclosingFrame()));
 
       try {
         return aliasedTypeNode.execute(frame, value);
       } finally {
-        VmUtils.setOwner(frame, prevOwner);
-        VmUtils.setReceiver(frame, prevReceiver);
+        setOwner(frame, prevOwner);
+        setReceiver(frame, prevReceiver);
       }
     }
 
@@ -2403,14 +2424,14 @@ public abstract class TypeNode extends PklNode {
     public Object 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()));
+      setOwner(frame, VmUtils.getOwner(typeAlias.getEnclosingFrame()));
+      setReceiver(frame, VmUtils.getReceiver(typeAlias.getEnclosingFrame()));
 
       try {
         return aliasedTypeNode.executeAndSet(frame, value);
       } finally {
-        VmUtils.setOwner(frame, prevOwner);
-        VmUtils.setReceiver(frame, prevReceiver);
+        setOwner(frame, prevOwner);
+        setReceiver(frame, prevReceiver);
       }
     }
 
@@ -2419,14 +2440,14 @@ public abstract class TypeNode extends PklNode {
     public Object executeEagerlyAndSet(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()));
+      setOwner(frame, VmUtils.getOwner(typeAlias.getEnclosingFrame()));
+      setReceiver(frame, VmUtils.getReceiver(typeAlias.getEnclosingFrame()));
 
       try {
         return aliasedTypeNode.executeEagerlyAndSet(frame, value);
       } finally {
-        VmUtils.setOwner(frame, prevOwner);
-        VmUtils.setReceiver(frame, prevReceiver);
+        setOwner(frame, prevOwner);
+        setReceiver(frame, prevReceiver);
       }
     }
 
@@ -2471,7 +2492,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       if ((other instanceof TypeAliasTypeNode typeAliasTypeNode)) {
         return aliasedTypeNode.isEquivalentTo(typeAliasTypeNode.aliasedTypeNode);
       }
@@ -2498,6 +2519,22 @@ public abstract class TypeNode extends PklNode {
     protected boolean isParametric() {
       return typeArgumentNodes.length > 0;
     }
+
+    // Note that mutating a frame's receiver and owner argument is very risky
+    // because any VmObject instantiated within the same root node execution
+    // holds a reference to (not immutable snapshot of) the frame
+    // via VmObjectLike.enclosingFrame.
+    // *Maybe* this works out for TypeAliasTypeNode because an object instantiated
+    // within a type constraint doesn't escape the constraint expression.
+    // If mutating receiver and owner can't be avoided, it would be safer
+    // to have VmObjectLike store them directly instead of storing enclosingFrame.
+    private static void setReceiver(Frame frame, Object receiver) {
+      frame.getArguments()[0] = receiver;
+    }
+
+    private static void setOwner(Frame frame, VmObjectLike owner) {
+      frame.getArguments()[1] = owner;
+    }
   }
 
   public static final class ConstrainedTypeNode extends TypeNode {
@@ -2581,7 +2618,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       // consider constrained types as always different
       return false;
     }
@@ -2622,7 +2659,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof AnyTypeNode;
     }
 
@@ -2650,7 +2687,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof StringTypeNode;
     }
 
@@ -2714,7 +2751,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof NumberTypeNode;
     }
 
@@ -2742,7 +2779,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof IntTypeNode;
     }
 
@@ -2787,7 +2824,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof FloatTypeNode;
     }
 
@@ -2832,7 +2869,7 @@ public abstract class TypeNode extends PklNode {
     }
 
     @Override
-    public boolean isEquivalentTo(TypeNode other) {
+    public boolean doIsEquivalentTo(TypeNode other) {
       return other instanceof BooleanTypeNode;
     }
 

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

@@ -197,14 +197,17 @@ public abstract class UnresolvedTypeNode extends PklNode {
   }
 
   public static final class Parameterized extends UnresolvedTypeNode {
+    private final VmLanguage language;
     @Child private ExpressionNode resolveTypeNode;
     @Children private final UnresolvedTypeNode[] typeArgumentNodes;
 
     public Parameterized(
         SourceSection sourceSection,
+        VmLanguage language,
         ExpressionNode resolveTypeNode,
         UnresolvedTypeNode[] typeArgumentNodes) {
       super(sourceSection);
+      this.language = language;
       this.resolveTypeNode = resolveTypeNode;
       this.typeArgumentNodes = typeArgumentNodes;
     }
@@ -238,12 +241,13 @@ public abstract class UnresolvedTypeNode extends PklNode {
         }
 
         if (clazz.isListingClass()) {
-          return new ListingTypeNode(sourceSection, typeArgumentNodes[0].execute(frame));
+          return new ListingTypeNode(sourceSection, language, typeArgumentNodes[0].execute(frame));
         }
 
         if (clazz.isMappingClass()) {
           return new MappingTypeNode(
               sourceSection,
+              language,
               typeArgumentNodes[0].execute(frame),
               typeArgumentNodes[1].execute(frame));
         }

pkl-core/src/main/java/org/pkl/core/externalreader/ExternalReaderProcessImpl.java

@@ -17,17 +17,16 @@ package org.pkl.core.externalreader;
 
 import java.io.IOException;
 import java.lang.ProcessBuilder.Redirect;
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Random;
-import java.util.Timer;
-import java.util.TimerTask;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
 import javax.annotation.concurrent.GuardedBy;
-import org.pkl.core.Duration;
 import org.pkl.core.evaluatorSettings.PklEvaluatorSettings.ExternalReader;
 import org.pkl.core.externalreader.ExternalReaderMessages.*;
 import org.pkl.core.messaging.MessageTransport;
@@ -152,40 +151,23 @@ final class ExternalReaderProcessImpl implements ExternalReaderProcess {
   @Override
   public void close() {
     synchronized (lock) {
+      if (closed) return;
       closed = true;
-      if (process == null || !process.isAlive()) {
-        return;
-      }
 
       try {
-        if (transport != null) {
+        if (transport != null && process != null && process.isAlive()) {
           transport.send(new CloseExternalProcess());
+          process.waitFor(CLOSE_TIMEOUT.toMillis(), TimeUnit.MILLISECONDS);
+        }
+      } catch (Exception ignored) {
+      } finally {
+        if (process != null) {
+          // no-op unless process is alive
+          process.destroyForcibly();
+        }
+        if (transport != null) {
           transport.close();
         }
-
-        // forcefully stop the process after the timeout
-        // note that both transport.close() and process.destroy() are safe to call multiple times
-        new Timer()
-            .schedule(
-                new TimerTask() {
-                  @Override
-                  public void run() {
-                    if (process != null) {
-                      transport.close();
-                      process.destroyForcibly();
-                    }
-                  }
-                },
-                CLOSE_TIMEOUT.inWholeMillis());
-
-        // block on process exit
-        process.onExit().get();
-      } catch (Exception e) {
-        transport.close();
-        process.destroyForcibly();
-      } finally {
-        process = null;
-        transport = null;
       }
     }
   }

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

@@ -113,7 +113,7 @@ public final class VmFunction extends VmObjectLike {
 
   @Override
   @TruffleBoundary
-  public void setCachedValue(Object key, Object value, ObjectMember objectMember) {
+  public void setCachedValue(Object key, Object value) {
     throw new VmExceptionBuilder()
         .bug("Class `VmFunction` does not support method `setCachedValue()`.")
         .build();

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

@@ -33,7 +33,7 @@ import org.pkl.core.util.Nullable;
 @TruffleLanguage.Registration(
     id = "pkl",
     name = "Pkl",
-    version = "0.27.0-dev",
+    version = "0.27.1",
     characterMimeTypes = VmLanguage.MIME_TYPE,
     contextPolicy = ContextPolicy.SHARED)
 public final class VmLanguage extends TruffleLanguage<VmContext> {

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

@@ -19,14 +19,13 @@ import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.frame.MaterializedFrame;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
 import org.graalvm.collections.UnmodifiableEconomicMap;
 import org.pkl.core.ast.member.ListingOrMappingTypeCastNode;
 import org.pkl.core.ast.member.ObjectMember;
 import org.pkl.core.util.EconomicMaps;
 import org.pkl.core.util.Nullable;
 
-public final class VmListing extends VmListingOrMapping<VmListing> {
+public final class VmListing extends VmListingOrMapping {
   private static final class EmptyHolder {
     private static final VmListing EMPTY =
         new VmListing(
@@ -47,7 +46,7 @@ public final class VmListing extends VmListingOrMapping<VmListing> {
       VmObject parent,
       UnmodifiableEconomicMap<Object, ObjectMember> members,
       int length) {
-    super(enclosingFrame, Objects.requireNonNull(parent), members, null, null, null);
+    super(enclosingFrame, parent, members);
     this.length = length;
   }
 
@@ -56,16 +55,10 @@ public final class VmListing extends VmListingOrMapping<VmListing> {
       VmObject parent,
       UnmodifiableEconomicMap<Object, ObjectMember> members,
       int length,
-      @Nullable VmListing delegate,
-      ListingOrMappingTypeCastNode typeCheckNode,
-      MaterializedFrame typeNodeFrame) {
-    super(
-        enclosingFrame,
-        Objects.requireNonNull(parent),
-        members,
-        delegate,
-        typeCheckNode,
-        typeNodeFrame);
+      ListingOrMappingTypeCastNode typeCastNode,
+      Object typeCheckReceiver,
+      VmObjectLike typeCheckOwner) {
+    super(enclosingFrame, parent, members, typeCastNode, typeCheckReceiver, typeCheckOwner);
     this.length = length;
   }
 
@@ -117,20 +110,6 @@ public final class VmListing extends VmListingOrMapping<VmListing> {
     return converter.convertListing(this, path);
   }
 
-  @Override
-  public VmListing withCheckedMembers(
-      ListingOrMappingTypeCastNode typeCheckNode, MaterializedFrame typeNodeFrame) {
-
-    return new VmListing(
-        getEnclosingFrame(),
-        Objects.requireNonNull(parent),
-        members,
-        length,
-        this,
-        typeCheckNode,
-        typeNodeFrame);
-  }
-
   @Override
   @TruffleBoundary
   public boolean equals(@Nullable Object obj) {
@@ -142,10 +121,14 @@ public final class VmListing extends VmListingOrMapping<VmListing> {
     force(false);
     other.force(false);
 
-    for (var i = 0L; i < length; i++) {
-      var value = getCachedValue(i);
+    var cursor = cachedValues.getEntries();
+    while (cursor.advance()) {
+      var key = cursor.getKey();
+      if (key instanceof Identifier) continue;
+
+      var value = cursor.getValue();
       assert value != null;
-      var otherValue = other.getCachedValue(i);
+      var otherValue = other.getCachedValue(key);
       if (!value.equals(otherValue)) return false;
     }
 
@@ -156,14 +139,16 @@ public final class VmListing extends VmListingOrMapping<VmListing> {
   @TruffleBoundary
   public int hashCode() {
     if (cachedHash != 0) return cachedHash;
-    // It's possible that the delegate has already computed its hash code.
-    // If so, we can go ahead and use it.
-    if (delegate != null && delegate.cachedHash != 0) return delegate.cachedHash;
 
     force(false);
     var result = 0;
-    for (var i = 0L; i < length; i++) {
-      var value = getCachedValue(i);
+    var cursor = cachedValues.getEntries();
+
+    while (cursor.advance()) {
+      var key = cursor.getKey();
+      if (key instanceof Identifier) continue;
+
+      var value = cursor.getValue();
       assert value != null;
       result = 31 * result + value.hashCode();
     }

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

@@ -16,159 +16,122 @@
 package org.pkl.core.runtime;
 
 import com.oracle.truffle.api.CompilerDirectives;
+import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.frame.MaterializedFrame;
 import com.oracle.truffle.api.nodes.IndirectCallNode;
-import org.graalvm.collections.EconomicMap;
-import org.graalvm.collections.EconomicSet;
 import org.graalvm.collections.UnmodifiableEconomicMap;
-import org.pkl.core.PklBugException;
 import org.pkl.core.ast.member.ListingOrMappingTypeCastNode;
 import org.pkl.core.ast.member.ObjectMember;
 import org.pkl.core.ast.type.TypeNode;
 import org.pkl.core.util.EconomicMaps;
-import org.pkl.core.util.EconomicSets;
 import org.pkl.core.util.Nullable;
 
-public abstract class VmListingOrMapping<SELF extends VmListingOrMapping<SELF>> extends VmObject {
-
-  /**
-   * A Listing or Mapping typecast creates a new object that contains a new typecheck node, and
-   * delegates member lookups to this delegate.
-   */
-  protected final @Nullable SELF delegate;
-
+public abstract class VmListingOrMapping extends VmObject {
+  // reified type of listing elements and mapping values
   private final @Nullable ListingOrMappingTypeCastNode typeCastNode;
-  private final MaterializedFrame typeNodeFrame;
-  private final EconomicMap<Object, ObjectMember> cachedMembers = EconomicMaps.create();
-  private final EconomicSet<Object> checkedMembers = EconomicSets.create();
+  private final @Nullable Object typeCheckReceiver;
+  private final @Nullable VmObjectLike typeCheckOwner;
+
+  public VmListingOrMapping(
+      MaterializedFrame enclosingFrame,
+      @Nullable VmObject parent,
+      UnmodifiableEconomicMap<Object, ObjectMember> members) {
+    super(enclosingFrame, parent, members);
+    typeCastNode = null;
+    typeCheckReceiver = null;
+    typeCheckOwner = null;
+  }
 
   public VmListingOrMapping(
       MaterializedFrame enclosingFrame,
       @Nullable VmObject parent,
       UnmodifiableEconomicMap<Object, ObjectMember> members,
-      @Nullable SELF delegate,
-      @Nullable ListingOrMappingTypeCastNode typeCastNode,
-      @Nullable MaterializedFrame typeNodeFrame) {
+      ListingOrMappingTypeCastNode typeCastNode,
+      Object typeCheckReceiver,
+      VmObjectLike typeCheckOwner) {
     super(enclosingFrame, parent, members);
-    this.delegate = delegate;
     this.typeCastNode = typeCastNode;
-    this.typeNodeFrame = typeNodeFrame;
+    this.typeCheckReceiver = typeCheckReceiver;
+    this.typeCheckOwner = typeCheckOwner;
   }
 
-  ObjectMember findMember(Object key) {
-    var member = EconomicMaps.get(cachedMembers, key);
-    if (member != null) {
-      return member;
-    }
-    if (delegate != null) {
-      return delegate.findMember(key);
-    }
-    // member is guaranteed to exist; this is only called if `getCachedValue()` returns non-null
-    // and `setCachedValue` will record the object member in `cachedMembers`.
-    throw PklBugException.unreachableCode();
-  }
-
-  public @Nullable ListingOrMappingTypeCastNode getTypeCastNode() {
-    return typeCastNode;
-  }
-
-  @Override
-  public void setCachedValue(Object key, Object value, ObjectMember objectMember) {
-    super.setCachedValue(key, value, objectMember);
-    EconomicMaps.put(cachedMembers, key, objectMember);
-  }
-
-  @Override
-  public boolean hasCachedValue(Object key) {
-    return super.hasCachedValue(key) || delegate != null && delegate.hasCachedValue(key);
-  }
-
-  @Override
-  public @Nullable Object getCachedValue(Object key) {
-    var myCachedValue = super.getCachedValue(key);
-    if (myCachedValue != null || delegate == null) {
-      return myCachedValue;
-    }
-    var memberValue = delegate.getCachedValue(key);
-    // if this object member appears inside `checkedMembers`, we have already checked its type
-    // and can safely return it.
-    if (EconomicSets.contains(checkedMembers, key)) {
-      return memberValue;
-    }
-    if (memberValue == null) {
-      return null;
-    }
-    // If a cached value already exists on the delegate, run a typecast on it.
-    // optimization: don't use `VmUtils.findMember` to avoid iterating over all members
-    var objectMember = findMember(key);
-    var ret = typecastObjectMember(objectMember, memberValue, IndirectCallNode.getUncached());
-    if (ret != memberValue) {
-      EconomicMaps.put(cachedValues, key, ret);
-    } else {
-      // optimization: don't add to own cached values if typecast results in the same value
-      EconomicSets.add(checkedMembers, key);
-    }
-    return ret;
-  }
-
-  @Override
-  public Object getExtraStorage() {
-    if (delegate != null) {
-      return delegate.getExtraStorage();
-    }
-    assert extraStorage != null;
-    return extraStorage;
-  }
-
-  /** Perform a typecast on this member, */
-  public Object typecastObjectMember(
-      ObjectMember member, Object memberValue, IndirectCallNode callNode) {
-    if (!(member.isEntry() || member.isElement()) || typeCastNode == null) {
-      return memberValue;
-    }
-    assert typeNodeFrame != null;
-    var ret = memberValue;
-    if (delegate != null) {
-      ret = delegate.typecastObjectMember(member, ret, callNode);
-    }
+  // Recursively executes type casts between `owner` and `this` and returns the resulting value.
+  public final Object executeTypeCasts(
+      Object value,
+      VmObjectLike owner,
+      IndirectCallNode callNode,
+      // if non-null, a stack frame for this member is inserted if a type cast fails
+      @Nullable ObjectMember member,
+      // Next type cast to be performed by the caller.
+      // Avoids repeating the same type cast in some cases.
+      @Nullable ListingOrMappingTypeCastNode nextTypeCastNode) {
+    var newNextTypeCastNode = typeCastNode != null ? typeCastNode : nextTypeCastNode;
+    @SuppressWarnings("DataFlowIssue")
+    var result =
+        this == owner
+            ? value
+            : ((VmListingOrMapping) parent)
+                .executeTypeCasts(value, owner, callNode, member, newNextTypeCastNode);
+    if (typeCastNode == null || typeCastNode == nextTypeCastNode) return result;
     var callTarget = typeCastNode.getCallTarget();
     try {
-      return callNode.call(
-          callTarget, VmUtils.getReceiver(typeNodeFrame), VmUtils.getOwner(typeNodeFrame), ret);
-    } catch (VmException vmException) {
+      return callNode.call(callTarget, typeCheckReceiver, typeCheckOwner, result);
+    } catch (VmException e) {
       CompilerDirectives.transferToInterpreter();
-      // treat typecheck as part of the call stack to read the original member if there is a
-      // source section for it.
-      var sourceSection = member.getBodySection();
-      if (!sourceSection.isAvailable()) {
-        sourceSection = member.getSourceSection();
+      if (member != null) {
+        VmUtils.insertStackFrame(member, callTarget, e);
       }
-      if (sourceSection.isAvailable()) {
-        vmException
-            .getInsertedStackFrames()
-            .put(callTarget, VmUtils.createStackFrame(sourceSection, member.getQualifiedName()));
-      }
-      throw vmException;
+      throw e;
     }
   }
 
-  public abstract SELF withCheckedMembers(
-      ListingOrMappingTypeCastNode typeCastNode, MaterializedFrame typeNodeFrame);
+  @Override
+  @TruffleBoundary
+  public final @Nullable Object getCachedValue(Object key) {
+    var result = EconomicMaps.get(cachedValues, key);
+    // if this object has members, `this[key]` may differ from `parent[key]`, so stop the search
+    if (result != null || !members.isEmpty()) return result;
 
-  /** Tells if this mapping/listing runs the same typechecks as {@code typeNode}. */
-  public boolean hasSameChecksAs(TypeNode typeNode) {
+    // Optimization: Recursively steal value from parent cache to avoid computing it multiple times.
+    // The current implementation has the following limitations and drawbacks:
+    // * It only works if a parent has, coincidentally, already cached `key`.
+    // * It turns getCachedValue() into an operation that isn't guaranteed to be fast and fail-safe.
+    // * It requires making VmObject.getCachedValue() non-final,
+    //   which is unfavorable for Truffle partial evaluation and JVM inlining.
+    // * It may not be worth its cost for constant members and members that are cheap to compute.
+
+    assert parent != null; // VmListingOrMapping always has a parent
+    result = parent.getCachedValue(key);
+    if (result == null) return null;
+
+    if (typeCastNode != null && !(key instanceof Identifier)) {
+      var callNode = IndirectCallNode.getUncached();
+      var callTarget = typeCastNode.getCallTarget();
+      try {
+        result = callNode.call(callTarget, typeCheckReceiver, typeCheckOwner, result);
+      } catch (VmException e) {
+        var member = VmUtils.findMember(parent, key);
+        assert member != null; // already found the member's cached value
+        VmUtils.insertStackFrame(member, callTarget, e);
+        throw e;
+      }
+    }
+    setCachedValue(key, result);
+    return result;
+  }
+
+  /**
+   * Tells whether the value type of this listing/mapping is known to be a subtype of {@code
+   * typeNode}. If {@code true}, type checks of individual values can be elided because
+   * listings/mappings are covariant in their value type.
+   */
+  public final boolean isValueTypeKnownSubtypeOf(TypeNode typeNode) {
+    if (typeNode.isNoopTypeCheck()) {
+      return true;
+    }
     if (typeCastNode == null) {
       return false;
     }
-    if (typeCastNode.getTypeNode().isEquivalentTo(typeNode)) {
-      return true;
-    }
-    // we can say the check is the same if the delegate has this check.
-    // when `Listing<Any>` delegates to `Listing<UInt>`, it has the same checks as a `UInt`
-    // typenode.
-    if (delegate != null) {
-      return delegate.hasSameChecksAs(typeNode);
-    }
-    return false;
+    return typeCastNode.getTypeNode().isEquivalentTo(typeNode);
   }
 }

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

@@ -18,7 +18,6 @@ package org.pkl.core.runtime;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.frame.MaterializedFrame;
 import java.util.Map;
-import java.util.Objects;
 import javax.annotation.concurrent.GuardedBy;
 import org.graalvm.collections.UnmodifiableEconomicMap;
 import org.pkl.core.ast.member.ListingOrMappingTypeCastNode;
@@ -27,7 +26,7 @@ import org.pkl.core.util.CollectionUtils;
 import org.pkl.core.util.EconomicMaps;
 import org.pkl.core.util.LateInit;
 
-public final class VmMapping extends VmListingOrMapping<VmMapping> {
+public final class VmMapping extends VmListingOrMapping {
 
   private int cachedEntryCount = -1;
 
@@ -50,24 +49,17 @@ public final class VmMapping extends VmListingOrMapping<VmMapping> {
       MaterializedFrame enclosingFrame,
       VmObject parent,
       UnmodifiableEconomicMap<Object, ObjectMember> members) {
-
-    super(enclosingFrame, Objects.requireNonNull(parent), members, null, null, null);
+    super(enclosingFrame, parent, members);
   }
 
   public VmMapping(
       MaterializedFrame enclosingFrame,
       VmObject parent,
       UnmodifiableEconomicMap<Object, ObjectMember> members,
-      VmMapping delegate,
-      ListingOrMappingTypeCastNode typeCheckNode,
-      MaterializedFrame typeNodeFrame) {
-    super(
-        enclosingFrame,
-        Objects.requireNonNull(parent),
-        members,
-        delegate,
-        typeCheckNode,
-        typeNodeFrame);
+      ListingOrMappingTypeCastNode typeCastNode,
+      Object typeCheckReceiver,
+      VmObjectLike typeCheckOwner) {
+    super(enclosingFrame, parent, members, typeCastNode, typeCheckReceiver, typeCheckOwner);
   }
 
   public static boolean isDefaultProperty(Object propertyKey) {
@@ -81,16 +73,12 @@ public final class VmMapping extends VmListingOrMapping<VmMapping> {
 
   @TruffleBoundary
   public VmSet getAllKeys() {
-    if (delegate != null) {
-      return delegate.getAllKeys();
-    }
     synchronized (this) {
       if (__allKeys == null) {
         // building upon parent's `getAllKeys()` should improve at least worst case efficiency
-        var parentKeys =
-            getParent() instanceof VmMapping mapping ? mapping.getAllKeys() : VmSet.EMPTY;
+        var parentKeys = parent instanceof VmMapping mapping ? mapping.getAllKeys() : VmSet.EMPTY;
         var builder = VmSet.builder(parentKeys);
-        for (var cursor = getMembers().getEntries(); cursor.advance(); ) {
+        for (var cursor = members.getEntries(); cursor.advance(); ) {
           var member = cursor.getValue();
           if (!member.isEntry()) continue;
           builder.add(cursor.getKey());
@@ -133,12 +121,17 @@ public final class VmMapping extends VmListingOrMapping<VmMapping> {
     if (this == obj) return true;
     if (!(obj instanceof VmMapping other)) return false;
 
-    if (getEntryCount() != other.getEntryCount()) return false;
     // could use shallow force, but deep force is cached
     force(false);
     other.force(false);
-    for (var key : getAllKeys()) {
-      var value = getCachedValue(key);
+    if (getEntryCount() != other.getEntryCount()) return false;
+
+    var cursor = cachedValues.getEntries();
+    while (cursor.advance()) {
+      Object key = cursor.getKey();
+      if (key instanceof Identifier) continue;
+
+      var value = cursor.getValue();
       assert value != null;
       var otherValue = other.getCachedValue(key);
       if (!value.equals(otherValue)) return false;
@@ -151,38 +144,34 @@ public final class VmMapping extends VmListingOrMapping<VmMapping> {
   @TruffleBoundary
   public int hashCode() {
     if (cachedHash != 0) return cachedHash;
-    // It's possible that the delegate has already computed its hash code.
-    // If so, we can go ahead and use it.
-    if (delegate != null && delegate.cachedHash != 0) return delegate.cachedHash;
 
     force(false);
     var result = 0;
-    for (var key : getAllKeys()) {
+    var cursor = cachedValues.getEntries();
+
+    while (cursor.advance()) {
+      var key = cursor.getKey();
       if (key instanceof Identifier) continue;
-      var value = getCachedValue(key);
+
+      var value = cursor.getValue();
       assert value != null;
       result += key.hashCode() ^ value.hashCode();
     }
+
     cachedHash = result;
     return result;
   }
 
+  // assumes mapping has been forced
   public int getEntryCount() {
     if (cachedEntryCount != -1) return cachedEntryCount;
-    cachedEntryCount = getAllKeys().getLength();
-    return cachedEntryCount;
-  }
 
-  @Override
-  @TruffleBoundary
-  public VmMapping withCheckedMembers(
-      ListingOrMappingTypeCastNode typeCheckNode, MaterializedFrame typeNodeFrame) {
-    return new VmMapping(
-        getEnclosingFrame(),
-        Objects.requireNonNull(getParent()),
-        getMembers(),
-        this,
-        typeCheckNode,
-        typeNodeFrame);
+    var result = 0;
+    for (var key : cachedValues.getKeys()) {
+      if (key instanceof Identifier) continue;
+      result += 1;
+    }
+    cachedEntryCount = result;
+    return result;
   }
 }

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

@@ -87,12 +87,12 @@ public abstract class VmObject extends VmObjectLike {
   }
 
   @Override
-  public void setCachedValue(Object key, Object value, ObjectMember objectMember) {
+  public final void setCachedValue(Object key, Object value) {
     EconomicMaps.put(cachedValues, key, value);
   }
 
   @Override
-  public boolean hasCachedValue(Object key) {
+  public final boolean hasCachedValue(Object key) {
     return EconomicMaps.containsKey(cachedValues, key);
   }
 

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

@@ -96,7 +96,7 @@ public abstract class VmObjectLike extends VmValue {
    * receiver.
    */
   @TruffleBoundary
-  public abstract void setCachedValue(Object key, Object value, ObjectMember objectMember);
+  public abstract void setCachedValue(Object key, Object value);
 
   /**
    * Prefer this method over {@link #getCachedValue} if the value is not required. (There is no

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

@@ -15,6 +15,7 @@
  */
 package org.pkl.core.runtime;
 
+import com.oracle.truffle.api.CallTarget;
 import com.oracle.truffle.api.CompilerDirectives;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.Truffle;
@@ -134,10 +135,6 @@ 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);
   }
@@ -158,10 +155,6 @@ 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];
@@ -261,17 +254,17 @@ public final class VmUtils {
 
     final var constantValue = member.getConstantValue();
     if (constantValue != null) {
-      var ret = constantValue;
-      // for a property, do a type check
+      var result = constantValue;
+      // for a property, Listing element, or Mapping value, do a type check
       if (member.isProp()) {
         var property = receiver.getVmClass().getProperty(member.getName());
         if (property != null && property.getTypeNode() != null) {
           var callTarget = property.getTypeNode().getCallTarget();
           try {
             if (checkType) {
-              ret = callNode.call(callTarget, receiver, property.getOwner(), constantValue);
+              result = callNode.call(callTarget, receiver, property.getOwner(), constantValue);
             } else {
-              ret =
+              result =
                   callNode.call(
                       callTarget,
                       receiver,
@@ -281,44 +274,52 @@ public final class VmUtils {
             }
           } catch (VmException e) {
             CompilerDirectives.transferToInterpreter();
-            // A failed property type check looks as follows in the stack trace:
-            // x: Int(isPositive)
-            // at ...
-            // x = -10
-            // at ...
-            // However, if the value of `x` is a parse-time constant (as in `x = -10`),
-            // there's no root node for it and hence no stack trace element.
-            // In this case, insert a stack trace element to make the stack trace look the same
-            // as in the non-constant case. (Parse-time constants are an internal optimization.)
-            e.getInsertedStackFrames()
-                .put(
-                    callTarget,
-                    createStackFrame(member.getBodySection(), member.getQualifiedName()));
+            insertStackFrame(member, callTarget, e);
             throw e;
           }
         }
-      } else if (receiver instanceof VmListingOrMapping<?> vmListingOrMapping) {
-        if (owner != receiver && owner instanceof VmListingOrMapping<?> vmListingOrMappingOwner) {
-          ret = vmListingOrMappingOwner.typecastObjectMember(member, ret, callNode);
-        }
-        ret = vmListingOrMapping.typecastObjectMember(member, ret, callNode);
+      } else if (receiver instanceof VmListingOrMapping listingOrMapping
+          && owner instanceof VmListingOrMapping) {
+        // `owner instanceof VmListingOrMapping` guards against
+        // PropertiesRenderer amending VmDynamic with VmListing (hack?)
+        result = listingOrMapping.executeTypeCasts(constantValue, owner, callNode, member, null);
       }
-      receiver.setCachedValue(memberKey, ret, member);
-      return ret;
+
+      receiver.setCachedValue(memberKey, result);
+      return result;
     }
 
     var callTarget = member.getCallTarget();
-    Object ret;
+    Object result;
     if (checkType) {
-      ret = callNode.call(callTarget, receiver, owner, memberKey);
+      result = callNode.call(callTarget, receiver, owner, memberKey);
     } else {
-      ret = callNode.call(callTarget, receiver, owner, memberKey, VmUtils.SKIP_TYPECHECK_MARKER);
+      result = callNode.call(callTarget, receiver, owner, memberKey, VmUtils.SKIP_TYPECHECK_MARKER);
     }
-    if (receiver instanceof VmListingOrMapping<?> vmListingOrMapping) {
-      ret = vmListingOrMapping.typecastObjectMember(member, ret, callNode);
+    receiver.setCachedValue(memberKey, result);
+    return result;
+  }
+
+  // A failed property type check looks as follows in the stack trace:
+  // x: Int(isPositive)
+  // at ...
+  // x = -10
+  // at ...
+  // However, if the value of `x` is a parse-time constant (as in `x = -10`),
+  // there's no root node for it and hence no stack trace element.
+  // In this case, insert a stack trace element to make the stack trace look the same
+  // as in the non-constant case. (Parse-time constants are an internal optimization.)
+  public static void insertStackFrame(
+      ObjectMember member, CallTarget location, VmException exception) {
+    var sourceSection = member.getBodySection();
+    if (!sourceSection.isAvailable()) {
+      sourceSection = member.getSourceSection();
+    }
+    if (sourceSection.isAvailable()) {
+      exception
+          .getInsertedStackFrames()
+          .put(location, createStackFrame(sourceSection, member.getQualifiedName()));
     }
-    receiver.setCachedValue(memberKey, ret, member);
-    return ret;
   }
 
   public static @Nullable ObjectMember findMember(VmObjectLike receiver, Object memberKey) {

pkl-core/src/main/java/org/pkl/core/stdlib/protobuf/RendererNodes.java

@@ -50,6 +50,7 @@ import org.pkl.core.runtime.VmDuration;
 import org.pkl.core.runtime.VmDynamic;
 import org.pkl.core.runtime.VmExceptionBuilder;
 import org.pkl.core.runtime.VmIntSeq;
+import org.pkl.core.runtime.VmLanguage;
 import org.pkl.core.runtime.VmList;
 import org.pkl.core.runtime.VmListing;
 import org.pkl.core.runtime.VmMap;
@@ -573,7 +574,8 @@ public final class RendererNodes {
         type =
             requiresWrapper()
                 ? null
-                : new ListingTypeNode(VmUtils.unavailableSourceSection(), valueType);
+                : new ListingTypeNode(
+                    VmUtils.unavailableSourceSection(), VmLanguage.get(null), valueType);
         return type;
       } else if (type instanceof MappingTypeNode mappingType) {
         var keyType = resolveType(mappingType.getKeyTypeNode());
@@ -587,7 +589,9 @@ public final class RendererNodes {
         }
         var valueType = resolveType(mappingType.getValueTypeNode());
         assert valueType != null : "Incomplete or malformed Mapping type";
-        mappingType = new MappingTypeNode(VmUtils.unavailableSourceSection(), keyType, valueType);
+        mappingType =
+            new MappingTypeNode(
+                VmUtils.unavailableSourceSection(), VmLanguage.get(null), keyType, valueType);
 
         type = requiresWrapper() ? null : mappingType;
         return type;

pkl-core/src/main/java/org/pkl/core/util/EconomicMaps.java

@@ -30,6 +30,10 @@ import org.graalvm.collections.UnmodifiableMapCursor;
 public final class EconomicMaps {
   private EconomicMaps() {}
 
+  public static <K, V> UnmodifiableEconomicMap<K, V> emptyMap() {
+    return EconomicMap.emptyMap();
+  }
+
   @TruffleBoundary
   public static <K, V> EconomicMap<K, V> create() {
     return EconomicMap.create();

pkl-core/src/test/files/LanguageSnippetTests/input-helper/listings/cacheStealingTypeCheck.pkl

@@ -0,0 +1,3 @@
+function isValid(str): Boolean = str.startsWith("a")
+
+foo: Listing<String(isValid(this))>(isDistinct)

pkl-core/src/test/files/LanguageSnippetTests/input/api/listing.pkl

@@ -27,12 +27,20 @@ local altered: Listing<Person> = (base) {
   [0] { name = "Wood Pigeon" }
 }
 
+local computedIndex: Listing<Person> = (base) {
+  [computeIndex()] { name = "Wood Pigeon" }
+}
+
+local function computeIndex() = 0
+
 facts {
   ["isEmpty"] {
     empty.isEmpty
     empty2.isEmpty
     !base.isEmpty
     !derived.isEmpty
+    !altered.isEmpty
+    !computedIndex.isEmpty
   }
   
   ["lastIndex"] {
@@ -41,6 +49,8 @@ facts {
     base.lastIndex == 2
     derived.lastIndex == 4
     duplicate.lastIndex == 5
+    altered.lastIndex == 2
+    computedIndex.lastIndex == 2
   }
 
   ["isDistinct"] {
@@ -49,6 +59,8 @@ facts {
     base.isDistinct
     derived.isDistinct
     !duplicate.isDistinct
+    altered.isDistinct
+    computedIndex.isDistinct
   }
 
   ["isDistinctBy()"] {
@@ -57,18 +69,24 @@ facts {
     base.isDistinctBy((it) -> it)
     derived.isDistinctBy((it) -> it)
     !duplicate.isDistinctBy((it) -> it)
+    altered.isDistinctBy((it) -> it)
+    computedIndex.isDistinctBy((it) -> it)
 
     empty.isDistinctBy((it) -> it.name)
     empty2.isDistinctBy((it) -> it.name)
     base.isDistinctBy((it) -> it.name)
     derived.isDistinctBy((it) -> it.name)
     !duplicate.isDistinctBy((it) -> it.name)
+    altered.isDistinctBy((it) -> it.name)
+    computedIndex.isDistinctBy((it) -> it.name)
 
     empty.isDistinctBy((it) -> it.getClass())
     empty2.isDistinctBy((it) -> it.getClass())
     !base.isDistinctBy((it) -> it.getClass())
     !derived.isDistinctBy((it) -> it.getClass())
     !duplicate.isDistinctBy((it) -> it.getClass())
+    !altered.isDistinctBy((it) -> it.getClass())
+    !computedIndex.isDistinctBy((it) -> it.getClass())
   }
   
   ["getOrNull"] {
@@ -85,24 +103,32 @@ facts {
     module.catch(() -> empty.first) == "Expected a non-empty Listing."
     base.first == base[0]
     derived.first == base[0]
+    altered.first != base[0]
+    computedIndex.first == altered.first
   }
   
   ["firstOrNull"] {
     empty.firstOrNull == null
     base.firstOrNull == base[0]
     derived.firstOrNull == base[0]
+    altered.firstOrNull != base[0]
+    computedIndex.firstOrNull == altered.first
   }
 
   ["last"] {
     module.catch(() -> empty.last) == "Expected a non-empty Listing."
     base.last == base[2]
     derived.last == derived[4]
+    altered.last == base[2]
+    computedIndex.last == base[2]
   }
 
   ["lastOrNull"] {
     empty.lastOrNull == null
     base.lastOrNull == base[2]
     derived.lastOrNull == derived[4]
+    altered.lastOrNull == base[2]
+    computedIndex.lastOrNull == base[2]
   }
 
   ["single"] {
@@ -135,6 +161,7 @@ facts {
     derived.contains(base[1])
     derived.contains(derived[3])
     !altered.contains(base[0])
+    !computedIndex.contains(base[0])
   }
 }
 
@@ -144,6 +171,17 @@ examples {
     empty2.length
     base.length
     derived.length
+    altered.length
+    computedIndex.length
+    
+    local elementsAndEntries = (base) {
+      new { name = "" }
+      [2] { name = "" }
+      [computeIndex()] { name = "" }
+      new { name = "" }
+      [1 + 0] { name = "" }
+    }
+    elementsAndEntries.length
   }
 
   ["toList()"] {
@@ -152,6 +190,8 @@ examples {
     base.toList()
     derived.toList()
     duplicate.toList()
+    altered.toList()
+    computedIndex.toList()
   }
 
   ["toSet()"] {
@@ -160,6 +200,8 @@ examples {
     base.toSet()
     derived.toSet()
     duplicate.toSet()
+    altered.toSet()
+    computedIndex.toSet()
   }
 
   ["distinct"] {
@@ -168,6 +210,8 @@ examples {
     base.distinct
     derived.distinct
     duplicate.distinct
+    altered.distinct
+    computedIndex.distinct
   }
 
   ["distinctBy()"] {
@@ -176,36 +220,48 @@ examples {
     base.distinctBy((it) -> it)
     derived.distinctBy((it) -> it)
     duplicate.distinctBy((it) -> it)
+    altered.distinctBy((it) -> it)
+    computedIndex.distinctBy((it) -> it)
 
     empty.distinctBy((it) -> it.name)
     empty2.distinctBy((it) -> it.name)
     base.distinctBy((it) -> it.name)
     derived.distinctBy((it) -> it.name)
     duplicate.distinctBy((it) -> it.name)
+    altered.distinctBy((it) -> it.name)
+    computedIndex.distinctBy((it) -> it.name)
 
     empty.distinctBy((it) -> it.getClass())
     empty2.distinctBy((it) -> it.getClass())
     base.distinctBy((it) -> it.getClass())
     derived.distinctBy((it) -> it.getClass())
     duplicate.distinctBy((it) -> it.getClass())
+    altered.distinctBy((it) -> it.getClass())
+    computedIndex.distinctBy((it) -> it.getClass())
   }
 
   ["fold"] {
     empty.fold(List(), (l, e) -> l.add(e))
     base.fold(List(), (l, e) -> l.add(e))
     derived.fold(List(), (l, e) -> l.add(e))
+    altered.fold(List(), (l, e) -> l.add(e))
+    computedIndex.fold(List(), (l, e) -> l.add(e))
   }
 
   ["foldIndexed"] {
     empty.foldIndexed(List(), (i, l, e) -> l.add(Pair(i, e)))
     base.foldIndexed(List(), (i, l, e) -> l.add(Pair(i, e)))
     derived.foldIndexed(List(), (i, l, e) -> l.add(Pair(i, e)))
+    altered.foldIndexed(List(), (i, l, e) -> l.add(Pair(i, e)))
+    computedIndex.foldIndexed(List(), (i, l, e) -> l.add(Pair(i, e)))
   }
 
 
   local baseNum = new Listing { 1; 2; 3 }
   local baseString = new Listing { "Pigeon"; "Barn Owl"; "Parrot" }
   local derivedString = (baseString) { "Albatross"; "Elf Owl" }
+  local alteredString = (baseString) { [0] = "Wood Pigeon" }
+  local computedIndexString = (baseString) { [computeIndex()] = "Wood Pigeon" }
 
   ["join"] {
     empty.join("")
@@ -215,5 +271,9 @@ examples {
     baseString.join("---")
     derivedString.join("")
     derivedString.join("\n")
+    alteredString.join("")
+    alteredString.join("\n")
+    computedIndexString.join("")
+    computedIndexString.join("\n")
   }
 }

pkl-core/src/test/files/LanguageSnippetTests/input/errors/listingTypeCheckError8.pkl

@@ -0,0 +1,6 @@
+local a = new Listing { new Listing { 0 } }
+local b = a as Listing<Listing<String>> 
+local c = (b) { new Listing { 1 } }
+local d = c as Listing<Listing<Int>>
+
+result = d

pkl-core/src/test/files/LanguageSnippetTests/input/errors/listingTypeCheckError9.pkl

@@ -0,0 +1,10 @@
+local a = new Listing { new Foo {} }
+local b = (a) { new Bar {} }
+local c = b as Listing<Bar>
+local d = (c) { new Foo {} }
+local e = d as Listing<Foo>
+
+result = e
+
+open class Foo
+class Bar extends Foo

pkl-core/src/test/files/LanguageSnippetTests/input/errors/mappingTypeCheckError11.pkl

@@ -0,0 +1,10 @@
+local a = new Mapping { [0] = new Foo {} }
+local b = (a) { [1] = new Bar {} }
+local c = b as Mapping<Int, Bar>
+local d = (c) { [2] = new Foo {} }
+local e = d as Mapping<Int, Foo>
+
+result = e
+
+open class Foo
+class Bar extends Foo

pkl-core/src/test/files/LanguageSnippetTests/input/listings/cacheStealing.pkl

@@ -0,0 +1,7 @@
+foo1: Listing<String> = new { "hello" }
+foo2: Listing<String|Int> = foo1
+
+res1 = foo1.isDistinct
+// steals isDistinct from foo1's VmListing.cachedValues but must not
+// perform a String|Int type check because isDistinct is not an element
+res2 = foo2.isDistinct

pkl-core/src/test/files/LanguageSnippetTests/input/listings/cacheStealingTypeCheck.pkl

@@ -0,0 +1,8 @@
+amends "../../input-helper/listings/cacheStealingTypeCheck.pkl"
+
+// this test covers a regression where the wrong receiver 
+// and owner was used to typecheck a stolen value
+foo {
+  "abcdx"
+  "ax"
+}

pkl-core/src/test/files/LanguageSnippetTests/input/types/helpers/originalTypealias.pkl

@@ -0,0 +1,5 @@
+const local lastName = "Birdo"
+
+typealias Birds = Listing<String(endsWith(lastName))>
+
+typealias Birds2 = Pair<Listing<String(endsWith(lastName))>, Int>

pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAlias1.pkl

@@ -1,5 +1,7 @@
 import "pkl:test"
 
+import "helpers/originalTypealias.pkl"
+
 typealias Simple = String
 const function simple(arg: Simple): Simple = arg
 
@@ -105,3 +107,8 @@ res19: LocalTypeAlias = "abc"
 typealias VeryComposite = Pair<Composite, Composite>
 
 res20: VeryComposite = Pair(Map("abc", List("def")), Map("abc", List("def")))
+
+// typealiases should be executed in their original context
+res21: originalTypealias.Birds = new { "John Birdo" }
+
+res22: originalTypealias.Birds2 = Pair(new Listing { "John Birdo" }, 0)

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

@@ -0,0 +1,3 @@
+import "helpers/originalTypealias.pkl"
+
+res: originalTypealias.Birds = new { "Jimmy Bird" }

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

@@ -4,6 +4,8 @@ facts {
     true
     true
     true
+    true
+    true
   }
   ["lastIndex"] {
     true
@@ -11,6 +13,8 @@ facts {
     true
     true
     true
+    true
+    true
   }
   ["isDistinct"] {
     true
@@ -18,6 +22,8 @@ facts {
     true
     true
     true
+    true
+    true
   }
   ["isDistinctBy()"] {
     true
@@ -35,6 +41,12 @@ facts {
     true
     true
     true
+    true
+    true
+    true
+    true
+    true
+    true
   }
   ["getOrNull"] {
     true
@@ -49,21 +61,29 @@ facts {
     true
     true
     true
+    true
+    true
   }
   ["firstOrNull"] {
     true
     true
     true
+    true
+    true
   }
   ["last"] {
     true
     true
     true
+    true
+    true
   }
   ["lastOrNull"] {
     true
     true
     true
+    true
+    true
   }
   ["single"] {
     true
@@ -91,6 +111,7 @@ facts {
     true
     true
     true
+    true
   }
 }
 examples {
@@ -99,6 +120,9 @@ examples {
     0
     3
     5
+    3
+    3
+    5
   }
   ["toList()"] {
     List()
@@ -134,6 +158,20 @@ examples {
     }, new {
       name = "Elf Owl"
     })
+    List(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
+    List(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
   }
   ["toSet()"] {
     Set()
@@ -167,6 +205,20 @@ examples {
     }, new {
       name = "Elf Owl"
     })
+    Set(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
+    Set(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
   }
   ["distinct"] {
     new {}
@@ -216,6 +268,28 @@ examples {
         name = "Elf Owl"
       }
     }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
   }
   ["distinctBy()"] {
     new {}
@@ -265,6 +339,28 @@ examples {
         name = "Elf Owl"
       }
     }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
     new {}
     new {}
     new {
@@ -312,6 +408,28 @@ examples {
         name = "Elf Owl"
       }
     }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+      new {
+        name = "Barn Owl"
+      }
+      new {
+        name = "Parrot"
+      }
+    }
     new {}
     new {}
     new {
@@ -329,6 +447,16 @@ examples {
         name = "Pigeon"
       }
     }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+    }
+    new {
+      new {
+        name = "Wood Pigeon"
+      }
+    }
   }
   ["fold"] {
     List()
@@ -350,6 +478,20 @@ examples {
     }, new {
       name = "Elf Owl"
     })
+    List(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
+    List(new {
+      name = "Wood Pigeon"
+    }, new {
+      name = "Barn Owl"
+    }, new {
+      name = "Parrot"
+    })
   }
   ["foldIndexed"] {
     List()
@@ -371,6 +513,20 @@ examples {
     }), Pair(4, new {
       name = "Elf Owl"
     }))
+    List(Pair(0, new {
+      name = "Wood Pigeon"
+    }), Pair(1, new {
+      name = "Barn Owl"
+    }), Pair(2, new {
+      name = "Parrot"
+    }))
+    List(Pair(0, new {
+      name = "Wood Pigeon"
+    }), Pair(1, new {
+      name = "Barn Owl"
+    }), Pair(2, new {
+      name = "Parrot"
+    }))
   }
   ["join"] {
     ""
@@ -386,5 +542,17 @@ examples {
     Albatross
     Elf Owl
     """
+    "Wood PigeonBarn OwlParrot"
+    """
+    Wood Pigeon
+    Barn Owl
+    Parrot
+    """
+    "Wood PigeonBarn OwlParrot"
+    """
+    Wood Pigeon
+    Barn Owl
+    Parrot
+    """
   }
 }

pkl-core/src/test/files/LanguageSnippetTests/output/errors/listingTypeCheckError8.err

@@ -0,0 +1,15 @@
+–– Pkl Error ––
+Expected value of type `String`, but got type `Int`.
+Value: 0
+
+x | local b = a as Listing<Listing<String>>
+                                   ^^^^^^
+at listingTypeCheckError8#b (file:///$snippetsDir/input/errors/listingTypeCheckError8.pkl)
+
+x | local a = new Listing { new Listing { 0 } }
+                                          ^
+at listingTypeCheckError8#a[#1][#1] (file:///$snippetsDir/input/errors/listingTypeCheckError8.pkl)
+
+xxx | text = renderer.renderDocument(value)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/listingTypeCheckError9.err

@@ -0,0 +1,15 @@
+–– Pkl Error ––
+Expected value of type `listingTypeCheckError9#Bar`, but got type `listingTypeCheckError9#Foo`.
+Value: new Foo {}
+
+x | local c = b as Listing<Bar>
+                           ^^^
+at listingTypeCheckError9#c (file:///$snippetsDir/input/errors/listingTypeCheckError9.pkl)
+
+x | local a = new Listing { new Foo {} }
+                            ^^^^^^^^^^
+at listingTypeCheckError9#a[#1] (file:///$snippetsDir/input/errors/listingTypeCheckError9.pkl)
+
+xxx | text = renderer.renderDocument(value)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/mappingTypeCheckError11.err

@@ -0,0 +1,15 @@
+–– Pkl Error ––
+Expected value of type `mappingTypeCheckError11#Bar`, but got type `mappingTypeCheckError11#Foo`.
+Value: new Foo {}
+
+x | local c = b as Mapping<Int, Bar>
+                                ^^^
+at mappingTypeCheckError11#c (file:///$snippetsDir/input/errors/mappingTypeCheckError11.pkl)
+
+x | local a = new Mapping { [0] = new Foo {} }
+                                  ^^^^^^^^^^
+at mappingTypeCheckError11#a[0] (file:///$snippetsDir/input/errors/mappingTypeCheckError11.pkl)
+
+xxx | text = renderer.renderDocument(value)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/listings/cacheStealing.pcf

@@ -0,0 +1,8 @@
+foo1 {
+  "hello"
+}
+foo2 {
+  "hello"
+}
+res1 = true
+res2 = true

pkl-core/src/test/files/LanguageSnippetTests/output/listings/cacheStealingTypeCheck.pcf

@@ -0,0 +1,4 @@
+foo {
+  "abcdx"
+  "ax"
+}

pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAlias1.pcf

@@ -38,3 +38,9 @@ res18 = "Expected value of type `Duration`, but got type `DataSize`. Value: 5.mb
 res18b = "Expected value of type `Duration`, but got type `DataSize`. Value: 5.mb"
 res19 = "abc"
 res20 = Pair(Map("abc", List("def")), Map("abc", List("def")))
+res21 {
+  "John Birdo"
+}
+res22 = Pair(new {
+  "John Birdo"
+}, 0)

pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasContext.err

@@ -0,0 +1,15 @@
+–– Pkl Error ––
+Type constraint `endsWith(lastName)` violated.
+Value: "Jimmy Bird"
+
+x | typealias Birds = Listing<String(endsWith(lastName))>
+                                     ^^^^^^^^^^^^^^^^^^
+at typeAliasContext#res (file:///$snippetsDir/input/types/helpers/originalTypealias.pkl)
+
+x | res: originalTypealias.Birds = new { "Jimmy Bird" }
+                                         ^^^^^^^^^^^^
+at typeAliasContext#res[#1] (file:///$snippetsDir/input/types/typeAliasContext.pkl)
+
+xxx | text = renderer.renderDocument(value)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)

pkl-doc/src/main/kotlin/org/pkl/doc/DocGenerator.kt

@@ -117,7 +117,7 @@ class DocGenerator(
   }
 
   private fun DocPackage.deletePackageDir() {
-    outputDir.resolve("$name/$version").deleteRecursively()
+    outputDir.resolve(IoUtils.encodePath("$name/$version")).deleteRecursively()
   }
 
   private fun createSymlinks(currentPackagesData: List<PackageData>) {

pkl-gradle/src/main/java/org/pkl/gradle/PklPlugin.java

@@ -18,6 +18,7 @@ package org.pkl.gradle;
 import java.io.File;
 import java.lang.reflect.InvocationTargetException;
 import java.nio.file.Files;
+import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Optional;
@@ -27,6 +28,7 @@ import org.gradle.api.GradleException;
 import org.gradle.api.NamedDomainObjectContainer;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
+import org.gradle.api.Transformer;
 import org.gradle.api.file.SourceDirectorySet;
 import org.gradle.api.plugins.Convention;
 import org.gradle.api.provider.Provider;
@@ -64,6 +66,7 @@ import org.pkl.gradle.task.PkldocTask;
 import org.pkl.gradle.task.ProjectPackageTask;
 import org.pkl.gradle.task.ProjectResolveTask;
 import org.pkl.gradle.task.TestTask;
+import org.pkl.gradle.utils.PluginUtils;
 
 @SuppressWarnings("unused")
 public class PklPlugin implements Plugin<Project> {
@@ -456,6 +459,9 @@ public class PklPlugin implements Plugin<Project> {
 
   private List<File> getTransitiveModules(AnalyzeImportsTask analyzeTask) {
     var outputFile = analyzeTask.getOutputFile().get().getAsFile().toPath();
+    if (!analyzeTask.getOnlyIf().isSatisfiedBy(analyzeTask)) {
+      return Collections.emptyList();
+    }
     try {
       var contents = Files.readString(outputFile);
       ImportGraph importGraph = ImportGraph.parseFromJson(contents);
@@ -470,9 +476,16 @@ public class PklPlugin implements Plugin<Project> {
   }
 
   private <T extends ModulesTask, S extends ModulesSpec> void configureModulesTask(
-      T task, S spec, @Nullable TaskProvider<AnalyzeImportsTask> analyzeImportsTask) {
+      T task,
+      S spec,
+      @Nullable TaskProvider<AnalyzeImportsTask> analyzeImportsTask,
+      @Nullable Transformer<List<?>, List<?>> mapSourceModules) {
     configureBaseTask(task, spec);
-    task.getSourceModules().set(spec.getSourceModules());
+    if (mapSourceModules != null) {
+      task.getSourceModules().set(spec.getSourceModules().map(mapSourceModules));
+    } else {
+      task.getSourceModules().set(spec.getSourceModules());
+    }
     task.getNoProject().set(spec.getNoProject());
     task.getProjectDir().set(spec.getProjectDir());
     task.getOmitProjectSettings().set(spec.getOmitProjectSettings());
@@ -484,6 +497,11 @@ public class PklPlugin implements Plugin<Project> {
     }
   }
 
+  private <T extends ModulesTask, S extends ModulesSpec> void configureModulesTask(
+      T task, S spec, @Nullable TaskProvider<AnalyzeImportsTask> analyzeImportsTask) {
+    configureModulesTask(task, spec, analyzeImportsTask, null);
+  }
+
   private TaskProvider<AnalyzeImportsTask> createAnalyzeImportsTask(ModulesSpec spec) {
     var outputFile =
         project
@@ -496,11 +514,26 @@ public class PklPlugin implements Plugin<Project> {
             spec.getName() + "GatherImports",
             AnalyzeImportsTask.class,
             task -> {
-              configureModulesTask(task, spec, null);
+              configureModulesTask(
+                  task,
+                  spec,
+                  null,
+                  (modules) ->
+                      // only need to analyze imports of file-based modules; it's unlikely that a
+                      // non-file-based module will import a file-based module due to security
+                      // manager trust levels (see
+                      // org.pkl.core.SecurityManagers.getDefaultTrustLevel).
+                      modules.stream()
+                          .map(PluginUtils::parseModuleNotationToUri)
+                          .filter(
+                              (it) ->
+                                  it.getScheme() == null || it.getScheme().equalsIgnoreCase("file"))
+                          .toList());
               task.setDescription("Compute the set of imports declared by input modules");
               task.setGroup("build");
               task.getOutputFormat().set(OutputFormat.JSON.toString());
               task.getOutputFile().set(outputFile);
+              task.onlyIf(ignored -> !task.getSourceModules().get().isEmpty());
             });
   }
 

pkl-gradle/src/main/java/org/pkl/gradle/task/BasePklTask.java

@@ -17,9 +17,6 @@ package org.pkl.gradle.task;
 
 import java.io.File;
 import java.net.URI;
-import java.net.URISyntaxException;
-import java.net.URL;
-import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.time.Duration;
@@ -31,10 +28,8 @@ import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import javax.inject.Inject;
 import org.gradle.api.DefaultTask;
-import org.gradle.api.InvalidUserDataException;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.file.DirectoryProperty;
-import org.gradle.api.file.FileSystemLocation;
 import org.gradle.api.model.ObjectFactory;
 import org.gradle.api.provider.ListProperty;
 import org.gradle.api.provider.MapProperty;
@@ -49,9 +44,9 @@ import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.TaskAction;
 import org.pkl.commons.cli.CliBaseOptions;
 import org.pkl.core.evaluatorSettings.Color;
-import org.pkl.core.util.IoUtils;
 import org.pkl.core.util.LateInit;
 import org.pkl.core.util.Nullable;
+import org.pkl.gradle.utils.PluginUtils;
 
 public abstract class BasePklTask extends DefaultTask {
   @Input
@@ -74,7 +69,7 @@ public abstract class BasePklTask extends DefaultTask {
 
   @Internal
   public Provider<Object> getParsedSettingsModule() {
-    return getSettingsModule().map(this::parseModuleNotation);
+    return getSettingsModule().map(PluginUtils::parseModuleNotation);
   }
 
   @InputFile
@@ -165,7 +160,7 @@ public abstract class BasePklTask extends DefaultTask {
               parseModulePath(),
               getProject().getProjectDir().toPath(),
               mapAndGetOrNull(getEvalRootDirPath(), Paths::get),
-              mapAndGetOrNull(getSettingsModule(), this::parseModuleNotationToUri),
+              mapAndGetOrNull(getSettingsModule(), PluginUtils::parseModuleNotationToUri),
               null,
               getEvalTimeout().getOrNull(),
               mapAndGetOrNull(getModuleCacheDir(), it1 -> it1.getAsFile().toPath()),
@@ -199,100 +194,6 @@ public abstract class BasePklTask extends DefaultTask {
     return getModulePath().getFiles().stream().map(File::toPath).collect(Collectors.toList());
   }
 
-  /**
-   * Parses the specified source module notation into a "parsed" notation which is then used for
-   * input path tracking and as an argument for the CLI API.
-   *
-   * <p>This method accepts the following input types:
-   *
-   * <ul>
-   *   <li>{@link URI} - used as is.
-   *   <li>{@link File} - used as is.
-   *   <li>{@link Path} - converted to a {@link File}. This conversion may fail because not all
-   *       {@link Path}s point to the local file system.
-   *   <li>{@link URL} - converted to a {@link URI}. This conversion may fail because {@link URL}
-   *       allows for URLs which are not compliant URIs.
-   *   <li>{@link CharSequence} - first, converted to a string. If this string is "URI-like" (see
-   *       {@link IoUtils#isUriLike(String)}), then we attempt to parse it as a {@link URI}, which
-   *       may fail. Otherwise, we attempt to parse it as a {@link Path}, which is then converted to
-   *       a {@link File} (both of these operations may fail).
-   *   <li>{@link FileSystemLocation} - converted to a {@link File} via the {@link
-   *       FileSystemLocation#getAsFile()} method.
-   * </ul>
-   *
-   * In case the returned value is determined to be a {@link URI}, then this URI is first checked
-   * for whether its scheme is {@code file}, like {@code file:///example/path}. In such case, this
-   * method returns a {@link File} corresponding to the file path in the URI. Otherwise, a {@link
-   * URI} instance is returned.
-   *
-   * @throws InvalidUserDataException In case the input is none of the types described above, or
-   *     when the underlying value cannot be parsed correctly.
-   */
-  protected Object parseModuleNotation(Object notation) {
-    if (notation instanceof URI uri) {
-      if ("file".equals(uri.getScheme())) {
-        return new File(uri.getPath());
-      }
-      return uri;
-    } else if (notation instanceof File) {
-      return notation;
-    } else if (notation instanceof Path path) {
-      try {
-        return path.toFile();
-      } catch (UnsupportedOperationException e) {
-        throw new InvalidUserDataException("Failed to parse Pkl module file path: " + notation, e);
-      }
-    } else if (notation instanceof URL url) {
-      try {
-        return parseModuleNotation(url.toURI());
-      } catch (URISyntaxException e) {
-        throw new InvalidUserDataException("Failed to parse Pkl module URI: " + notation, e);
-      }
-    } else if (notation instanceof CharSequence) {
-      var s = notation.toString();
-      if (IoUtils.isUriLike(s)) {
-        try {
-          return parseModuleNotation(IoUtils.toUri(s));
-        } catch (URISyntaxException e) {
-          throw new InvalidUserDataException("Failed to parse Pkl module URI: " + s, e);
-        }
-      } else {
-        try {
-          return Paths.get(s).toFile();
-        } catch (InvalidPathException | UnsupportedOperationException e) {
-          throw new InvalidUserDataException("Failed to parse Pkl module file path: " + s, e);
-        }
-      }
-    } else if (notation instanceof FileSystemLocation location) {
-      return location.getAsFile();
-    } else {
-      throw new InvalidUserDataException(
-          "Unsupported value of type "
-              + notation.getClass()
-              + " used as a module path: "
-              + notation);
-    }
-  }
-
-  protected URI parseModuleNotationToUri(Object m) {
-    var parsed1 = parseModuleNotation(m);
-    return parsedModuleNotationToUri(parsed1);
-  }
-
-  /**
-   * Converts either a file or a URI to a URI. We convert a file to a URI via the {@link
-   * IoUtils#createUri(String)} because other ways of conversion can make relative paths into
-   * absolute URIs, which may break module loading.
-   */
-  private URI parsedModuleNotationToUri(Object notation) {
-    if (notation instanceof File file) {
-      return IoUtils.createUri(file.getPath());
-    } else if (notation instanceof URI uri) {
-      return uri;
-    }
-    throw new IllegalArgumentException("Invalid parsed module notation: " + notation);
-  }
-
   protected List<Pattern> patternsFromStrings(List<String> patterns) {
     return patterns.stream().map(Pattern::compile).collect(Collectors.toList());
   }

pkl-gradle/src/main/java/org/pkl/gradle/task/ModulesTask.java

@@ -37,8 +37,8 @@ import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.TaskAction;
 import org.pkl.commons.cli.CliBaseOptions;
 import org.pkl.core.evaluatorSettings.Color;
-import org.pkl.core.util.IoUtils;
 import org.pkl.core.util.Pair;
+import org.pkl.gradle.utils.PluginUtils;
 
 public abstract class ModulesTask extends BasePklTask {
   // We expose the contents of this property as task inputs via the sourceModuleFiles
@@ -84,7 +84,7 @@ public abstract class ModulesTask extends BasePklTask {
   @Override
   protected List<URI> getSourceModulesAsUris() {
     return getSourceModules().get().stream()
-        .map(this::parseModuleNotationToUri)
+        .map(PluginUtils::parseModuleNotationToUri)
         .collect(Collectors.toList());
   }
 
@@ -117,7 +117,7 @@ public abstract class ModulesTask extends BasePklTask {
     var files = new ArrayList<File>();
     var uris = new ArrayList<URI>();
     for (var m : modules) {
-      var parsed = parseModuleNotation(m);
+      var parsed = PluginUtils.parseModuleNotation(m);
       if (parsed instanceof File file) {
         files.add(file);
       } else if (parsed instanceof URI uri) {
@@ -127,28 +127,6 @@ public abstract class ModulesTask extends BasePklTask {
     return Pair.of(files, uris);
   }
 
-  /**
-   * Converts either a file or a URI to a URI. We convert a relative file to a URI via the {@link
-   * IoUtils#createUri(String)} because other ways of conversion can make relative paths into
-   * absolute URIs, which may break module loading.
-   */
-  private URI parsedModuleNotationToUri(Object notation) {
-    if (notation instanceof File file) {
-      if (file.isAbsolute()) {
-        return file.toPath().toUri();
-      }
-      return IoUtils.createUri(IoUtils.toNormalizedPathString(file.toPath()));
-    } else if (notation instanceof URI uri) {
-      return uri;
-    }
-    throw new IllegalArgumentException("Invalid parsed module notation: " + notation);
-  }
-
-  protected URI parseModuleNotationToUri(Object m) {
-    var parsed1 = parseModuleNotation(m);
-    return parsedModuleNotationToUri(parsed1);
-  }
-
   @TaskAction
   @Override
   public void runTask() {
@@ -172,7 +150,7 @@ public abstract class ModulesTask extends BasePklTask {
               parseModulePath(),
               getProject().getProjectDir().toPath(),
               mapAndGetOrNull(getEvalRootDirPath(), Paths::get),
-              mapAndGetOrNull(getSettingsModule(), this::parseModuleNotationToUri),
+              mapAndGetOrNull(getSettingsModule(), PluginUtils::parseModuleNotationToUri),
               getProjectDir().isPresent() ? getProjectDir().get().getAsFile().toPath() : null,
               getEvalTimeout().getOrNull(),
               mapAndGetOrNull(getModuleCacheDir(), it1 -> it1.getAsFile().toPath()),

pkl-gradle/src/main/java/org/pkl/gradle/utils/PluginUtils.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.gradle.utils;
+
+import java.io.File;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.gradle.api.InvalidUserDataException;
+import org.gradle.api.file.FileSystemLocation;
+import org.pkl.core.util.IoUtils;
+
+public class PluginUtils {
+  private PluginUtils() {}
+
+  /**
+   * Parses the specified source module notation into a "parsed" notation which is then used for
+   * input path tracking and as an argument for the CLI API.
+   *
+   * <p>This method accepts the following input types:
+   *
+   * <ul>
+   *   <li>{@link URI} - used as is.
+   *   <li>{@link File} - used as is.
+   *   <li>{@link Path} - converted to a {@link File}. This conversion may fail because not all
+   *       {@link Path}s point to the local file system.
+   *   <li>{@link URL} - converted to a {@link URI}. This conversion may fail because {@link URL}
+   *       allows for URLs which are not compliant URIs.
+   *   <li>{@link CharSequence} - first, converted to a string. If this string is "URI-like" (see
+   *       {@link IoUtils#isUriLike(String)}), then we attempt to parse it as a {@link URI}, which
+   *       may fail. Otherwise, we attempt to parse it as a {@link Path}, which is then converted to
+   *       a {@link File} (both of these operations may fail).
+   *   <li>{@link FileSystemLocation} - converted to a {@link File} via the {@link
+   *       FileSystemLocation#getAsFile()} method.
+   * </ul>
+   *
+   * In case the returned value is determined to be a {@link URI}, then this URI is first checked
+   * for whether its scheme is {@code file}, like {@code file:///example/path}. In such case, this
+   * method returns a {@link File} corresponding to the file path in the URI. Otherwise, a {@link
+   * URI} instance is returned.
+   *
+   * @throws InvalidUserDataException In case the input is none of the types described above, or
+   *     when the underlying value cannot be parsed correctly.
+   */
+  public static Object parseModuleNotation(Object notation) {
+    if (notation instanceof URI uri) {
+      if ("file".equals(uri.getScheme())) {
+        return new File(uri.getPath());
+      }
+      return uri;
+    } else if (notation instanceof File) {
+      return notation;
+    } else if (notation instanceof Path path) {
+      try {
+        return path.toFile();
+      } catch (UnsupportedOperationException e) {
+        throw new InvalidUserDataException("Failed to parse Pkl module file path: " + notation, e);
+      }
+    } else if (notation instanceof URL url) {
+      try {
+        return parseModuleNotation(url.toURI());
+      } catch (URISyntaxException e) {
+        throw new InvalidUserDataException("Failed to parse Pkl module URI: " + notation, e);
+      }
+    } else if (notation instanceof CharSequence) {
+      var s = notation.toString();
+      if (IoUtils.isUriLike(s)) {
+        try {
+          return parseModuleNotation(IoUtils.toUri(s));
+        } catch (URISyntaxException e) {
+          throw new InvalidUserDataException("Failed to parse Pkl module URI: " + s, e);
+        }
+      } else {
+        try {
+          return Paths.get(s).toFile();
+        } catch (InvalidPathException | UnsupportedOperationException e) {
+          throw new InvalidUserDataException("Failed to parse Pkl module file path: " + s, e);
+        }
+      }
+    } else if (notation instanceof FileSystemLocation location) {
+      return location.getAsFile();
+    } else {
+      throw new InvalidUserDataException(
+          "Unsupported value of type "
+              + notation.getClass()
+              + " used as a module path: "
+              + notation);
+    }
+  }
+
+  /**
+   * Converts either a file or a URI to a URI. We convert a relative file to a URI via the {@link
+   * IoUtils#createUri(String)} because other ways of conversion can make relative paths into
+   * absolute URIs, which may break module loading.
+   */
+  public static URI parsedModuleNotationToUri(Object notation) {
+    if (notation instanceof File file) {
+      if (file.isAbsolute()) {
+        return file.toPath().toUri();
+      }
+      return IoUtils.createUri(IoUtils.toNormalizedPathString(file.toPath()));
+    } else if (notation instanceof URI uri) {
+      return uri;
+    }
+    throw new IllegalArgumentException("Invalid parsed module notation: " + notation);
+  }
+
+  public static URI parseModuleNotationToUri(Object m) {
+    var parsed1 = PluginUtils.parseModuleNotation(m);
+    return parsedModuleNotationToUri(parsed1);
+  }
+}

pkl-gradle/src/main/java/org/pkl/gradle/utils/package-info.java

@@ -0,0 +1,4 @@
+@NonnullByDefault
+package org.pkl.gradle.utils;
+
+import org.pkl.core.util.NonnullByDefault;

pkl-gradle/src/test/kotlin/org/pkl/gradle/PkldocGeneratorsTest.kt

@@ -15,13 +15,17 @@
  */
 package org.pkl.gradle
 
+import java.nio.file.Path
 import kotlin.io.path.readText
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import org.pkl.commons.test.PackageServer
 
 class PkldocGeneratorsTest : AbstractTest() {
   @Test
-  fun `generate docs`() {
+  fun `generate docs`(@TempDir tempDir: Path) {
+    PackageServer.populateCacheDir(tempDir)
     writeFile(
       "build.gradle",
       """
@@ -32,7 +36,8 @@ class PkldocGeneratorsTest : AbstractTest() {
       pkl {
         pkldocGenerators {
           pkldoc {
-            sourceModules = ["person.pkl", "doc-package-info.pkl"]
+            moduleCacheDir = file("${tempDir.toUri()}")
+            sourceModules = ["package://localhost:0/birds@0.5.0", "person.pkl", "doc-package-info.pkl"]
             outputDir = file("build/pkldoc")
             settingsModule = "pkl:settings"
           }
@@ -94,6 +99,39 @@ class PkldocGeneratorsTest : AbstractTest() {
     checkTextContains(moduleFile.readText(), "<html>", "Person", "Address", "other")
     checkTextContains(personFile.readText(), "<html>", "name", "addresses")
     checkTextContains(addressFile.readText(), "<html>", "street", "zip")
+
+    val birdsPackageFile = baseDir.resolve("localhost(3a)0/birds/0.5.0/index.html")
+    assertThat(birdsPackageFile).exists()
+  }
+
+  @Test
+  fun `generate docs only for package`(@TempDir tempDir: Path) {
+    PackageServer.populateCacheDir(tempDir)
+    writeFile(
+      "build.gradle",
+      """
+      plugins {
+        id "org.pkl-lang"
+      }
+
+      pkl {
+        pkldocGenerators {
+          pkldoc {
+            moduleCacheDir = file("${tempDir.toUri()}")
+            sourceModules = ["package://localhost:0/birds@0.5.0"]
+            outputDir = file("build/pkldoc")
+            settingsModule = "pkl:settings"
+          }
+        }
+      }
+    """
+    )
+
+    runTask("pkldoc")
+
+    val baseDir = testProjectDir.resolve("build/pkldoc")
+    val birdsPackageFile = baseDir.resolve("localhost(3a)0/birds/0.5.0/index.html")
+    assertThat(birdsPackageFile).exists()
   }
 
   @Test