CFE crash inferring array type involving extension type

[liamappelbe]

The crash is caused by this line of code: final list = toObjCObject(['abc', obj]);. See below for the full stack trace.

I tried a few experiments:

• Replacing the call to toObjCObject with a call to print still crashes.
• Adding an explicit type param to the list literal, <Object>['abc', obj] fixes the crash.
• Replacing obj with an inline NSObject() still crashes, but replacing it with Object() fixes the crash. NSObject is an extension type.
• Trying to remove all the other tests from the file fixes the crash, so unfortunately I haven't been able to create a minimal repro.

So it seems to be something to do with trying to infer the type of the list literal, when one of the elements is an extension type.

Dart SDK version: 3.9.2 (stable)

Full crash stack trace:

liama@liama-mac ~/d/n/p/objective_c ((3ba9a109))> dart test/converter_test.dart
Crash when compiling file:///Users/liama/dev/native/pkgs/objective_c/test/converter_test.dart at character offset 425:
RangeError (length): Invalid value: Not in inclusive range 0..1: 2

#0      List.[] (dart:core-patch/growable_array.dart)
#1      ClosedWorldClassHierarchy._getLegacyLeastUpperBoundInternal (package:kernel/class_hierarchy.dart:878:37)
#2      ClosedWorldClassHierarchy.getLegacyLeastUpperBoundFromSupertypeLists (package:kernel/class_hierarchy.dart:984:12)
#3      StandardBounds._getLegacyLeastUpperBound (package:kernel/src/standard_bounds.dart:938:24)
#4      StandardBounds.getStandardUpperBoundInternal (package:kernel/src/standard_bounds.dart:830:18)
#5      TypeSchemaStandardBounds.getStandardUpperBoundInternal (package:front_end/src/type_inference/standard_bounds.dart:42:18)
#6      StandardBounds._getStandardUpperBound (package:kernel/src/standard_bounds.dart:542:12)
#7      StandardBounds.getStandardUpperBound (package:kernel/src/standard_bounds.dart:535:12)
#8      OperationsCfe.lubInternal (package:front_end/src/type_inference/type_inference_engine.dart:766:28)
#9      TypeAnalyzerOperationsMixin.typeSchemaLub (package:_fe_analyzer_shared/src/type_inference/type_analyzer_operations.dart:1059:7)
#10     MergedTypeConstraint.mergeInTypeSchemaLower (package:_fe_analyzer_shared/src/type_inference/type_constraint.dart:160:36)
#11     MergedTypeConstraint.mergeIn (package:_fe_analyzer_shared/src/type_inference/type_constraint.dart:148:7)
#12     TypeConstraintGatherer.computeConstraints (package:front_end/src/type_inference/type_constraint_gatherer.dart:195:12)
#13     TypeSchemaEnvironment._chooseTypes (package:front_end/src/type_inference/type_schema_environment.dart:426:18)
#14     TypeSchemaEnvironment.chooseFinalTypes (package:front_end/src/type_inference/type_schema_environment.dart:409:7)
#15     InferenceVisitorImpl.visitListLiteral (package:front_end/src/type_inference/inference_visitor.dart:2865:45)
#16     ListLiteral.accept1 (package:kernel/src/ast/expressions.dart:4166:9)
#17     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#18     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#19     InferenceVisitorBase._inferInvocation.inferArgument (package:front_end/src/type_inference/inference_visitor_base.dart:1961:22)
#20     InferenceVisitorBase._inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:2026:44)
#21     InferenceVisitorBase.inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:1665:12)
#22     InferenceVisitorImpl.visitStaticInvocation (package:front_end/src/type_inference/inference_visitor.dart:8715:40)
#23     StaticInvocation.accept1 (package:kernel/src/ast/expressions.dart:2606:9)
#24     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#25     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#26     InferenceVisitorImpl.visitVariableDeclaration (package:front_end/src/type_inference/inference_visitor.dart:9307:11)
#27     VariableDeclaration.accept (package:kernel/src/ast/statements.dart:1704:43)
#28     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#29     InferenceVisitorImpl._visitStatements (package:front_end/src/type_inference/inference_visitor.dart:913:50)
#30     InferenceVisitorImpl.visitBlock (package:front_end/src/type_inference/inference_visitor.dart:934:31)
#31     Block.accept (package:kernel/src/ast/statements.dart:103:43)
#32     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#33     InferenceVisitorBase.inferLocalFunction (package:front_end/src/type_inference/inference_visitor_base.dart:2607:51)
#34     InferenceVisitorImpl.visitFunctionNode (package:front_end/src/type_inference/inference_visitor.dart:1963:12)
#35     InferenceVisitorImpl.visitFunctionExpression (package:front_end/src/type_inference/inference_visitor.dart:2001:9)
#36     FunctionExpression.accept1 (package:kernel/src/ast/expressions.dart:4612:9)
#37     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#38     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#39     InferenceVisitorBase._inferInvocation.inferArgument (package:front_end/src/type_inference/inference_visitor_base.dart:1961:22)
#40     InferenceVisitorBase._inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:2085:46)
#41     InferenceVisitorBase.inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:1665:12)
#42     InferenceVisitorImpl.visitStaticInvocation (package:front_end/src/type_inference/inference_visitor.dart:8715:40)
#43     StaticInvocation.accept1 (package:kernel/src/ast/expressions.dart:2606:9)
#44     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#45     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#46     InferenceVisitorImpl.visitExpressionStatement (package:front_end/src/type_inference/inference_visitor.dart:1396:40)
#47     ExpressionStatement.accept (package:kernel/src/ast/statements.dart:50:43)
#48     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#49     InferenceVisitorImpl._visitStatements (package:front_end/src/type_inference/inference_visitor.dart:913:50)
#50     InferenceVisitorImpl.visitBlock (package:front_end/src/type_inference/inference_visitor.dart:934:31)
#51     Block.accept (package:kernel/src/ast/statements.dart:103:43)
#52     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#53     InferenceVisitorBase.inferLocalFunction (package:front_end/src/type_inference/inference_visitor_base.dart:2607:51)
#54     InferenceVisitorImpl.visitFunctionNode (package:front_end/src/type_inference/inference_visitor.dart:1963:12)
#55     InferenceVisitorImpl.visitFunctionExpression (package:front_end/src/type_inference/inference_visitor.dart:2001:9)
#56     FunctionExpression.accept1 (package:kernel/src/ast/expressions.dart:4612:9)
#57     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#58     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#59     InferenceVisitorBase._inferInvocation.inferArgument (package:front_end/src/type_inference/inference_visitor_base.dart:1961:22)
#60     InferenceVisitorBase._inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:2085:46)
#61     InferenceVisitorBase.inferInvocation (package:front_end/src/type_inference/inference_visitor_base.dart:1665:12)
#62     InferenceVisitorImpl.visitStaticInvocation (package:front_end/src/type_inference/inference_visitor.dart:8715:40)
#63     StaticInvocation.accept1 (package:kernel/src/ast/expressions.dart:2606:9)
#64     InferenceVisitorImpl._inferExpression (package:front_end/src/type_inference/inference_visitor.dart:291:27)
#65     InferenceVisitorImpl.inferExpression (package:front_end/src/type_inference/inference_visitor.dart:329:40)
#66     InferenceVisitorImpl.visitExpressionStatement (package:front_end/src/type_inference/inference_visitor.dart:1396:40)
#67     ExpressionStatement.accept (package:kernel/src/ast/statements.dart:50:43)
#68     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#69     InferenceVisitorImpl._visitStatements (package:front_end/src/type_inference/inference_visitor.dart:913:50)
#70     InferenceVisitorImpl.visitBlock (package:front_end/src/type_inference/inference_visitor.dart:934:31)
#71     Block.accept (package:kernel/src/ast/statements.dart:103:43)
#72     InferenceVisitorImpl.inferStatement (package:front_end/src/type_inference/inference_visitor.dart:274:26)
#73     TypeInferrerImpl.inferFunctionBody (package:front_end/src/type_inference/type_inferrer.dart:197:17)
#74     BodyBuilder.finishFunction (package:front_end/src/kernel/body_builder.dart:1262:43)
#75     DietListener.buildFunctionBody (package:front_end/src/source/diet_listener.dart:1287:19)
#76     DietListener.endTopLevelMethod (package:front_end/src/source/diet_listener.dart:383:7)
#77     Parser.parseTopLevelMethod (package:_fe_analyzer_shared/src/parser/parser_impl.dart:4304:14)
#78     Parser.parseTopLevelMemberImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:3996:14)
#79     Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:626:14)
#80     Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:411:15)
#81     SourceLoader.buildBody (package:front_end/src/source/source_loader.dart:1236:12)
<asynchronous suspension>
#82     SourceLoader.buildBodies (package:front_end/src/source/source_loader.dart:769:7)
<asynchronous suspension>
#83     KernelTarget.buildComponent.<anonymous closure> (package:front_end/src/kernel/kernel_target.dart:653:7)
<asynchronous suspension>
#84     withCrashReporting (package:front_end/src/base/crash.dart:139:12)
<asynchronous suspension>
#85     KernelTarget.buildComponent (package:front_end/src/kernel/kernel_target.dart:647:12)
<asynchronous suspension>
#86     _buildInternal (package:front_end/src/kernel_generator_impl.dart:209:19)
<asynchronous suspension>
#87     withCrashReporting (package:front_end/src/base/crash.dart:139:12)
<asynchronous suspension>
#88     generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:45:12)
<asynchronous suspension>
#89     CompilerContext.clear (package:front_end/src/base/compiler_context.dart:77:3)
<asynchronous suspension>
#90     generateKernel (package:front_end/src/kernel_generator_impl.dart:43:10)
<asynchronous suspension>
#91     kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:107:11)
<asynchronous suspension>
#92     SingleShotCompilerWrapper.compileInternal (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:464:15)
<asynchronous suspension>
#93     Compiler.compile.<anonymous closure> (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:237:45)
<asynchronous suspension>
#94     _processLoadRequest (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:1024:37)
<asynchronous suspension>

[liamappelbe]

Even with that <Object>['abc', obj] workaround, I still get the crash when I try to run multiple tests at once. This is blocking my PR from landing, because it breaks CI: https://github.com/dart-lang/native/actions/runs/18735882908/job/53442406952?pr=2723#step:7:59

[liamappelbe]

Still reproducible on Flutter 3.38/Dart 3.10: https://github.com/dart-lang/native/actions/runs/18741081238/job/53457472670?pr=2723#step:7:57

[dcharkes]

cc @chloestefantsova

[chloestefantsova]

@liamappelbe Could you please apply the following patch in order to produce more diagnostics? Alternatively, it would be helpful for me to know how to build the tool locally, so I could examine the failure.

diff --git a/pkg/kernel/lib/class_hierarchy.dart b/pkg/kernel/lib/class_hierarchy.dart
index 62de8ac5da7..039e09811b9 100644
--- a/pkg/kernel/lib/class_hierarchy.dart
+++ b/pkg/kernel/lib/class_hierarchy.dart
@@ -819,6 +819,7 @@ class ClosedWorldClassHierarchy
   @override
   InterfaceType getLegacyLeastUpperBound(
       InterfaceType type1, InterfaceType type2) {
+    print("!!! ClosedWorldClassHierarchy.getLegacyLeastUpperBound: type1=${type1} type2=${type2}");
     // The algorithm is: first we compute a list of superclasses for both types,
     // ordered from greatest to least depth, and ordered by topological sort
     // index within each depth.  Due to the sort order, we can find the
@@ -863,6 +864,7 @@ class ClosedWorldClassHierarchy
       _ClassInfo? info2,
       List<_ClassInfo> classInfos1,
       List<_ClassInfo> classInfos2) {
+    print("!!! ClosedWorldClassHierarchy._getLegacyLeastUpperBoundInternal: type1=${type1} type2=${type2} info1=${info1} info2=${info2} classInfos1=${classInfos1} classInfos2=${classInfos2}");
     assert(type1 is! InterfaceType || info1 != null);
     assert(type2 is! InterfaceType || info2 != null);
 
@@ -959,6 +961,7 @@ class ClosedWorldClassHierarchy
       TypeDeclarationType type2,
       List<InterfaceType> supertypes1,
       List<InterfaceType> supertypes2) {
+    print("!!! ClosedWorldClassHierarchy.getLegacyLeastUpperBoundFromSupertypeLists: type1=${type1} type2=${type2} supertypes1=${supertypes1} supertypes2=${supertypes2}");
     assert(supertypes1.isNotEmpty || type1 is ExtensionType);
     assert(supertypes2.isNotEmpty || type2 is ExtensionType);
 
@@ -1842,6 +1845,11 @@ class _ClassInfo {
   int topologicalIndex = 0;
   int depth = 0;
 
+  @override
+  String toString() {
+    return "_ClassInfo(classNode=${classNode}, topologicalIndex=${topologicalIndex}, depth=${depth})";
+  }
+
   // Super types must always occur before subtypes in these lists.
   // For example:
   //
diff --git a/pkg/kernel/lib/src/standard_bounds.dart b/pkg/kernel/lib/src/standard_bounds.dart
index 8aa8496add2..b5a307ee4ac 100644
--- a/pkg/kernel/lib/src/standard_bounds.dart
+++ b/pkg/kernel/lib/src/standard_bounds.dart
@@ -561,6 +561,8 @@ mixin StandardBounds {
   }
 
   DartType getStandardUpperBoundInternal(DartType type1, DartType type2) {
+    print(
+        "!!! StandardBounds.getStandardUpperBoundInternal: type1=${type1} type2=${type2}");
     DartType typeWithoutNullabilityMarker1 =
         computeTypeWithoutNullabilityMarker(type1);
     DartType typeWithoutNullabilityMarker2 =
@@ -879,6 +881,8 @@ mixin StandardBounds {
 
   DartType _getLegacyLeastUpperBound(
       TypeDeclarationType type1, TypeDeclarationType type2) {
+    print(
+        "!!! StandardBounds._getLegacyLeastUpperBound: type1=${type1} type2=${type2}");
     if (type1 is InterfaceType && type2 is InterfaceType) {
       return hierarchy.getLegacyLeastUpperBound(type1, type2);
     } else if (type1 is ExtensionType || type2 is ExtensionType) {
@@ -893,19 +897,19 @@ mixin StandardBounds {
 
       int computeExtensionTypeDeclarationDepth(
           ExtensionTypeDeclaration extensionTypeDeclaration,
-          List<InterfaceType> superInterfaceType) {
+          List<InterfaceType> superInterfaceTypes) {
         int? depth = extensionTypeDeclarationDepth[extensionTypeDeclaration];
         if (depth == null) {
           int maxDepth = 0;
           for (DartType implemented in extensionTypeDeclaration.implements) {
             if (implemented is ExtensionType) {
               int supertypeDepth = computeExtensionTypeDeclarationDepth(
-                  implemented.extensionTypeDeclaration, superInterfaceType);
+                  implemented.extensionTypeDeclaration, superInterfaceTypes);
               if (supertypeDepth >= maxDepth) {
                 maxDepth = supertypeDepth + 1;
               }
             } else if (implemented is InterfaceType) {
-              superInterfaceType.add(implemented);
+              superInterfaceTypes.add(implemented);
             }
           }

[liamappelbe]

That PR branch is still in active development, so I've made a new PR without any of the work arounds: dart-lang/native#2726

Alternatively, it would be helpful for me to know how to build the tool locally, so I could examine the failure.

You don't need to do anything special to repro the failure. Just pull down that branch, navigate to pkgs/objective_c and run dart test/converter_test.dart. If you want to actually run the tests and have them pass you'd just need to run dart test/setup.dart (which builds a dylib), but that's not necessary to repro the compiler crash. The tests will only run on mac, but you can probably repro the compiler crash on any OS.

[chloestefantsova]

Thanks for preparing the branch for testing, @liamappelbe. I've uploaded a CL that seems to resolve the issue. PTAL.

https://dart-review.googlesource.com/c/sdk/+/457360