[compiler] (inline classes/pattern)-related crash.

[modulovalue]

The compiler crashes with the following message when compiling the following code:

Error compiling to JavaScript:
lib/main.dart:
Internal Error: The compiler crashed when compiling this element.

The compiler is broken.

When compiling the above element, the compiler crashed. It is not
possible to tell if this is caused by a problem in your program or
not. Regardless, the compiler should not crash.

The Dart team would greatly appreciate if you would take a moment to
report this problem at http://dartbug.com/new.

Please include the following information:

* the name and version of your operating system,

* the Dart SDK build number (3.1.0-169.0.dev), and

* the entire message you see here (including the full stack trace
  below as well as the source location above).

The compiler crashed: Crash when compiling file:///tmp/dartpadZJKOKV/lib/main.dart at character offset 198:
lib/main.dart:19:10: Internal problem: Unsupported operation: 'Object field target InlineClassRepresentationAccessTarget(ObjectAccessTargetKind.inlineClassRepresentation,InlineType(FooBar),InlineType(FooBar))'.
    case FooBar(i: final a): 
         ^

#0      internalProblem (package:front_end/src/fasta/problems.dart:52:5)
#1      unsupported (package:front_end/src/fasta/problems.dart:85:10)
#2      InferenceVisitorImpl.visitObjectPattern (package:front_end/src/fasta/type_inference/inference_visitor.dart:10509:20)
#3      ObjectPattern.accept1 (package:kernel/src/ast/patterns.dart:622:15)
#4      InferenceVisitorImpl.dispatchPattern (package:front_end/src/fasta/type_inference/inference_visitor.dart:9479:12)
#5      TypeAnalyzer.analyzeSwitchStatement (package:_fe_analyzer_shared/src/type_inference/type_analyzer.dart:1829:11)
#6      InferenceVisitorImpl.visitPatternSwitchStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:8395:9)
#7      PatternSwitchStatement.accept (package:kernel/src/ast/patterns.dart:1820:14)
#8      InferenceVisitorImpl.inferStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:238:26)
#9      InferenceVisitorImpl.visitLabeledStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:2070:43)
#10     LabeledStatement.accept (package:kernel/ast.dart:9998:43)
#11     InferenceVisitorImpl.inferStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:238:26)
#12     InferenceVisitorImpl._visitStatements (package:front_end/src/fasta/type_inference/inference_visitor.dart:848:50)
#13     InferenceVisitorImpl.visitBlock (package:front_end/src/fasta/type_inference/inference_visitor.dart:869:31)
#14     Block.accept (package:kernel/ast.dart:9788:43)
#15     InferenceVisitorImpl.inferStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:238:26)
#16     TypeInferrerImpl.inferFunctionBody (package:front_end/src/fasta/type_inference/type_inferrer.dart:202:17)
#17     BodyBuilder.finishFunction (package:front_end/src/fasta/kernel/body_builder.dart:1263:43)
#18     DietListener.buildFunctionBody (package:front_end/src/fasta/source/diet_listener.dart:1137:19)
#19     DietListener.endTopLevelMethod (package:front_end/src/fasta/source/diet_listener.dart:387:5)
#20     Parser.parseTopLevelMethod (package:_fe_analyzer_shared/src/parser/parser_impl.dart:3757:14)
#21     Parser.parseTopLevelMemberImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:3514:14)
#22     Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:624:14)
#23     Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:414:15)
#24     SourceLoader.buildBody (package:front_end/src/fasta/source/source_loader.dart:1266:12)
<asynchronous suspension>
#25     SourceLoader.buildBodies (package:front_end/src/fasta/source/source_loader.dart:672:7)
<asynchronous suspension>
#26     KernelTarget.buildComponent.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:609:7)
<asynchronous suspension>
#27     withCrashReporting (package:front_end/src/fasta/crash.dart:136:12)
<asynchronous suspension>
#28     KernelTarget.buildComponent (package:front_end/src/fasta/kernel/kernel_target.dart:590:12)
<asynchronous suspension>
#29     _buildInternal (package:front_end/src/kernel_generator_impl.dart:208:19)
<asynchronous suspension>
#30     withCrashReporting (package:front_end/src/fasta/crash.dart:136:12)
<asynchronous suspension>
#31     compile.<anonymous closure> (package:front_end/src/api_unstable/dart2js.dart:200:37)
<asynchronous suspension>
#32     compile (package:front_end/src/api_unstable/dart2js.dart:198:36)
<asynchronous suspension>
#33     _loadFromSource (package:compiler/src/phase/load_kernel.dart:303:29)
<asynchronous suspension>
#34     run (package:compiler/src/phase/load_kernel.dart:404:36)
<asynchronous suspension>
#35     Compiler.loadKernel (package:compiler/src/compiler.dart:388:9)
<asynchronous suspension>
#36     Compiler.produceKernel (package:compiler/src/compiler.dart:395:36)
<asynchronous suspension>
#37     Compiler.runSequentialPhases (package:compiler/src/compiler.dart:711:20)
<asynchronous suspension>
#38     Compiler.runInternal.<anonymous closure> (package:compiler/src/compiler.dart:311:7)
<asynchronous suspension>
#39     Compiler.runInternal (package:compiler/src/compiler.dart:310:5)
<asynchronous suspension>
#40     Compiler.run.<anonymous closure> (package:compiler/src/compiler.dart:231:11)
<asynchronous suspension>
#41     main (package:compiler/src/dart2js.dart:1241:3)
<asynchronous suspension>

abstract class Foo {}

inline class FooBar implements Foo {
  final int i;
  
  const FooBar(this.i);
}

inline class FooBaz implements Foo {
  final int i;
  
  const FooBaz(this.i);
}

void main() {
  final a = FooBar(0);
  switch (a) {
    case FooBar(i: final a): 
      print("FooBar $a");
  }
}

Reproducible on DartPad:

master channel
Use Flutter version 3.12.0-2.0.pre and Dart version 3.1.0-169.0.dev
+ Dart experiments: --enable-experiment=inline-class

[eernstg]

This crash would be caused by missing parts of the implementation of inline classes (the implementation isn't yet complete).

The crash occurred when the example program was running in dart-pad, but it seems to be associated with the common front end.

@johnniwinther, do you agree that this might well be a CFE issue?

abstract class Foo {}

inline class FooBar implements Foo { // (1)
  final int i;
  
  const FooBar(this.i);
}

inline class FooBaz implements Foo { // (2)
  final int i;
  
  const FooBaz(this.i);
}

void main() {
  final a = FooBar(0);
  switch (a) {
    case FooBar(i: final a): 
      print("FooBar $a");
  }
}

(1) and (2) should be reported as compile-time errors. There is ongoing discussion about an extension to the inline class feature which will allow an inline class to have a non-inline class in its implements clause (dart-lang/language#3090), but in the current feature specification it is a compile-time error.

An inline class used in an object pattern (like case FooBar(i: final a)) should amount to a dynamic type check (which is equivalent to a is int) which will succeed, followed by matching of the subpattern that reads i. So the program (where implements Foo has been removed such that there are no compile-time errors) should print 'FooBar 0'.

It actually crashes, in a very similar way as the program with implements Foo, so the main thing is probably the occurrence of an inline class in an object pattern.

[johnniwinther]

This is a CFE issue. The implementation of inline classes cannot rely on the existing implementation for regular classes so we need to rework all such parts, including the handling in patterns.

[eernstg]

Thx!