Compiler crashing when using pattern in collection-for

[mmcdon20]

Likely just due to not being implemented yet, but I am trying out the patterns and records features and came across a compiler crash.

Using Dart SDK version: 3.0.0-229.0.dev (dev) (Fri Feb 10 20:38:38 2023 -0800) on "windows_x64".

Take this example

void main() {
  print(left([(1,2), (3, 4)])); // expecting [1, 3]
}

List<A> left<A, B>(List<(A, B)> pairs) => [for (var (a, _) in pairs) a];

compiled with dart --enable-experiment=records,patterns bin/example.dart

Crash when compiling file:///C:/Users/mmcdo/Documents/projects/project/bin/example.dart at character offset 110:
Null check operator used on a null value

#0      InferenceVisitorImpl.inferElement (package:front_end/src/fasta/type_inference/inference_visitor.dart:2262:40)       
#1      InferenceVisitorImpl.visitListLiteral (package:front_end/src/fasta/type_inference/inference_visitor.dart:2382:42)   
#2      ListLiteral.accept1 (package:kernel/ast.dart:8684:9)
#3      InferenceVisitorImpl._inferExpression (package:front_end/src/fasta/type_inference/inference_visitor.dart:263:27)    
#4      InferenceVisitorImpl.inferExpression (package:front_end/src/fasta/type_inference/inference_visitor.dart:298:40)     
#5      InferenceVisitorImpl.visitReturnStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:7281:11)
#6      ReturnStatement.accept (package:kernel/ast.dart:10766:43)
#7      InferenceVisitorImpl.inferStatement (package:front_end/src/fasta/type_inference/inference_visitor.dart:241:26)      
#8      TypeInferrerImpl.inferFunctionBody (package:front_end/src/fasta/type_inference/type_inferrer.dart:196:17)
#9      BodyBuilder.finishFunction (package:front_end/src/fasta/kernel/body_builder.dart:1344:43)
#10     DietListener.buildFunctionBody (package:front_end/src/fasta/source/diet_listener.dart:1123:19)
#11     DietListener.endTopLevelMethod (package:front_end/src/fasta/source/diet_listener.dart:376:5)
#12     Parser.parseTopLevelMethod (package:_fe_analyzer_shared/src/parser/parser_impl.dart:3682:14)
#13     Parser.parseTopLevelMemberImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:3424:14)
#14     Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:606:14)
#15     Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:403:15)
#16     SourceLoader.buildBody (package:front_end/src/fasta/source/source_loader.dart:1267:12)
<asynchronous suspension>
#17     SourceLoader.buildBodies (package:front_end/src/fasta/source/source_loader.dart:676:7)
<asynchronous suspension>
#18     KernelTarget.buildComponent.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:611:7)       
<asynchronous suspension>
#19     withCrashReporting (package:front_end/src/fasta/crash.dart:136:12)
<asynchronous suspension>
#20     _buildInternal (package:front_end/src/kernel_generator_impl.dart:206:19)
<asynchronous suspension>
#21     withCrashReporting (package:front_end/src/fasta/crash.dart:136:12)
<asynchronous suspension>
#22     generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:48:12)
<asynchronous suspension>
#23     generateKernel (package:front_end/src/kernel_generator_impl.dart:47:10)
<asynchronous suspension>
#24     kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#25     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:407:11)       
<asynchronous suspension>
#26     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:215:45)
<asynchronous suspension>
#27     _processLoadRequest (file:///C:/b/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:889:37)
<asynchronous suspension>

[asashour]

• sdk/282602 for the OP crash
• Please provide a test case for the crash of collection-if pattern, in a separate issue if the stacktrace is different.
• I guess the last point should also be better in a separate issue.