Crash with invalid named mixin application

[scheglov]

mixin M {}
class A = void Function() with M;

main() {}

I see from dart run:

Crash when compiling file:///Users/scheglov/tmp/333/test.dart,
at character offset null:
type 'Null' is not a subtype of type 'String'
#0      extractName (package:front_end/src/fasta/source/source_library_builder.dart:5243:51)
#1      SourceLibraryBuilder.applyMixins (package:front_end/src/fasta/source/source_library_builder.dart:2147:28)
#2      SourceLibraryBuilder.addNamedMixinApplication (package:front_end/src/fasta/source/source_library_builder.dart:2352:17)
#3      OutlineBuilder.endNamedMixinApplication (package:front_end/src/fasta/source/outline_builder.dart:2105:22)
#4      Parser.parseNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2223:14)
#5      Parser.parseClassOrNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2202:14)
#6      Parser.parseTopLevelKeywordDeclaration (package:_fe_analyzer_shared/src/parser/parser_impl.dart:564:14)
#7      Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:497:14)
#8      Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:377:15)
#9      SourceLoader.buildOutline (package:front_end/src/fasta/source/source_loader.dart:1114:37)
<asynchronous suspension>
#10     SourceLoader.buildOutlines (package:front_end/src/fasta/source/source_loader.dart:1004:7)
<asynchronous suspension>
#11     KernelTarget.computeNeededPrecompilations.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:364:7)
<asynchronous suspension>
#12     withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#13     generateKernelInternal.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:99:11)
<asynchronous suspension>
#14     withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#15     generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#16     generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#17     kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#18     SingleShotCompilerWrapper.compileInternal (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:400:11)
<asynchronous suspension>
#19     Compiler.compile.<anonymous closure> (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:216:45)
<asynchronous suspension>
#20     _processLoadRequest (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:894:37)
<asynchronous suspension>


#0      extractName (package:front_end/src/fasta/source/source_library_builder.dart:5243:51)
#1      SourceLibraryBuilder.applyMixins (package:front_end/src/fasta/source/source_library_builder.dart:2147:28)
#2      SourceLibraryBuilder.addNamedMixinApplication (package:front_end/src/fasta/source/source_library_builder.dart:2352:17)
#3      OutlineBuilder.endNamedMixinApplication (package:front_end/src/fasta/source/outline_builder.dart:2105:22)
#4      Parser.parseNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2223:14)
#5      Parser.parseClassOrNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2202:14)
#6      Parser.parseTopLevelKeywordDeclaration (package:_fe_analyzer_shared/src/parser/parser_impl.dart:564:14)
#7      Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:497:14)
#8      Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:377:15)
#9      SourceLoader.buildOutline (package:front_end/src/fasta/source/source_loader.dart:1114:37)
<asynchronous suspension>
#10     SourceLoader.buildOutlines (package:front_end/src/fasta/source/source_loader.dart:1004:7)
<asynchronous suspension>
#11     KernelTarget.computeNeededPrecompilations.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:364:7)
<asynchronous suspension>
#12     withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#13     generateKernelInternal.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:99:11)
<asynchronous suspension>
#14     withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#15     generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#16     generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#17     kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#18     SingleShotCompilerWrapper.compileInternal (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:400:11)
<asynchronous suspension>
#19     Compiler.compile.<anonymous closure> (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:216:45)
<asynchronous suspension>
#20     _processLoadRequest (org-dartlang-kernel-service:///pkg/vm/bin/kernel_service.dart:894:37)
<asynchronous suspension>

[scheglov]

Similar code causes a crash in the analyzer AstBuilder (lines might be slightly different):

  type 'GenericFunctionTypeImpl' is not a subtype of type 'NamedType' in type cast
  #0      AstBuilder.endNamedMixinApplication (package:analyzer/src/fasta/ast_builder.dart:2146:26)
  #1      Parser.parseNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2223:14)
  #2      Parser.parseClassOrNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2202:14)
  #3      Parser.parseTopLevelKeywordDeclaration (package:_fe_analyzer_shared/src/parser/parser_impl.dart:564:14)
  #4      Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:497:14)
  #5      Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:377:15)
  #6      Parser.parseCompilationUnit2 (package:analyzer/src/generated/parser.dart:108:32)
  #7      Parser.parseCompilationUnit (package:analyzer/src/generated/parser.dart:104:12)
  #8      FileState._parse (package:analyzer/src/dart/analysis/file_state.dart:550:23)

Which raises a question - does the parser know whether it is a function type or a named type? If it does, it would be nice to report an error and recover.

[scheglov]

And similar issue with extends void Function(), and least in the analyzer.

  type 'GenericFunctionTypeImpl' is not a subtype of type 'NamedType?' in type cast
  #0      AstBuilder.handleClassExtends (package:analyzer/src/fasta/ast_builder.dart:2725:27)
  #1      Parser.parseClassExtendsSeenExtendsClause (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2391:14)
  #2      Parser.parseClassExtendsOpt (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2362:15)
  #3      Parser.parseClassHeaderOpt (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2255:13)
  #4      Parser.parseClass (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2242:13)
  #5      Parser.parseClassOrNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2206:14)
  #6      Parser.parseTopLevelKeywordDeclaration (package:_fe_analyzer_shared/src/parser/parser_impl.dart:564:14)
  #7      Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:497:14)
  #8      Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:377:15)
  #9      Parser.parseCompilationUnit2 (package:analyzer/src/generated/parser.dart:108:32)
  #10     Parser.parseCompilationUnit (package:analyzer/src/generated/parser.dart:104:12)
  #11     FileState._parse (package:analyzer/src/dart/analysis/file_state.dart:550:23)

[scheglov]

...and for with clause.

  type 'GenericFunctionTypeImpl' is not a subtype of type 'NamedType' in type cast
  #0      StackImpl.popList (package:_fe_analyzer_shared/src/parser/stack_listener.dart:597:25)
  #1      AstBuilder.popTypedList (package:analyzer/src/fasta/ast_builder.dart:4140:11)
  #2      AstBuilder.endTypeList (package:analyzer/src/fasta/ast_builder.dart:2505:10)
  #3      Parser.parseTypeList (package:_fe_analyzer_shared/src/parser/parser_impl.dart:975:14)
  #4      Parser.parseClassWithClauseOpt (package:_fe_analyzer_shared/src/parser/parser_impl.dart:1270:15)
  #5      Parser.parseClassHeaderOpt (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2256:13)
  #6      Parser.parseClass (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2242:13)
  #7      Parser.parseClassOrNamedMixinApplication (package:_fe_analyzer_shared/src/parser/parser_impl.dart:2206:14)
  #8      Parser.parseTopLevelKeywordDeclaration (package:_fe_analyzer_shared/src/parser/parser_impl.dart:564:14)
  #9      Parser.parseTopLevelDeclarationImpl (package:_fe_analyzer_shared/src/parser/parser_impl.dart:497:14)
  #10     Parser.parseUnit (package:_fe_analyzer_shared/src/parser/parser_impl.dart:377:15)
  #11     Parser.parseCompilationUnit2 (package:analyzer/src/generated/parser.dart:108:32)
  #12     Parser.parseCompilationUnit (package:analyzer/src/generated/parser.dart:104:12)
  #13     FileState._parse (package:analyzer/src/dart/analysis/file_state.dart:550:23)

[jensjoha]

@johnniwinther why was I assigned to this?

I initially thought it was some sort of parsing error, but the parser seems to conform to the spec to me, e.g.

<classDeclaration> ::=
  \ABSTRACT? \CLASS{} <identifier> <typeParameters>?
  \gnewline{} <superclass>? <interfaces>?
  \gnewline{} `{' (<metadata> <classMemberDeclaration>)* `}'
  \alt \ABSTRACT? \CLASS{} <mixinApplicationClass>

<mixinApplicationClass> ::= \gnewline{}
  <identifier> <typeParameters>? `=' <mixinApplication> `;'

<mixinApplication> ::= <typeNotVoid> <mixins> <interfaces>?

<interfaces> ::= \IMPLEMENTS{} <typeNotVoidList>

<superclass> ::= \EXTENDS{} <typeNotVoid> <mixins>?
    \alt <mixins>

<mixins> ::= \WITH{} <typeNotVoidList>

<typeNotVoidList> ::= <typeNotVoid> (`,' <typeNotVoid>)*

<typeNotVoid> ::= <functionType> `?'?
  \alt <typeNotVoidNotFunction>

<functionType> ::= <functionTypeTails>
  \alt <typeNotFunction> <functionTypeTails>

<functionTypeTails> ::= <functionTypeTail> `?'? <functionTypeTails>
  \alt <functionTypeTail>

<functionTypeTail> ::= \FUNCTION{} <typeParameters>? <parameterTypeList>

<typeNotFunction> ::= \VOID{}
  \alt <typeNotVoidNotFunction>

As I read it all of these should be OK:

mixin M {}
class X {}

class A = void Function() with M;
class B = void Function() with void Function();
class C = void Function() with void Function() implements void Function();
class D extends X with void Function() {}
class E extends void Function() {}

main() {}

[johnniwinther]

This sounds like this is an issue in both the CFE and analyzer. Reassigning.

[scheglov]

@eernstg Is this correct? Do we allow function types as superclasses? Just syntactically or also semantically?

It looks that 10.9 forbids using type aliases that are not classes, but nothing about function types written directly.