co19/LanguageFeatures/Extension-types/static_analysis_extension_types_A05_t02

[scheglov]

FAILED: dart2analyzer-none release_arm64 co19/LanguageFeatures/Extension-types/static_analysis_extension_types_A05_t02
Expected: Pass
Actual: MissingCompileTimeError

--- Command "dart2analyzer" (took 07.000554s):
DART_CONFIGURATION=ReleaseARM64 sdk/bin/dart --packages=.dart_tool/package_config.json pkg/analyzer_cli/bin/analyzer.dart --use-analysis-driver-memory-byte-store --dart-sdk=/Users/scheglov/Source/Dart/sdk.git/sdk/sdk -Dtest_runner.configuration=custom-configuration-1 --enable-experiment=inline-class --ignore-unrecognized-flags --packages=/Users/scheglov/Source/Dart/sdk.git/sdk/.dart_tool/package_config.json --format=json /Users/scheglov/Source/Dart/sdk.git/sdk/tests/co19/src/LanguageFeatures/Extension-types/static_analysis_extension_types_A05_t02.dart

static error failures:
- Unexpected error at line 22, column 18, length 1: COMPILE_TIME_ERROR.TYPE_PARAMETER_SUPERTYPE_OF_ITS_BOUND

--- Re-run this test:
python3 tools/test.py -m release -c dart2analyzer -a arm64 co19/LanguageFeatures/Extension-types/static_analysis_extension_types_A05_t02

@eernstg confirmed in chat that this is a valid diagnostic.

[sgrekhov]

Ok, the test is

// SharedOptions=--enable-experiment=inline-class

extension type V<T extends V<T>>(T id) {} // COMPILE_TIME_ERROR.TYPE_PARAMETER_SUPERTYPE_OF_ITS_BOUND

main() {
  List<V> l = [];
//     ^
// [analyzer] unspecified
// [cfe] unspecified
}

@eernstg please clarify why here T is a supertype of V<T>? If so, then the following should work but it doesn't

extension type V<T extends V<T>>(T id) {
  test(T t) {
    T t0 = V<T>(t); // COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
  }
}

If T is a supertype of its bound (V<T>) then V<T> should be assignable to T but it doesn't

[eernstg]

extension type V<T extends V<T>>(T id) {} is an error because an extension type declaration must have type parameter declarations that are correct also after extension type erasure. In this case we get extension type V<T extends T>(T id) {}, and the type parameter declaration T extends T is an error.

However, it sounds like error message doesn't mention the extension type erasure, and it would probably be helpful if it did.