Analyzer does not throw a compile error for the type which is not well bounded.

[iarkh]

Dart SDK version: 2.15.0-116.0.dev (dev) (Thu Sep 16 09:47:01 2021 -0700) on "windows_x64"

Analyzer does not throw a compile error for the types which are not well-bounded.

For example, dart throws a compile error whereas analyzer passes without any error or warning with the following source code example:

class A<X> {}
typedef G<X extends A<X>, Y extends A<Y>> = X Function(Y);

main() {
  print(G == int);
}

Seems like this is a bug in analyzer because G is not a well-bounded type so a error should be thrown here.

See also Issue #44786 evaluation: runtime behavior is correct, so I suppose #44786 should be closed a fixed.

Dart sample output is:

test.dart:5:9: Error: Inferred type argument 'A<dynamic>' doesn't conform to the bound 'A<X>' of the type variable 'X' on 'G'.
 - 'A' is from 'test.dart'.
Try specifying type arguments explicitly so that they conform to the bounds.
  print(G == int);
        ^
test.dart:2:11: Context: This is the type variable whose bound isn't conformed to.
typedef G<X extends A<X>, Y extends A<Y>> = X Function(Y);
          ^
test.dart:5:9: Context: If you want 'G<A<dynamic>, A<Never>>' to be a super-bounded type, note that the inverted type 'G<A<Never>, A<Object?>>' must then satisfy its bounds, which it does not.
 - 'A' is from 'test.dart'.
 - 'Object' is from 'dart:core'.
  print(G == int);
        ^

[eernstg]

so I suppose #44786 should be closed a fixed.

I commented on #44786. I think it is alive, and it is now an analyzer issue.

[eernstg]

#44786 should be closed

Sorry, I did not notice that #44786 is now a duplicate of this one (the only thing in #44786 still on the table was exactly the same thing as the issue which is reported here). So I just closed #44786 as a duplicate of this one.

[srawlins]

Analyzer still does not report an error.

[eernstg]

Right, the raw G means G<A<dynamic>, A<Never>> by instantiation to bound, and that type is not well-bounded (it doesn't satisfy the declared bounds, and it is also not super bounded), so we should get a compile-time error at G.