Dart and analyzer behaves in the different ways when call a raw non-function typedef constructor

[iarkh]

Dart SDK version: 2.13.0-216.0.dev (dev) (Wed Apr 7 15:12:05 2021 -0700) on "windows_x64"

Here is a source code example:

class C<X> {}
typedef A<X extends C<X>> = C<X>;

main() {
  A();
}

Analyzer throws a compile error here whereas dart silently passes.

Sample output is:

$> dart test.dart

$ dartanalyzer test.dart
Analyzing test.dart...
  error - Couldn't infer type parameter 'X'.

Tried to infer 'C<Object?>' for 'X' which doesn't work:
  Type parameter 'X' is declared to extend 'C<X>' producing 'C<C<Object?>>'.

Consider passing explicit type argument(s) to the generic.

 - test.dart:5:3 - could_not_infer
1 error found.

Please also note that both analyzer and dart don't throws a compile error for the following code:

class C<X> {}
typedef A<X extends C<X>> = C<X>;

main() {
  A a = throw "Error";
}

[eernstg]

The instance creation A() is an error because inference yields A<C<Object?>>(), and A<C<Object?>> is not a regular-bounded type (cf. this rule).

The analyzer reports the error correctly, but the front end does not report it.

[eernstg]

Thanks, @stefantsov!