Implement implicit call method tear-offs with extension typed receivers

[eernstg]

This implementation issue is associated with the proposal in dart-lang/language#3467, that is, the proposal to support implicit call method tear-offs for receivers whose static type is an extension type.

Consider the following example:

extension type Ext(Function it) {
  String call() => 'call from Ext: ${it()}';
}

class C {
  String call() => 'call from C';
}

class D {
  Function get fgetter => Ext(C()); // (1)
}

void main() {
  var d = D();
  print(d.fgetter());
}

At (1) in this example, we evaluate the expression Ext(C()) with a context type of Function. Following the treatment of a receiver of an interface type that has a method named call, this expression should be implicitly transformed into Ext(C()).call, and the resulting program would then be type correct.

(Of course, C() will be subject to the same transformation because that's the case that we already support, yielding Ext(C().call).call.)

This issue serves as a request to implement this feature. It may be implemented in the analyzer already, but the CFE reports an error when Ext(...) is encountered with context type Function. I'll create subtask issues for both, and then the analyzer subtask may be trivial.

Subtasks:

• [analyzer] Implement implicit call method tear-offs with extension typed receivers #54340
• [cfe] Implement implicit call method tear-offs with extension typed receivers #54341

[eernstg]

Oh, @johnniwinther, perhaps it was #54341 that should have been closed?

[johnniwinther]

Yes

[eernstg]

Done.