fuzzy arrows and covariant generics require more checks

[jmesserly]

related to #27259, we're missing tests in covariant generic casts:

typedef F(x);
main() {
  F f = (int hi) => print(hi.isEven);
  List<dynamic> l = <String>['1'];
  l.map(f).toList();
}

DDC doesn't catch this at all and prints 'null'. VM does:

Unhandled exception:
NoSuchMethodError: Class 'String' has no instance getter 'isEven'.
Receiver: "1"
Tried calling: isEven

[leafpetersen]

Just to be clear, my preferred solution for this is not adding more checks, but getting rid of fuzzy arrows.

[jmesserly]

Good point Leaf! I've filed: #29299 and I'll mark this one blocked until we can get our internal code cleaned up w.r.t. fuzzy arrows and change static type system behavior.

[jmesserly]

Blocked on #29630

[jmesserly]

We're removing fuzzy arrow support from DDC runtime, so this is obsolete.