Type-inference error not equating dynamic and Object

[floitschG]

/cc @leafpetersen

Take the following code:

void foo(void Function(Object) f) {  }

void main() {
  var f = (dynamic x) { };
  foo(f);
}

This should work: f has type dynamic -> void, or as the inference currently infers: dynamic -> Null.

However I get the following error message:

The argument type '(dynamic) → Null' can't be assigned to the parameter type '(Object) → void'.

I can remove this error message in two ways:

1. change from dynamic to Object (which should be the same thing).
2. change the return type from Null to void (by making it a nested function).

Neither should be necessary.

[leafpetersen]

It will work as soon as I land the change to eliminate fuzzy arrows... :)

Changing the return type is a red herring - making a nested function changes it from a function typed variable (fuzzy arrow type) which can be re-assigned, to a concrete function which cannot be re-assigned (non-fuzzy arrow).

#29630