third party unbased callable will cause problems

```py
# third_party.py
def f(fn: Callable[[A], None]) -> Callable[[A], None]: ...

class A:
@f
def foo(self): ...

# my code
A().foo() # error: missing self arg
```

Reproduce the example from third_party.py, including the Callable decorator and the A().foo() call. Trace how the type checker handles the third-party callable and method binding; the work is done when the shown call no longer reports a missing self argument.

Written by the indexing model from the issue text.