Typechecker rejects callable argument in virtual method call

[BI71317]

The compiler fails to typecheck this program:

class A:
    def f(self, block: CallableTrait[[], bool]):
        return False

class B(A):
    def f(self, block: CallableTrait[[], bool]):
        return block()

def make_base() -> A:
    return B()

print(make_base().f(lambda: False or True))
print(make_base().f(lambda: True and False))

B inherits from A. The function make_base is annotated as returning A, but it actually returns an instance of B.
So it should dispatch to B.f, execute the passed lambda, and return the lambda result.
However, it looks like the program fails during typechecking before it can get as far as calling either A.f or B.f.

Result

$ codon run -release 04_factory_base_return_callable.codon 
04_factory_base_return_callable.codon:15 (1-44): error: cannot typecheck 'print(make_base().f(lambda: False or True))'
04_factory_base_return_callable.codon:16 (1-45): error: cannot typecheck 'print(make_base().f(lambda: True and False))'

Expected to print:

True
False

[BI71317]

Seems related to #687 in the broad sense that this also happens around inheritance/type inference.

But I think the concrete failure mode is different as it does not seem specific to lambdas or CallableTrait.

# Mutation: use concrete Function type instead of CallableTrait.

class A:
    def f(self, block: Function[[], bool]):
        return False

class B(A):
    def f(self, block: Function[[], bool]):
        return block()

def make_base() -> A:
    return B()

def yes():
    return True

def no():
    return False

print(make_base().f(yes))
print(make_base().f(no))

Result

$ codon run -release 14_factory_base_return_function.codon 
rtti.codon:96 (19-58): error: 'Function[Tuple,bool]' does not match expected type 'yes()'
╰─ 14_factory_base_return_function.codon:20 (7-25): error: during the realization of _thunk_dispatch(slf: A, cls_id: int, *args: Tuple[yes()], F: f[A,Function[Tuple,bool]])