Typechecker rejects callable argument in virtual method call

The compiler fails to typecheck this program:

```python
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
```bash
$ 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
```

Start by running 04_factory_base_return_callable.codon with the reported codon run -release command and inspect the typechecking path for the two virtual calls using CallableTrait arguments. Done means the program typechecks and prints True followed by False, as shown in the expected output.

Written by the indexing model from the issue text.