Autotyping fails to account for implicit returns

[charliermarsh]

Given:

def func(x: int):
    if x:
        return 1

We infer a return type of int, rather than Optional[int].

[charliermarsh]

@MichaReiser - Do you think it's feasible to use the unreachable code graph to implement this?

[MichaReiser]

@MichaReiser - Do you think it's feasible to use the unreachable code graph to implement this?

Using the control flow graph is an option. Although I fear that building the control flow graph just for this might be a bit overkill because we aren't interested in control flows, but only care about exit nodes of the function. I would need to look into it again but from what I remember is that Hindley milner is AST based. We could potentially implement a subset of it. But it heavily depends on how accurate the type analysis should be.