`unreachable` doesn't work with `if` statements

[DetachHead]

Describe the Bug

if False:
    print("unreachable") # no error

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeSIEYABAGKpRwyIA661H1xAThOgC4AKFiACu6bjFQBjABapssEQEoQAGhBlJYKKUL9cAWygUy-WbnQBaAG4xucCJeoBeaiIDMhAIwAWEWw88DD8ru4gcPy80vwB6ADa9ty4DgC6bJgwQdKo-DCYYSJJKSLu6BCGxFAQ0hD8VgqR3DL10lCocHCFIMXccRVVNXVWAymhbkXcyX0gZQPVtfy6VpmQ6PkN-FEQ2KJ53b1xhhCdfADmVnC4otzSMAdTJSBs6JZWMPjyopEQdlaGuTkD2mcVe9UkAEdRBBJJgrABrGCkBrSO6dYFPNi4YgwaziYgyeHnDEzMqw8SYDCtDrjcKHWZsclYKlWaSWTB1JzsCY9R6ktjidZotDcZFsyqoXhXbl0vmlAXoIXwEXI-ikHGsyx2Bxckny9DiSQyeSKe48%2BllQ1SOQKWD-QGyVkdM2ykEMg0SeC4KA2W0wFYU%2BwNKBQPXu8RqnFw0bcWmTN2Wg1MaNnV6SMNlX28DB3f4nAH8IHmuXuvi%2B6pwzJs5oGbhhkAAXw0LV%2BMFo0BgFDQWDwRDIjaAA

(Only applicable for extension issues) IDE Information

No response

[DetachHead]

it doesn't catch this either:

def example():
    return 1
    print(1)

i think it only works on return and yield statements (the exact examples provided inthe docs) but nothing else?

[connernilsen]

Okay, landing a suite of diffs that should address this and some other forms of reachability right now. I think we might be able to mark this closed soon, but will give it a bit of time to see if there are any complaints about it or things that were missed.

[DetachHead]

thanks for fixing those! here's another case i noticed:

from typing import Literal

def example(value: Literal[False]):
    if value:
        print(1) # no error

[connernilsen]

Okay, landing a fix for the other case you found right now! I'm also waiting for review on #3720, so hopefully should cover most forms of unreachability soon

[yangdanny97]

The original issue is fixed in the sandbox

[connernilsen]

Yeah, I'm leaving this issue open a little longer to track a few other unreachability things I'm looking at, but plan to close it this week

[connernilsen]

Alright, finished landing the rest of my stack + a few bug fixes. If there are any further issues or missing cases, please open a new issue for them :)