Type narrowing not working after calling a NoReturn function

Hi! I love this project. It's blazingly fast and i use it daily. i found what i believe is a bug with type narrowing after calling a function typed as NoReturn

Summary

When a function with return type NoReturn is called inside an if block to guard against None, ty does not narrow the type of the variable in subsequent code. The variable still shows as str | None instead of being narrowed to str.

Minimal Reproduction

from typing import NoReturn


def raise_error() -> NoReturn:
    """Raise an error."""
    msg = "This is a test error"
    raise ValueError(msg)


data: dict[str, str] = {}

api_key = data.get("api_key")
if not api_key:
    raise_error()


def use_api_key(api_key: str) -> None:
    """Use an API key."""
    api_key.startswith("sk_")


use_api_key(api_key)  # <-- Error reported here

Expected Behavior

After the if not api_key: raise_error() block, ty should understand that:

1. The raise_error() function never returns (it's typed as NoReturn)
2. Therefore, if execution continues past that point, api_key cannot be None or falsy
3. The type of api_key should be narrowed from str | None to str

This is the same behavior as if you used raise ValueError() directly in the if block.

Actual Behavior

ty reports an error on the use_api_key(api_key) call:

Argument to function `use_api_key` is incorrect: Expected `str`, found `str | None`
  invalid-argument-type

Environment

• ty version: 0.0.11
• OS: Linux
• Python version: 3.12+

Workaround

Currently, I have to add an explicit api_key = "" after the guard, which defeats the purpose of having the NoReturn typed function.

Version

0.0.11