assert_type fails to fail for NoReturn

[ghost]

Bug Report

In a case that mypy deems impossible (i.e. type narrowed to NoReturn), it's currently impossible to cause assert_type to fail.

Similarly, reveal_type has no effect in the case of NoReturn.

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=10400960688da44ab22b58df6c297f50

Expected Behavior

Three assert_type failures.

Actual Behavior

Only one assert_type failure.

[sobolevn]

This happens because mypy does not execute code for Literal[False] branches in if.

Check this:

"""All three of these assert_type should fail, but only one does, currently."""
import typing_extensions as t

def f(x: int | bool):
    if isinstance(x, str):
        reveal_type(x)  # not executed

[sobolevn]

This does not look like a bug to me.