Parameters of the form type[typevar] cause issues with type refinement

[Pluviolithic]

When defining a function with the type of a TypeVar as one of the parameters and a return value of that same TypeVar, Mypy incorrectly traverses type refinement branches and throws an incompatible return value type error.

To Reproduce

Example A
Related variant Example B
Example C

Example A at-a-glance:

from typing import TypeVar, reveal_type

Test = TypeVar(
    "Test", int, str, bool
)

def get_test(t: type[Test]) -> Test:
    if isinstance(t, int):
        reveal_type(t)
        return 1
    elif isinstance(t, str):
        reveal_type(t)
        return "asdf"
    else:
        reveal_type(t)
        return True

Expected Behavior

I do not expect mypy to identify issues with the code. Even though the types are narrowed, they still return correctly in conjunction with what is passed in for t, which I believe to be technically correct.

Actual Behavior

main.py:15: note: Revealed type is "type[builtins.int]"
main.py:15: note: Revealed type is "type[builtins.str]"
main.py:15: note: Revealed type is "type[builtins.bool]"
main.py:16: error: Incompatible return value type (got "bool", expected "str")  [return-value]
Found 1 error in 1 file (checked 1 source file)

Workaround

A simple workaround is to just wrap the return value with a call to t. Playground example here. Even though the workaround is "simple," code modifications like this shouldn't be necessary to use a typechecker.

Environment

• Mypy version used: 1.13.0
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.12

[brianschubert]

Closing per the explanation given at microsoft/pyright#9568 (comment).

Also note that bool is a subclass of int. You should probably check for bool before int case in the fixed code to avoid taking the int branch in both cases.

[Pluviolithic]

Appreciate it, thanks.