Cannot infer value of constrained type parameter when calling function with union

Bug Report

I have a function that takes in either a list of X or a list of Y, and returns a list of the same X or Y that was input. When calling the function with a variable that's either list of X or a list of Y, I expect it to work the same as calling the function with either.

To Reproduce

from typing import TypeVar

StrOrInt = TypeVar("StrOrInt", str, int)

def func(vals: list[StrOrInt]) -> list[StrOrInt]:
    return vals

def action(strs: list[str], ints: list[int]) -> None:
    reveal_type(func(strs))
    reveal_type(func(ints))

    strOrInt: list[str] | list[int] = strs if strs else ints
    reveal_type(func(strOrInt))

Expected Behavior

test.py:9: note: Revealed type is "builtins.list[builtins.str]"
test.py:10: note: Revealed type is "builtins.list[builtins.int]"
test.py:13: note: Revealed type is "builtins.list[builtins.str] | builtins.list[builtins.int]"

Actual Behavior

test.py:9: note: Revealed type is "builtins.list[builtins.str]"
test.py:10: note: Revealed type is "builtins.list[builtins.int]"
test.py:13: error: Cannot infer value of type parameter "StrOrInt" of "func"  [misc]
test.py:13: note: Revealed type is "builtins.list[Any]"

Your Environment

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

Start by running the supplied Python reproducer with mypy and compare the three revealed types with the expected output. Investigate type-parameter inference for a list[str] | list[int] argument; done means the union call is accepted and reveals list[str] | list[int] without an inference error.