Bug Report

In a stub file, with--python-version=3.9, mypy emits false positive errors for the following type aliases:

fromtypingimportCallablefromtyping_extensionsimportTypeAliasX=int|Callable[[],str|bool]XX:TypeAlias=int|Callable[[],str|bool]Y=int|Callable[[str|bool],str]YY:TypeAlias=int|Callable[[str|bool],str]

For all of these, mypy's error message is:

error: Unsupported left operand type for | ("Type[str]")  [operator]

Note that this snippet works fine in a.py or.pyi file with--python-version 3.10. It's only--python-version 3.9 with a.pyi file that has the bug.

To Reproduce

1. cd into an up-to-date local clone of mypy with an editable install.
2. Copy the above snippet into atest.pyi file.
3. Runmypy test.pyi --python-version 3.9

Expected Behavior

No error should be emitted. PEP 604 syntax should be legal in stub files, even with--python-version 3.9.

Actual Behavior

False-positive errors are emitted.

Your Environment

• Mypy version used:c660354
• Mypy command-line flags:--python-version 3.9
• Python version used: 3.10

Cc.@ilevkivskyi (x-ref#12393).