mypy reports functions with identical signatures as not having identical signatures

[ltworf]

Bug Report

Doing a conditional import confuses mypy.

Use mypy on this:

try:
    from emoji import emojize
    reveal_type(emojize)
except ModuleNotFoundError:
    def emojize(string: str, use_aliases=False, delimiters=(':', ':'), variant=None, language='en'):
        return string
    reveal_type(emojize)

The result is

test.py:3: note: Revealed type is 'def (string: builtins.str, use_aliases: builtins.bool =, delimiters: Tuple[builtins.str, builtins.str] =) -> builtins.str'
test.py:5: error: All conditional function variants must have identical signatures
test.py:7: note: Revealed type is 'def (string: builtins.str, use_aliases: builtins.bool =, delimiters: Tuple[builtins.str, builtins.str] =) -> builtins.str'
Found 1 error in 1 file (checked 1 source file)

Expected Behavior

It should work (I copied the function signature from the module) or at the very least return a useful error message.

Complaining about non identical signatures while printing identical signatures doesn't seem the correct behaviour to me.

Your Environment

mypy 0.812
Python 3.9.2

[ltworf]

Ok reveal type is not so smart, i have to do it in 2 different runs.

Still it'd be nice to show a diff so one can see what's wrong.

[ltworf]

It was all particularly difficult because the emoji module is actually not annotated, but mypy is picking a pyi file from

python3-jedi: /usr/lib/python3/dist-packages/jedi/third_party/typeshed/third_party/2and3/emoji.pyi

which annotated the module wrong, skipping some parameters (that maybe were added later on).

So to conclude, this is more of a feature request now.

[bersbersbers]

Maybe you want to change the title of this issue to state the feature you are requesting. Is it Show a diff between signatures in case of "All conditional function variants must have identical signatures"?

[hauntsaninja]

I fixed this in #13604