mypy does not work correctly with nested overloaded, raising has incompatible type overloaded function [arg-type]

[sobolevn]

• Are you reporting a bug, or opening a feature request?

Bug.

• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.

Reproduction link: https://github.com/sobolevn/mypy-bug-410

Here's what is going wrong. In returns we have a custom mypy plugin that create curry functions. It works like so:

from returns.curry import curry

@curry
def first(a: int, b: int) -> int:
    ...

@curry
def second(a: int, b: int, c: int) -> int:
    ...

reveal_type(first)
reveal_type(second)

It works perfectly fine:

example.py:11: note: Revealed type is 'Overload(def (a: builtins.int) -> def (b: builtins.int) -> builtins.int, def (a: builtins.int, b: builtins.int) -> builtins.int)'
example.py:12: note: Revealed type is 'Overload(def (a: builtins.int) -> Overload(def (b: builtins.int, c: builtins.int) -> builtins.int, def (b: builtins.int) -> def (c: builtins.int) -> builtins.int), def (a: builtins.int, b: builtins.int) -> def (c: builtins.int) -> builtins.int, def (a: builtins.int, b: builtins.int, c: builtins.int) -> builtins.int)'

Ok, here's the next step. I try to pass both first and second functions as values to be wrapped by some other type:

class Result(Generic[_ValueType]):
    @classmethod
    def from_value(self, inner_value: _ValueType) -> 'Result[_ValueType]':
        return Result(inner_value)

reveal_type(
    Result.from_value(first),
)
reveal_type(
    Result.from_value(second),
)

And here's the problem, first works:

example.py:23: note: Revealed type is 'example.Result[Overload(def (a: builtins.int) -> def (b: builtins.int) -> builtins.int, def (a: builtins.int, b: builtins.int) -> builtins.int)]'

While second does not:

example.py:35: note: Revealed type is 'example.Result[Overload(def (a: builtins.int) -> Overload(def (b: builtins.int, c: builtins.int) -> builtins.int, def (b: builtins.int) -> def (c: builtins.int) -> builtins.int), def (a: builtins.int, b: builtins.int) -> def (c: builtins.int) -> builtins.int, def (a: builtins.int, b: builtins.int, c: builtins.int) -> builtins.int)]'
example.py:35: error: Argument 1 to "from_value" of "Result" has incompatible type overloaded function; expected overloaded function  [arg-type]

This part looks like an issue with mypy to me:

example.py:35: error: Argument 1 to "from_value" of "Result" has incompatible type overloaded function; expected overloaded function  [arg-type]

Build output: https://github.com/sobolevn/mypy-bug-410/runs/783959567?check_suite_focus=true#step:5:12

• What are the versions of mypy and Python you are using?
  Do you see the same issue after installing mypy from Git master?

[email protected], other version like 0.770 are also affected
python: 3.6, 3.7, 3.8

• What are the mypy flags you are using? (For example --strict-optional)

Full list is in the reproduction repo, here: https://github.com/sobolevn/mypy-bug-410/blob/master/setup.cfg#L2

Related:

• Original issue: Problems with overloads / mypy bug dry-python/returns#410
• @curry source code: https://github.com/dry-python/returns/blob/master/returns/contrib/mypy/_features/curry.py
• @curry tests: https://github.com/dry-python/returns/tree/master/typesafety/test_curry/test_curry

[sobolevn]

Duplicate of #8978