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Breaks under __future__.annotations #104

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jtrakk opened this issue Jun 16, 2019 · 0 comments · May be fixed by #114
Open

Breaks under __future__.annotations #104

jtrakk opened this issue Jun 16, 2019 · 0 comments · May be fixed by #114

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@jtrakk
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jtrakk commented Jun 16, 2019

Annotations are becoming string-valued by default in a future version. This feature is accessible in Python 3.7 with from __future__ import annotations.

This breaks the current implementation of multipledispatch.dispatch():

from __future__ import annotations

import multipledispatch


@multipledispatch.dispatch()
def func(x):
    raise NotImplementedError(x)


@multipledispatch.dispatch()
def func(x: int):
    return f"x {x} int"


print(func(1))

Traceback (most recent call last):
  File "/home/user/tmp/single.py", line 11, in <module>
    @multipledispatch.dispatch()
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/multipledispatch/core.py", line 68, in _
    dispatcher.add(types, func)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/multipledispatch/dispatcher.py", line 225, in add
    (typ, str_sig, self.name))
TypeError: Tried to dispatch on non-type: int
In signature: <int>
In function: func

The solution that functools.singledispatch uses is to call typing.get_type_hints() to evaluate the hint strings.
@JacobHayes JacobHayes linked a pull request Apr 18, 2021 that will close this issue
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Add minimal typing support and fix py3.10 JacobHayes/multipledispatch
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@jtrakk