Description

bvolkmer

opened on Mar 4, 2025

Issue body actions

Bug report

Bug description:

When using singledispatchmethod, the register decorator function raises an exception if self is annotated with typing.Self:

TypeError: Invalid annotation for 'self'. typing.Self is not a class.

Minimal example:

from functools import singledispatchmethod
from typing import Self


class Foo:
    @singledispatchmethod
    def bar(self: Self, arg: int | str) -> int | str: ...

    @bar.register
    def _(self: Self, arg: int) -> int:
        return arg


foo = Foo()

print(foo.bar(1))

The workaround is to remove the typing.Self annotation for the _ function.

(Same for singledispatch but that should not be used in that case anyway)

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-130827: Support typing.Self annotations in singledispatchmethod() #130829
• gh-84644: Fix singledispatch annotation parsing #143465

Activity

1. bvolkmer

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Mar 4, 2025
2. ZeroIntensity

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-typing

   on Mar 4, 2025
3. ZeroIntensity commented on Mar 4, 2025

   

   ZeroIntensity

   on Mar 4, 2025

   Member

   More actions

   Presumably, we want to:

   • Disallow Self on singledispatch.
   • But allow it on singledispatchmethod.

   That seems easy enough, but we'll probably need a new internal helper to hide any talking between singledispatch and singledispatchmethod. I'll submit a fix.
4. ZeroIntensity

   added a commit that references this issue on Mar 4, 2025

   pythongh-130827: Support typing.Self in singledispatchmethod()

   d466dc4
5. ZeroIntensity

   added

   type-featureA feature request or enhancementA feature request or enhancement

   and removed

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Apr 2, 2025
6. johnslavik

   added 2 commits that reference this issue on Jan 6, 2026

   Add pythonGH-130827 test

   3115fd7

   Merge pythonGH-130827 test into `test_method_type_ann_register`

   57965a9

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