python / python/mypy

Should a method name shadow outer names when quoted or with PEP563?

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#18,525 4 comentarios 0 reacciones 0 asignados Ver en GitHub

Nadie ha tomado este issue todavía.

bug topic-quoted-annotations topic-runtime-semantics
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Python
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Descripción

Bug Report

If a class defines a method with a name shadowing outer name, mypy always rejects it in annotations.

To Reproduce

Consider the following snippet (playground):

#from __future__ import annotations

from typing import get_type_hints, get_origin

class Foo:
    def list(self) -> None: ...
    
    def method(self) -> list[str]:  # E: Function "__main__.Foo.list" is not valid as a type  [valid-type]
        return [""]

Foo().method().append("")  # E: "list?[builtins.str]" has no attribute "append"  [attr-defined]

if get_origin(get_type_hints(Foo.method)['return']) is list:
    print("Resolved to builtins.list")
else:
    print("Resolved as something else")

When run against it, mypy is producing a correct valid-type error, matching runtime behaviour.

$ mypy a.py
a.py:8: error: Function "a.Foo.list" is not valid as a type  [valid-type]
a.py:8: note: Perhaps you need "Callable[...]" or a callback protocol?
a.py:11: error: "list?[builtins.str]" has no attribute "append"  [attr-defined]
Found 2 errors in 1 file (checked 1 source file)

$ pyright a.py
/tmp/tmp.StzhaQlnmA/a.py
  /tmp/tmp.StzhaQlnmA/a.py:8:25 - error: Expected class but received "(self: Self@Foo) -> None" (reportGeneralTypeIssues)
1 error, 0 warnings, 0 informations 

$ python a.py
Traceback (most recent call last):
  File "/tmp/tmp.StzhaQlnmA/a.py", line 5, in <module>
    class Foo:
    ...<3 lines>...
            return [""]
  File "/tmp/tmp.StzhaQlnmA/a.py", line 8, in Foo
    def method(self) -> list[str]:  # E: Function "__main__.Foo.list" is not valid as a type  [valid-type]
                        ~~~~^^^^^
TypeError: 'function' object is not subscriptable

Now let's uncomment the future import or quote list[int] (both behave equivalently).

from __future__ import annotations

from typing import get_type_hints, get_origin

class Foo:
    def list(self) -> None: ...
    
    def method(self) -> list[str]:  # E: Function "__main__.Foo.list" is not valid as a type  [valid-type]
        return [""]

Foo().method().append("")  # E: "list?[builtins.str]" has no attribute "append"  [attr-defined]

if get_origin(get_type_hints(Foo.method)['return']) is list:
    print("Resolved to builtins.list")
else:
    print("Resolved as something else")
$ mypy a.py
a.py:8: error: Function "a.Foo.list" is not valid as a type  [valid-type]
a.py:8: note: Perhaps you need "Callable[...]" or a callback protocol?
a.py:11: error: "list?[builtins.str]" has no attribute "append"  [attr-defined]
Found 2 errors in 1 file (checked 1 source file)

$ pyright a.py
0 errors, 0 warnings, 0 informations 

$ python a.py
Resolved to builtins.list

Runtime resolution also (unsurprisingly, probably) works as intended, so mypy does not model runtime semantics correctly?

Expected Behavior

Snippet with PEP563 enabled should pass mypy check

Actual Behavior

a.py:8: error: Function "a.Foo.list" is not valid as a type  [valid-type]
a.py:8: note: Perhaps you need "Callable[...]" or a callback protocol?
a.py:11: error: "list?[builtins.str]" has no attribute "append"  [attr-defined]
Found 2 errors in 1 file (checked 1 source file)

Your Environment

  • Mypy version used: 1.14.1 and latest master
  • Mypy command-line flags: N/A
  • Mypy configuration options from mypy.ini (and other config files): N/A
  • Python version used: 3.13

Guía de contribución

Abrir la guía de contribución

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

Línea de trabajo

Empieza ejecutando mypy contra el reproductor proporcionado con y sin anotaciones entre comillas o con PEP 563 habilitado, comparando el resultado con la resolución en tiempo de ejecución y pyright. Rastrea la ruta de resolución de nombres de las anotaciones para los nombres de métodos que ocultan nombres externos; después, añade cobertura para los casos demostrados y verifica que las comprobaciones esperadas pasen.

Escrito por el modelo de indexación a partir del texto del issue.

Evaluación

Stack tecnológico
python
Área
compilers
Tipo de issue
Error
Dificultad
4/5
Tiempo estimado
3-5 días
Estado de actividad
Estancado
Claridad
Bastante claro
Aptitud para principiantes
42/100

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