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bugmypy got something wrongmypy got something wrongtopic-quoted-annotationsDetecting problems with quoted annotationsDetecting problems with quoted annotationstopic-runtime-semanticsmypy doesn't model runtime semantics correctlymypy doesn't model runtime semantics correctly
Description
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
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bugmypy got something wrongmypy got something wrongtopic-quoted-annotationsDetecting problems with quoted annotationsDetecting problems with quoted annotationstopic-runtime-semanticsmypy doesn't model runtime semantics correctlymypy doesn't model runtime semantics correctly