Inline staticmethod assignment on subclass fails with Incompatible types in assignment
#4574
Comments
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There must be a little more going on than you show, since if I type that example into mypy: class Base:
def foo(self) -> None:
a = self.static_foo()
class Sub(Base):
static_foo = staticmethod(lambda: 5)I get a much simpler error: |
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Well, this example doesn't error at all, which is closer: 1 from typing import Any, Dict
2
3 class Base(object):
4 def __init__(self, dikt):
5 # type: (Dict[Any, Any]) -> None
6 object.__setattr__(self, '_dict', dikt)
7
8 def __getattr__(self, name):
9 # type: (str) -> Any
10 return self._dict[name]
11
12 def __setattr__(self, name, val):
13 # type: (str, Any) -> None
14 if name in self._dict:
15 self._dict[name] = val
16 else:
17 object.__setattr__(self, name, val)
18
19 def foo(self):
20 # type: () -> None
21 a = self.static_foo()
22
23
24
25 class SubClass(Base):
26 static_foo = staticmethod(lambda: 5) |
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This does repro (though in my actual example, there is no staticmethod declared on the base class (???). 1 from typing import Any, Dict
2
3 class Base(object):
4 def __init__(self, dikt):
5 # type: (Dict[Any, Any]) -> None
6 object.__setattr__(self, '_dict', dikt)
7
8 def __getattr__(self, name):
9 # type: (str) -> Any
10 return self._dict[name]
11
12 def __setattr__(self, name, val):
13 # type: (str, Any) -> None
14 if name in self._dict:
15 self._dict[name] = val
16 else:
17 object.__setattr__(self, name, val)
18
19 def foo(self):
20 # type: () -> None
21 a = self.static_foo()
22
23 @staticmethod
24 def static_foo():
25 # type: () -> int
26 return 0
27
28
29 class SubClass(Base):
30 static_foo = staticmethod(lambda: 5)
31
32 def __init__(self, *args, **kwargs):
33 # type: (*Any, **Any) -> None
34 super(SubClass, self).__init__(*args, **kwargs) |
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More minimal repro: class Base(object):
def foo(self) -> None:
a = self.static_foo()
@staticmethod
def static_foo() -> int:
return 0
class SubClass(Base):
static_foo = staticmethod(lambda: 5) |
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And to clarify, this gives the following error: Now it's very clear that the error is caused by mypy's lack of understanding of how As to why it gave this same error for you with the real version of the original code, even though there was no definition of |
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Improving mypy's understanding of inline usage of staticmethod seems tractable/higher priority. Given how clever this code is, someone may have monkey patched something somewhere to the same effect of the minimal example. |
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The false-positive error is no longer emitted on mypy 0.930+. |
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@AlexWaygood this is error is back, at least with mypy 0.950 and 3.7 <= python <= 3.9: |
Hah! This bug was never fixed. The reason I thought it was is because I was testing on 3.10, and the typeshed stub (correctly) states that |
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Thanks @youtux :) |
* Changed inline staticmethod assignment in subclasses
* In <py310, the staticmethod typeshed stub doesn't correcetly
define the `__call__`. See python/mypy#4574
* Removed py2-only exception block
* Inlined `_Encoder` protocol from typeshed for typecasting.
* Changed inline staticmethod assignment in subclasses
* In <py310, the staticmethod typeshed stub doesn't correcetly
define the `__call__`. See python/mypy#4574
* Add tests to cover these methods
* Removed py2-only exception block
* Inlined `_Encoder` protocol from typeshed for typecasting.
squash! R Add type annotations
* Add mypy dependency * Update pre-commit * Test pre-commit * Test pre-commit * Set files to check * Only check mypy at push * Fix type * Fix type * Fix type * Fix type * Fix missing methods from EEGModuleMixin, not nice... * Fix types * Remove staticmethod(..) from IdentityTransform * Fix type * Undo IdentityTransform not staticmethod * Ignore check for staticmethods in transforms because of python/mypy#4574 * Ignore BaseConcatDataset.split for now * Fix type * Fix type * Fix type * Fix types * Fix types * Fix types * Fix types * Add future import * Fix type * Fix types * Fix types * Ignore type staticmethod * Ignore type staticmethod * Fix type * Ignore import error for preprocessors * Update whats_new.rst
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3.9, the last version affected by this bug, has 8 more months before it hits EOL. I don't think it is worth fixing this. |
A simplification of some old code I am trying to add mypy to:
Results in the error:
error: Incompatible types in assignment (expression has type "staticmethod", base class "Job" defined the type as "Callable[[], int]")Oddly, as far as I can tell,
static_foois not actually defined on the base class.This is using Dropbox's mypy setup, with --strict-optional. I am actually not sure which version we're on, but can look it up and edit this issue.
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