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Correctly handle cls in protocol classmethod #11119

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Merged
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Nov 19, 2021
Merged

Correctly handle cls in protocol classmethod #11119

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8053fb1
Correctly handle cls in protocol classmethod (#11115)
nullie Sep 16, 2021
258c393
Added argument name to the bind_self call
nullie Sep 21, 2021
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3 changes: 2 additions & 1 deletion mypy/subtypes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -710,7 +710,8 @@ def find_node_type(node: Union[Var, FuncBase], itype: Instance, subtype: Type) -
and node.is_initialized_in_class
and not node.is_staticmethod)):
assert isinstance(typ, FunctionLike)
signature = bind_self(typ, subtype)
signature = bind_self(typ, subtype,
is_classmethod=isinstance(node, Var) and node.is_classmethod)
if node.is_property:
assert isinstance(signature, CallableType)
typ = signature.ret_type
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31 changes: 31 additions & 0 deletions test-data/unit/check-selftype.test
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Expand Up @@ -802,6 +802,37 @@ class Bad(metaclass=Meta):
Good.do_x()
Bad.do_x() # E: Invalid self argument "Type[Bad]" to attribute function "do_x" with type "Callable[[Type[T]], T]"

[case testSelfTypeProtocolClassmethodMatch]
from typing import Type, TypeVar, Protocol

T = TypeVar('T')

class HasDoX(Protocol):
@classmethod
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What about @staticmethod? Does it fall into the same problem?

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staticmethod doesn't have this problem, because there's no self/cls to bind

def do_x(cls: Type[T]) -> T:
...

class Good:
@classmethod
def do_x(cls) -> 'Good':
...

class Bad:
@classmethod
def do_x(cls) -> Good:
...

good: HasDoX = Good()
bad: HasDoX = Bad()
[builtins fixtures/classmethod.pyi]
[out]
main:21: error: Incompatible types in assignment (expression has type "Bad", variable has type "HasDoX")
main:21: note: Following member(s) of "Bad" have conflicts:
main:21: note: Expected:
main:21: note: def do_x(cls) -> Bad
main:21: note: Got:
main:21: note: def do_x(cls) -> Good

[case testSelfTypeNotSelfType]
# Friendlier error messages for common mistakes. See #2950
class A:
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