[issue42812] @overload-ing method of parent class without actual implementation
Yurii Karabas
report at bugs.python.org
Sun Jan 3 12:18:04 EST 2021
Yurii Karabas <1998uriyyo at gmail.com> added the comment:
`mypy` will produce an error on such code:
```
class Parent:
def foo(self, **kwargs):
"""Argument names of foo vary depending on the child class."""
class Child(Parent):
@overload
def foo(self, a, b):
pass
def foo(self, **kwargs):
return super().foo(**kwargs)
```
Result
```
temp.py:10: error: Single overload definition, multiple required
temp.py:10: error: Signature of "foo" incompatible with supertype "Parent"
Found 2 errors in 1 file (checked 1 source file)
```
In case if you want to add an overload for method I would recommend to use such pattern:
```
class Parent:
def foo(self, **kwargs):
"""Argument names of foo vary depending on the child class."""
class Child(Parent):
@overload
def foo(self, a, b):
pass
@overload
def foo(self, **kwargs):
pass
def foo(self, **kwargs):
return super().foo(**kwargs)
```
So signature of `foo` will still match to parent class signature, but it will also have an overloaded variant.
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<https://bugs.python.org/issue42812>
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