MyPy does not consider the setter signature when type-checking assignments of properties

[wjakob]

Bug Report
It is a relatively common design pattern that a property setter might be more accepting of various inputs and then perform a conversion internally to conform the input to the right type (in fact, this might be the very reason that a @property is used, as opposed to merely storing data in an attribute).

PyRight accepts the following code without warnings or errors. MyPy does not:

To Reproduce

class C:
    @property
    def x(self, /) -> int:
        return 1

    @x.setter
    def x(self, value: float | int, /) -> None:
        pass

c = C()
c.x = 3.0

Expected Behavior

Accepted without errors or warnings.

Actual Behavior

q.py:11: error: Incompatible types in assignment (expression has type "float", variable has type "int")  [assignment]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: mypy 1.8.0 (compiled: yes)
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.12.2

[AlexWaygood]

Thanks! Closing as a duplicate of #3004