Bug Report

When type checking the binding parameters of a match case expression, the binding completely fails if the class has a generic superclass and the match is located in a generic function, though the binding succeeds if the enclosing function is not generic.

To Reproduce

fromtypingimportAnyclassMyBase[T]:passclassMyData(MyBase[int]):__match_args__= ("a","b")def__init__(self,a:str,b:bool)->None:self.a=aself.b=bdefhandle_mydata_ok(val:MyBase[Any])->None:matchval:caseMyData(_a,_b):passdefhandle_mydata_not_ok[T](val:MyBase[T])->None:matchval:caseMyData(_a,_b):pass

https://mypy-play.net/?mypy=latest&python=3.12&gist=d8b1f6586d82fab7ead1a3d76a9962cf

Expected Behavior

mypy should report no type errors for bothhandle_mydata_ok andhandle_mydata_not_ok

Actual Behavior

main.py:20: error: Class "__main__.MyData" has no attribute "a"  [misc]main.py:20: error: Class "__main__.MyData" has no attribute "b"  [misc]Found 2 errors in 1 file (checked 1 source file)

Your Environment

Check the mypy-play link for the reproduction.

• Mypy version used: 1.16.1
• Mypy command-line flags: none
• Mypy configuration options frommypy.ini (and other config files): none
• Python version used: 3.12