type-checking of __delete__ in descriptor protocol is insufficient

Bug Report

I have a descriptor which prevents del t.a by changing the "instance" type on delete. pyright fails on this correctly, but mypy does not.

To Reproduce

from typing import Literal, NewType, TypeVar


NotSupported = NewType("NotSupported", bool)


class Prop:
    """This is a descriptor class."""
    def __get__(self, o: object, otype: object) -> str:
        return "get-result"
    
    def __delete__(self, o: NotSupported) -> None:
        raise NotImplementedError("Don't do this")

class A:
    p = Prop()

a = A()
del a.p

Expected Behavior

I expect mypy to report an error at the line del a.p. pyright reports the error

Cannot delete member "p" for type "A"PylancereportGeneralTypeIssues

Actual Behavior

No error is reported.

Your Environment

• Mypy version used: 1.1.1
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files):

  show_error_codes = True
  check_untyped_defs = True
  strict_optional = True
  no_implicit_optional = False
  warn_redundant_casts = True
  

• Python version used: 3.11

Start by running mypy 1.1.1 against the descriptor reproducer in the issue, especially the __delete__ method and del a.p. Trace the descriptor type-checking path and make the check reject the deletion as shown; done means mypy reports an error at del a.p without breaking valid descriptor deletion.