Hashing of unhashable objects is not detected

Bug Report

False negatives for hashing unhashable objects

To Reproduce

class Unhashable1:
    def __eq__(self, other: object) -> bool:
        return False


class Unhashable2:
    __hash__ = None  


for obj in Unhashable1(), Unhashable2():
    try:
        hash(obj)
    except TypeError:
        pass
    else:
        raise AssertionError(f"{obj} should be unhashable")

    try:
        obj in set()
    except TypeError:
        pass
    else:
        raise AssertionError(f"{obj} should be unhashable")

    try:
        obj in {}
    except TypeError:
        pass
    else:
        raise AssertionError(f"{obj} should be unhashable")

    try:
        s = {obj}  
    except TypeError:
        pass
    else:
        raise AssertionError(f"{obj} should be unhashable")

    try:
        d = {obj: "value"}
    except TypeError:
        pass
    else:
        raise AssertionError(f"{obj} should be unhashable")

Expected Behavior

5 errors to be reported

Actual Behavior

No errors reported (other than the __hash__ = None false positive)

Your Environment

• Mypy version used: 1.18.2
• Python version used: 3.12

Start with the supplied Python reproduction and trace mypy's handling of hashability for membership tests, set literals, and dictionary literals. Confirm the fix by adding or running checks that report errors for both example classes in all five operations.