[mypyc] Call __delattr__ of a class that inherits __setattr__

[rheard]

Fixes mypyc/mypyc#1241

del obj.attr and delattr() go through tp_setattro. The wrapper for that slot was only generated for a class that defines __setattr__, and it calls __delattr__ only if that class has one. A subclass that defines __delattr__ and inherits __setattr__ also inherited the wrapper, so its __delattr__ was never called:

class Base:
    def __setattr__(self, name: str, value: object) -> None: ...

class Sub(Base):
    def __delattr__(self, name: str) -> None: ...  # not called by del or delattr()

Now a class that defines __delattr__ and inherits __setattr__ from a native class gets a wrapper of its own, which calls its __delattr__ and the inherited __setattr__. tp_setattro is filled for every class that has a wrapper, so the slot table is keyed on the wrapper instead of on __setattr__.

The errors for __setattr__ in a class that allows interpreted subclasses or inherits from a non-native class are still reported only where __setattr__ is defined.

A native class that inherits __setattr__ from a non-native class doesn't get a wrapper. The slot it inherits from the non-native class looks up both methods at runtime, so that case already worked.

[JukkaL]

Looks good!

[ilevkivskyi]

This broke master btw.

[ilevkivskyi]

https://github.com/python/mypy/actions/runs/38714453707/job/116353613664

build/__native.c:152:20: error: initialization of ‘int (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘int (*)(struct _object *, struct _object *, struct _object *)’} from incompatible pointer type ‘PyObject * (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *, struct _object *)’} [-Werror=incompatible-pointer-types]
  152 |     .tp_setattro = CPyDunder___setattr____wrapperSetAttr,
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
build/__native.c:152:20: note: (near initialization for ‘CPyType_SetAttr_template_.tp_setattro’)
build/__native.c:464:20: error: initialization of ‘int (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘int (*)(struct _object *, struct _object *, struct _object *)’} from incompatible pointer type ‘PyObject * (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *, struct _object *)’} [-Werror=incompatible-pointer-types]
  464 |     .tp_setattro = CPyDunder___setattr____wrapperDelAttr,
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
build/__native.c:464:20: note: (near initialization for ‘CPyType_DelAttr_template_.tp_setattro’)
build/__native.c:743:20: error: initialization of ‘int (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘int (*)(struct _object *, struct _object *, struct _object *)’} from incompatible pointer type ‘PyObject * (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *, struct _object *)’} [-Werror=incompatible-pointer-types]
  743 |     .tp_setattro = CPyDunder___setattr____wrapperDelAttrOverridden,
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
build/__native.c:743:20: note: (near initialization for ‘CPyType_DelAttrOverridden_template_.tp_setattro’)
build/__native.c:892:20: error: initialization of ‘int (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘int (*)(struct _object *, struct _object *, struct _object *)’} from incompatible pointer type ‘PyObject * (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *, struct _object *)’} [-Werror=incompatible-pointer-types]
  892 |     .tp_setattro = CPyDunder___setattr____wrapperDelAttrInSubSubclass,
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
build/__native.c:892:20: note: (near initialization for ‘CPyType_DelAttrInSubSubclass_template_.tp_setattro’)
build/__native.c:1043:20: error: initialization of ‘int (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘int (*)(struct _object *, struct _object *, struct _object *)’} from incompatible pointer type ‘PyObject * (*)(PyObject *, PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *, struct _object *)’} [-Werror=incompatible-pointer-types]
 1043 |     .tp_setattro = CPyDunder___setattr____wrapperSetAttrOverridden,
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
build/__native.c:1043:20: note: (near initialization for ‘CPyType_SetAttrOverridden_template_.tp_setattro’)

[JukkaL]

#22209 should fix CI.