fix: Allow merging stubs into alias targets

Author: pawamoy

src/griffe/merger.py

@@ -63,7 +63,11 @@ def _merge_stubs_members(obj: Module | Class, stubs: Module | Class) -> None:
                 continue
             obj_member = obj.get_member(member_name)
             with suppress(AliasResolutionError, CyclicAliasError):
-                if obj_member.kind is not stub_member.kind:
+                # An object's canonical location can differ from its equivalent stub location.
+                # Devs usually declare stubs at the public location of the corresponding object,
+                # not the canonical one. Therefore, we must allow merging stubs into the target of an alias,
+                # as long as the stub and target are of the same kind.
+                if obj_member.kind is not stub_member.kind and not obj_member.is_alias:
                     logger.debug(
                         f"Cannot merge stubs for {obj_member.path}: kind {stub_member.kind.value} != {obj_member.kind.value}",
                     )