Retrieve class or static info from node instead of type (#5261)

Fixes #5259

This partially undo changes made in https://github.com/python/mypy/pull/5224/files. It is more safe to retrieve class and static flags directly from nodes, since callable types have often definition not set (especially after de-serialization). Also being class or static method is not really a property of type itself, it is rather an "access flag" for a given name in symbol table (similar to how a variable can be settable).

Author: ilevkivskyi

mypy/checker.py

@@ -1221,22 +1221,32 @@ def check_method_override_for_base_with_name(
             # Construct the type of the overriding method.
             if isinstance(defn, FuncBase):
                 typ = self.function_type(defn)  # type: Type
+                override_class_or_static = defn.is_class or defn.is_static
             else:
                 assert defn.var.is_ready
                 assert defn.var.type is not None
                 typ = defn.var.type
+                override_class_or_static = defn.func.is_class or defn.func.is_static
             if isinstance(typ, FunctionLike) and not is_static(context):
                 typ = bind_self(typ, self.scope.active_self_type())
             # Map the overridden method type to subtype context so that
             # it can be checked for compatibility.
             original_type = base_attr.type
+            original_node = base_attr.node
             if original_type is None:
-                if isinstance(base_attr.node, FuncDef):
-                    original_type = self.function_type(base_attr.node)
-                elif isinstance(base_attr.node, Decorator):
-                    original_type = self.function_type(base_attr.node.func)
+                if isinstance(original_node, FuncBase):
+                    original_type = self.function_type(original_node)
+                elif isinstance(original_node, Decorator):
+                    original_type = self.function_type(original_node.func)
                 else:
                     assert False, str(base_attr.node)
+            if isinstance(original_node, FuncBase):
+                original_class_or_static = original_node.is_class or original_node.is_static
+            elif isinstance(original_node, Decorator):
+                fdef = original_node.func
+                original_class_or_static = fdef.is_class or fdef.is_static
+            else:
+                original_class_or_static = False  # a variable can't be class or static
             if isinstance(original_type, AnyType) or isinstance(typ, AnyType):
                 pass
             elif isinstance(original_type, FunctionLike) and isinstance(typ, FunctionLike):
@@ -1253,6 +1263,8 @@ def check_method_override_for_base_with_name(
                                     defn.name(),
                                     name,
                                     base.name(),
+                                    original_class_or_static,
+                                    override_class_or_static,
                                     context)
             elif is_equivalent(original_type, typ):
                 # Assume invariance for a non-callable attribute here. Note
@@ -1267,6 +1279,8 @@ def check_method_override_for_base_with_name(
 
     def check_override(self, override: FunctionLike, original: FunctionLike,
                        name: str, name_in_super: str, supertype: str,
+                       original_class_or_static: bool,
+                       override_class_or_static: bool,
                        node: Context) -> None:
         """Check a method override with given signatures.
 
@@ -1289,8 +1303,7 @@ def check_override(self, override: FunctionLike, original: FunctionLike,
             fail = True
 
         if isinstance(original, FunctionLike) and isinstance(override, FunctionLike):
-            if ((original.is_classmethod() or original.is_staticmethod()) and
-                    not (override.is_classmethod() or override.is_staticmethod())):
+            if original_class_or_static and not override_class_or_static:
                 fail = True
 
         if fail:

mypy/types.py

@@ -645,12 +645,6 @@ def with_name(self, name: str) -> 'FunctionLike': pass
     @abstractmethod
     def get_name(self) -> Optional[str]: pass
 
-    @abstractmethod
-    def is_classmethod(self) -> bool: pass
-
-    @abstractmethod
-    def is_staticmethod(self) -> bool: pass
-
 
 FormalArgument = NamedTuple('FormalArgument', [
     ('name', Optional[str]),
@@ -834,12 +828,6 @@ def with_name(self, name: str) -> 'CallableType':
     def get_name(self) -> Optional[str]:
         return self.name
 
-    def is_classmethod(self) -> bool:
-        return isinstance(self.definition, FuncBase) and self.definition.is_class
-
-    def is_staticmethod(self) -> bool:
-        return isinstance(self.definition, FuncBase) and self.definition.is_static
-
     def max_fixed_args(self) -> int:
         n = len(self.arg_types)
         if self.is_var_arg:
@@ -1058,12 +1046,6 @@ def with_name(self, name: str) -> 'Overloaded':
     def get_name(self) -> Optional[str]:
         return self._items[0].name
 
-    def is_classmethod(self) -> bool:
-        return self._items[0].is_classmethod()
-
-    def is_staticmethod(self) -> bool:
-        return self._items[0].is_staticmethod()
-
     def accept(self, visitor: 'TypeVisitor[T]') -> T:
         return visitor.visit_overloaded(self)
 

test-data/unit/check-classes.test

@@ -4376,3 +4376,19 @@ class C1(object):
 main:4: error: Revealed local types are:
 main:4: error: t: builtins.str
 main:4: error: y: builtins.float
+
+[case testClassMethodOverride]
+from typing import Callable, Any
+
+def deco(f: Callable[..., Any]) -> Callable[..., Any]: ...
+
+class B:
+    @classmethod
+    def meth(cls, x: int) -> int: ...
+
+class C(B):
+    @classmethod
+    @deco
+    def meth(cls, x: int) -> int: ...
+[builtins fixtures/classmethod.pyi]
+[out]