[red-knot] Inline SubclassOfType::as_instance_type_of_metaclass() (#…

…15556)

crates/red_knot_python_semantic/src/types.rs

@@ -1311,7 +1311,13 @@ impl<'db> Type<'db> {
 
             (Type::SubclassOf(subclass_of_ty), other)
             | (other, Type::SubclassOf(subclass_of_ty)) => {
-                other.is_disjoint_from(db, subclass_of_ty.as_instance_type_of_metaclass(db))
+                let metaclass_instance_ty = match subclass_of_ty.subclass_of() {
+                    // for `type[Any]`/`type[Unknown]`/`type[Todo]`, we know the type cannot be any larger than `type`,
+                    // so although the type is dynamic we can still determine disjointness in some situations
+                    ClassBase::Dynamic(_) => KnownClass::Type.to_instance(db),
+                    ClassBase::Class(class) => class.metaclass(db).to_instance(db),
+                };
+                other.is_disjoint_from(db, metaclass_instance_ty)
             }
 
             (Type::KnownInstance(known_instance), Type::Instance(InstanceType { class }))

crates/red_knot_python_semantic/src/types/subclass_of.rs

@@ -68,15 +68,6 @@ impl<'db> SubclassOfType<'db> {
         Type::from(self.subclass_of).member(db, name)
     }
 
-    /// A class `T` is an instance of its metaclass `U`,
-    /// so the type `type[T]` is a subtype of the instance type `U`.
-    pub(crate) fn as_instance_type_of_metaclass(&self, db: &'db dyn Db) -> Type<'db> {
-        match self.subclass_of {
-            ClassBase::Dynamic(_) => KnownClass::Type.to_instance(db),
-            ClassBase::Class(class) => class.metaclass(db).to_instance(db),
-        }
-    }
-
     /// Return `true` if `self` is a subtype of `other`.
     ///
     /// This can only return `true` if `self.subclass_of` is a [`ClassBase::Class`] variant;