qapi: Dumb down QAPISchema.lookup_entity()

QAPISchema.lookup_entity() takes an optional type argument, a subtype
of QAPISchemaDefinition, and returns that type or None.  Callers can
use this to save themselves an isinstance() test.

The only remaining user of this convenience feature is .lookup_type().
But we don't actually save anything anymore there: we still need the
isinstance() to help mypy over the hump.

Drop the .lookup_entity() argument, and adjust .lookup_type().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240315152301.3621858-26-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
[Commit message typo fixed]

scripts/qapi/schema.py

@@ -1157,20 +1157,14 @@ def _def_definition(self, defn: QAPISchemaDefinition) -> None:
                 defn.info, "%s is already defined" % other_defn.describe())
         self._entity_dict[defn.name] = defn
 
-    def lookup_entity(
-        self,
-        name: str,
-        typ: Optional[type] = None,
-    ) -> Optional[QAPISchemaDefinition]:
-        ent = self._entity_dict.get(name)
-        if typ and not isinstance(ent, typ):
-            return None
-        return ent
+    def lookup_entity(self,name: str) -> Optional[QAPISchemaEntity]:
+        return self._entity_dict.get(name)
 
     def lookup_type(self, name: str) -> Optional[QAPISchemaType]:
-        typ = self.lookup_entity(name, QAPISchemaType)
-        assert typ is None or isinstance(typ, QAPISchemaType)
-        return typ
+        typ = self.lookup_entity(name)
+        if isinstance(typ, QAPISchemaType):
+            return typ
+        return None
 
     def resolve_type(
         self,