Assert t.alias is not None before keying seen-aliases sets

Author: RogerJinIS

mypy/semanal_typeargs.py

@@ -85,12 +85,12 @@ def visit_block(self, o: Block) -> None:
 
     def visit_type_alias_type(self, t: TypeAliasType) -> None:
         super().visit_type_alias_type(t)
+        assert t.alias is not None, f"Unfixed type alias {t.type_ref}"
         if t.is_recursive:
             if t.alias in self.seen_aliases:
                 # Avoid infinite recursion on recursive type aliases.
                 return
             self.seen_aliases.add(t.alias)
-        assert t.alias is not None, f"Unfixed type alias {t.type_ref}"
         is_error, is_invalid = self.validate_args(
             t.alias.name, tuple(t.args), t.alias.alias_tvars, t
         )

mypy/server/deps.py

@@ -980,10 +980,10 @@ def visit_instance(self, typ: Instance) -> list[str]:
         return triggers
 
     def visit_type_alias_type(self, typ: TypeAliasType) -> list[str]:
+        assert typ.alias is not None
         if typ.alias in self.seen_aliases:
             return []
         self.seen_aliases.add(typ.alias)
-        assert typ.alias is not None
         trigger = make_trigger(typ.alias.fullname)
         triggers = [trigger]
         for arg in typ.args:

mypy/type_visitor.py

@@ -456,6 +456,7 @@ def visit_type_alias_type(self, t: TypeAliasType, /) -> T:
         # Skip type aliases already visited to avoid infinite recursion.
         # We track by the TypeAlias node so that recursive aliases with varying
         # type arguments are still caught.
+        assert t.alias is not None, f"Unfixed type alias {t.type_ref}"
         if self.seen_aliases is None:
             self.seen_aliases = set()
         elif t.alias in self.seen_aliases:
@@ -600,6 +601,7 @@ def visit_type_alias_type(self, t: TypeAliasType, /) -> bool:
         # Skip type aliases already visited to avoid infinite recursion.
         # We track by the TypeAlias node so that recursive aliases with varying
         # type arguments are still caught.
+        assert t.alias is not None, f"Unfixed type alias {t.type_ref}"
         if self.seen_aliases is None:
             self.seen_aliases = set()
         elif t.alias in self.seen_aliases: