.

Author: hamdanal

mypy/semanal.py

@@ -3782,7 +3782,7 @@ def analyze_type_alias_type_params(self, rvalue: CallExpr) -> TypeVarLikeList:
         have_type_var_tuple = False
         for tp_expr in type_params:
             if isinstance(tp_expr, StarExpr):
-                tp_expr.valid = True
+                tp_expr.valid = False
             self.analyze_type_expr(tp_expr)
             try:
                 base = self.expr_to_unanalyzed_type(tp_expr)
@@ -3818,7 +3818,8 @@ def analyze_type_alias_type_params(self, rvalue: CallExpr) -> TypeVarLikeList:
                     code=codes.TYPE_VAR,
                 )
                 continue
-            declared_tvars.append(tvar)
+            if tvar:
+                declared_tvars.append(tvar)
         return declared_tvars
 
     def disable_invalid_recursive_aliases(

test-data/unit/check-type-aliases.test

@@ -1147,7 +1147,7 @@ partially_generic2: Ta3[int] = {1: "a"}  # E: Dict entry 0 has incompatible type
 Ta4 = TypeAliasType("Ta4", Tuple[Unpack[Ts]], type_params=(Ts, Ts1))  # E: Can only use one type var tuple in type_params argument to TypeAliasType
 
 Ta5 = TypeAliasType("Ta5", Dict)  # Unlike old style aliases, this is not generic
-non_generic_dict: Ta5[int, str]  # E: Bad number of arguments for type alias, expected: 0, given: 2
+non_generic_dict: Ta5[int, str]  # E: Bad number of arguments for type alias, expected 0, given 2
 
 [builtins fixtures/dict.pyi]