Polymorphs

core_parsing.cpp

@@ -733,6 +733,7 @@ parse_struct(Token *pos, Ast_Kind kind) {
                 compiler_error(it->pos, "All struct arguments are required to be polymorphic");
             }
         }
+        params = params.tight_copy(pctx->perm);
     }
 
     Ast_Scope *scope = begin_decl_scope(scratch.arena, token_get());