Use uniform initialization for aggregate trait

This prevents us from doing narrowing conversions, but it's necessary
for initializing base class values. Overall, I'd rather take the latter
over the former. Explicit casts/ctor can be used to explicitly narrow.

Author: jeaye

lib/CppInterOp/CppInterOp.cpp

@@ -4165,7 +4165,7 @@ int get_aggregate_ctor_predicate_wrapper_code(compat::Interpreter& I,
     helper_buf << "()\n"
                   "{\n";
     indent(helper_buf, ++indent_level);
-    helper_buf << "return requires { T( std::declval<Args>()... ); };\n";
+    helper_buf << "return requires { T{ std::declval<Args>()... }; };\n";
     indent(helper_buf, --indent_level);
     helper_buf << "}\n";