[PATCH] c++/reflection: add assert to eval_type_trait

[Jason Merrill]

On 1/29/26 5:30 AM, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> -- >8 --
> As discussed in
> <https://gcc.gnu.org/pipermail/gcc-patches/2026-January/705756.html>.
> 
> Since we check eval_is_type in process_metafunction:
> 
>    if (eval_is_type (ht) != boolean_true_node)
>       return throw_exception_nontype (loc, ctx, fun, non_constant_p,
> 				     jump_target);
> 
> finish_trait_expr should never return error_mark_node.  We can ensure
> that it's so by adding an assert.
> 
> gcc/cp/ChangeLog:
> 
> 	* reflect.cc (eval_type_trait): Assert that finish_trait_expr didn't
> 	return error_mark_node.
> ---
>   gcc/cp/reflect.cc | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
> index bdeec2f0f38..fa039ac6d60 100644
> --- a/gcc/cp/reflect.cc
> +++ b/gcc/cp/reflect.cc
> @@ -3919,6 +3919,7 @@ static tree
>   eval_type_trait (location_t loc, tree type1, tree type2, cp_trait_kind kind)
>   {
>     tree r = finish_trait_expr (loc, kind, type1, type2);
> +  gcc_checking_assert (r != error_mark_node);
>     STRIP_ANY_LOCATION_WRAPPER (r);
>     return r;
>   }
> 
> base-commit: b20e68022a3f49010028dc01dab570c68071e3db