https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109876
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
> Instead, we should probably treat num as value-dependent even though it
> actually isn't.
An attempt to implement that:
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27969,6 +27969,12 @@ value_dependent_expression_p (tree expression)
else if (TYPE_REF_P (TREE_TYPE (expression)))
/* FIXME cp_finish_decl doesn't fold reference initializers. */
return true;
+ else if (DECL_DECLARED_CONSTEXPR_P (expression)
+ && TREE_STATIC (expression)
+ && !DECL_NAMESPACE_SCOPE_P (expression)
+ && DECL_INITIAL (expression)
+ && TREE_CODE (DECL_INITIAL (expression)) == IMPLICIT_CONV_EXPR)
+ return true;
return false;
case DYNAMIC_CAST_EXPR:
