[Bug c++/124173] [16 Regression] template argument deduction/substitution failed with nullptr_t in C++11/14 since r16-7582

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124173

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Though, unsure if that C++14 in there is pre-C++14 draft or post C++14 draft.
If the latter, maybe
--- gcc/cp/pt.cc.jj     2026-02-20 13:29:35.824439071 +0100
+++ gcc/cp/pt.cc        2026-02-20 20:13:05.074572910 +0100
@@ -7690,10 +7690,12 @@ convert_nontype_argument (tree type, tre
          /* EXPR may have become value-dependent.  */
          val_dep_p = value_dependent_expression_p (expr);
        }
-      else if (TYPE_PTR_OR_PTRMEM_P (type))
+      else if (TYPE_PTR_OR_PTRMEM_P (type)
+              || NULLPTR_TYPE_P (type))
        {
          tree folded = maybe_constant_value (expr, NULL_TREE, mce_true);
-         if (TYPE_PTR_P (type) ? integer_zerop (folded)
+         if ((TYPE_PTR_P (type) || NULLPTR_TYPE_P (type))
+             ? integer_zerop (folded)
              : null_member_pointer_value_p (folded))
            expr = folded;
        }