From: Patrick Palka <ppalka@redhat.com>
Date: Wed, 19 Jul 2023 20:11:38 +0000 (-0400)
Subject: c++: deducing empty type vs non-type argument pack
X-Git-Tag: basepoints/gcc-15~7483
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74477d25a2c9e6790f3bc1e8b908fc32013614ca;p=thirdparty%2Fgcc.git

c++: deducing empty type vs non-type argument pack

Within a template parameter list, a non-type template parameter pack is
represented as a PARM_DECL.  But in a couple of spots where we need to
deduce and create an empty argument pack, we test for TEMPLATE_PARM_INDEX
(within a template parameter list) instead of for PARM_DECL, and so we
end up creating a TYPE_ARGUMENT_PACK even in the non-type case.  This
patch fixes this (seemingly harmless) bug.

gcc/cp/ChangeLog:

	* pt.cc (type_unification_real): Test for PARM_DECL instead
	of TEMPLATE_PARM_INDEX to distinguish a type vs non-type
	template parameter pack.
	(type_targs_deducible_from): Likewise.
---

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index d882e9dd1178..21b08a6266a5 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -23367,7 +23367,7 @@ type_unification_real (tree tparms,
 	    {
 	      tree arg;
 
-	      if (TREE_CODE (tparm) == TEMPLATE_PARM_INDEX)
+	      if (TREE_CODE (tparm) == PARM_DECL)
 		{
 		  arg = make_node (NONTYPE_ARGUMENT_PACK);
 		  TREE_CONSTANT (arg) = 1;
@@ -30398,7 +30398,7 @@ type_targs_deducible_from (tree tmpl, tree type)
 	if (template_parameter_pack_p (tparm))
 	  {
 	    tree arg;
-	    if (TREE_CODE (tparm) == TEMPLATE_PARM_INDEX)
+	    if (TREE_CODE (tparm) == PARM_DECL)
 	      {
 		arg = make_node (NONTYPE_ARGUMENT_PACK);
 		TREE_CONSTANT (arg) = 1;