FreeChainXenon/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

c++: alias CTAD and copy deduction guide [PR115198]

Browse source 
Here we're neglecting to update DECL_NAME during the alias CTAD guide
transformation, which causes copy_guide_p to return false for the
transformed copy deduction guide since DECL_NAME is still __dguide_C
with TREE_TYPE C<B, T> but it should be __dguide_A with TREE_TYPE A<T>
(i.e. C<false, T>).  This ultimately results in ambiguity during
overload resolution between the copy deduction guide vs copy ctor guide.

This patch makes us update DECL_NAME of a transformed guide accordingly
during alias/inherited CTAD.

	PR c++/115198

gcc/cp/ChangeLog:

	* pt.cc (alias_ctad_tweaks): Update DECL_NAME of the transformed
	guides.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/class-deduction-alias22.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
(cherry picked from commit 06ebb7c6f31fe42ffdea6f51ac1ba1f6b058c090)
This commit is contained in:
Patrick Palka 2024-06-25 12:59:24 -04:00
parent 33a9c4dd5f
commit a00a8d46ea
2 changed files with 19 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
gcc/cp/pt.cc
View file

@ -30338,13 +30338,14 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
any). */
enum { alias, inherited } ctad_kind;
tree atype, fullatparms, utype;
tree atype, fullatparms, utype, name;
if (TREE_CODE (tmpl) == TEMPLATE_DECL)
{
ctad_kind = alias;
atype = TREE_TYPE (tmpl);
fullatparms = DECL_TEMPLATE_PARMS (tmpl);
utype = DECL_ORIGINAL_TYPE (DECL_TEMPLATE_RESULT (tmpl));
name = dguide_name (tmpl);
}
else
{
@ -30352,6 +30353,8 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
atype = NULL_TREE;
fullatparms = TREE_PURPOSE (tmpl);
utype = TREE_VALUE (tmpl);
name = dguide_name (TPARMS_PRIMARY_TEMPLATE
(INNERMOST_TEMPLATE_PARMS (fullatparms)));
}
tsubst_flags_t complain = tf_warning_or_error;
@ -30447,6 +30450,7 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
}
if (g == error_mark_node)
continue;
DECL_NAME (g) = name;
if (nfparms == 0)
{
/* The targs are all non-dependent, so g isn't a template. */

14
gcc/testsuite/g++.dg/cpp2a/class-deduction-alias22.C Normal file
View file

@ -0,0 +1,14 @@
// PR c++/115198
// { dg-do compile { target c++20 } }
template<bool B, class T>
struct C {
C() = default;
C(const C&) = default;
};
template<class T>
using A = C<false, T>;
C<false, int> c;
A a = c; // { dg-bogus "ambiguous" }