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* [gcc(refs/users/jason/heads/alias-ctad)] c++: CTAD for less-specialized alias template [PR102529]
@ 2023-02-09 23:01 Jason Merrill
0 siblings, 0 replies; only message in thread
From: Jason Merrill @ 2023-02-09 23:01 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:e88e0337bac56ee087314fc26206bc86332c0dfc
commit e88e0337bac56ee087314fc26206bc86332c0dfc
Author: Jason Merrill <jason@redhat.com>
Date: Thu Feb 9 12:58:35 2023 -0800
c++: CTAD for less-specialized alias template [PR102529]
DR 2664
PR c++/102529
gcc/cp/ChangeLog:
* pt.cc (alias_ctad_tweaks): Continue after deduction failure.
gcc/testsuite/ChangeLog:
* g++.dg/DRs/dr2664.C: New test.
* g++.dg/cpp2a/class-deduction-alias15.C: New test.
Diff:
---
gcc/cp/pt.cc | 4 +++-
gcc/testsuite/g++.dg/DRs/dr2664.C | 17 +++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/class-deduction-alias15.C | 18 ++++++++++++++++++
3 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 35d8ce709c3..68488a0d018 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30057,7 +30057,9 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
tree targs = make_tree_vec (len);
int err = unify (ftparms, targs, ret, utype, UNIFY_ALLOW_NONE, false);
if (err)
- continue;
+ /* CWG2664: Discard any deductions, still build the guide. */
+ for (unsigned i = 0; i < len; ++i)
+ TREE_VEC_ELT (targs, i) = NULL_TREE;
/* The number of parms for f' is the number of parms for A plus
non-deduced parms of f. */
diff --git a/gcc/testsuite/g++.dg/DRs/dr2664.C b/gcc/testsuite/g++.dg/DRs/dr2664.C
new file mode 100644
index 00000000000..f6bf8e2ecef
--- /dev/null
+++ b/gcc/testsuite/g++.dg/DRs/dr2664.C
@@ -0,0 +1,17 @@
+// CWG 2664
+// { dg-do compile { target c++20 } }
+
+template <class S1, class S2> struct C {
+ C(...);
+};
+
+template<class T1> C(T1) -> C<T1, T1>;
+template<class T1, class T2> C(T1, T2) -> C<T1 *, T2>;
+
+template<class V1, class V2> using A = C<V1, V2>;
+
+C c1{""};
+A a1{""};
+
+C c2{"", 1};
+A a2{"", 1};
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias15.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias15.C
new file mode 100644
index 00000000000..db615faf8e2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias15.C
@@ -0,0 +1,18 @@
+// PR c++/102529
+// { dg-do compile { target c++20 } }
+
+template <typename T>
+struct C {
+ template <typename U>
+ C(U);
+};
+
+template <typename U>
+C(U) -> C<U*>;
+
+template <typename T>
+ requires true
+using A = C<T>;
+
+C ok(1); // ok, a is a C<int*>
+A bad(2); // fails
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