From: Patrick Palka <ppalka@redhat.com>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH] c++: deduction for dependent class type of NTTP [PR105110]
Date: Wed, 30 Mar 2022 17:51:07 -0400 [thread overview]
Message-ID: <20220330215107.1833323-1-ppalka@redhat.com> (raw)
Here deduction for the P/A pair V/a spuriously fails with
types ‘A<T>’ and ‘const A<int>’ have incompatible cv-qualifiers
because the argument type is const, whereas the parameter type is
non-const.
Since the type of an NTTP is always cv-unqualified, it seems natural to
ignore cv-qualifiers on the argument type before attempting to unify the
two types.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
PR c++/105110
gcc/cp/ChangeLog:
* pt.cc (unify) <case TEMPLATE_PARM_INDEX>: Ignore cv-quals on
on the argument type of an NTTP before deducing from it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/nontype-class52.C: New test.
---
gcc/cp/pt.cc | 5 +++--
gcc/testsuite/g++.dg/cpp2a/nontype-class52.C | 13 +++++++++++++
2 files changed, 16 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class52.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 1acb5990c5c..cdd75d3b6ac 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -24271,8 +24271,9 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
&& !(strict & UNIFY_ALLOW_INTEGER)
&& TEMPLATE_PARM_LEVEL (parm) <= TMPL_ARGS_DEPTH (targs))
{
- /* Deduce it from the non-type argument. */
- tree atype = TREE_TYPE (arg);
+ /* Deduce it from the non-type argument. As above, ignore
+ top-level quals here too. */
+ tree atype = cv_unqualified (TREE_TYPE (arg));
RECUR_AND_CHECK_FAILURE (tparms, targs,
tparm, atype,
UNIFY_ALLOW_NONE, explain_p);
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C
new file mode 100644
index 00000000000..56163376afb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C
@@ -0,0 +1,13 @@
+// PR c++/105110
+// { dg-do compile { target c++20 } }
+
+template<class> struct A { };
+
+template<auto> struct B { };
+
+template<class T, A<T> V> void f(B<V>);
+
+int main() {
+ constexpr A<int> a;
+ f(B<a>{});
+}
--
2.35.1.693.g805e0a6808
next reply other threads:[~2022-03-30 21:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-30 21:51 Patrick Palka [this message]
2022-04-01 18:08 ` Jason Merrill
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