From 9583f781e17d4da881ee64db43af939402331413 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Wed, 12 Jun 2024 20:05:05 -0400
Subject: c++: visibility wrt concept-id as targ [PR115283]

Like with alias templates, it seems we don't maintain visibility flags
for concepts either, so min_vis_expr_r should ignore them for now.
Otherwise after r14-6789 we may incorrectly give a function template that
uses a concept-id in its signature internal linkage.

	PR c++/115283

gcc/cp/ChangeLog:

	* decl2.cc (min_vis_expr_r) <case TEMPLATE_DECL>: Ignore
	concepts.

gcc/testsuite/ChangeLog:

	* g++.dg/template/linkage5.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
(cherry picked from commit b1fe718cbe0c8883af89f52e0aad3ebf913683de)
---
 gcc/cp/decl2.cc                          |  5 +++--
 gcc/testsuite/g++.dg/template/linkage5.C | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/linkage5.C

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 806a2a4bc69..88933be732d 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -2710,9 +2710,10 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void *data)
       break;
 
     case TEMPLATE_DECL:
-      if (DECL_ALIAS_TEMPLATE_P (t))
+      if (DECL_ALIAS_TEMPLATE_P (t) || standard_concept_p (t))
 	/* FIXME: We don't maintain TREE_PUBLIC / DECL_VISIBILITY for
-	   alias templates so we can't trust it here (PR107906).  */
+	   alias templates so we can't trust it here (PR107906).  Ditto
+	   for concepts.  */
 	break;
       t = DECL_TEMPLATE_RESULT (t);
       /* Fall through.  */
diff --git a/gcc/testsuite/g++.dg/template/linkage5.C b/gcc/testsuite/g++.dg/template/linkage5.C
new file mode 100644
index 00000000000..7e8f93f546f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/linkage5.C
@@ -0,0 +1,14 @@
+// PR c++/115283
+// { dg-final { scan-assembler "(weak|glob)\[^\n\]*_Z1fIiEv1AIX1CIT_EEE" } }
+// { dg-do compile { target c++20 } }
+
+template<class T>
+concept C = true;
+
+template<bool B>
+struct A { };
+
+template<class T>
+void f(A<C<T>>) { }
+
+template void f<int>(A<true>);
-- 
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