From 7ce078ceca42f184f6f60c3ca921b6e07cf2c4bd Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Wed, 3 May 2023 13:32:55 -0400
Subject: [PATCH] c++: over-eager friend matching [PR109649]

A bug in the simplification I did around 91618; at this point X<int>::f has
DECL_IMPLICIT_INSTANTIATION set, but we've already identified what template
it corresponds to, so we don't want to call check_explicit_specialization.

To distinguish this case we need to look at DECL_TI_TEMPLATE.  grokfndecl
has for a long time set it to the OVERLOAD in this case, while the new cases
I added for 91618 were leaving DECL_TEMPLATE_INFO null; let's adjust them to
match.

	PR c++/91618
	PR c++/109649

gcc/cp/ChangeLog:

	* friend.cc (do_friend): Don't call check_explicit_specialization if
	DECL_TEMPLATE_INFO is already set.
	* decl2.cc (check_classfn): Set DECL_TEMPLATE_INFO.
	* name-lookup.cc (set_decl_namespace): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/template/friend77.C: New test.
---
 gcc/cp/decl2.cc                          |  1 +
 gcc/cp/friend.cc                         |  3 ++-
 gcc/cp/name-lookup.cc                    |  1 +
 gcc/testsuite/g++.dg/template/friend77.C | 19 +++++++++++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/friend77.C

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 9594be4092c..b510cdac554 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -855,6 +855,7 @@ check_classfn (tree ctype, tree function, tree template_parms)
 
 	 So tell check_explicit_specialization to look for a match.  */
       SET_DECL_IMPLICIT_INSTANTIATION (function);
+      DECL_TEMPLATE_INFO (function) = build_template_info (fns, NULL_TREE);
       matched = function;
     }
 
diff --git a/gcc/cp/friend.cc b/gcc/cp/friend.cc
index b36de2b20bb..5ab5c1fec73 100644
--- a/gcc/cp/friend.cc
+++ b/gcc/cp/friend.cc
@@ -661,7 +661,8 @@ do_friend (tree scope, tree declarator, tree decl,
   if (decl == error_mark_node)
     return error_mark_node;
 
-  if (!class_template_depth && DECL_IMPLICIT_INSTANTIATION (decl))
+  if (!class_template_depth && DECL_IMPLICIT_INSTANTIATION (decl)
+      && TREE_CODE (DECL_TI_TEMPLATE (decl)) != TEMPLATE_DECL)
     /* "[if no non-template match is found,] each remaining function template
        is replaced with the specialization chosen by deduction from the
        friend declaration or discarded if deduction fails."
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 8fd5733c1e2..ad03141df43 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -5938,6 +5938,7 @@ set_decl_namespace (tree decl, tree scope, bool friendp)
 
 	 So tell check_explicit_specialization to look for a match.  */
       SET_DECL_IMPLICIT_INSTANTIATION (decl);
+      DECL_TEMPLATE_INFO (decl) = build_template_info (old, NULL_TREE);
       return;
     }
 
diff --git a/gcc/testsuite/g++.dg/template/friend77.C b/gcc/testsuite/g++.dg/template/friend77.C
new file mode 100644
index 00000000000..f232cb10756
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend77.C
@@ -0,0 +1,19 @@
+// PR c++/109649
+
+template <typename>
+class X
+{
+  void f(){}
+};
+
+class Y
+{
+  friend void X<int>::f();	// { dg-error "private" }
+};
+
+int main()
+{
+  X<int> t;
+  t.f();			// { dg-error "private" }
+  Y b;
+}