From: Patrick Palka <ppalka@redhat.com>
Date: Mon, 10 Aug 2020 13:39:29 +0000 (-0400)
Subject: c++: constraints and address of template-id
X-Git-Tag: releases/gcc-10.3.0~1037
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8679d8886383d77e3cc5b79b861b046e11f66a37;p=thirdparty%2Fgcc.git

c++: constraints and address of template-id

When resolving the address of a template-id, we need to drop functions
whose associated constraints are not satisfied, as per [over.over].  We
do so in resolve_address_of_overloaded_function, but not in
resolve_overloaded_unification or resolve_nondeduced_context, which
seems like an oversight.

gcc/cp/ChangeLog:

	* pt.c (resolve_overloaded_unification): Drop functions with
	unsatisfied constraints.
	(resolve_nondeduced_context): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-fn5.C: New test.
	* g++.dg/concepts/fn8.C: Generalize dg-error directive to accept
	"no matching function ..." diagnostic.
	* g++.dg/cpp2a/concepts-fn1.C: Likewise.
	* g++.dg/cpp2a/concepts-ts2.C: Likewise.
	* g++.dg/cpp2a/concepts-ts3.C: Likewise.

(cherry picked from commit 41fd9d26108fc98bbffce3d99d218a6a09fa80c6)
---

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f05f9a69900f..45efe3839d09 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -22163,7 +22163,11 @@ resolve_overloaded_unification (tree tparms,
 	  if (subargs != error_mark_node
 	      && !any_dependent_template_arguments_p (subargs))
 	    {
-	      elem = TREE_TYPE (instantiate_template (fn, subargs, tf_none));
+	      fn = instantiate_template (fn, subargs, tf_none);
+	      if (!constraints_satisfied_p (fn))
+		continue;
+
+	      elem = TREE_TYPE (fn);
 	      if (try_one_overload (tparms, targs, tempargs, parm,
 				    elem, strict, sub_strict, addr_p, explain_p)
 		  && (!goodfn || !same_type_p (goodfn, elem)))
@@ -22301,7 +22305,8 @@ resolve_nondeduced_context (tree orig_expr, tsubst_flags_t complain)
 		  badfn = fn;
 		  badargs = subargs;
 		}
-	      else if (elem && (!goodfn || !decls_match (goodfn, elem)))
+	      else if (elem && (!goodfn || !decls_match (goodfn, elem))
+		       && constraints_satisfied_p (elem))
 		{
 		  goodfn = elem;
 		  ++good;
diff --git a/gcc/testsuite/g++.dg/concepts/fn8.C b/gcc/testsuite/g++.dg/concepts/fn8.C
index ed9008099087..32df5a556c0f 100644
--- a/gcc/testsuite/g++.dg/concepts/fn8.C
+++ b/gcc/testsuite/g++.dg/concepts/fn8.C
@@ -24,5 +24,5 @@ template<typename T>
   void g(T x) { }
 
 int main () {
-  g(&f<int>); // { dg-error "no matches" }
+  g(&f<int>); // { dg-error "no match" }
 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-fn1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-fn1.C
index 9287ab8e5d7b..bf12ee573f07 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-fn1.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-fn1.C
@@ -170,7 +170,7 @@ template<typename T> void g(T x) { }
 void driver_3 () 
 {
   g(&ok<int>);
-  g(&err<int>); // { dg-error "no matches" }
+  g(&err<int>); // { dg-error "no match" }
 }
 
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-fn5.C b/gcc/testsuite/g++.dg/cpp2a/concepts-fn5.C
new file mode 100644
index 000000000000..8f00a760d7eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-fn5.C
@@ -0,0 +1,17 @@
+// Verify we check associated constraints when resolving the address of a
+// template-id.
+// { dg-do compile { target c++20 } }
+
+void id(auto) { }
+
+template <typename>
+int f() { return 0; }
+
+template <typename T> requires requires { T::fail(); }
+auto f() { T::fail(); }
+
+int main() {
+  using U = decltype(&f<int>);
+  (void)&f<int>;
+  id(&f<int>);
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ts2.C b/gcc/testsuite/g++.dg/cpp2a/concepts-ts2.C
index f731bac8c2a3..b88c968012b0 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-ts2.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ts2.C
@@ -173,7 +173,7 @@ template<typename T> void g(T x) { }
 void driver_3 () 
 {
   g(&ok<int>);
-  g(&err<int>); // { dg-error "no matches" }
+  g(&err<int>); // { dg-error "no match" }
 }
 
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ts3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-ts3.C
index 434a5e2651b0..22372e525ae4 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-ts3.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ts3.C
@@ -173,7 +173,7 @@ template<typename T> void g(T x) { }
 void driver_3 () 
 {
   g(&ok<int>);
-  g(&err<int>); // { dg-error "no matches" }
+  g(&err<int>); // { dg-error "no match" }
 }