From: Patrick Palka <ppalka@redhat.com>
Date: Sat, 18 Apr 2020 10:22:14 +0000 (-0400)
Subject: c++: Abbreviated function template return type [PR92187]
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=e43b28ae7f09c0b7a30ab0dd976db761eeb1b0f9;p=gcc.git

c++: Abbreviated function template return type [PR92187]

When updating an auto return type of an abbreviated function template in
splice_late_return_type, we should also propagate PLACEHOLDER_TYPE_CONSTRAINTS
(and cv-qualifiers) of the original auto node.

gcc/cp/ChangeLog:

	PR c++/92187
	* pt.c (splice_late_return_type): Propagate cv-qualifiers and
	PLACEHOLDER_TYPE_CONSTRAINTS from the original auto node to the new one.

gcc/testsuite/ChangeLog:

	PR c++/92187
	* g++.dg/concepts/abbrev5.C: New test.
	* g++.dg/concepts/abbrev6.C: New test.
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b89b6d88fd3..45c422f5950 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-18  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/92187
+	* pt.c (splice_late_return_type): Propagate cv-qualifiers and
+	PLACEHOLDER_TYPE_CONSTRAINTS from the original auto node to the new one.
+
 2020-04-17  Patrick Palka  <ppalka@redhat.com>
 
 	PR c++/94483
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0a8ec3198d2..9e39f46a090 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -29032,10 +29032,17 @@ splice_late_return_type (tree type, tree late_return_type)
     {
       tree idx = get_template_parm_index (*auto_node);
       if (TEMPLATE_PARM_LEVEL (idx) <= processing_template_decl)
-	/* In an abbreviated function template we didn't know we were dealing
-	   with a function template when we saw the auto return type, so update
-	   it to have the correct level.  */
-	*auto_node = make_auto_1 (TYPE_IDENTIFIER (*auto_node), true);
+	{
+	  /* In an abbreviated function template we didn't know we were dealing
+	     with a function template when we saw the auto return type, so update
+	     it to have the correct level.  */
+	  tree new_auto = make_auto_1 (TYPE_IDENTIFIER (*auto_node), false);
+	  PLACEHOLDER_TYPE_CONSTRAINTS (new_auto)
+	    = PLACEHOLDER_TYPE_CONSTRAINTS (*auto_node);
+	  TYPE_CANONICAL (new_auto) = canonical_type_parameter (new_auto);
+	  new_auto = cp_build_qualified_type (new_auto, TYPE_QUALS (*auto_node));
+	  *auto_node = new_auto;
+	}
     }
   return type;
 }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e5d0d92344c..08bef53e911 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-18  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/92187
+	* g++.dg/concepts/abbrev5.C: New test.
+	* g++.dg/concepts/abbrev6.C: New test.
+
 2020-04-17  Jeff Law  <law@redhat.com>
 
 	PR rtl-optimization/90275
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev5.C b/gcc/testsuite/g++.dg/concepts/abbrev5.C
new file mode 100644
index 00000000000..de594b5c1df
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev5.C
@@ -0,0 +1,15 @@
+// PR c++/92187
+// { dg-do compile { target concepts } }
+
+template <typename>
+concept C = false;
+
+C auto f(auto)
+{
+  return 42; // { dg-error "deduced return type" }
+}
+
+void foo()
+{
+  f(0);
+}
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev6.C b/gcc/testsuite/g++.dg/concepts/abbrev6.C
new file mode 100644
index 00000000000..862675e5193
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev6.C
@@ -0,0 +1,12 @@
+// { dg-do compile { target concepts } }
+
+const auto &f(auto)
+{
+  static int n;
+  return n;
+}
+
+void foo()
+{
+  f(5) = 0; // { dg-error "read-only" }
+}