PR c++/80990 use cv-qualifiers in class template argument deduction

gcc/cp:

	PR c++/80990
	* pt.c (do_class_deduction): Build qualified type.

gcc/testsuite:

	PR c++/80990
	* g++.dg/cpp1z/class-deduction39.C: New.

From-SVN: r248966

gcc/cp/ChangeLog

+2017-06-07  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR c++/80990
+	* pt.c (do_class_deduction): Build qualified type.
+
 2017-06-06  Nathan Sidwell  <nathan@acm.org>
 
 	* name-lookup.c (suggest_alternatives_for): Use qualified lookup

gcc/cp/pt.c

@@ -25367,7 +25367,7 @@ do_class_deduction (tree ptype, tree tmpl, tree init, int flags,
   --cp_unevaluated_operand;
   release_tree_vector (args);
 
-  return TREE_TYPE (t);
+  return cp_build_qualified_type (TREE_TYPE (t), cp_type_quals (ptype));
 }
 
 /* Replace occurrences of 'auto' in TYPE with the appropriate type deduced

gcc/testsuite/ChangeLog

+2017-06-07  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR c++/80990
+	* g++.dg/cpp1z/class-deduction39.C: New.
+
 2017-06-07  Marek Polacek  <polacek@redhat.com>
 
 	PR sanitizer/80932

gcc/testsuite/g++.dg/cpp1z/class-deduction39.C

+// { dg-options -std=c++1z }
+
+template <class T> struct A { };
+
+A<int> a;
+const A c = a;
+volatile A v = a;
+const volatile A cv = a;
+
+template <class,class> struct same;
+template <class T> struct same<T,T> {};
+
+same<decltype(c), const A<int>> s1;
+same<decltype(v), volatile A<int>> s2;
+same<decltype(cv), const volatile A<int>> s3;