PR c++/87150 - wrong ctor with maybe-rvalue semantics.

	* call.c (struct conversion): Update commentary.
	(standard_conversion): Set rvaluedness_matches_p if LOOKUP_PREFER_RVALUE
	for ck_base.

	* g++.dg/cpp0x/move-return2.C: New test.

From-SVN: r264172

gcc/cp/ChangeLog

+2018-09-08  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87150 - wrong ctor with maybe-rvalue semantics.
+	* call.c (struct conversion): Update commentary.
+	(standard_conversion): Set rvaluedness_matches_p if LOOKUP_PREFER_RVALUE
+	for ck_base.
+
 2018-09-08  Jason Merrill  <jason@redhat.com>
 
 	PR c++/86678 - constexpr function with non-constant after return.

gcc/cp/call.c

@@ -102,10 +102,10 @@ struct conversion {
   BOOL_BITFIELD base_p : 1;
   /* If KIND is ck_ref_bind, true when either an lvalue reference is
      being bound to an lvalue expression or an rvalue reference is
-     being bound to an rvalue expression.  If KIND is ck_rvalue,
+     being bound to an rvalue expression.  If KIND is ck_rvalue or ck_base,
      true when we are treating an lvalue as an rvalue (12.8p33).  If
-     KIND is ck_base, always false.  If ck_identity, we will be
-     binding a reference directly or decaying to a pointer.  */
+     ck_identity, we will be binding a reference directly or decaying to
+     a pointer.  */
   BOOL_BITFIELD rvaluedness_matches_p: 1;
   BOOL_BITFIELD check_narrowing: 1;
   /* Whether check_narrowing should only check TREE_CONSTANTs; used
@@ -1425,6 +1425,9 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
 	 type.  A temporary object is created to hold the result of
 	 the conversion unless we're binding directly to a reference.  */
       conv->need_temporary_p = !(flags & LOOKUP_NO_TEMP_BIND);
+      if (flags & LOOKUP_PREFER_RVALUE)
+	/* Tell convert_like_real to set LOOKUP_PREFER_RVALUE.  */
+	conv->rvaluedness_matches_p = true;
     }
   else
     return NULL;

gcc/testsuite/ChangeLog

 2018-09-08  Marek Polacek  <polacek@redhat.com>
 
+	PR c++/87150 - wrong ctor with maybe-rvalue semantics.
+	* g++.dg/cpp0x/move-return2.C: New test.
+
+2018-09-08  Marek Polacek  <polacek@redhat.com>
+
 	* c-c++-common/array-init.c: Add dg-prune-output.
 	* g++.dg/cpp0x/lambda/lambda-const-this.C: Add dg-warning.
 	* g++.dg/cpp0x/lambda/lambda-in-class-neg.C: Likewise.

gcc/testsuite/g++.dg/cpp0x/move-return2.C

+// PR c++/87150
+// { dg-do compile { target c++11 } }
+
+struct S1 { S1(S1 &&); };
+struct S2 : S1 {};
+
+S1
+f (S2 s)
+{
+  return s; // { dg-error "use of deleted function" }
+}