c++: bad direct reference binding via conv fn [PR113064]

When computing a direct reference binding via a conversion function
yields a bad conversion, reference_binding incorrectly commits to that
conversion instead of trying a conversion via a temporary.  This causes
us to reject the first testcase because the bad direct conversion to B&&
via the && conversion operator prevents us from considering the good
conversion via the & conversion operator and a temporary.  (Similar
story for the second testcase.)

This patch fixes this by making reference_binding not prematurely commit
to such a bad direct conversion.  We still fall back to it if using a
temporary also fails (otherwise the diagnostic for cpp0x/explicit7.C
regresses).

	PR c++/113064

gcc/cp/ChangeLog:

	* call.cc (reference_binding): Still try a conversion via a
	temporary if a direct conversion was bad.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/rv-conv4.C: New test.
	* g++.dg/cpp0x/rv-conv5.C: New test.

2 files changed, 39 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-conv4.C b/gcc/testsuite/g++.dg/cpp0x/rv-conv4.C
new file mode 100644
index 0000000..7ecd2dc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/rv-conv4.C
@@ -0,0 +1,16 @@
+// PR c++/113064
+// { dg-do compile { target c++11 } }
+
+struct B { };
+
+struct A {
+  operator B() &;
+  operator B&&() &&;
+};
+
+void f(B&&);
+
+int main() {
+  A a;
+  f(a);
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-conv5.C b/gcc/testsuite/g++.dg/cpp0x/rv-conv5.C
new file mode 100644
index 0000000..dcb6fc6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/rv-conv5.C
@@ -0,0 +1,23 @@
+// PR c++/113064
+// { dg-do compile { target c++11 } }
+
+struct no_copy {
+  no_copy() = default;
+
+  no_copy(const no_copy&) = delete;
+  no_copy(no_copy&&);
+
+  no_copy& operator=(const no_copy&) = delete;
+  no_copy& operator=(no_copy&&);
+};
+
+struct A {
+  operator no_copy() &;
+  operator no_copy&&() && = delete;
+};
+
+int main() {
+  no_copy nc;
+  A a;
+  nc = a;
+}