Here we were wrongly treating binding a const lvalue ref to an xvalue as
direct binding, which is wrong under [dcl.init.ref] and [over.match.ref].
Tested x86_64-pc-linux-gnu, applying to trunk.
* call.c (build_user_type_conversion_1): Don't use a conversion to a
reference of the wrong rvalueness for direct binding.
---
gcc/cp/call.c | 8 +++++++
.../20_util/is_constructible/value-2.cc | 6 ++++--
gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C | 21 +++++++++++++++++++
gcc/cp/ChangeLog | 6 ++++++
4 files changed, 39 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 98aa5ee89f7..bf48ae2c27a 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4039,6 +4039,14 @@ build_user_type_conversion_1 (tree totype, tree expr,
int flags,
rettype, totype,
EXPR_LOCATION (expr));
}
+ else if (TYPE_REF_P (totype) && !ics->rvaluedness_matches_p
+ && TREE_CODE (TREE_TYPE (totype)) != FUNCTION_TYPE)
+ {
+ /* If we are called to convert to a reference type, we are trying
+ to find a direct binding per [over.match.ref], so rvaluedness
+ must match for non-functions. */
+ cand->viable = 0;
+ }
else if (DECL_NONCONVERTING_P (cand->fn)
&& ics->rank > cr_exact)
{
diff --git a/libstdc++-v3/testsuite/20_util/is_constructible/value-2.cc
b/libstdc++-v3/testsuite/20_util/is_constructible/value-2.cc
index 0fdbab8e2d4..57487df500b 100644
--- a/libstdc++-v3/testsuite/20_util/is_constructible/value-2.cc
+++ b/libstdc++-v3/testsuite/20_util/is_constructible/value-2.cc
@@ -806,10 +806,12 @@ static_assert(!std::is_constructible<int&&,
ExplicitTo<int>>::value, "Error");
// Binding through reference-compatible type is required to perform
// direct-initialization as described in [over.match.ref] p. 1 b. 1:
static_assert(std::is_constructible<int&, ExplicitTo<int&>>::value, "Error");
-static_assert(std::is_constructible<const int&, ExplicitTo<int&&>>::value,
- "Error");
static_assert(std::is_constructible<int&&, ExplicitTo<int&&>>::value, "Error");
+// But an xvalue doesn't count for direct binding.
+static_assert(!std::is_constructible<const int&, ExplicitTo<int&&>>::value,
+ "Error");
+
// Binding through temporary behaves like copy-initialization,
// see [dcl.init.ref] p. 5, very last sub-bullet:
static_assert(!std::is_constructible<const int&, ExplicitTo<double&&>>::value,
diff --git a/gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C
b/gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C
new file mode 100644
index 00000000000..42a135dbf44
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C
@@ -0,0 +1,21 @@
+// PR c++/86521
+// { dg-do compile { target c++11 } }
+
+template <class T> T&& move (T&);
+
+struct Dest {
+ Dest() = default;
+ Dest( Dest && ) = default;
+ Dest( Dest const & ) = delete;
+};
+
+struct Source {
+ Dest val;
+ operator Dest () && { return move( val ); }
+ operator Dest const & () const & { return val; }
+};
+
+int main() {
+ Source x;
+ Dest d(move(x)); // { dg-error "ambiguous" }
+}
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 8cad038fd1c..33402399886 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-11 Jason Merrill <ja...@redhat.com>
+
+ PR c++/86521 - wrong overload resolution with ref-qualifiers.
+ * call.c (build_user_type_conversion_1): Don't use a conversion to a
+ reference of the wrong rvalueness for direct binding.
+
2019-03-11 Martin Liska <mli...@suse.cz>
* cvt.c (build_expr_type_conversion): Wrap apostrophes
base-commit: c860979e3e331e884e482ec46928e4113f6a6d71
--
2.20.1
