conv_binds_ref_to_prvalue was expecting that if a user-defined
conversion uses a conversion function returning a reference, the
conversion will have reference type. This wasn't the case, because
build_user_type_conversion_1 strips the reference from the return type
to get the type of the conversion.
It seems to me that in the case of direct binding to a reference, we
want the conversion to have reference type.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 819e3be84751834a5e70df910f1d1726ea1b82f5
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Apr 4 20:27:29 2018 -0400
PR c++/85215 - ICE with copy-init from conversion.
* call.c (merge_conversion_sequences): Fix type of direct binding
sequence.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 7c99e8ad910..f2ada2768de 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -3642,6 +3642,12 @@ merge_conversion_sequences (conversion *user_seq, conversion *std_seq)
(*t)->bad_p = true;
}
+ if ((*t)->rvaluedness_matches_p)
+ /* We're binding a reference directly to the result of the conversion.
+ build_user_type_conversion_1 stripped the REFERENCE_TYPE from the return
+ type, but we want it back. */
+ user_seq->type = TREE_TYPE (TREE_TYPE (user_seq->cand->fn));
+
/* Replace the identity conversion with the user conversion
sequence. */
*t = user_seq;
diff --git a/gcc/testsuite/g++.dg/cpp1z/elide3.C b/gcc/testsuite/g++.dg/cpp1z/elide3.C
new file mode 100644
index 00000000000..ca4d24708a8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/elide3.C
@@ -0,0 +1,15 @@
+// PR c++/85215
+// { dg-do compile { target c++11 } }
+
+template <typename _Tp> struct vector {
+ vector(vector &&) noexcept;
+};
+
+template <typename T> struct any_container {
+ operator vector<T> &&();
+};
+
+void f (any_container<int> c)
+{
+ vector<int> shape (c);
+}
