From 14e320dbc10cc796fd7ca0b6c44e0c9ac0901da9 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Tue, 28 Jan 2020 12:26:10 -0500 Subject: [PATCH] c++: Allow template rvalue-ref conv to bind to lvalue ref. When I implemented the [over.match.ref] rule that a reference conversion function needs to match l/rvalue of the target reference type it changed our handling of this testcase. It seems to me that our current behavior is what the standard says, but it doesn't seem desirable, and all the other compilers have our old behavior. So let's limit the change to non-templates until there's some clarification from the committee. PR c++/90546 * call.c (build_user_type_conversion_1): Allow a template conversion returning an rvalue reference to bind directly to an lvalue. --- gcc/cp/ChangeLog | 4 ++++ gcc/cp/call.c | 2 ++ gcc/testsuite/g++.dg/cpp0x/rv-conv3.C | 15 +++++++++++++++ 3 files changed, 21 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp0x/rv-conv3.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 259b0c717b9..a110efe90c0 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,5 +1,9 @@ 2020-01-28 Jason Merrill + PR c++/90546 + * call.c (build_user_type_conversion_1): Allow a template conversion + returning an rvalue reference to bind directly to an lvalue. + PR c++/90731 * decl.c (grokdeclarator): Propagate eh spec from typedef. diff --git a/gcc/cp/call.c b/gcc/cp/call.c index 009cb85ad60..fde29f8f631 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -4115,6 +4115,8 @@ build_user_type_conversion_1 (tree totype, tree expr, int flags, EXPR_LOCATION (expr)); } else if (TYPE_REF_P (totype) && !ics->rvaluedness_matches_p + /* Limit this to non-templates for now (PR90546). */ + && !cand->template_decl && TREE_CODE (TREE_TYPE (totype)) != FUNCTION_TYPE) { /* If we are called to convert to a reference type, we are trying diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-conv3.C b/gcc/testsuite/g++.dg/cpp0x/rv-conv3.C new file mode 100644 index 00000000000..5f727fcc0d5 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/rv-conv3.C @@ -0,0 +1,15 @@ +// PR c++/90546 +// { dg-do link { target c++11 } } + +struct Foo { }; +void test(const Foo&) {} +Foo f; +struct Bar { + template operator T&&(); +}; +template<> Bar::operator const Foo&&() { + return static_cast(f); +} +int main() { + test(Bar{}); +}