squiid/llvm
1
0
Fork 0
Code Issues Pull requests Activity

[libcxx/variant] Correctly propagate return type of the visitor.

Browse source 
The tests for it were missing so I've added them.

Reviewed By: #libc, EricWF

Differential Revision: https://reviews.llvm.org/D86006
This commit is contained in:
Michael Park 2020-08-17 10:53:59 -07:00
parent df4756ec6c
commit e0ec7a0206
No known key found for this signature in database
GPG key ID: EFA0BFDA521B99FD
2 changed files with 68 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
libcxx/include/variant
View file

@ -595,7 +595,7 @@ struct __base {
__visit_alt_impl(index_sequence<_Is...>, _Vis&& __vis, _Vs&&... __vs) {
using __multi = __multi<__uncvref_t<_Vs>::__size()...>;
constexpr auto __dispatch = [](auto... __is) {
return +[](_Vis&& __vis_, _Vs&&... __vs_) {
return +[](_Vis&& __vis_, _Vs&&... __vs_) -> decltype(auto) {
return __invoke_constexpr(
_VSTD::forward<_Vis>(__vis_),
__access::__base::__get_alt<decltype(__is)::value>(

76
libcxx/test/std/utilities/variant/variant.visit/visit.pass.cpp
View file

@ -45,25 +45,28 @@ inline constexpr CallType operator|(CallType LHS, CallType RHS) {
struct ForwardingCallObject {
template <class... Args> bool operator()(Args &&...) & {
template <class... Args>
ForwardingCallObject& operator()(Args&&...) & {
set_call<Args &&...>(CT_NonConst | CT_LValue);
return true;
return *this;
}
template <class... Args> bool operator()(Args &&...) const & {
template <class... Args>
const ForwardingCallObject& operator()(Args&&...) const & {
set_call<Args &&...>(CT_Const | CT_LValue);
return true;
return *this;
}
// Don't allow the call operator to be invoked as an rvalue.
template <class... Args> bool operator()(Args &&...) && {
template <class... Args>
ForwardingCallObject&& operator()(Args&&...) && {
set_call<Args &&...>(CT_NonConst | CT_RValue);
return true;
return std::move(*this);
}
template <class... Args> bool operator()(Args &&...) const && {
template <class... Args>
const ForwardingCallObject&& operator()(Args&&...) const && {
set_call<Args &&...>(CT_Const | CT_RValue);
return true;
return std::move(*this);
}
template <class... Args> static void set_call(CallType type) {
@ -239,6 +242,60 @@ void test_argument_forwarding() {
}
}
void test_return_type() {
using Fn = ForwardingCallObject;
Fn obj{};
const Fn &cobj = obj;
{ // test call operator forwarding - no variant
static_assert(std::is_same_v<decltype(std::visit(obj)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj))), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj))), const Fn&&>);
}
{ // test call operator forwarding - single variant, single arg
using V = std::variant<int>;
V v(42);
static_assert(std::is_same_v<decltype(std::visit(obj, v)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj, v)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj), v)), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj), v)), const Fn&&>);
}
{ // test call operator forwarding - single variant, multi arg
using V = std::variant<int, long, double>;
V v(42l);
static_assert(std::is_same_v<decltype(std::visit(obj, v)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj, v)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj), v)), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj), v)), const Fn&&>);
}
{ // test call operator forwarding - multi variant, multi arg
using V = std::variant<int, long, double>;
using V2 = std::variant<int *, std::string>;
V v(42l);
V2 v2("hello");
static_assert(std::is_same_v<decltype(std::visit(obj, v, v2)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj, v, v2)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj), v, v2)), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj), v, v2)), const Fn&&>);
}
{
using V = std::variant<int, long, double, std::string>;
V v1(42l), v2("hello"), v3(101), v4(1.1);
static_assert(std::is_same_v<decltype(std::visit(obj, v1, v2, v3, v4)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj, v1, v2, v3, v4)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj), v1, v2, v3, v4)), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj), v1, v2, v3, v4)), const Fn&&>);
}
{
using V = std::variant<int, long, double, int*, std::string>;
V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
static_assert(std::is_same_v<decltype(std::visit(obj, v1, v2, v3, v4)), Fn&>);
static_assert(std::is_same_v<decltype(std::visit(cobj, v1, v2, v3, v4)), const Fn&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(obj), v1, v2, v3, v4)), Fn&&>);
static_assert(std::is_same_v<decltype(std::visit(std::move(cobj), v1, v2, v3, v4)), const Fn&&>);
}
}
struct ReturnFirst {
template <class... Args> constexpr int operator()(int f, Args &&...) const {
return f;
@ -368,6 +425,7 @@ void test_caller_accepts_nonconst() {
int main(int, char**) {
test_call_operator_forwarding();
test_argument_forwarding();
test_return_type();
test_constexpr();
test_exceptions();
test_caller_accepts_nonconst();