Fix PR31916 - std::visit rejects visitors accepting lvalue arguments
A static assertion was misfiring since it checked
is_callable<Visitor, decltype(__variant_alt<T>.value)>. However
the decltype expression doesn't capture the value category as
required. This patch applies extra braces to decltype to fix
that.
llvm-svn: 294612
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: a18ef6f1f9d2a32519192feedadb7814461db488
diff --git a/include/variant b/include/variant
index fb7cb2e..099e6c3 100644
--- a/include/variant
+++ b/include/variant
@@ -578,7 +578,7 @@
constexpr decltype(auto) operator()(_Alts&&... __alts) const {
__std_visit_exhaustive_visitor_check<
_Visitor,
- decltype(_VSTD::forward<_Alts>(__alts).__value)...>();
+ decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
_VSTD::forward<_Alts>(__alts).__value...);
}
diff --git a/test/std/utilities/variant/variant.visit/visit.pass.cpp b/test/std/utilities/variant/variant.visit/visit.pass.cpp
index 46d2258..408a65c 100644
--- a/test/std/utilities/variant/variant.visit/visit.pass.cpp
+++ b/test/std/utilities/variant/variant.visit/visit.pass.cpp
@@ -283,9 +283,20 @@
#endif
}
+// See http://llvm.org/PR31916
+void test_caller_accepts_nonconst() {
+ struct A {};
+ struct Visitor {
+ void operator()(A&) {}
+ };
+ std::variant<A> v;
+ std::visit(Visitor{}, v);
+}
+
int main() {
test_call_operator_forwarding();
test_argument_forwarding();
test_constexpr();
test_exceptions();
+ test_caller_accepts_nonconst();
}