https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96645
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Summary|std::variant default |[9/10/11 Regression]
|constructor |std::variant default
| |constructor
Last reconfirmed| |2020-08-17
Status|UNCONFIRMED |NEW
Known to fail| |10.2.0, 11.0, 9.3.0
Component|libstdc++ |c++
Known to work| |8.4.0
CC| |jason at gcc dot gnu.org
Keywords| |rejects-valid
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is not a bug in std::variant:
template<bool B>
struct bool_constant
{
static constexpr bool value = B;
using type = bool_constant;
};
using true_type = bool_constant<true>;
template<typename T>
struct is_default_constructible
: bool_constant<__is_constructible(T)>
{ };
void testVarStruct()
{
struct DataWithStruct {
struct A {
int number = 5; // compiles, if remove initialization
};
is_default_constructible<A>::type t = true_type{};
};
}
v.C: In function 'void testVarStruct()':
v.C:22:47: error: could not convert 'true_type{}' from 'bool_constant<true>' to
'bool_constant<false>'
22 | is_default_constructible<A>::type t = true_type{};
| ^~~~~~~~~~~
| |
| bool_constant<true>
This stopped working with r269032 which changed the result of the
__is_constructible built-in.
Clang also rejects this, for the same reason, but EDG accepts it.
