https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78058
Bug ID: 78058
Summary: Complex initialization of nested std::optional does
not work
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: akrzemi1 at gmail dot com
Target Milestone: ---
The following program fails to compile:
```
#include <cassert>
#include <optional>
using std::optional;
using std::nullopt;
using std::in_place;
int main()
{
optional<optional<optional<int>>> o (in_place, in_place, nullopt);
assert (o);
assert (*o);
assert (!**o);
}
```
Overload resolution cannot find the right constructor. I expect this to
compile, the meaning is described with the assertions.
The middle optional is initialized with two arguments {in_place, nullopt},
which means that the innermost optional is initialized with nullptr.
The same program compiles with the reference implementation:
https://github.com/akrzemi1/Optional
