https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86521
Matthijs van Duin <matthijsvanduin at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |matthijsvanduin at gmail dot
com
--- Comment #3 from Matthijs van Duin <matthijsvanduin at gmail dot com> ---
First off, your example is more complicated than it needs to be. A more minimal
test case would be:
#include <utility>
struct Dest {
Dest() = default;
Dest( Dest && ) = default;
Dest( Dest const & ) = delete;
};
struct Source {
Dest val;
operator Dest () && {
return std::move( val );
}
operator Dest const & () const & {
return val;
}
};
int main() {
Source x;
static_cast<Dest>( std::move( x ) );
}
Second, notice that the two conversions are not really directly comparable
since one converts to directly Dest while the other converts to an expression
used to invoke a constructor of Dest. While it seems desirable for the former
to take preference over the latter, I'm not enough of a language lawyer to be
able to figure out what the C++ standard actually requires overload resolution
to do in this situation.
Replacing
operator Dest () && {
by
operator Dest && () && {
fixes the problem, and has the additional benefit of avoiding unnecessary
temporary materialization in situations like:
void foo( Dest && );
int main() {
Source x;
foo( std::move( x ) );
}
