On Monday, 4 November 2013 at 07:02:26 UTC, Lars T. Kyllingstad
wrote:
I was quite surprised to see that the following program
compiles just fine with DMD:
struct S
{
@disable this(this);
int n;
}
S createS(int i)
{
S s;
s.n = i;
return s;
}
void main(string[] args)
{
auto foo = createS(1);
foo = createS(2);
}
I already knew that the compiler was allowed to elide copies on
return from functions, but I thought this was an optimisation,
and not part of the language proper. I would have expected the
compiler to complain that createS() can't return an S since S's
postblit constructor is disabled.
My question is therefore, is this by design? Can I rely on
this to work in the future, and on all compilers? If this is
the case, it really should be added to the spec. (Or maybe
it's there already, but I couldn't find it.)
Lars
My understanding is that your example illustrates a *move*, not a
*copy*. AFAICT, non-copyable structs would be next to useless if
we couldn't move them.
