foo() below takes by-ref. Normally, rvalues cannot be passed to it:
struct S
{
ref S memFunc()
{
return this;
}
}
void foo(ref S s)
{}
void main()
{
// As expected, fails to compile:
// foo(S());
// No problem: Just call a function that returns ref... :)
foo(S().memFunc());
}
Obviously, it is the same problem for rvalues returned from functions:
S bar()
{
return S();
}
foo(bar().memFunc()); // <-- compiles
This may be a trap especially in opAssign() because it is recommended to
return by-ref unless there is a reason not to. (I wonder whether this is
a reason not to. :) )
struct S
{
ref S opAssign(S rhs)
{
return this;
}
}
void foo(ref S s)
{}
void main()
{
// As expected, fails to compile:
// foo(S());
// No problem; just assign... :)
foo(S() = S());
}
Allowing assignment to rvalue feels like a bug there but I don't think
we can prevent the programmer from doing S().memFunc() as in the first case.
Ali
P.S. I should have checked before writing this post. The following bugs
seem related:
http://d.puremagic.com/issues/show_bug.cgi?id=1596
http://d.puremagic.com/issues/show_bug.cgi?id=3008
No, I haven't read them yet.
