Officially, opEquals has to have the signature:
struct Foo {
bool opEquals(const ref Foo x) const {...}
}
But this disallows comparisons with rvalues.
eg,
Foo bar() { Foo x = 1; return x; }
Foo y=1;
assert( y == bar() ); // doesn't compile
You can get around this by declaring a non-ref opEquals.
But this fails if Foo has a destructor.
If a struct has a destructor, it cannot be const(this is bug 3606)
---
struct S {
~this() {}
}
void main() {
const S z;
}
---
bug.d(6): Error: destructor bug.S.~this () is not callable using
argument types ()
-------
Likewise, it can't be a const parameter (this is bug 4338).
void foo(const S a) {}
It works to have it as a const ref parameter.
Everything will work if you declare a const ~this(), but that seems a
little nonsensical. And you cannot have both const and non-const ~this().
I'm a bit uncertain as to how this is all supposed to work.
(1) Should temporaries be allowed to be passed as 'const ref'?
(2) If a struct has a destructor, should it be passable as a const
parameter? And if so, should the destructor be called?
