I am trying to build a struct with equality testing, using this code:

struct Foo
{
    const bool opEquals(Foo f)
    {
        return true;
    }
}

This gives me the error that the parameter should be of type "ref const Foo". Fine.

struct Foo
{
    const bool opEquals(ref const Foo f)
    {
        return true;
    }
}

This, however, does not work with code like:

Foo bar()
{
    return Foo();
}

assert(Foo() == bar());

"function Foo.opEquals(ref const const(Foo) f) const is not callable using
argument types (Foo)" and "bar() is not an lvalue".

How can I do this?

On Monday, August 29, 2011 22:41:26 Sean Eskapp wrote:
> I am trying to build a struct with equality testing, using this code:
> 
> struct Foo
> {
>     const bool opEquals(Foo f)
>     {
>         return true;
>     }
> }
> 
> This gives me the error that the parameter should be of type "ref const Foo". Fine.
> 
> struct Foo
> {
>     const bool opEquals(ref const Foo f)
>     {
>         return true;
>     }
> }
> 
> This, however, does not work with code like:
> 
> Foo bar()
> {
>     return Foo();
> }
> 
> assert(Foo() == bar());
> 
> "function Foo.opEquals(ref const const(Foo) f) const is not callable using
> argument types (Foo)" and "bar() is not an lvalue".
> 
> How can I do this?

http://d.puremagic.com/issues/show_bug.cgi?id=3659

http://stackoverflow.com/questions/6986175/const-ref-and-rvalue-in-d

- Jonathan M Davis

== Quote from Jonathan M Davis (jmdavisProg@gmx.com)'s article
> On Monday, August 29, 2011 22:41:26 Sean Eskapp wrote:
> > I am trying to build a struct with equality testing, using this code:
> >
> > struct Foo
> > {
> >     const bool opEquals(Foo f)
> >     {
> >         return true;
> >     }
> > }
> >
> > This gives me the error that the parameter should be of type "ref const Foo". Fine.
> >
> > struct Foo
> > {
> >     const bool opEquals(ref const Foo f)
> >     {
> >         return true;
> >     }
> > }
> >
> > This, however, does not work with code like:
> >
> > Foo bar()
> > {
> >     return Foo();
> > }
> >
> > assert(Foo() == bar());
> >
> > "function Foo.opEquals(ref const const(Foo) f) const is not callable using
> > argument types (Foo)" and "bar() is not an lvalue".
> >
> > How can I do this?
> http://d.puremagic.com/issues/show_bug.cgi?id=3659 http://stackoverflow.com/questions/6986175/const-ref-and-rvalue-in-d - Jonathan M Davis

Ah, thanks!