Re: opEquals on shared object

[jj75607 via Digitalmars-d-learn]

On Thursday, 30 June 2016 at 12:21:03 UTC, Steven Schveighoffer 
wrote:
On 6/30/16 6:26 AM, jj75607 wrote:
Hello!
I need to overload opEquals on shared class C

shared class C
{
    override bool opEquals(Object o) { return false; }
}

But compilation fails with the message:
Error: function f700.C.opEquals does not override any 
function, did you
mean to override 'object.Object.opEquals'?

What am I doing wrong?

Object.opEquals is not marked shared. You can't override a 
non-shared method with a shared one.

You need to remove override.

But... unfortunately, this may not work in practice. The 
opEquals handling for objects is pretty much screwed unless you 
have unshared mutable objects. I think it may work for const 
objects, but not in a good way.

-Steve

Thanks!

But what should I do to fix that code?

shared class C
{
    bool opEquals(Object o) { return false; }
}

class A(T)
{
    void f(T a, T b)
    {
        if(a == b)
            writeln("equals");
        else
            writeln("non equals");
    }
}

        
int main(string[] argv)
{
        auto a1 = new A!int;
        a1.f(1,2);

        auto a2 = new A!(shared(C));
        shared C c = new shared(C);
        a2.f(c,c);
        

        return 0;
}

It fails with
    Error: none of the overloads of 'opEquals' are callable using 
argument types (shared(C), shared(C))