Hello,

I seem to have a problem when I use a template mixin and then try to overload operators both in the mixin and in a struct from where it's instantiated.
So the idea is that I have a few operators defined in the mixin, then a few more in the struct, and I want to forward all operations not explicitly defined in the struct to the ones in the mixin (and I don't want to do alias this for a variety of unrelated reasons).

Basically the simplest code that gives me problems is:

import std.stdio;

mixin template Impl(T) {
    T v;
    int opBinary(string s: "+")(T other) {
        writeln("Single +");
        return 0;
    }
    int opBinary(string s: "+")(T[] other) {
        writeln("Array +");
        return 0;
    }
}

struct Pt {
    mixin Impl!float impl;

    int opBinary(string s: "*")(float other) {
        writeln("Single *");
        return 0;
    }

    int opBinary(string s, T)(T v) {
        //Pt already has opBinary defined, so the operators in the mixin not visible
        //Thought that delegating to the mixin should be done this way
        writeln("Delegate ", s);
        return impl.opBinary!(s)(v);
    }
}


void main() {
    Pt pt;
    int r = pt + [1f, 2f];
    writeln("R: ", r);
}

This results in an infinite loop though. Seems like Pt.opBinary!("+", float[]) is called over and over. Which is a bit un-intuitive to me - I'm not sure why calling impl.opBinary!(s) can result in endless recursion.

The problem appears only when I have 2 operators in the mixin that I try to forward to - e.g. the two overloads of "+" in this case. If I have just 1, it works ok, if I have none, the error message is helpful.

Any ideas what I'm doing wrong?
Thanks!

On Friday, 11 October 2019 at 12:45:59 UTC, Boyan Lazov wrote:
> Any ideas what I'm doing wrong?

Nothing, it's a bug.
https://issues.dlang.org/show_bug.cgi?id=19476

On Friday, 11 October 2019 at 13:13:46 UTC, Dennis wrote:
> On Friday, 11 October 2019 at 12:45:59 UTC, Boyan Lazov wrote:
>> Any ideas what I'm doing wrong?
>
> Nothing, it's a bug.
> https://issues.dlang.org/show_bug.cgi?id=19476

Alright, I see
Well, the alias workaround works, so that seems just as good. Thanks!