On Saturday, 12 December 2020 at 17:36:57 UTC, Tobias Pankrath
wrote:
I want to wrap e.g. an int and implement basic arithmetic. In
the provided example [1] I use two mixin templates to
separately implement scaling (multiplication with int/double)
and addition and subtraction with the type itself.
In the end I want to have several distinct wrappers and allow
specific operations between them and int / double. It's
important that the return values are typed correctly, otherwise
I could use std.typecons.Proxy.
My problem is that both overloads of opBinary work, but not at
the same time. As soon as I mixin both templates, they stop to
work. If I just paste the implementation into the body of
WrapInt, they work both at the same time though.
Could someone explain the mechanics behind it?
Thanks!
[1] https://run.dlang.io/is/WbG987
Functions from different mixin templates can't overload each
other. The reason for this is that, when you mix in a mixin
template, it does not *actually* add the declarations inside it
to a current scope: instead, it adds them to a new scope, and
then (essentially) "imports" them into the current scope.
IMO this is one of the stupider design decisions in D, but it's
unlikely it will ever be fixed. The easiest workaround is to use
string mixins instead, which work the way you'd expect them to.
