Confusion on implementing Add_Assign on struct

[sww1235]

I am working on creating a custom generic type similar to Wrapping<T> that allows specifying a maximum and minimum bound and wrapping within that inclusive range.

My code so far is here which is a modified copy of the source of the Wrapping<T> from the main rust source code. I haven't cleaned up the documentation yet, so please ignore that.

My intention is to swap this for some locations in another project that currently use Wrapping<T> and a mod operation for the range restriction, but I wanted the restriction to come from the type so I don't forget to add the mod.

I implemented all the normal math operation traits, and even used the forward_ref* macros to try and resolve some potential headaches.

I am still having an issue when trying to add_assign my RangedWrapping<T,U> type when it is the type of a struct field.

When creating a normal variable, the add_assign works just fine, but as soon as I try and use it on a struct field, I get the following error:

binary assignment operation += cannot be applied to type RangedWrapping<usize, usize>

I have been googling my fingers off, and can't find an explanation for why normal variables work, but not struct fields, especially since Wrapping<T> works in the same scenario.

Thanks in advance.

[quinedot]

I'm pretty sure it's because you've put this bound everywhere:

    T: Add<i32, Output = T>,
    U: Add<i32, Output = T>,

You only actually use it in fn wrap, I think, to add 1. See if you can use something like num_traits::One instead.

Playground with the bounds removed and wrap hackily modified (not a proper fix).

And I'm pretty sure your "creating a normal variable" cases work because they all just create a RangedWrapping<i32, i32>, satisfying the bound.

[sww1235]

Thank you. the Add<i32, Output = T> was indeed the issue. I just had to remember to remove the trait bound from all the trait implemnetations, and not just wrap().