Mutators with type parameters need to pass type parameters to inner call when associated type is used

[azriel91]

Heya, I came across this use case:

trait HasS {
    type MyS: Default + AddAssign;
}

struct HasSImpl;

impl HasS for HasSImpl {
    type MyS = u32;
}

#[derive(Debug, PartialEq, TypedBuilder)]
struct Foo<S: Default + AddAssign> {
    #[builder(via_mutators, mutators(
        fn x_plus<H>(self, s: <H as HasS>::MyS)
        // ^^^^^^ cannot infer type of the type parameter `H` declared on the method `x_plus`
        where H: HasS<MyS = S> {
            self.x += s;
        }
    ))]
    x: S,
}

The issue in the generated code:

impl<S: Default + AddAssign> FooBuilder<S, ((S,),)> {
    // ..
    fn x_plus<H>(self, s: <H as HasS>::MyS) -> FooBuilder<S, ((S,),)>
    where
        H: HasS<MyS = S>,
    {
        // ..

        {
            let (s) = __args;
            __mutator.x_plus::<H>(s);
            //              ^^^^^
            //              this was missing
        }

        //..
    }
}

I've got a PR incoming to fix it.

[azriel91]

Heya @idanarye, would you have time to look at #158?

Should be easy™