如何在引用而不是引用值上调用特征方法？

Question

I have a reference ( foo ) that implements the trait IntoIterator<Item = &T> . I want to call the trait method into_iter directly on foo (ie the reference itself) and not *foo (the referenced value), as seems to be happening, since the type of *foo also implements IntoIterator (albeit with Item = T ). I've tried UFCS, but even that doesn't seem to do the trick.

Here's my actual code:

fn csl_join<'a, V, T>(value: &V) -> String 
    where V: IntoIterator<Item = &'a T>, 
          T: 'a + ToString 
{
    itertools::join(value.into_iter().map(|v: &T| v.to_string()), ",")
}

Answer 1

I ended up solving this issue just after posting it, thanks to @LukasKalbertodt's helpful comments. It turns out I simply wanted the type bound to be &V: IntoIterator<Item = &T> , to match the intended usage in the function body (duh!).

So the code becomes:

fn csl_join<'a, 'b, V, T>(value: &'a V) -> String
    where V: 'a,
          &'a V: IntoIterator<Item = &'b T>,
          T: ToString + 'b
{
    itertools::join(value.into_iter().map(|v: &T| v.to_string()), ",")
}

I'll leave this here in case it assists someone else, by chance.