{"ast_node_type":"impl","tokens":[{"end":68,"kind":"keyword","start":0,"text":"//"}]}
            // - the applicable impl `impl<T> Trait<i32> for Vec<T>`
            // - a goal `<Vec<u32> as Trait<i32>>::Assoc<u64>`
            // - and the impl which defines `Assoc` being `impl<T, U> Trait<U> for Vec<T>`