syntax_data: {"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // obligation will normalize to `<$0 as Iterator>::Item = $1` and
context_before:         // When we instantiate, say, `V => IntoIter<u32>, U => $0`, the last
context_after:         // `$1: Copy`, so we must ensure the obligations are emitted in