syntax_data: {"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // `[U]: 'a`, that implies that `U: 'a`. Similarly, if
context_before:                 // often elaborate this. For example, if we know that
context_after:                 // we know `&'a U: 'b`, then we know that `'a: 'b` and