syntax_data: {"ast_node_type":"variable","tokens":[{"end":73,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let cause = self.cause(ObligationCauseCode::ArrayLen(t));
context_before:                 // Here we just check that it's of type usize.
context_after:                 self.out.push(traits::Obligation::with_depth(