syntax_data: {"ast_node_type":"variable","tokens":[{"end":57,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let end = relation.relate(end_a, end_b)?;
context_before:                 let start = relation.relate(start_a, start_b)?;
context_after:                 Ok(tcx.mk_pat(ty::PatternKind::Range { start, end }))