syntax_data: {"ast_node_type":"variable","tokens":[{"end":50,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let ty = relation.relate(a_ty, b_ty)?;
context_before:         (ty::Pat(a_ty, a_pat), ty::Pat(b_ty, b_pat)) => {
context_after:             let pat = relation.relate(a_pat, b_pat)?;