syntax_data: {"ast_node_type":"variable","tokens":[{"end":67,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let trait_ref = relation.relate(a.trait_ref, b.trait_ref)?;
context_before:     ) -> RelateResult<I, ty::TraitPredicate<I>> {
context_after:         if a.polarity != b.polarity {