syntax_data: {"ast_node_type":"variable","tokens":[{"end":74,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:             if let Some(parent_trait_pred) = predicate.as_trait_clause() {
context_before:         let extend = |traits::PredicateObligation { predicate, mut cause, .. }| {
context_after:                 cause = cause.derived_cause(