syntax_data: {"ast_node_type":"variable","tokens":[{"end":69,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:     if let Some(assoc_item) = ancestors.leaf_def(tcx, assoc_def_id) {
context_before:     let ancestors = trait_def.ancestors(tcx, impl_def_id)?;
context_after:         // Ensure that the impl is constrained, otherwise projection may give us