syntax_data: {"ast_node_type":"other","tokens":[{"end":50,"kind":"keyword","start":0,"text":"placeholder_trait_ref:"}]}
source_snippet:         placeholder_trait_ref: ty::TraitRef<'tcx>,
context_before:         obligation: &PolyTraitObligation<'tcx>,
context_after:         trait_bound: ty::PolyTraitRef<'tcx>,