syntax_data: {"ast_node_type":"other","tokens":[{"end":56,"kind":"keyword","start":0,"text":"key:"}]}
source_snippet:     key: PseudoCanonicalInput<'tcx, ty::TraitRef<'tcx>>,
context_before:     tcx: TyCtxt<'tcx>,
context_after: ) -> Result<&'tcx ImplSource<'tcx, ()>, CodegenObligationError> {