syntax_data: {"ast_node_type":"other","tokens":[{"end":71,"kind":"keyword","start":0,"text":"key:"}]}
source_snippet:     key: ty::PseudoCanonicalInput<'tcx, (DefId, GenericArgsRef<'tcx>)>,
context_before:     tcx: TyCtxt<'tcx>,
context_after: ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {