syntax_data: {"ast_node_type":"other","tokens":[{"end":41,"kind":"keyword","start":0,"text":"instance:"}]}
source_snippet:     instance: Option<ty::Instance<'tcx>>,
context_before:     extra_args: &[Ty<'tcx>],
context_after: ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {