syntax_data: {"ast_node_type":"other","tokens":[{"end":22,"kind":"keyword","start":0,"text":"tcx:"}]}
source_snippet:     tcx: TyCtxt<'tcx>,
context_before: pub(super) struct ReverseMapper<'tcx> {
context_after:     map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,