syntax_data: {"ast_node_type":"other","tokens":[{"end":35,"kind":"keyword","start":0,"text":"b_region:"}]}
source_snippet:         b_region: ty::Region<'tcx>,
context_before:         a_region: ty::Region<'tcx>,
context_after:     ) -> SelectionResult<'tcx, PredicateObligations<'tcx>> {