syntax_data: {"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"FIRST_VARIANT..tcx.coroutine_layout(def_id,"}]}
source_snippet:         FIRST_VARIANT..tcx.coroutine_layout(def_id, self.args).unwrap().variant_fields.next_index()
context_before:         // FIXME requires optimized MIR
context_after:     }