syntax_data: {"ast_node_type":"other","tokens":[{"end":82,"kind":"keyword","start":0,"text":"(MaybeReachable::Reachable(this),"}]}
source_snippet:             (MaybeReachable::Reachable(this), MaybeReachable::Reachable(old)) => {
context_before:             }
context_after:                 this.fmt_diff_with(old, ctxt, f)