syntax_data: {"ast_node_type":"variable","tokens":[{"end":77,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let really_allows_unstable_options = match_is_nightly_build(matches);
context_before:         let has_z_unstable_option = matches.opt_strs("Z").iter().any(|x| *x == "unstable-options");
context_after:         let mut nightly_options_on_stable = 0;