syntax_data: {"ast_node_type":"variable","tokens":[{"end":86,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let unstable_features = UnstableFeatures::from_environment(crate_name.as_deref());
context_before:     let crate_name = matches.opt_str("crate-name");
context_after:     // Parse any `-l` flags, which link to native libraries.