syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"\"select"}]}
source_snippet:         "select target processor (`rustc --print target-cpus` for details)"),
context_before:     target_cpu: Option<String> = (None, parse_opt_string, [TRACKED],
context_after:     target_feature: String = (String::new(), parse_target_feature, [TRACKED],