syntax_data: {"ast_node_type":"other","tokens":[{"end":66,"kind":"keyword","start":0,"text":"opt_level:"}]}
source_snippet:     opt_level: String = ("0".to_string(), parse_string, [TRACKED],
context_before:         "disable LLVM's SLP vectorization pass"),
context_after:         "optimization level (0-3, s, or z; default: 0)"),