syntax_data: {"ast_node_type":"other","tokens":[{"end":102,"kind":"keyword","start":0,"text":"\"MIR"}]}
source_snippet:         "MIR optimization level (0-4; default: 1 in non optimized builds and 2 in optimized builds)"),
context_before:     mir_opt_level: Option<usize> = (None, parse_opt_number, [TRACKED],
context_after:     mir_preserve_ub: bool = (false, parse_bool, [TRACKED],