syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"codegen_units:"}]}
source_snippet:     codegen_units: Option<usize> = (None, parse_opt_number, [UNTRACKED],
context_before:         "choose the code model to use (`rustc --print code-models` for details)"),
context_after:         "divide crate into N units to optimize in parallel"),