syntax_data: {"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"autodiff:"}]}
source_snippet:     autodiff: Vec<crate::config::AutoDiff> = (Vec::new(), parse_autodiff, [TRACKED],
context_before:         "make cfg(version) treat the current version as incomplete (default: no)"),
context_after:         "a list of autodiff flags to enable