syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"extract_const_value(cx,"}]}
source_snippet:                                         extract_const_value(cx, ty, end)
context_before:                                             .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?,
context_after:                                             .unwrap()