syntax_data: {"ast_node_type":"other","tokens":[{"end":42,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // Also, don't safety check custom MIR
context_before:     assert!(!tcx.is_typeck_child(def.to_def_id()));
context_after:     if tcx.has_attr(def, sym::custom_mir) {