syntax_data: {"ast_node_type":"other","tokens":[{"end":61,"kind":"keyword","start":0,"text":"BecameNewSibling(Option<FutureCompatOverlapError<'tcx>>),"}]}
source_snippet:     BecameNewSibling(Option<FutureCompatOverlapError<'tcx>>),
context_before:     /// The impl was inserted as a new child in this group of children.