syntax_data: {"ast_node_type":"impl","tokens":[{"end":36,"kind":"keyword","start":0,"text":"on_ambiguity:"}]}
source_snippet:         on_ambiguity: impl FnOnce(),
context_before:         mut for_each: impl FnMut(&mut Self, ty::Clause<'tcx>, usize) -> ControlFlow<T, ()>,
context_after:     ) -> ControlFlow<T, ()> {