syntax_data: {"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:     for cnum in iter::once(LOCAL_CRATE).chain(tcx.crates(()).iter().copied()) {
context_before:     let mut impls = Vec::new();
context_after:         for &impl_def_id in tcx.crate_incoherent_impls((cnum, simp)) {