syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // cycle error if the specialization graph is currently being built.
context_before:     // If there is no such item in that impl, this function will fail with a
context_after:     if let Some(&impl_item_id) = tcx.impl_item_implementor_ids(impl_def_id).get(&assoc_def_id) {