syntax_data: {"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"\"`opaque_types_defined_by`"}]}
source_snippet:                 "`opaque_types_defined_by` not defined for {} `{item:?}`",
context_before:                 tcx.def_span(item),
context_after:                 kind.descr(item.to_def_id())