syntax_data: {"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"tcx.def_span(leaf_def.item.def_id),"}]}
source_snippet:                     tcx.def_span(leaf_def.item.def_id),
context_before:                 let guar = tcx.dcx().span_delayed_bug(
context_after:                     "missing value for assoc item in impl",