syntax_data: {"ast_node_type":"variable","tokens":[{"end":94,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, DUMMY_SP);
context_before:                 Err(tail_ty) => {
context_after:                     Ty::new_projection(tcx, metadata_def_id, [tail_ty])