syntax_data: {"ast_node_type":"variable","tokens":[{"end":45,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let ty = field.ty(tcx, args);
context_before:                 let span = tcx.def_ident_span(field.did).unwrap();
context_after:                 try_visit!(visitor.visit(span, ty));