syntax_data: {"ast_node_type":"variable","tokens":[{"end":44,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let arg_ty = body.exprs[arg].ty;
context_before:         &ExprKind::Unary { op, arg } if check_unop(op) => {
context_after:             let arg = recurse_build(tcx, body, arg, root_span)?;