if_chain! {
    if let ExprKind::Block(ref block) = expr.node;
    if let Some(trailing_expr) = &block.expr;
    if block.stmts.len() == 1;
    if let StmtKind::Semi(ref e, _) = block.stmts[0].node
    if let ExprKind::Tup(ref elements) = e.node;
    if elements.len() == 0;
    then {
        // report your lint here
    }
}
if_chain! {
    then {
        // report your lint here
    }
}