if_chain! {
    if let Expr_::ExprBlock(ref block) = stmt.node;
    if let Expr_::ExprMatch(ref expr, ref arms, MatchSource::ForLoopDesugar) = block.node;
    // unimplemented: `ExprMatch` is not further destructured at the moment
    if let Expr_::ExprPath(ref path) = block.node;
    if match_qpath(path, &["_result"]);
    then {
        // report your lint here
    }
}
if_chain! {
    if let Expr_::ExprBlock(ref block) = expr.node;
    if let Expr_::ExprMatch(ref expr, ref arms, MatchSource::ForLoopDesugar) = block.node;
    // unimplemented: `ExprMatch` is not further destructured at the moment
    if let Expr_::ExprPath(ref path) = block.node;
    if match_qpath(path, &["_result"]);
    then {
        // report your lint here
    }
}