Unused MIR statement directly before return #70531

fn map(x: Option<Box<()>>) -> Option<Box<()>> {
    match x {
        None => None,
        Some(x) => Some(x),
    }
}

// WARNING: This output format is intended for human consumers only
// and is subject to change without notice. Knock yourself out.
fn  map(_1: std::option::Option<std::boxed::Box<()>>) -> std::option::Option<std::boxed::Box<()>> {
    debug x => _1;                       // in scope 0 at a.rs:1:8: 1:9
    let mut _0: std::option::Option<std::boxed::Box<()>>; // return place in scope 0 at a.rs:1:31: 1:46
    let mut _2: isize;                   // in scope 0 at a.rs:3:9: 3:13
    let _3: std::boxed::Box<()>;         // in scope 0 at a.rs:4:14: 4:15
    let mut _4: std::boxed::Box<()>;     // in scope 0 at a.rs:4:25: 4:26
    let mut _5: isize;                   // in scope 0 at a.rs:6:1: 6:2
    scope 1 {
        debug x => _3;                   // in scope 1 at a.rs:4:14: 4:15
    }

    bb0: {
        _2 = discriminant(_1);           // bb0[0]: scope 0 at a.rs:3:9: 3:13
        switchInt(move _2) -> [0isize: bb3, 1isize: bb1, otherwise: bb2]; // bb0[1]: scope 0 at a.rs:3:9: 3:13
    }

    bb1: {
        StorageLive(_3);                 // bb1[0]: scope 0 at a.rs:4:14: 4:15
        _3 = move ((_1 as Some).0: std::boxed::Box<()>); // bb1[1]: scope 0 at a.rs:4:14: 4:15
        StorageLive(_4);                 // bb1[2]: scope 1 at a.rs:4:25: 4:26
        _4 = move _3;                    // bb1[3]: scope 1 at a.rs:4:25: 4:26
        ((_0 as Some).0: std::boxed::Box<()>) = move _4; // bb1[4]: scope 1 at a.rs:4:20: 4:27
        discriminant(_0) = 1;            // bb1[5]: scope 1 at a.rs:4:20: 4:27
        StorageDead(_4);                 // bb1[6]: scope 1 at a.rs:4:26: 4:27
        StorageDead(_3);                 // bb1[7]: scope 0 at a.rs:4:27: 4:28
        goto -> bb4;                     // bb1[8]: scope 0 at a.rs:2:5: 5:6
    }

    bb2: {
        unreachable;                     // bb2[0]: scope 0 at a.rs:2:11: 2:12
    }

    bb3: {
        discriminant(_0) = 0;            // bb3[0]: scope 0 at a.rs:3:17: 3:21
        goto -> bb4;                     // bb3[1]: scope 0 at a.rs:2:5: 5:6
    }

    bb4: {
        _5 = discriminant(_1);           // bb4[0]: scope 0 at a.rs:6:1: 6:2
        return;                          // bb4[1]: scope 0 at a.rs:6:2: 6:2
    }
}