Rust bug

main.rs

fn main() {
    loop {
        let beacon = {
            match true {
                false => 4,
                true => break,
            }
        };
        drop(&beacon);
    }
}

rustc.main.-------.mir_map.0.mir

// MIR for `main`
// source = MirSource { def_id: DefId(0/0:3 ~ main[317d]::main[0]), promoted: None }
// pass_name = mir_map
// disambiguator = 0

fn main() -> (){
    let mut _0: ();                      // return place
    scope 1 {
        let _2: i32;                     // "beacon" in scope 1 at src/main.rs:3:13: 3:19
    }
    scope 2 {
    }
    let mut _1: ();
    let mut _3: bool;
    let mut _4: u8;
    let mut _5: !;
    let mut _6: ();
    let mut _7: &i32;

    bb0: {                              
        goto -> bb1;                     // bb0[0]: scope 0 at src/main.rs:2:5: 10:6
    }

    bb1: {                              
        falseUnwind -> [real: bb3, cleanup: bb4]; // bb1[0]: scope 0 at src/main.rs:2:5: 10:6
    }

    bb2: {                              
        goto -> bb29;                    // bb2[0]: scope 0 at src/main.rs:11:2: 11:2
    }

    bb3: {                              
        StorageLive(_2);                 // bb3[0]: scope 0 at src/main.rs:3:13: 3:19
        StorageLive(_3);                 // bb3[1]: scope 0 at src/main.rs:4:19: 4:23
        _3 = const true;                 // bb3[2]: scope 0 at src/main.rs:4:19: 4:23
                                         // ty::Const
                                         // + ty: bool
                                         // + val: Value(Scalar(Bits { defined: 8, bits: 1 }))
                                         // mir::Constant
                                         // + span: src/main.rs:4:19: 4:23
                                         // + ty: bool
                                         // + literal: const true
        _4 = discriminant(_3);           // bb3[3]: scope 0 at src/main.rs:4:13: 7:14
        switchInt(_3) -> [false: bb11, otherwise: bb10]; // bb3[4]: scope 0 at src/main.rs:5:17: 5:22
    }

    bb4: {                               // cleanup
        resume;                          // bb4[0]: scope 0 at src/main.rs:1:1: 11:2
    }

    bb5: {                              
        _2 = const 4i32;                 // bb5[0]: scope 0 at src/main.rs:5:26: 5:27
                                         // ty::Const
                                         // + ty: i32
                                         // + val: Value(Scalar(Bits { defined: 32, bits: 4 }))
                                         // mir::Constant
                                         // + span: src/main.rs:5:26: 5:27
                                         // + ty: i32
                                         // + literal: const 4i32
        goto -> bb14;                    // bb5[1]: scope 0 at src/main.rs:4:13: 7:14
    }

    bb6: {                              
        _0 = ();                         // bb6[0]: scope 0 at src/main.rs:6:25: 6:30
        goto -> bb15;                    // bb6[1]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb7: {                              
        falseEdges -> [real: bb12, imaginary: bb8]; // bb7[0]: scope 0 at src/main.rs:5:17: 5:22
    }

    bb8: {                              
        falseEdges -> [real: bb13, imaginary: bb9]; // bb8[0]: scope 0 at src/main.rs:6:17: 6:21
    }

    bb9: {                              
        unreachable;                     // bb9[0]: scope 0 at src/main.rs:4:13: 7:14
    }

    bb10: {                             
        goto -> bb8;                     // bb10[0]: scope 0 at src/main.rs:6:17: 6:21
    }

    bb11: {                             
        goto -> bb7;                     // bb11[0]: scope 0 at src/main.rs:5:17: 5:22
    }

    bb12: {                             
        goto -> bb5;                     // bb12[0]: scope 0 at src/main.rs:5:17: 5:22
    }

    bb13: {                             
        goto -> bb6;                     // bb13[0]: scope 0 at src/main.rs:6:17: 6:21
    }

    bb14: {                             
        StorageDead(_3);                 // bb14[0]: scope 0 at src/main.rs:8:10: 8:11
        StorageLive(_7);                 // bb14[1]: scope 1 at src/main.rs:9:14: 9:21
        _7 = &_2;                        // bb14[2]: scope 1 at src/main.rs:9:14: 9:21
        _6 = const std::mem::drop(move _7) -> [return: bb28, unwind: bb4]; // bb14[3]: scope 1 at src/main.rs:9:9: 9:22
                                         // ty::Const
                                         // + ty: fn(&i32) {std::mem::drop::<&i32>}
                                         // + val: Value(Scalar(Bits { defined: 0, bits: 0 }))
                                         // mir::Constant
                                         // + span: src/main.rs:9:9: 9:13
                                         // + ty: fn(&i32) {std::mem::drop::<&i32>}
                                         // + literal: const std::mem::drop
    }

    bb15: {                             
        goto -> bb16;                    // bb15[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb16: {                             
        goto -> bb17;                    // bb16[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb17: {                             
        goto -> bb18;                    // bb17[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb18: {                             
        goto -> bb19;                    // bb18[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb19: {                             
        goto -> bb20;                    // bb19[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb20: {                             
        StorageDead(_3);                 // bb20[0]: scope 0 at src/main.rs:8:10: 8:11
        goto -> bb21;                    // bb20[1]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb21: {                             
        goto -> bb22;                    // bb21[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb22: {                             
        goto -> bb23;                    // bb22[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb23: {                             
        goto -> bb24;                    // bb23[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb24: {                             
        goto -> bb25;                    // bb24[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb25: {                             
        goto -> bb2;                     // bb25[0]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb26: {                             
        _5 = ();                         // bb26[0]: scope 0 at src/main.rs:6:25: 6:30
        unreachable;                     // bb26[1]: scope 0 at src/main.rs:6:25: 6:30
    }

    bb27: {                             
        StorageDead(_5);                 // bb27[0]: scope 0 at src/main.rs:6:29: 6:30
        goto -> bb14;                    // bb27[1]: scope 0 at src/main.rs:4:13: 7:14
    }

    bb28: {                             
        StorageDead(_7);                 // bb28[0]: scope 1 at src/main.rs:9:21: 9:22
        _1 = ();                         // bb28[1]: scope 0 at src/main.rs:2:10: 10:6
        StorageDead(_2);                 // bb28[2]: scope 0 at src/main.rs:10:5: 10:6
        goto -> bb1;                     // bb28[3]: scope 0 at src/main.rs:2:5: 10:6
    }

    bb29: {                             
        return;                          // bb29[0]: scope 0 at src/main.rs:11:2: 11:2
    }
}