- // MIR for `map` before SimplifyLocals
+ // MIR for `map` after SimplifyLocals
  
  fn map(_1: std::option::Option<std::boxed::Box<()>>) -> std::option::Option<std::boxed::Box<()>> {
      debug x => _1;                       // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:1:8: 1:9
      let mut _0: std::option::Option<std::boxed::Box<()>>; // return place in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:1:31: 1:46
      let mut _2: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
-     let _3: std::boxed::Box<()>;         // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:14: 4:15
-     let mut _4: std::boxed::Box<()>;     // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:25: 4:26
-     let mut _5: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
-     let mut _6: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
      scope 1 {
          debug x => ((_0 as Some).0: std::boxed::Box<()>); // in scope 1 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:14: 4:15
      }
  
      bb0: {
          _2 = discriminant(_1);           // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
          switchInt(move _2) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
      }
  
      bb1: {
          _0 = move _1;                    // scope 1 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:20: 4:27
          goto -> bb3;                     // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:2:5: 5:6
      }
  
      bb2: {
          _0 = const std::option::Option::<std::boxed::Box<()>>::None; // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
                                           // ty::Const
                                           // + ty: std::option::Option<std::boxed::Box<()>>
                                           // + val: Value(Scalar(0x0000000000000000))
                                           // mir::Constant
                                           // + span: $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
                                           // + literal: Const { ty: std::option::Option<std::boxed::Box<()>>, val: Value(Scalar(0x0000000000000000)) }
          goto -> bb3;                     // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:2:5: 5:6
      }
  
      bb3: {
-         _5 = discriminant(_1);           // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
          return;                          // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:2: 6:2
      }
  }