- // MIR for `main` before ConstProp
+ // MIR for `main` after ConstProp
  
  fn main() -> () {
      let mut _0: ();                      // return place in scope 0 at $DIR/boxes.rs:+0:11: +0:11
      let _1: i32;                         // in scope 0 at $DIR/boxes.rs:+1:9: +1:10
      let mut _2: i32;                     // in scope 0 at $DIR/boxes.rs:+1:13: +1:22
      let mut _3: std::boxed::Box<i32>;    // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _4: usize;                   // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _5: usize;                   // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _6: *mut u8;                 // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _7: std::boxed::Box<i32>;    // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _8: *const i32;              // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      let mut _9: *const i32;              // in scope 0 at $DIR/boxes.rs:+1:14: +1:22
      scope 1 {
          debug x => _1;                   // in scope 1 at $DIR/boxes.rs:+1:9: +1:10
      }
      scope 2 {
      }
  
      bb0: {
          StorageLive(_1);                 // scope 0 at $DIR/boxes.rs:+1:9: +1:10
          StorageLive(_2);                 // scope 0 at $DIR/boxes.rs:+1:13: +1:22
          StorageLive(_3);                 // scope 0 at $DIR/boxes.rs:+1:14: +1:22
-         _4 = SizeOf(i32);                // scope 2 at $DIR/boxes.rs:+1:14: +1:22
-         _5 = AlignOf(i32);               // scope 2 at $DIR/boxes.rs:+1:14: +1:22
+         _4 = const 4_usize;              // scope 2 at $DIR/boxes.rs:+1:14: +1:22
+         _5 = const 4_usize;              // scope 2 at $DIR/boxes.rs:+1:14: +1:22
          _6 = alloc::alloc::exchange_malloc(move _4, move _5) -> bb1; // scope 2 at $DIR/boxes.rs:+1:14: +1:22
                                           // mir::Constant
                                           // + span: $DIR/boxes.rs:13:14: 13:22
                                           // + literal: Const { ty: unsafe fn(usize, usize) -> *mut u8 {alloc::alloc::exchange_malloc}, val: Value(<ZST>) }
      }
  
      bb1: {
          StorageLive(_7);                 // scope 0 at $DIR/boxes.rs:+1:14: +1:22
          _7 = ShallowInitBox(move _6, i32); // scope 0 at $DIR/boxes.rs:+1:14: +1:22
          _8 = (((_7.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32); // scope 0 at $DIR/boxes.rs:+1:19: +1:21
          (*_8) = const 42_i32;            // scope 0 at $DIR/boxes.rs:+1:19: +1:21
          _3 = move _7;                    // scope 0 at $DIR/boxes.rs:+1:14: +1:22
          StorageDead(_7);                 // scope 0 at $DIR/boxes.rs:+1:21: +1:22
          _9 = (((_3.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32); // scope 0 at $DIR/boxes.rs:+1:13: +1:22
          _2 = (*_9);                      // scope 0 at $DIR/boxes.rs:+1:13: +1:22
          _1 = Add(move _2, const 0_i32);  // scope 0 at $DIR/boxes.rs:+1:13: +1:26
          StorageDead(_2);                 // scope 0 at $DIR/boxes.rs:+1:25: +1:26
          drop(_3) -> [return: bb2, unwind: bb3]; // scope 0 at $DIR/boxes.rs:+1:26: +1:27
      }
  
      bb2: {
          StorageDead(_3);                 // scope 0 at $DIR/boxes.rs:+1:26: +1:27
          _0 = const ();                   // scope 0 at $DIR/boxes.rs:+0:11: +2:2
          StorageDead(_1);                 // scope 0 at $DIR/boxes.rs:+2:1: +2:2
          return;                          // scope 0 at $DIR/boxes.rs:+2:2: +2:2
      }
  
      bb3 (cleanup): {
          resume;                          // scope 0 at $DIR/boxes.rs:+0:1: +2:2
      }
  }