rust/tests/mir-opt/const_prop/while_let_loops.change_loop_body.ConstProp.diff

- // MIR for `change_loop_body` before ConstProp
+ // MIR for `change_loop_body` after ConstProp
  
  fn change_loop_body() -> () {
      let mut _0: ();
      let mut _1: i32;
      let mut _2: ();
      let mut _3: std::option::Option<u32>;
      let mut _4: isize;
      let mut _5: !;
      let mut _6: !;
      let _7: ();
      let mut _8: !;
      scope 1 {
          debug _x => _1;
          scope 2 {
          }
      }
  
      bb0: {
          StorageLive(_1);
          _1 = const 0_i32;
          StorageLive(_3);
          _3 = Option::<u32>::None;
-         _4 = discriminant(_3);
-         switchInt(move _4) -> [1: bb1, otherwise: bb3];
+         _4 = const 0_isize;
+         switchInt(const 0_isize) -> [1: bb1, otherwise: bb3];
      }
  
      bb1: {
          switchInt(((_3 as Some).0: u32)) -> [0: bb2, otherwise: bb3];
      }
  
      bb2: {
          _1 = const 1_i32;
          _0 = const ();
          goto -> bb4;
      }
  
      bb3: {
          StorageLive(_7);
          _0 = const ();
          StorageDead(_7);
          goto -> bb4;
      }
  
      bb4: {
          StorageDead(_3);
          StorageDead(_1);
          return;
      }
  }