- // MIR for `main` before Derefer
+ // MIR for `main` after Derefer
  
  fn main() -> () {
      let mut _0: ();
      let mut _1: std::slice::Iter<'_, i32>;
      let mut _2: &[i32; 2];
      let _3: [i32; 2];
      let mut _4: std::slice::Iter<'_, i32>;
      let mut _5: ();
      let _6: ();
      let mut _7: std::option::Option<&i32>;
      let mut _8: &mut std::slice::Iter<'_, i32>;
      let mut _9: &mut std::slice::Iter<'_, i32>;
      let mut _10: isize;
      let mut _11: !;
      let mut _13: i32;
      let mut _14: &[i32; 2];
+     let mut _15: &i32;
      scope 1 {
          debug iter => _4;
          let _12: i32;
          scope 2 {
              debug foo => _12;
          }
      }
  
      bb0: {
          StorageLive(_1);
          StorageLive(_2);
          _14 = const main::promoted[0];
          _2 = &(*_14);
          _1 = <&[i32; 2] as IntoIterator>::into_iter(move _2) -> [return: bb1, unwind: bb8];
      }
  
      bb1: {
          StorageDead(_2);
          PlaceMention(_1);
          StorageLive(_4);
          _4 = move _1;
          goto -> bb2;
      }
  
      bb2: {
          StorageLive(_6);
          StorageLive(_7);
          StorageLive(_8);
          StorageLive(_9);
          _9 = &mut _4;
          _8 = &mut (*_9);
          _7 = <std::slice::Iter<'_, i32> as Iterator>::next(move _8) -> [return: bb3, unwind: bb8];
      }
  
      bb3: {
          StorageDead(_8);
          PlaceMention(_7);
          _10 = discriminant(_7);
          switchInt(move _10) -> [0: bb6, 1: bb5, otherwise: bb4];
      }
  
      bb4: {
          unreachable;
      }
  
      bb5: {
          StorageLive(_12);
-         _12 = copy (*((_7 as Some).0: &i32));
+         _15 = deref_copy ((_7 as Some).0: &i32);
+         _12 = copy (*_15);
          StorageLive(_13);
          _13 = copy _12;
          _6 = std::mem::drop::<i32>(move _13) -> [return: bb7, unwind: bb8];
      }
  
      bb6: {
          _0 = const ();
          StorageDead(_9);
          StorageDead(_7);
          StorageDead(_6);
          StorageDead(_4);
          StorageDead(_1);
          return;
      }
  
      bb7: {
          StorageDead(_13);
          StorageDead(_12);
          StorageDead(_9);
          StorageDead(_7);
          StorageDead(_6);
          _5 = const ();
          goto -> bb2;
      }
  
      bb8 (cleanup): {
          resume;
      }
  }