message: Remove unnecessary unsafe inside unsafe function
  Summary: The function is already unsafe
diff: @@ -565,9 +565,7 @@ impl Heap {
  // Otherwise the Value is constrainted by the borrow_mut, when
  // we consider values to be kept alive permanently, other than
  // when a GC happens
  - f(Value::new_ptr_query_is_str(unsafe {
  - cast::ptr_lifetime(x)
  - }))
  + f(Value::new_ptr_query_is_str(cast::ptr_lifetime(x)))
  })
  }
  