message: Fix casts for `count` check
diff: @@ -146,7 +146,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  // `File::sync_all` does the checks that are done when closing a file. We do this to
  // to handle possible errors correctly.
  let result = this.try_unwrap_io_result(handle.file.sync_all().map(|_| 0i32));
  - // Now we actually drop the handle.
  + // Now we actually close the file.
  drop(handle);
  // And return the result.
  result
  @@ -180,7 +180,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  if let Ok(c) = result {
  // Check that we read less than `i64::MAX` bytes.
  - if c > (i64::max_value() as usize) {
  + if (c as u64) > (i64::max_value() as u64) {
  throw_unsup_format!("Number of read bytes {} is larger than the maximum value", c);
  }
  // If reading to `bytes` did not fail, we write those bytes to the buffer.
  @@ -217,7 +217,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  if let Ok(c) = result {
  // Check that we wrote less than `i64::MAX` bytes.
  - if c > (i64::max_value() as usize) {
  + if (c as u64) > (i64::max_value() as u64) {
  throw_unsup_format!("Number of written bytes {} is larger than the maximum value", c);
  }
  }
  