message: Simpler cast in StarlarkStr
  Summary: Minor code cleanup.
diff: @@ -56,7 +56,7 @@ pub struct StarlarkStr {
  // Followed by an unsized block, meaning this type is unsized.
  // But we can't mark it as such since we really want &StarlarkStr to
  // take up only one word.
  - body: (),
  + body: [u8; 0],
  }
  impl Debug for StarlarkStr {
  @@ -71,13 +71,13 @@ impl StarlarkStr {
  Self {
  len,
  hash: atomic::AtomicU64::new(0),
  - body: (),
  + body: [],
  }
  }
  pub fn unpack(&self) -> &str {
  unsafe {
  - let slice = slice::from_raw_parts(&self.body as *const () as *const u8, self.len);
  + let slice = slice::from_raw_parts(self.body.as_ptr(), self.len);
  str::from_utf8_unchecked(slice)
  }
  }
  