message: make TLS state private to TLS module
diff: @@ -18,17 +18,17 @@ pub struct TlsEntry<'tcx> {
  /// The data for this key. None is used to represent NULL.
  /// (We normalize this early to avoid having to do a NULL-ptr-test each time we access the data.)
  /// Will eventually become a map from thread IDs to `Scalar`s, if we ever support more than one thread.
  - pub(crate) data: Option<Scalar<Tag>>,
  - pub(crate) dtor: Option<ty::Instance<'tcx>>,
  + data: Option<Scalar<Tag>>,
  + dtor: Option<ty::Instance<'tcx>>,
  }
  #[derive(Debug)]
  pub struct TlsData<'tcx> {
  /// The Key to use for the next thread-local allocation.
  - pub(crate) next_key: TlsKey,
  + next_key: TlsKey,
  /// pthreads-style thread-local storage.
  - pub(crate) keys: BTreeMap<TlsKey, TlsEntry<'tcx>>,
  + keys: BTreeMap<TlsKey, TlsEntry<'tcx>>,
  }
  impl<'tcx> Default for TlsData<'tcx> {
  