message: Regain compatibility with Gazebo 0.2.1
  Summary: Fixes a CI failure in GitHub.
diff: @@ -34,9 +34,13 @@ pub(crate) struct StmtProfile(Option<Box<StmtProfileData>>);
  // A cheap unowned unique identifier per file/CodeMap,
  // somewhat delving into internal details.
  // Remains unique because we take a reference to the CodeMap.
  -#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy, Dupe)]
  +#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy)]
  struct FileId(*const crate::codemap::File);
  +// FIXME(ndmitchell): Release Gazebo 0.2.2 and use a derive.
  +// Can't derive Dupe until Gazebo 0.2.2 which gives a Dupe instance to pointers
  +impl Dupe for FileId {}
  +
  impl FileId {
  const EMPTY: FileId = FileId(ptr::null());
  