message: refactor(error): turn Void from an empty enum to a struct
diff: @@ -55,11 +55,11 @@ pub enum Error {
  }
  #[doc(hidden)]
  -pub enum Void {}
  +pub struct Void(());
  impl fmt::Debug for Void {
  fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
  - match *self {}
  + unreachable!()
  }
  }
  @@ -87,7 +87,7 @@ impl StdError for Error {
  Uri(ref e) => e.description(),
  Io(ref e) => e.description(),
  Utf8(ref e) => e.description(),
  - Error::__Nonexhaustive(ref void) => match *void {}
  + Error::__Nonexhaustive(..) => unreachable!(),
  }
  }
  @@ -96,7 +96,7 @@ impl StdError for Error {
  Io(ref error) => Some(error),
  Uri(ref error) => Some(error),
  Utf8(ref error) => Some(error),
  - Error::__Nonexhaustive(ref void) => match *void {},
  + Error::__Nonexhaustive(..) => unreachable!(),
  _ => None,
  }
  }
  