message: Process untagged unions
diff: @@ -955,6 +955,8 @@ impl<'a, 'tcx, M: Machine<'tcx>> EvalContext<'a, 'tcx, M> {
  let variant_def = adt_def.struct_variant();
  use rustc::ty::layout::Layout::*;
  match *self.type_layout(ty)? {
  + UntaggedUnion { ref variants } =>
  + Ok(TyAndPacked { ty: variant_def.fields[field_index].ty(self.tcx, substs), packed: variants.packed }),
  Univariant { ref variant, .. } =>
  Ok(TyAndPacked { ty: variant_def.fields[field_index].ty(self.tcx, substs), packed: variant.packed }),
  _ => Err(EvalError::Unimplemented(format!("get_field_ty can't handle struct type: {:?}, {:?}", ty, ty.sty))),
  @@ -988,8 +990,9 @@ impl<'a, 'tcx, M: Machine<'tcx>> EvalContext<'a, 'tcx, M> {
  StructWrappedNullablePointer { ref nonnull, .. } => {
  Ok(nonnull.offsets[field_index])
  }
  + UntaggedUnion { .. } => Ok(Size::from_bytes(0)),
  _ => {
  - let msg = format!("can't handle type: {:?}, with layout: {:?}", ty, layout);
  + let msg = format!("get_field_offset: can't handle type: {:?}, with layout: {:?}", ty, layout);
  Err(EvalError::Unimplemented(msg))
  }
  }
  @@ -1006,8 +1009,9 @@ impl<'a, 'tcx, M: Machine<'tcx>> EvalContext<'a, 'tcx, M> {
  Vector { count , .. } |
  Array { count, .. } => Ok(count),
  Scalar { .. } => Ok(0),
  + UntaggedUnion { .. } => Ok(1),
  _ => {
  - let msg = format!("can't handle type: {:?}, with layout: {:?}", ty, layout);
  + let msg = format!("get_field_count: can't handle type: {:?}, with layout: {:?}", ty, layout);
  Err(EvalError::Unimplemented(msg))
  }
  }
  