message: Special case ZST's in Rvalue::Repeat
  Fixes by preventing a hang for [(); usize::MAX], which is used in
  a test of libcore.
diff: @@ -660,7 +660,9 @@ fn is_fat_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
  .val
  .try_to_bits(fx.tcx.data_layout.pointer_size)
  .unwrap();
  - if fx.clif_type(operand.layout().ty) == Some(types::I8) {
  + if operand.layout().size.bytes() == 0 {
  + // Do nothing for ZST's
  + } else if fx.clif_type(operand.layout().ty) == Some(types::I8) {
  let times = fx.bcx.ins().iconst(fx.pointer_type, times as i64);
  // FIXME use emit_small_memset where possible
  let addr = lval.to_ptr().get_addr(fx);
  