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Co-authored-by: Daira-Emma Hopwood <[email protected]>

components/zcash_address/src/kind/unified.rs

@@ -241,12 +241,15 @@ impl MetadataItem {
  "Expiry time must be a 64-bit little-endian value.".to_string(),
  )
  }),
+ (R0, ExpiryHeight | ExpiryTime) => Err(ParseError::NotUnderstood(typecode.into())),
  (R0 | R1, MustUnderstand(tc)) => Err(ParseError::NotUnderstood(tc)),
+ // This implementation treats the 0xC0..OxFD range as unknown metadata for both R0 and
+ // R1, as no typecodes were specified in this range for R0 and were "reclaimed" as
+ // metadata codes by ZIP 316 at the time R1 was introduced.
  (R0 | R1, Unknown(typecode)) => Ok(MetadataItem::Unknown {
  typecode,
  data: data.to_vec(),
  }),
- (R0, ExpiryHeight | ExpiryTime) => Err(ParseError::NotUnderstood(typecode.into())),
  }
  }
 
@@ -564,9 +567,7 @@ pub(crate) mod private {
  return Err(ParseError::InvalidTypecodeOrder);
  } else if t_code == prev_code {
  return Err(ParseError::DuplicateTypecode(t));
- } else if t == Typecode::Data(DataTypecode::P2sh)
- && prev_code == Some(u32::from(DataTypecode::P2pkh))
- {
+ } else if t == Typecode::P2SH && prev_code == Some(u32::from(DataTypecode::P2pkh)) {
  // P2pkh and P2sh can only be in that order and next to each other,
  // otherwise we would detect an out-of-order or duplicate typecode.
  return Err(ParseError::BothP2phkAndP2sh);
@@ -604,7 +605,6 @@ pub trait Encoding: private::SealedContainer {
  /// invariants concerning the composition of a unified container are
  /// violated:
  /// * the item list may not contain two items having the same typecode
- /// * the item list may not contain only transparent items (or no items)
  /// * the item list may not contain both P2PKH and P2SH items.
  fn try_from_items(
  revision: Revision,