Merge rust-bitcoin/rust-bitcoin#778: Fixups for taproot improvements

62a27a51e2 Document that serde impl of LeafVersion uses u8 in consensus encoding (Dr Maxim Orlovsky)
73e6ce4e53 Re-export Witness at crate level. Closes #770 (Dr Maxim Orlovsky)
6364ebd927 Code style fixups to taproot key functions (Dr Maxim Orlovsky)
7514f2ca18 Tweaked  -> untweaked keys conversions (Dr Maxim Orlovsky)

Pull request description:

  This addresses @Kixunil review comments in #696 post-merge

  Update: also closes nits from issues #764 and #770

ACKs for top commit:
  Kixunil:
    ACK 62a27a51e2
  sanket1729:
    utACK 62a27a51e2

Tree-SHA512: 2f10393abab41d1c82f4733d83bf85bd82e268a2891c156eb89744c0fc444fdfec4d60deec2dda6fde2e5881989625c18b9c5ca21d360018edba69b6d2a85eae

src/blockdata/script.rs

@@ -344,9 +344,6 @@ impl Script {
     }
 
     /// Generates P2TR for key spending path for a known [`TweakedPublicKey`].
-    ///
-    /// NB: Make sure that the used key is indeed tweaked (for instance, it comes from `rawtr`
-    /// descriptor content); otherwise please use [`Script::new_v1_p2tr`] method.
     pub fn new_v1_p2tr_tweaked(output_key: TweakedPublicKey) -> Script {
         Script::new_witness_program(WitnessVersion::V1, &output_key.serialize())
     }
@@ -414,7 +411,7 @@ impl Script {
 
     #[inline]
     fn witness_version(&self) -> Option<WitnessVersion> {
-        WitnessVersion::from_opcode(self.0[0].into()).ok()
+        self.0.get(0).and_then(|opcode| WitnessVersion::from_opcode(opcodes::All::from(*opcode)).ok())
     }
 
     /// Checks whether a script pubkey is a p2sh output

src/lib.rs

@@ -124,6 +124,7 @@ pub use blockdata::transaction::TxIn;
 pub use blockdata::transaction::TxOut;
 pub use blockdata::transaction::OutPoint;
 pub use blockdata::transaction::EcdsaSigHashType;
+pub use blockdata::witness::Witness;
 pub use consensus::encode::VarInt;
 pub use network::constants::Network;
 pub use util::Error;

src/util/schnorr.rs

@@ -128,12 +128,11 @@ impl TapTweak for UntweakedKeyPair {
     ///
     /// # Returns
     /// The tweaked key and its parity.
-    fn tap_tweak<C: Verification>(self, secp: &Secp256k1<C>, merkle_root: Option<TapBranchHash>) -> TweakedKeyPair {
+    fn tap_tweak<C: Verification>(mut self, secp: &Secp256k1<C>, merkle_root: Option<TapBranchHash>) -> TweakedKeyPair {
         let pubkey = XOnlyPublicKey::from_keypair(&self);
         let tweak_value = TapTweakHash::from_key_and_tweak(pubkey, merkle_root).into_inner();
-        let mut output_key = self.clone();
-        output_key.tweak_add_assign(&secp, &tweak_value).expect("Tap tweak failed");
-        TweakedKeyPair(output_key)
+        self.tweak_add_assign(&secp, &tweak_value).expect("Tap tweak failed");
+        TweakedKeyPair(self)
     }
 
     fn dangerous_assume_tweaked(self) -> TweakedKeyPair {
@@ -189,6 +188,20 @@ impl TweakedKeyPair {
     }
 }
 
+impl From<TweakedPublicKey> for XOnlyPublicKey {
+    #[inline]
+    fn from(pair: TweakedPublicKey) -> Self {
+        pair.0
+    }
+}
+
+impl From<TweakedKeyPair> for KeyPair {
+    #[inline]
+    fn from(pair: TweakedKeyPair) -> Self {
+        pair.0
+    }
+}
+
 /// A BIP340-341 serialized schnorr signature with the corresponding hash type.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]

src/util/taproot.rs

@@ -869,6 +869,7 @@ impl fmt::UpperHex for LeafVersion {
     }
 }
 
+/// Serializes LeafVersion as u8 using consensus encoding
 #[cfg(feature = "serde")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl ::serde::Serialize for LeafVersion {
@@ -880,6 +881,7 @@ impl ::serde::Serialize for LeafVersion {
     }
 }
 
+/// Deserializes LeafVersion as u8 using consensus encoding
 #[cfg(feature = "serde")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<'de> ::serde::Deserialize<'de> for LeafVersion {