From af1628667939912992abf8f04027dfdca18f2241 Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Wed, 25 May 2022 17:16:54 +1000
Subject: [PATCH] Implement TryFrom sha256::Hash for TaprootMerkleBranch

TryFrom` became available in Rust 1.34 so we can use it now we have
bumped our MSRV.

Add a macro for implementing `TryFrom` for various lists of
`sha256::Hash` types. Use the macro to for vec, slice, and boxed slice.
---
 src/util/sighash.rs |  4 ++--
 src/util/taproot.rs | 39 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/src/util/sighash.rs b/src/util/sighash.rs
index a3b6abce..81734711 100644
--- a/src/util/sighash.rs
+++ b/src/util/sighash.rs
@@ -1113,7 +1113,7 @@ mod tests {
             } else {
                 Some(hex_hash!(TapBranchHash, inp["given"]["merkleRoot"].as_str().unwrap()))
             };
-            let hash_ty = SchnorrSighashType::from_u8(inp["given"]["hashType"].as_u64().unwrap() as u8).unwrap();
+            let hash_ty = SchnorrSighashType::try_from(inp["given"]["hashType"].as_u64().unwrap() as u8).unwrap();
 
             let expected_internal_pk = hex_hash!(XOnlyPublicKey, inp["intermediary"]["internalPubkey"].as_str().unwrap());
             let expected_tweak = hex_hash!(TapTweakHash, inp["intermediary"]["tweak"].as_str().unwrap());
@@ -1124,7 +1124,7 @@ mod tests {
             let (expected_key_spend_sig, expected_hash_ty) = if sig_str.len() == 128 {
                 (secp256k1::schnorr::Signature::from_str(sig_str).unwrap(), SchnorrSighashType::Default)
             } else {
-                let hash_ty = SchnorrSighashType::from_u8(Vec::<u8>::from_hex(&sig_str[128..]).unwrap()[0]).unwrap();
+                let hash_ty = SchnorrSighashType::try_from(Vec::<u8>::from_hex(&sig_str[128..]).unwrap()[0]).unwrap();
                 (secp256k1::schnorr::Signature::from_str(&sig_str[..128]).unwrap(), hash_ty)
             };
 
diff --git a/src/util/taproot.rs b/src/util/taproot.rs
index 3cd050d6..afdba369 100644
--- a/src/util/taproot.rs
+++ b/src/util/taproot.rs
@@ -20,6 +20,7 @@ use crate::prelude::*;
 use crate::io;
 use secp256k1::{self, Secp256k1};
 
+use core::convert::TryFrom;
 use core::fmt;
 use core::cmp::Reverse;
 
@@ -672,6 +673,18 @@ impl TaprootMerkleBranch {
         }
     }
 
+    /// Creates a merkle proof from list of hashes.
+    ///
+    /// # Errors
+    /// If inner proof length is more than [`TAPROOT_CONTROL_MAX_NODE_COUNT`] (128).
+    fn from_collection<T: AsRef<[sha256::Hash]> + Into<Vec<sha256::Hash>>>(collection: T) -> Result<Self, TaprootError> {
+        if collection.as_ref().len() > TAPROOT_CONTROL_MAX_NODE_COUNT {
+            Err(TaprootError::InvalidMerkleTreeDepth(collection.as_ref().len()))
+        } else {
+            Ok(TaprootMerkleBranch(collection.into()))
+        }
+    }
+
     /// Serializes to a writer.
     ///
     /// # Returns
@@ -704,12 +717,9 @@ impl TaprootMerkleBranch {
     /// # Errors
     ///
     /// If inner proof length is more than [`TAPROOT_CONTROL_MAX_NODE_COUNT`] (128).
+    #[deprecated(since = "0.29.0", note = "use try_from instead")]
     pub fn from_inner(inner: Vec<sha256::Hash>) -> Result<Self, TaprootError> {
-        if inner.len() > TAPROOT_CONTROL_MAX_NODE_COUNT {
-            Err(TaprootError::InvalidMerkleTreeDepth(inner.len()))
-        } else {
-            Ok(TaprootMerkleBranch(inner))
-        }
+        Self::try_from(inner)
     }
 
     /// Returns the inner list of hashes.
@@ -718,6 +728,25 @@ impl TaprootMerkleBranch {
     }
 }
 
+macro_rules! impl_try_from {
+    ($from:ty) => {
+        impl TryFrom<$from> for TaprootMerkleBranch {
+            type Error = TaprootError;
+
+            /// Creates a merkle proof from list of hashes.
+            ///
+            /// # Errors
+            /// If inner proof length is more than [`TAPROOT_CONTROL_MAX_NODE_COUNT`] (128).
+            fn try_from(v: $from) -> Result<Self, Self::Error> {
+                TaprootMerkleBranch::from_collection(v)
+            }
+        }
+    }
+}
+impl_try_from!(&[sha256::Hash]);
+impl_try_from!(Vec<sha256::Hash>);
+impl_try_from!(Box<[sha256::Hash]>);
+
 /// Control block data structure used in Tapscript satisfaction.
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]