Merge rust-bitcoin/rust-bitcoin#1874: Add `ValidationError`

0f74eb6876 Remove the unused crate::Error (Tobin C. Harding)
74154c2294 Add block::ValidationError (Tobin C. Harding)
3a9b5526b3 Move BlockHash From impls (Tobin C. Harding)

Pull request description:

  Remove the `crate::Error` and replace its usage with `block::ValidationError`.

ACKs for top commit:
  apoelstra:
    ACK 0f74eb6876
  Kixunil:
    ACK 0f74eb6876

Tree-SHA512: 80b2c98d3d8f7c3f060c8ea2d94e1ebe118c07d0dcf91f6d13aed00df2cb0b15bf5e295ec0976d88d81e029cf7d3e8e4a1fe70120db57e49bbd8dd229291836b

bitcoin/src/blockdata/block.rs

@@ -16,7 +16,6 @@ use super::Weight;
 use crate::blockdata::script;
 use crate::blockdata::transaction::Transaction;
 use crate::consensus::{encode, Decodable, Encodable};
-use crate::error::Error::{self, BlockBadProofOfWork, BlockBadTarget};
 pub use crate::hash_types::BlockHash;
 use crate::hash_types::{TxMerkleNode, WitnessCommitment, WitnessMerkleNode, Wtxid};
 use crate::internal_macros::impl_consensus_encoding;
@@ -72,16 +71,16 @@ impl Header {
     pub fn difficulty_float(&self) -> f64 { self.target().difficulty_float() }
 
     /// Checks that the proof-of-work for the block is valid, returning the block hash.
-    pub fn validate_pow(&self, required_target: Target) -> Result<BlockHash, Error> {
+    pub fn validate_pow(&self, required_target: Target) -> Result<BlockHash, ValidationError> {
         let target = self.target();
         if target != required_target {
-            return Err(BlockBadTarget);
+            return Err(ValidationError::BadTarget);
         }
         let block_hash = self.block_hash();
         if target.is_met_by(block_hash) {
             Ok(block_hash)
         } else {
-            Err(BlockBadProofOfWork)
+            Err(ValidationError::BadProofOfWork)
         }
     }
 
@@ -337,6 +336,22 @@ impl Block {
     }
 }
 
+impl From<Header> for BlockHash {
+    fn from(header: Header) -> BlockHash { header.block_hash() }
+}
+
+impl From<&Header> for BlockHash {
+    fn from(header: &Header) -> BlockHash { header.block_hash() }
+}
+
+impl From<Block> for BlockHash {
+    fn from(block: Block) -> BlockHash { block.block_hash() }
+}
+
+impl From<&Block> for BlockHash {
+    fn from(block: &Block) -> BlockHash { block.block_hash() }
+}
+
 /// An error when looking up a BIP34 block height.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[non_exhaustive]
@@ -375,20 +390,35 @@ impl std::error::Error for Bip34Error {
     }
 }
 
-impl From<Header> for BlockHash {
-    fn from(header: Header) -> BlockHash { header.block_hash() }
+/// A block validation error.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ValidationError {
+    /// The header hash is not below the target.
+    BadProofOfWork,
+    /// The `target` field of a block header did not match the expected difficulty.
+    BadTarget,
 }
 
-impl From<&Header> for BlockHash {
-    fn from(header: &Header) -> BlockHash { header.block_hash() }
+impl fmt::Display for ValidationError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use ValidationError::*;
+
+        match *self {
+            BadProofOfWork => f.write_str("block target correct but not attained"),
+            BadTarget => f.write_str("block target incorrect"),
+        }
+    }
 }
 
-impl From<Block> for BlockHash {
-    fn from(block: Block) -> BlockHash { block.block_hash() }
-}
+#[cfg(feature = "std")]
+impl std::error::Error for ValidationError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        use self::ValidationError::*;
 
-impl From<&Block> for BlockHash {
-    fn from(block: &Block) -> BlockHash { block.block_hash() }
+        match *self {
+            BadProofOfWork | BadTarget => None,
+        }
+    }
 }
 
 #[cfg(test)]
@@ -528,7 +558,7 @@ mod tests {
 
         // test with zero target
         match some_header.validate_pow(Target::ZERO) {
-            Err(BlockBadTarget) => (),
+            Err(ValidationError::BadTarget) => (),
             _ => panic!("unexpected result from validate_pow"),
         }
 
@@ -536,7 +566,7 @@ mod tests {
         let mut invalid_header: Header = some_header;
         invalid_header.version.0 += 1;
         match invalid_header.validate_pow(invalid_header.target()) {
-            Err(BlockBadProofOfWork) => (),
+            Err(ValidationError::BadProofOfWork) => (),
             _ => panic!("unexpected result from validate_pow"),
         }
     }

bitcoin/src/error.rs

@@ -2,53 +2,8 @@
 
 //! Contains error types and other error handling tools.
 
-use core::fmt;
-
-use internals::write_err;
-
-use crate::consensus::encode;
 pub use crate::parse::ParseIntError;
 
-/// A general error code, other errors should implement conversions to/from this
-/// if appropriate.
-#[derive(Debug)]
-#[non_exhaustive]
-pub enum Error {
-    /// Encoding error
-    Encode(encode::Error),
-    /// The header hash is not below the target
-    BlockBadProofOfWork,
-    /// The `target` field of a block header did not match the expected difficulty
-    BlockBadTarget,
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match *self {
-            Error::Encode(ref e) => write_err!(f, "encoding error"; e),
-            Error::BlockBadProofOfWork => f.write_str("block target correct but not attained"),
-            Error::BlockBadTarget => f.write_str("block target incorrect"),
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-impl std::error::Error for Error {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        use self::Error::*;
-
-        match self {
-            Encode(e) => Some(e),
-            BlockBadProofOfWork | BlockBadTarget => None,
-        }
-    }
-}
-
-#[doc(hidden)]
-impl From<encode::Error> for Error {
-    fn from(e: encode::Error) -> Error { Error::Encode(e) }
-}
-
 /// Impls std::error::Error for the specified type with appropriate attributes, possibly returning
 /// source.
 macro_rules! impl_std_error {

bitcoin/src/lib.rs

@@ -134,7 +134,6 @@ pub use crate::blockdata::{constants, opcodes};
 pub use crate::consensus::encode::VarInt;
 pub use crate::crypto::key::{self, PrivateKey, PublicKey};
 pub use crate::crypto::{ecdsa, sighash};
-pub use crate::error::Error;
 pub use crate::hash_types::{
     BlockHash, PubkeyHash, ScriptHash, Txid, WPubkeyHash, WScriptHash, Wtxid,
 };