From 95ad91cdb64c8870d3eb992090bab7a70d1369b9 Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Thu, 20 Feb 2025 13:57:27 +1100
Subject: [PATCH] hashes: Remove the GeneralHash trait

Now that we are able to unambiguously go from a hash engine to its
associated hash type there is no longer any need for the `GeneralHash`
trait.

Please note that IMO this concept of a general hash type as opposed to
one where one can hash arbitrary data still exists in the codebase - it
is implicitly in the `hash_newtype` macro.

Remove the `GeneralHash` trait.
---
 hashes/src/internal_macros.rs |  6 -----
 hashes/src/lib.rs             | 46 -----------------------------------
 2 files changed, 52 deletions(-)

diff --git a/hashes/src/internal_macros.rs b/hashes/src/internal_macros.rs
index fee359a9e..5e9599322 100644
--- a/hashes/src/internal_macros.rs
+++ b/hashes/src/internal_macros.rs
@@ -26,12 +26,6 @@ macro_rules! hash_trait_impls {
         #[cfg(not(feature = "hex"))]
         $crate::impl_debug_only!(Hash, { $bits / 8 }, $reverse $(, $gen: $gent)*);
 
-        impl<$($gen: $gent),*> $crate::GeneralHash for Hash<$($gen),*> {
-            type Engine = HashEngine<$($gen),*>;
-
-            fn from_engine(e: Self::Engine) -> Hash<$($gen),*> { Self::from_engine(e) }
-        }
-
         #[cfg(feature = "serde")]
         $crate::serde_impl!(Hash, { $bits / 8} $(, $gen: $gent)*);
 
diff --git a/hashes/src/lib.rs b/hashes/src/lib.rs
index 4201b0ea0..b3962214c 100644
--- a/hashes/src/lib.rs
+++ b/hashes/src/lib.rs
@@ -208,52 +208,6 @@ pub trait HashEngine: Clone {
     fn finalize(self) -> Self::Hash;
 }
 
-/// Trait describing hash digests which can be constructed by hashing arbitrary data.
-///
-/// Some methods have been bound to engines which implement Default, which is
-/// generally an unkeyed hash function.
-pub trait GeneralHash: Hash {
-    /// A hashing engine which bytes can be serialized into. It is expected
-    /// to implement the `io::Write` trait, and to never return errors under
-    /// any conditions.
-    type Engine: HashEngine;
-
-    /// Constructs a new engine.
-    fn engine() -> Self::Engine
-    where
-        Self::Engine: Default,
-    {
-        Self::Engine::default()
-    }
-
-    /// Produces a hash from the current state of a given engine.
-    fn from_engine(e: Self::Engine) -> Self;
-
-    /// Hashes some bytes.
-    fn hash(data: &[u8]) -> Self
-    where
-        Self::Engine: Default,
-    {
-        let mut engine = Self::engine();
-        engine.input(data);
-        Self::from_engine(engine)
-    }
-
-    /// Hashes all the byte slices retrieved from the iterator together.
-    fn hash_byte_chunks<B, I>(byte_slices: I) -> Self
-    where
-        B: AsRef<[u8]>,
-        I: IntoIterator<Item = B>,
-        Self::Engine: Default,
-    {
-        let mut engine = Self::engine();
-        for slice in byte_slices {
-            engine.input(slice.as_ref());
-        }
-        Self::from_engine(engine)
-    }
-}
-
 /// Trait which applies to hashes of all types.
 pub trait Hash:
     Copy + Clone + PartialEq + Eq + PartialOrd + Ord + hash::Hash + convert::AsRef<[u8]>