hashes: Remove FromSliceError

diff --git a/hashes/src/error.rs b/hashes/src/error.rs
deleted file mode 100644
index ce2c82af..00000000
--- a/hashes/src/error.rs
+++ /dev/null
@@ -1,42 +0,0 @@
-// SPDX-License-Identifier: CC0-1.0
-
-//! Error code for the `hashes` crate.
-
-use core::convert::Infallible;
-use core::fmt;
-
-/// Attempted to create a hash from an invalid length slice.
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct FromSliceError(pub(crate) FromSliceErrorInner);
-
-impl From<Infallible> for FromSliceError {
-    fn from(never: Infallible) -> Self { match never {} }
-}
-
-impl FromSliceError {
-    /// Returns the expected slice length.
-    pub fn expected_length(&self) -> usize { self.0.expected }
-
-    /// Returns the invalid slice length.
-    pub fn invalid_length(&self) -> usize { self.0.got }
-}
-
-/// Attempted to create a hash from an invalid length slice.
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub(crate) struct FromSliceErrorInner {
-    pub(crate) expected: usize,
-    pub(crate) got: usize,
-}
-
-impl From<Infallible> for FromSliceErrorInner {
-    fn from(never: Infallible) -> Self { match never {} }
-}
-
-impl fmt::Display for FromSliceError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "invalid slice length {} (expected {})", self.0.got, self.0.expected)
-    }
-}
-
-#[cfg(feature = "std")]
-impl std::error::Error for FromSliceError {}
diff --git a/hashes/src/lib.rs b/hashes/src/lib.rs
index 4f7e1d3a..1829ad2a 100644
--- a/hashes/src/lib.rs
+++ b/hashes/src/lib.rs
@@ -91,8 +91,6 @@ pub mod _export {
     }
 }
 
-#[deprecated(since = "TBD", note = "unused now that `Hash::from_slice` is deprecated")]
-mod error;
 mod internal_macros;
 
 pub mod cmp;
@@ -153,11 +151,6 @@ pub use sha512_256::Hash as Sha512_256;
 #[doc(inline)]
 pub use siphash24::Hash as Siphash24;
 
-/// Attempted to create a hash from an invalid length slice.
-#[deprecated(since = "TBD", note = "unused now that `Hash::from_slice` is deprecated")]
-#[allow(deprecated_in_future)]
-pub type FromSliceError = crate::error::FromSliceError; // Alias instead of re-export so we can deprecate it.
-
 /// Tagged SHA-256: Type alias for the [`sha256t::Hash`] hash type.
 pub type Sha256t<T> = sha256t::Hash<T>;
 
diff --git a/hashes/tests/api.rs b/hashes/tests/api.rs
index afa3f9c2..bdb10145 100644
--- a/hashes/tests/api.rs
+++ b/hashes/tests/api.rs
@@ -14,7 +14,7 @@
 // Import using module style e.g., `sha256::Hash`.
 use bitcoin_hashes::{
     hash160, hash_newtype, hkdf, hmac, ripemd160, sha1, sha256, sha256d, sha256t, sha256t_tag,
-    sha384, sha3_256, sha512, sha512_256, siphash24, FromSliceError, Hash, HashEngine,
+    sha384, sha3_256, sha512, sha512_256, siphash24, Hash, HashEngine,
 };
 // Import using type alias style e.g., `Sha256`.
 use bitcoin_hashes::{
@@ -165,7 +165,6 @@ struct Keyed<T: Hash> {
 // These derives are the policy of `rust-bitcoin` not Rust API guidelines.
 #[derive(Debug, Clone, PartialEq, Eq)] // All public types implement Debug (C-DEBUG).
 struct Errors {
-    a: FromSliceError,
     b: hkdf::MaxLengthError,
     c: sha256::MidstateError,
 }