message: Remove unneeded BlockInfo trait impl
diff: //! Just to comply with the Digest contract.
  //!
  //! Adapted from `sha2` [sha256.rs](https://github.com/RustCrypto/hashes/blob/master/sha2/src/sha256.rs)
  -use sha2::digest::consts::{U28, U32, U64};
  +use sha2::digest::consts::{U28, U32};
  use sha2::digest::generic_array::GenericArray;
  -use sha2::digest::{BlockInput, FixedOutputDirty, Reset, Update};
  -
  -// FIXME?: Remove unneeded BlockInput / BlockSize
  -type BlockSize = U64;
  +use sha2::digest::{FixedOutputDirty, Reset, Update};
  use sha2::digest;
  @@ -26,10 +23,6 @@ impl Default for Sha256 {
  }
  }
  -impl BlockInput for Sha256 {
  - type BlockSize = BlockSize;
  -}
  -
  impl Update for Sha256 {
  fn update(&mut self, hash: impl AsRef<[u8]>) {
  assert_eq!(hash.as_ref().len(), 32);
  @@ -65,10 +58,6 @@ impl Default for Sha224 {
  }
  }
  -impl BlockInput for Sha224 {
  - type BlockSize = BlockSize;
  -}
  -
  impl Update for Sha224 {
  fn update(&mut self, hash: impl AsRef<[u8]>) {
  assert_eq!(hash.as_ref().len(), 28);
  