message: Add comment explaining why WasmHash is implemented the way it is
diff: @@ -35,6 +35,9 @@ impl From<io::Error> for Error {
  ///
  /// [`Cache`]: trait.Cache.html
  #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
  +// WasmHash is made up of two 32 byte arrays instead of a 64 byte array
  +// because derive only works on fixed sized arrays size 32 or below
  +// TODO: fix this when this gets fixed by improved const generics
  pub struct WasmHash([u8; 32], [u8; 32]);
  impl WasmHash {
  