feat(rust): add marshalling for Hhex

librustzcash-wrapper/src/lib.rs

@@ -272,6 +272,12 @@ impl<RW> ToHaskell<RW> for Hhex {
     }
 }
 
+impl<RW> FromHaskell<RW> for Hhex {
+    fn from_haskell(buf: &mut &[u8], _tag: PhantomData<RW>) -> Result<Self> {
+        let x = Hhex::deserialize(buf)?;
+        Ok(x)
+    }
+}
 
 #[derive(Debug, BorshSerialize, BorshDeserialize)]
 pub struct Haction {