Update note position calculation

Reviewed-on: #69

librustzcash-wrapper/src/lib.rs

@@ -1247,16 +1247,8 @@ pub extern "C" fn rust_wrapper_read_sapling_position(
     let wit_in: Vec<u8> = marshall_from_haskell_var(wit, wit_len, RW);
     let wit_reader = Cursor::new(wit_in);
     let iw: IncrementalWitness<Node, SAPLING_DEPTH> = read_incremental_witness(wit_reader).unwrap();
-    let path = iw.path();
-    match path {
-        Some(p) => {
-            let pos = p.position();
+    let pos = iw.witnessed_position();
     return u64::from(pos);
-        },
-        None => {
-            return 0;
-        }
-    }
 }
 
 #[no_mangle]

test/Spec.hs

@@ -1113,18 +1113,20 @@ main = do
                                 MainNet
                                 External
                                 p
-                        dn `shouldNotBe` Nothing
-
+                        dn `shouldBe` Nothing
       describe "Generate an ExchangeAddress (MainNet) from transparent address" $ do
         let ta = decodeTransparentAddress "t1dMjvesbzdG41xgKaGU3HgwYJwSgbCK54e"
         it "Try to generate valid ExchangeAddress from Transparent Address" $ do
           case ta of
             Nothing -> assertFailure "Failed to decode transparent address"
             Just t -> do
-              case  (tr_type (ta_receiver t) ) of
-                P2SH -> assertFailure "P2SH not supported for ExchengeAddress generation" 
+              case (tr_type (ta_receiver t)) of
+                P2SH ->
+                  assertFailure
+                    "P2SH not supported for ExchengeAddress generation"
                 P2PKH -> do
-                  let exch = encodeExchangeAddress (ta_network t) (ta_receiver t)
+                  let exch =
+                        encodeExchangeAddress (ta_network t) (ta_receiver t)
                   case exch of
                     Nothing -> assertFailure "Failed to encode Exchange address"
                     Just addr -> do