Raise an error in the case that sprout version < 1.

Co-authored-by: Daira Hopwood <daira@jacaranda.org>

zcash_primitives/src/transaction/mod.rs

@@ -84,8 +84,13 @@ impl TxVersion {
                     "Unknown transaction format",
                 )),
             }
-        } else {
+        } else if version >= 1 {
             Ok(TxVersion::Sprout(version))
+        } else {
+            Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "Unknown transaction format",
+            ))
         }
     }
 

zcash_primitives/src/transaction/tests.rs

@@ -5,9 +5,6 @@ use proptest::prelude::*;
 
 use crate::{constants::SPENDING_KEY_GENERATOR, redjubjub::PrivateKey};
 
-#[cfg(all(feature = "test-dependencies", feature = "zfuture"))]
-use crate::consensus::BranchId;
-
 use super::{
     components::Amount,
     sighash::{signature_hash, SignableInput},