fix: remove usage of u1 (#16)

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>

Author: vezenovm

src/encoding.nr

@@ -110,7 +110,7 @@ unconstrained fn __split_into_base4_5bit_slices(encoded: Field) -> [u32; 13] {
 /// Split an input Field element `e` (known to be 64 bits) into slices that can be efficiently composed to produce inputs to `EncodedChoose`
 unconstrained fn __decompose_e(e: Field) -> [u32; 9] {
     let mut r: [u32; 9] = [0; 9];
-    let mut bytes = e.to_le_bytes::<8>();
+    let bytes = e.to_le_bytes::<8>();
     let b8to14 = bytes[1] & 63;
     let b14to16 = bytes[1] >> 6;
     let b16to18 = bytes[2] & 3;
@@ -142,7 +142,7 @@ unconstrained fn __decompose_e(e: Field) -> [u32; 9] {
 /// Split an input Field element `a` (known to be 64 bits) into slices that can be efficiently composed to produce inputs to `EncodedMajority`
 unconstrained fn __decompose_a(a: Field) -> [u32; 9] {
     let mut r: [u32; 9] = [0; 9];
-    let mut bytes = a.to_le_bytes::<8>();
+    let bytes = a.to_le_bytes::<8>();
     let b24to28 = bytes[3] & 15;
     let b28to32 = bytes[3] >> 4;
     let b32to34 = bytes[4] & 3;
@@ -210,7 +210,7 @@ unconstrained fn __decompose_witness(w: Field) -> [u32; 12] {
 /// # Cost
 /// 40 gates
 pub(crate) fn encode_message_extension(w: Field) -> EncodedWitness {
-    //Safety: split input into slices with the following bit sizes:
+    // Safety: split input into slices with the following bit sizes:
     //   1, 5, 1, 1, 8, 3, 8, 8, 8, 9, 9, 3
     //        We need to validate the correctness of these slice claims by asserting their sum equals `w`,
     //        and we also need to validate the bit range of each slice

src/lib.nr

@@ -64,7 +64,7 @@ pub fn sha512_compression(_input: INT_BLOCK, _state: STATE) -> STATE {
 /// Input is the message to be hashed, produces a 64-byte output
 /// The `IS_SHA512` generic is used to toggle whether a SHA384 or SHA512 hash is desired
 /// (the only diff between SHA384/SHA512 are different initial starting constants, and the SHA384 hash output is truncated)
-fn digest<let N: u32, let IS_SHA512: u1>(msg: [u8; N]) -> [u8; 64] {
+fn digest<let N: u32, let IS_SHA512: u8>(msg: [u8; N]) -> [u8; 64] {
     // noir-fmt:ignore
     let mut h: [u64; 8] = if IS_SHA512 == 1 {
         SHA512_INITIAL_HASH_VALUES
@@ -121,7 +121,8 @@ fn digest<let N: u32, let IS_SHA512: u1>(msg: [u8; N]) -> [u8; 64] {
 /// The `IS_SHA512` generic is used to toggle whether a SHA384 or SHA512 hash is desired
 ///
 /// (the only diff between SHA384/SHA512 are different initial starting constants, and the SHA384 hash output is truncated)
-fn digest_var<let N: u32, let IS_SHA512: u1>(msg: BoundedVec<u8, N>) -> [u8; 64] {
+fn digest_var<let N: u32, let IS_SHA512: u8>(msg: BoundedVec<u8, N>) -> [u8; 64] {
+    std::static_assert(IS_SHA512 <= 1, "IS_SHA512 must be 0 or 1");
     // noir-fmt:ignore
     let mut h: [u64; 8] = if IS_SHA512 == 1 {
         SHA512_INITIAL_HASH_VALUES
@@ -190,11 +191,11 @@ fn digest_var<let N: u32, let IS_SHA512: u1>(msg: BoundedVec<u8, N>) -> [u8; 64]
 /// methods here are interface-compatible with sha256 blackbox fns
 pub mod sha512 {
     pub fn digest<let N: u32>(msg: [u8; N]) -> [u8; 64] {
-        crate::digest::<_, 1_u1>(msg)
+        crate::digest::<_, 1_u8>(msg)
     }
 
     pub fn sha512_var<let N: u32>(msg: BoundedVec<u8, N>) -> [u8; 64] {
-        crate::digest_var::<_, 1_u1>(msg)
+        crate::digest_var::<_, 1_u8>(msg)
     }
 
     // Fuzz testing the sha512 implementation
@@ -288,7 +289,7 @@ pub mod sha512 {
 
 pub mod sha384 {
     pub fn digest<let N: u32>(msg: [u8; N]) -> [u8; 48] {
-        let full_result = crate::digest::<_, 0_u1>(msg);
+        let full_result = crate::digest::<_, 0_u8>(msg);
         let mut r: [u8; 48] = [0; 48];
         for i in 0..48 {
             r[i] = full_result[i];
@@ -297,7 +298,7 @@ pub mod sha384 {
     }
 
     pub fn sha384_var<let N: u32>(msg: BoundedVec<u8, N>) -> [u8; 48] {
-        let full_result = crate::digest_var::<_, 0_u1>(msg);
+        let full_result = crate::digest_var::<_, 0_u8>(msg);
         let mut r: [u8; 48] = [0; 48];
         for i in 0..48 {
             r[i] = full_result[i];