chore(brillig): Fix brillig radix instruction return vector size (#2350)

crates/nargo_cli/tests/execution_success/brillig_to_le_bytes/src/main.nr

@@ -1,14 +1,13 @@
 use dep::std;
 
-unconstrained fn main(x : Field) -> pub [u8; 4] {
+unconstrained fn main(x : Field) -> pub [u8; 31] {
     // The result of this byte array will be little-endian
     let byte_array = x.to_le_bytes(31);
-    let mut first_four_bytes = [0; 4];
-    for i in 0..4 {
-        first_four_bytes[i] = byte_array[i];
+    assert(byte_array.len() == 31);
+
+    let mut bytes = [0; 31];
+    for i in 0..31 {
+        bytes[i] = byte_array[i];
     }
-    // Issue #617 fix
-    // We were incorrectly mapping our output array from bit decomposition functions during acir generation
-    first_four_bytes[3] = byte_array[31];
-    first_four_bytes
+    bytes
 }

crates/nargo_cli/tests/execution_success/to_le_bytes/src/main.nr

@@ -1,14 +1,13 @@
 use dep::std;
 
-fn main(x : Field) -> pub [u8; 4] {
+fn main(x : Field) -> pub [u8; 31] {
     // The result of this byte array will be little-endian
     let byte_array = x.to_le_bytes(31);
-    let mut first_four_bytes = [0; 4];
-    for i in 0..4 {
-        first_four_bytes[i] = byte_array[i];
+    assert(byte_array.len() == 31);
+
+    let mut bytes = [0; 31];
+    for i in 0..31 {
+        bytes[i] = byte_array[i];
     }
-    // Issue #617 fix
-    // We were incorrectly mapping our output array from bit decomposition functions during acir generation
-    first_four_bytes[3] = byte_array[31];
-    first_four_bytes
+    bytes
 }

crates/noirc_evaluator/src/ssa/acir_gen/acir_ir/acir_variable.rs

@@ -780,16 +780,6 @@ impl AcirContext {
             limb_vars.reverse();
         }
 
-        // For legacy reasons (see #617) the to_radix interface supports 256 bits even though
-        // FieldElement::max_num_bits() is only 254 bits. Any limbs beyond the specified count
-        // become zero padding.
-        let max_decomposable_bits: u32 = 256;
-        let limb_count_with_padding = max_decomposable_bits / bit_size;
-        let zero = self.add_constant(FieldElement::zero());
-        while limb_vars.len() < limb_count_with_padding as usize {
-            limb_vars.push(AcirValue::Var(zero, result_element_type.clone()));
-        }
-
         Ok(vec![AcirValue::Array(limb_vars.into())])
     }