fix(ssa): Handle right shift with constants (#2481)

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

@@ -10,4 +10,14 @@ fn main(x: u64) {
 	// shifts on runtime values
 	assert(x << 1 == 128);
 	assert(x >> 2 == 16);
+
+	regression_2250();
 }
+
+fn regression_2250() {
+	let a: u1 = 1 >> 1;
+	assert(a == 0);
+
+	let b: u32 = 1 >> 32;
+	assert(b == 0);
+}

crates/noirc_evaluator/src/ssa/ir/instruction.rs

@@ -610,8 +610,8 @@ impl Binary {
 
         if let (Some(lhs), Some(rhs)) = (lhs, rhs) {
             // If the rhs of a division is zero, attempting to evaluate the divison will cause a compiler panic.
-            // Thus, we do not evaluate this divison as we want to avoid triggering a panic and a division by zero
-            // should fail to satisfy constraints laid down during ACIR generation.
+            // Thus, we do not evaluate this divison as we want to avoid triggering a panic,
+            // and division by zero should be handled by laying down constraints during ACIR generation.
             if matches!(self.operator, BinaryOp::Div) && rhs == FieldElement::zero() {
                 return SimplifyResult::None;
             }
@@ -756,6 +756,16 @@ impl Binary {
 
                 let lhs = truncate(lhs.try_into_u128()?, *bit_size);
                 let rhs = truncate(rhs.try_into_u128()?, *bit_size);
+
+                // The divisor is being truncated into the type of the operand, which can potentially
+                // lead to the rhs being zero.
+                // If the rhs of a division is zero, attempting to evaluate the divison will cause a compiler panic.
+                // Thus, we do not evaluate the division in this method, as we want to avoid triggering a panic,
+                // and the operation should be handled by ACIR generation.
+                if matches!(self.operator, BinaryOp::Div) && rhs == 0 {
+                    return None;
+                }
+
                 let result = function(lhs, rhs);
                 truncate(result, *bit_size).into()
             }

crates/noirc_evaluator/src/ssa/ssa_gen/context.rs

@@ -247,7 +247,7 @@ impl<'a> FunctionContext<'a> {
         self.builder.insert_binary(lhs, BinaryOp::Mul, pow)
     }
 
-    /// Insert ssa instructions which computes lhs << rhs by doing lhs/2^rhs
+    /// Insert ssa instructions which computes lhs >> rhs by doing lhs/2^rhs
     fn insert_shift_right(&mut self, lhs: ValueId, rhs: ValueId) -> ValueId {
         let base = self.builder.field_constant(FieldElement::from(2_u128));
         let pow = self.pow(base, rhs);