message: Special case for int+int
  Summary: This check is cheap, so try it first.
diff: @@ -529,6 +529,16 @@ impl<'v> Value<'v> {
  /// Add two [`Value`]s together. Will first try using [`radd`](StarlarkValue::radd),
  /// before falling back to [`add`](StarlarkValue::add).
  pub fn add(self, other: Value<'v>, heap: &'v Heap) -> anyhow::Result<Value<'v>> {
  + // Fast special case for ints.
  + if let Some(ls) = self.unpack_int() {
  + if let Some(rs) = other.unpack_int() {
  + // On overflow take the slow path below.
  + if let Some(sum) = ls.checked_add(rs) {
  + return Ok(Value::new_int(sum));
  + }
  + }
  + }
  +
  // Addition of string is super common and pretty cheap, so have a special case for it.
  if let Some(ls) = self.unpack_str() {
  if let Some(rs) = other.unpack_str() {
  