Function EvalOptionalOr

eval/eval/optional_or_step.cc:126–163

Shared implementation for optional or. If return value is Ok, the result is assigned to the result reference argument.

// If return value is Ok, the result is assigned to the result reference
// argument.
absl::Status EvalOptionalOr(OptionalOrKind kind, const Value& lhs,
                            const Value& rhs, const AttributeTrail& lhs_attr,
                            const AttributeTrail& rhs_attr, Value& result,
                            AttributeTrail& result_attr) {
  if (InstanceOf<ErrorValue>(lhs) || InstanceOf<UnknownValue>(lhs)) {
    result = lhs;
    result_attr = lhs_attr;
    return absl::OkStatus();
  }

  auto lhs_optional_value = As<OptionalValue>(lhs);
  if (!lhs_optional_value.has_value()) {
    result = MakeNoOverloadError(kind);
    result_attr = AttributeTrail();
    return absl::OkStatus();
  }

  if (lhs_optional_value->HasValue()) {
    if (kind == OptionalOrKind::kOrValue) {
      result = lhs_optional_value->Value();
    } else {
      result = lhs;
    }
    result_attr = lhs_attr;
    return absl::OkStatus();
  }

  if (kind == OptionalOrKind::kOrOptional && !InstanceOf<ErrorValue>(rhs) &&
      !InstanceOf<UnknownValue>(rhs) && !InstanceOf<OptionalValue>(rhs)) {
    result = MakeNoOverloadError(kind);
    result_attr = AttributeTrail();
    return absl::OkStatus();
  }

  result = rhs;
  result_attr = rhs_attr;
  return absl::OkStatus();
}

absl::Status OptionalOrStep::Evaluate(ExecutionFrame* frame) const {
  if (!frame->value_stack().HasEnough(2)) {