private boolean isStringLikeExpression(Expression expression) {
    if (expression instanceof ConstantExpression) {
      return expression.getType().getTypeClass() == String.class;
    }
    if (expression instanceof GStringExpression) return true;
    return false;
  }
Treat the nonsensical `!!` prefix as opt-out from implicit conditions
spock-core/src/main/java/org/spockframework/compiler/ConditionRewriter.java