DynamicKeyName(Expression target,
    Expression nameExpression) 
{
        this.target = target; 
        this.nameExpression = nameExpression;
}

 Expression _deepClone(String name,
    Expression subst) 
{
    	return new DynamicKeyName(target.deepClone(name, subst), nameExpression.deepClone(name, subst));
}

 TemplateModel _getAsTemplateModel(Environment env) throws TemplateException 
{
        TemplateModel targetModel = target.getAsTemplateModel(env);
        assertNonNull(targetModel, target, env);
        if (nameExpression instanceof Range) {
            return dealWithRangeKey(targetModel, (Range) nameExpression, env);
        }
        TemplateModel keyModel = nameExpression.getAsTemplateModel(env);
        if(keyModel == null) {
            if(env.isClassicCompatible()) {
                keyModel = TemplateScalarModel.EMPTY_STRING;
            }
            else {
                assertNonNull(keyModel, nameExpression, env);
            }
        }
        if (keyModel instanceof TemplateNumberModel) {
            int index = EvaluationUtil.getNumber(keyModel, nameExpression, env).intValue();
            return dealWithNumericalKey(targetModel, index, env);
        }
        if (keyModel instanceof TemplateScalarModel) {
            String key = EvaluationUtil.getString((TemplateScalarModel)keyModel, nameExpression, env);
            return dealWithStringKey(targetModel, key, env);
        }
        throw invalidTypeException(keyModel, nameExpression, env, "number, range, or string");
}

 public String getCanonicalForm() 
{
        return target.getCanonicalForm() 
               + "[" 
               + nameExpression.getCanonicalForm() 
               + "]";
}

 boolean isLiteral() 
{
        return constantValue != null || (target.isLiteral() && nameExpression.isLiteral());
}