Matthias\SymfonyServiceDefinitionValidator\ArgumentValidator::validateExpressionResult PHP Method

    private function validateExpressionResult($className, Expression $expression, $allowsNull, ExpressionLanguage $expressionLanguage)
    {
        try {
            $result = $expressionLanguage->evaluate($expression, array('container' => $this->containerBuilder));
        } catch (\Exception $exception) {
            throw new InvalidExpressionException($expression, $exception);
        }
        if ($result === null) {
            if ($allowsNull) {
                return;
            }
            throw new TypeHintMismatchException(sprintf('Argument for type-hint "%s" is an expression that evaluates to null, which is not allowed', $className));
        }
        if (!is_object($result)) {
            throw new TypeHintMismatchException(sprintf('Argument for type-hint "%s" is an expression that evaluates to a non-object', $className));
        }
        $resultingClass = get_class($result);
        $this->validateClass($className, $resultingClass);
    }