Pinq\Queries\Functions\ProjectionBase::getReturnValueExpression PHP Method

    public final function getReturnValueExpression()
    {
        $this->verifyNotInternal(__FUNCTION__);
        return $this->returnValueExpression;
    }

 public function compileReturn(ProjectionBase $projectionFunction)
 {
     $returnExpression = $projectionFunction->getReturnValueExpression() ?: O\Expression::value(null);
     return $this->compile($returnExpression, $projectionFunction);
 }