I've written a trigger but keep getting the same error, I'm unsure what the error is, when I run my test class the message reads: Variable does not exist: productIdToQli

My trigger is below and I've boldened the issue, does anyone know what Im doing wrong? 

trigger QuotetoOppSync on OpportunityLineItem (after insert) {

//Query opportunity line items
    List<OpportunityLineItem> olis= [SELECT Id, PricebookEntry.Product2Id, OpportunityId, Start_date__c, Duration__c,
                             End_date__c FROM
                                    OpportunityLineItem WHERE Id IN: Trigger.new];
    //Get a list of all opp ids:
    List<id> oppids= new List<id>();
    for (opportunityLineItem oli:olis){
        oppIds.add(oli.OpportunityId);
    }
   
    //Query QuoteLineItems by Opportunity ID
    Map<Id, QuotelineItem> producttoQli = new Map<Id, QuoteLineItem>();
    List<QuoteLineItem> qlis=[SELECT Id, PricebookEntry.Product2Id, Start_date__c, Duration__c,
                             End_date__c, Quote.OpportunityId FROM QuoteLineItem WHERE Quote.OpportunityId IN :oppIds];
    if(qlis!=null){
        for(QuoteLineItem qli:qlis){
            productIdToQli.put(qli.PricebookEntry.Product2Id, qli);
        }
    }
//Iterate across quote line items
    for (OpportunityLineItem oli : Olis) {
       
        Quotelineitem qli=productIdToQli.get(oli.PricebookEntry.productId);
        if(qli!=null){
            if(qli.Start_Date__c!=null){ oli.Start_Date__c=qli.Start_Date__c;}
            If(qli.Duration__c!=null) {oli.Duration__c=qli.Duration__c;}
            if(qli.End_Date__c!=null){ oli.End_Date__c=qli.End_Date__c;}
        }
    }
    //Update
    update olis;
}