Can't emit an array of obligations formed from an array of values about ergo HOT 1 OPEN

@frbrkoala Thanks for the bug report / feature request.

Just a quick update:

1. I was able to reproduce the issue. See the archive attached based on your example.
   [email protected]

2. The $coll exception is a runtime error which comes from an inconsistency between the Ergo type checker and the compiler. I think the intended behavior is for the suggested logic to fail type checking (with an error that the emit should be a singleton object).

3. This is a perfectly valid and useful requirement imho. I think there might be two ways to support this. First being your suggestion i.e., allow emit to take either a single item or an array (which would make it polymorphic). Second might be to keep emit over single items but generalize where emit is allowed and notably allow it use inside foreach. This would look something as follows (both options probably need work):

contract MyContractLogic over MyContract state State {
  
  //Iterate through an array of vendors and emit an event for each of them
  clause notifyVendors(request : NotifyVendorsReq) : NotifyVendorsRes emits VendorNotification[] {

    foreach vendor in contract.vendors
    return
       emit  VendorNotification {
          code: request.notificationCode,
          description: request.description,
          vendor: vendor
       };
    
    return NotifyVendorsRes{ output: "Received " ++ request.notificationCode ++ " " ++ request.description ++ " and sent notification to vendors " ++ toString(contract.vendors) }
  }
}

from ergo.