Type Tests against Open Records

[DavePearce]

There is currently a bug related to type testing against open records. The following from OpenRecord_Valid_4 illustrates:

type OpenRecord is {int x, ...}

function getField(OpenRecord r) -> int:
    if r is {int x}:
        return r.x
    else:
        if r is {int y, int x}:
            return r.x + r.y
        else:
            return -r.x

This is translated as:

function OpenRecord_Valid_4$getField$Q10OpenRecord(r) {
   if(is$Q10OpenRecordr1I1x(r))  {
      return r.x;
   } else  { ... }
}
function is$Q10OpenRecordr1I1x(v) {
   if(((typeof v.x) === "undefined") || ((typeof v.x) !== "number"))  {
      return false;
   }
   return true;
}

We can see that the test is not sufficient because it's not checking the number of fields.