Possible bug in unification about links HOT 3 CLOSED

var db = database "stefan";

var exists = compose(not, empty);

typename Data = (parent : Int, value  : String);

typename CompilationContext = TableHandle(Data,Data,Data);

sig filterConstraint : (CompilationContext) ~> (Data) -> Bool
fun filterConstraint (data) {
  var aa = fun (x) {
             for (text <-- data)
             where ( true )
               [(val = text.value)]
             };
  fun (x) {
    exists(
      for (a <- aa(x))
      where (a.val == "b")
        [()]
    )
  }
}

var data = table ("ciawfb_data") with Data from db;
var filter = filterConstraint(data);
query {
  for (r <-- data)
  where (filter(r))
    [r]
}

var exists = compose(not, empty);

sig filterConstraint : () -> Bool
fun filterConstraint () {
  exists([()])
}

query {
  [(x=filterConstraint())]
}

fun exists(xs) {not(empty(xs))}

var exists = fun (xs) {compose(not, empty)(xs)};