Rec = type {x:: int, y:: int}.

test = function(base:: int):: int; entry() {
  fields = intrinsic rec_fields("Rec"):: [string]; i12n(on()).
  
  result = loop fold(fields->field:: string, {undef, 0}->ctx):: {rec:: Rec, id:: int}
  {
    { (ctx["rec"]::Rec) : {[field] = base + ctx["id"] }, ctx["id"]+1 }:: {rec:: Rec, id:: int}
  }.
  
  result["rec"]["y"]
}