examples/Markus/polymorphic_value_shouldfail.spl

   1 // This is an example why you need the value restriction.
   2 // This program should give a type error in some way.
   3
   4 // The empty list [] usually has polymorphic type forall a.[a], but you
   5 // cannot give the variable l this type. See below what can go wrong.
   6
   7 f()
   8 {
   9   var l = [];
  10   // If l has polymorphic type forall a . [a], the next two lines are possible.
  11   l = 1:l;
  12   l = True:l;
  13   return;
  14 }
  15 main() {return;}