Coerce comprehension expression to var int in case of sets. Currently…

… this at least triggers an error message rather than crashing, but it will work as soon as var set comprehensions are supported. Fixes #135.

include/minizinc/ast.hh

@@ -643,6 +643,8 @@ namespace MiniZinc {
     Expression* where(void) const { return _where; }
     /// Return generator body
     Expression* e(void) const { return _e; }
+    /// Set generator body
+    void e(Expression* e0) { _e = e0; }
     /// Re-construct (used for copying)
     void init(Expression* e, Generators& g);
   };

lib/typecheck.cpp

@@ -918,6 +918,10 @@ namespace MiniZinc {
               "set comprehension expression must be scalar, but is `"
               +c.e()->type().toString(_env)+"'");
         tt.st(Type::ST_SET);
+        if (tt.isvar()) {
+          c.e(addCoercion(_env, _model, c.e(), Type::varint())());
+          tt.bt(Type::BT_INT);
+        }
       } else {
         if (c.e()->type().dim() != 0)
           throw TypeError(_env,c.e()->loc(),