[Nice-commit] Nice/src/mlsub/typing/lowlevel Engine.java,1.37,1.38

[Daniel B. <bo...@us...>]

Update of /cvsroot/nice/Nice/src/mlsub/typing/lowlevel
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv22896/src/mlsub/typing/lowlevel

Modified Files:
	Engine.java 
Log Message:
Do not allow a soft type variable to become greater than Object if it is
already constrained to be smaller than another type, as that is obviously
unsafe.


Index: Engine.java
===================================================================
RCS file: /cvsroot/nice/Nice/src/mlsub/typing/lowlevel/Engine.java,v
retrieving revision 1.37
retrieving revision 1.38
diff -C2 -d -r1.37 -r1.38
*** Engine.java	9 Jun 2005 11:56:59 -0000	1.37
--- Engine.java	17 Jun 2005 14:14:08 -0000	1.38
***************
*** 269,278 ****
                   rigid element, it will have its type.
                   it is still possible for it to be greater than Top
!                  (and therefore equal to Top). For this, we just need to
!                  forget its previous kind.
                */
                if (k1 == mlsub.typing.TopMonotype.TopKind.instance &&
                    e2 instanceof mlsub.typing.MonotypeVar &&
!                   ! isRigid(e2))
                  {
                    ((mlsub.typing.MonotypeVar) e2).resetKind(k1);
--- 269,279 ----
                   rigid element, it will have its type.
                   it is still possible for it to be greater than Top
!                  (and therefore equal to Top), provided it is "free upwards",
!                  that is, has no constraint to be smaller than another element.
!                  For this, we just need to forget its previous kind.
                */
                if (k1 == mlsub.typing.TopMonotype.TopKind.instance &&
                    e2 instanceof mlsub.typing.MonotypeVar &&
!                   ! isRigid(e2) && isFreeUpwards(e2))
                  {
                    ((mlsub.typing.MonotypeVar) e2).resetKind(k1);
***************
*** 341,344 ****
--- 342,346 ----
    }
  
+   public static final int INVALID = -1;
    private static final int FLOATING = -3;
    private static final int RIGID = -4;
***************
*** 358,361 ****
--- 360,388 ----
    }
  
+   static boolean isFreeUpwards(Element e)
+   {
+     if (e instanceof mlsub.typing.Monotype)
+       {
+         mlsub.typing.Monotype m = (mlsub.typing.Monotype) e;
+ 
+         // If there is a constructed equivalent, it is the one that
+         // has been getting the constraints (in particular its head).
+         m = m.equivalent();
+         if (m.head() != null)
+           e = m.head();
+         else
+           e = m;
+       }
+ 
+     if (e.getId() == FLOATING)
+       /// XXX check frozen leqs?
+       return true;
+ 
+     if (e.getId() < 0)
+       return false;
+ 
+     return getConstraint(e.getKind()).isFreeUpwards(e);
+   }
+ 
    /****************************************************************
     * Simplification
***************
*** 1001,1004 ****
--- 1028,1046 ----
      }
  
+ 
+     boolean isFreeUpwards(Element e)
+     {
+       final int id = e.getId();
+ 
+       // If there is any i with a id <: i constraint, return false
+       // TODO: handle cases when id <: i where i is non rigid, but not free
+       // upwards
+       for (int i = 0; i < k0.firstNonRigid(); i++)
+         if (i != id && k0.wasEntered(id, i))
+           return false;
+ 
+       return true;
+     }
+ 
      void mark()
      {