[Nice-commit] Nice/src/nice/tools/typing Types.java,1.5,1.6

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

Update of /cvsroot/nice/Nice/src/nice/tools/typing
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv26138/src/nice/tools/typing

Modified Files:
	Types.java 
Log Message:
Do not allow overriding involving specialization of type parameters, as this is
unsafe since dispatch does not consider type parameters.


Index: Types.java
===================================================================
RCS file: /cvsroot/nice/Nice/src/nice/tools/typing/Types.java,v
retrieving revision 1.5
retrieving revision 1.6
diff -C2 -d -r1.5 -r1.6
*** Types.java	2 Mar 2004 12:18:41 -0000	1.5
--- Types.java	17 Mar 2004 00:36:46 -0000	1.6
***************
*** 273,275 ****
--- 273,324 ----
      return true;
    }
+ 
+   /**
+      @returns true if the spec type specializes type parameters of the original
+        type (which can not be checked at runtime during dispatch, and therefore
+        should not count as overriding).
+   */
+   public static boolean typeParameterDispatch(Polytype spec, Polytype origin)
+   {
+     Monotype[] originalParams = parameters(origin);
+ 
+     if (originalParams.length == 0)
+       return false;
+ 
+     Typing.enter();
+     try {
+ 
+       try {
+         Polytype clonedSpec = spec.cloneType();
+ 
+         Constraint.enter(origin.getConstraint());
+         Constraint.enter(clonedSpec.getConstraint());
+ 
+         // For all argument types ...
+         Monotype[] args = MonotypeVar.news(originalParams.length);
+         Typing.introduce(args);
+ 
+         // ... that can be used for the first method ...
+         Typing.leq(args, originalParams);
+ 
+         // ... and that will be dispatched to the specialized method ...
+         Typing.leqHead(args, parameters(clonedSpec));
+ 
+         Typing.implies();
+ 
+         // ... check that those args fit in the 'specialized' method ...
+         Constraint.enter(spec.getConstraint());
+         Typing.leq(args, parameters(spec));
+       }
+       finally {
+         Typing.leave();
+       }
+     }
+     catch (TypingEx ex) {
+       return true;
+     }
+ 
+     // OK, no covariant dispatch
+     return false;
+   }
  }