Value equality

[Brian Goetz]

> another possible choice is to not allow == on value type (and on a T bound by any),
> it makes the semantics far easier to understand, you can only use == on something which fit into a 32/64 bits,
> in that case primitive types need to have an equals.
>

This wouldn't go well when migrating existing generic code to 
any-generic.  Consider code like:

class Bag<T> {
     void contains(T t) {
         for (T e : this)
             if (t == e || t.equals(e))
                 return true;
         return false;
     }

When we anyfy this code, if == were not allowed on values, this code 
would break.  (You might suggest in this case we constant-fold it to 
false, but that is not likely to seem intuitive either.)

Would be nice to minimize the amount of change to anyfy this case, 
beyond sticking an 'any' in front of T -- existing well-behaved generic 
code should require little or no change (for some definition of 
'well-behaved').