> Also it will be useful to produce warning when polymorphic comparison
> occurs.

Here's another problem: I wrote about 20,000 lines where I used the built in
equality for
a particular type (that represented terms in a theorem prover).  Now I want
to implement
my own equality function on the type, and never user built-in equality.  I
can see 
Ocaml has generally made the right choice in not having
equality types like SML, but in this situation some sort of annotation +
warning would
be incredibly useful, since as it stands the Ocaml type system doesn't help
me find all those horrible
uses of built-in equality that I coded into my program, when you really feel
like it should...

Don

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