GADT problems

[Philippa Cowderoy]

[sent to list as well this time]

On Mon, 2008-09-15 at 14:00 +0100, Simon Peyton-Jones wrote:
> Ah -- you used an *existential* there!  Yes, existentially-bound type variables are rigid.  They stand for themselves, as it were.
> 
> That resolves the mystery -- but it existentials admittedly introduce a new complication
> 
> How should this be clarified?
> 

For me, "existentially-bound variables are rigid" works well enough.
They're a somewhat non-obvious case of 'coming from an annotation'
though, and it does warrant mention.

-- 
Philippa Cowderoy <flippa at flippac.org>