[Haskell] ANNOUNCE: GHC version 7.6.1

[Thomas DuBuisson]

On Thu, Sep 6, 2012 at 10:33 AM, Felipe Almeida Lessa
<felipe.lessa at gmail.com> wrote:
> On Thu, Sep 6, 2012 at 1:05 PM, Ian Lynagh <ian at well-typed.com> wrote:
>>   * It is now possible to defer type errors until runtime using the
>>     -fdefer-type-errors flag.
>
> I don't remember if this was part of the motivation in creating this
> feature, but it has a nice use case:  asserting on a test suite that
> something should *not* type check.

We're getting more meta than Haskell provides cleanly, but all
significant uses I can currently think of for something like that
would require universal quantification over types:

Forall types t.
  t `notElem` someTypes --> fails (tyUnification t MyType)

I'm curious what your thinking is here.

Thomas