Re: [Haskell] ANNOUNCE: GHC version 7.6.1

On Thu, Sep 6, 2012 at 10:33 AM, Felipe Almeida Lessa wrote:

On Thu, Sep 6, 2012 at 1:05 PM, Ian Lynagh 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