ANNOUNCE: GHC version 7.4.1

[Simon Peyton-Jones]

|    =============================================================
|     The (Interactive) Glasgow Haskell Compiler -- version 7.4.1
|    =============================================================
...
|   * There is a new feature kind polymorphism (-XPolyKinds).
|     A side-effect of this is that, when the extension is not enabled, in
|     certain circumstances kinds are now defaulted to * rather than being
|     inferred.

Just to clarify, kind polymorphism is in 7.4, but it's not a fully-supported feature.  We already know there are bugs, and it's not even fully implemented (notably, you can't give a polymorphic kind *signature* yet).  

But, except in so far as they represent regressions, we won't push bug fixes into the 7.4 branch.   Please DO give kind polymorphism a try, and DO report bugs; but if you want the fixes you'll need to use the HEAD.

Why did we do it this way? Because implementing kind polymorphism entailed quite a bit of code upheaval. If we hadn't put that upheaval in the branch we'd have ended up fixing other bugs twice, once in the branch and once in the HEAD.

Simon