Kind error in GHC-7.4.1, works in GHC-7.2.2

[Simon Peyton-Jones]

It should not have worked before.  Consider

	I#  $   3#

($) is a polymorphic function and takes two *pointer* arguments.  If we actually called it with I# and 3# as arguments we might seg-fault when we call the GC when allocating the box.  

Polymorphic type variables (in this case in the type of ($)) can only be instantiated with boxed types.

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-
| users-bounces at haskell.org] On Behalf Of Roel van Dijk
| Sent: 09 February 2012 19:57
| To: glasgow-haskell-users at haskell.org
| Subject: Kind error in GHC-7.4.1, works in GHC-7.2.2
| 
| Hello,
| 
| I have some code that compiled fine in GHC-7.2.2 but fails in
| GHC-7.4.1 with a kind error.
| 
| 
| {-# LANGUAGE MagicHash, NoImplicitPrelude, PackageImports #-}
| import "base" Data.Function ( ($) )
| import "base" GHC.Exts ( Int(I#) )
| import "base" Prelude ( Integral, fromIntegral, toInteger )
| import "integer-gmp" GHC.Integer.Logarithms ( integerLogBase# )
| 
| intLog :: (Integral a) => a -> a
| intLog x = fromIntegral $ I# $ integerLogBase# 10 (toInteger x)
| 
| 
| This results in the following error:
| 
|     Couldn't match kind `#' against `*'
|     In the second argument of `($)', namely
|       `I# $ integerLogBase# 10 (toInteger x)'
|     In the expression:
|       fromIntegral $ I# $ integerLogBase# 10 (toInteger x)
|     In an equation for `intLog':
|         intLog x = fromIntegral $ I# $ integerLogBase# 10 (toInteger x)
| 
| 
| Simply eliminating some $'s using parenthesis solves the problem:
| 
| intLog x = fromIntegral $ I# (integerLogBase# 10 (toInteger x))
| 
| Why do I get the above kind error? Could it be a bug in GHC?
| 
| _______________________________________________
| Glasgow-haskell-users mailing list
| Glasgow-haskell-users at haskell.org
| http://www.haskell.org/mailman/listinfo/glasgow-haskell-users