On Tue, Sep 28, 2010 at 10:10 PM, David Fox
I'm seeing errors like this in various places, which I guess are coming from the new type checker:
Data/Array/Vector/Prim/BUArr.hs:663:3: Couldn't match type `s' with `s3' because this skolem type variable would escape: `s3' This skolem is bound by the polymorphic type `forall s. ST s a' The following variables have types that mention s fill0 :: MBUArr s e -> ST s Int (bound at Data/Array/Vector/Prim/BUArr.hs:669:5) In the first argument of `runST', namely `(do { marr <- newMBU n; n' <- fill0 marr; unsafeFreezeMBU marr n' })'
GHC no longer generalizes local bindings - which means that while previously the 'where' defined function would have had a type:
fill0 :: forall s . ... -> ST s Int
Where the elipsis indicates an unspecified portion of the local type signature. I would recommend writing a type signature, but that requires writing a type signature for it's helper function:
fill s i = ...
Except I don't know how to write a type signature for this. The value 's' passed in is bound by pattern matching on this guy's constructor: data Stream a = forall s. Stream (s -> Step s a) !s Int in the top-level function, so I don't even know if it has a type I can name. I'll try to boil this down to something I can put on hpaste. Antoine