| CODE THAT PRODUCES THE ERROR
|
| module Foo where
|
| import MutableArray
| import ByteArray
| import ST
| import PrelArrExtra
|
| class Foo t where
|
| foo :: t -> ByteArray ix
|
| instance Ix ix => Foo (forall s. MutableByteArray s ix) where
|
| foo x = runST(unsafeFreezeByteArray x)
No, it's not legal to have a for-all type in the argument of a type
constructor like that!
Foo (forall s. stuff) is Not Kosher
But it's a compiler bug that it's not caught more gracefully.
-fglasgow-exts is too liberal! Thanks for reporting it.
Simon
