GHC tells me to use RankNTypes when it's already enabled
I was stumped for a while today because GHC kept telling me to turn on RankNTypes
even when it was already enabled! I eventually realized this was the problem:
{-# LANGUAGE RankNTypes #-}
module Bug where
foo :: foral a. a -> a
foo x = x
$ ghc Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
Bug.hs:4:15: error:
Illegal symbol '.' in type
Perhaps you intended to use RankNTypes or a similar language
extension to enable explicit-forall syntax: forall <tvs>. <type>
That is, the real culprit was misspelling forall
as foral
.
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |