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  • #959

Closed
Open
Opened Oct 23, 2006 by Ian Lynagh <igloo@earth.li>@trac-igloo

Debugging info(?) leaks out: "Urk! Inventing strangely-kinded void TyCon"

With GHC 6.6, this module:

module G where

testL = foo undefined

class Foo t where
    foo :: m a -> t m a

leaks some debugging info(?):

Urk! Inventing strangely-kinded void TyCon:
    :t{tc ae2}
    (* -> *) -> * -> *

tmp.hs:4:8:
    Ambiguous type variable `t' in the constraint:
      `Foo t' arising from use of `foo' at tmp.hs:4:8-20
    Possible cause: the monomorphism restriction applied to the following:
      testL :: forall (m :: * -> *) a. t m a (bound at tmp.hs:4:0)
    Probable fix: give these definition(s) an explicit type signature
                  or use -fno-monomorphism-restriction

I haven't managed to get this message in an acceptable program.

(found by fasta on IRC)

Trac metadata
Trac field Value
Version 6.6
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
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Blocking
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Operating system Unknown
Architecture Unknown
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Reference: ghc/ghc#959