[GHC] #4186: -dcore-lint and -fstrict-dicts break anything that uses a type class

[GHC]

#4186: -dcore-lint and -fstrict-dicts break anything that uses a type class
-----------------------------+----------------------------------------------
  Reporter:  LouisWasserman  |          Owner:  simonpj         
      Type:  bug             |         Status:  closed          
  Priority:  normal          |      Milestone:  7.2.1           
 Component:  Compiler        |        Version:  6.12.3          
Resolution:  fixed           |       Keywords:                  
  Testcase:                  |      Blockedby:                  
Difficulty:                  |             Os:  Unknown/Multiple
  Blocking:                  |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown    |  
-----------------------------+----------------------------------------------
Changes (by batterseapower):

  * status:  new => closed
  * resolution:  => fixed


Old description:

> {{{
> lowasser at lowasser:~$ cat Foo2.hs
> module Foo2 where
>
> foo = return 0 :: IO Int
> lowasser at lowasser:~$ ghc --make Foo2 -fforce-recomp -fdicts-strict
> -XRank2Types -dcore-lint
> [1 of 1] Compiling Foo2             ( Foo2.hs, Foo2.o )
> *** Core Lint Errors: in result of Desugar ***
> {-# LINE 3 "Foo2.hs #-}:
>     [RHS of $dMonad_adw :: GHC.Base.Monad GHC.Types.IO]
>     Recursive or top-level binder has strict demand info: $dMonad_adw
>     Binder's demand info: T
> *** Offending Program ***
> Rec {
> Foo2.foo :: GHC.Types.IO GHC.Types.Int
> LclIdX
> []
> Foo2.foo =
>   letrec {
>     $dMonad_adw :: GHC.Base.Monad GHC.Types.IO
>     LclId
>     []
>     $dMonad_adw = GHC.Base.$fMonadIO;
>     return_adv :: forall a_adu. a_adu -> GHC.Types.IO a_adu
>     LclId
>     []
>     return_adv = GHC.Base.return @ GHC.Types.IO $dMonad_adw; } in
>   return_adv @ GHC.Types.Int (GHC.Types.I# 0)
> foo_adx :: GHC.Types.IO GHC.Types.Int
> LclId
> []
> foo_adx = Foo2.foo
> end Rec }
>
> *** End of Offense ***
>

> <no location info>:
> Compilation had errors
>
> }}}
>
> [ticket:4181] may be an instance of this.

New description:

 {{{
 lowasser at lowasser:~$ cat Foo2.hs
 module Foo2 where

 foo = return 0 :: IO Int
 lowasser at lowasser:~$ ghc --make Foo2 -fforce-recomp -fdicts-strict
 -XRank2Types -dcore-lint
 [1 of 1] Compiling Foo2             ( Foo2.hs, Foo2.o )
 *** Core Lint Errors: in result of Desugar ***
 {-# LINE 3 "Foo2.hs #-}:
     [RHS of $dMonad_adw :: GHC.Base.Monad GHC.Types.IO]
     Recursive or top-level binder has strict demand info: $dMonad_adw
     Binder's demand info: T
 *** Offending Program ***
 Rec {
 Foo2.foo :: GHC.Types.IO GHC.Types.Int
 LclIdX
 []
 Foo2.foo =
   letrec {
     $dMonad_adw :: GHC.Base.Monad GHC.Types.IO
     LclId
     []
     $dMonad_adw = GHC.Base.$fMonadIO;
     return_adv :: forall a_adu. a_adu -> GHC.Types.IO a_adu
     LclId
     []
     return_adv = GHC.Base.return @ GHC.Types.IO $dMonad_adw; } in
   return_adv @ GHC.Types.Int (GHC.Types.I# 0)
 foo_adx :: GHC.Types.IO GHC.Types.Int
 LclId
 []
 foo_adx = Foo2.foo
 end Rec }

 *** End of Offense ***


 <no location info>:
 Compilation had errors

 }}}

 [ticket:4181] may be an instance of this.

--

Comment:

 I can't reproduce this with HEAD (actually, 7.1.20110517) so I'm closing
 the bug.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4186#comment:9>
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