[GHC] #10748: Associated type families regression

6 Aug 2015

      #10748: Associated type families regression
-------------------------------------+-------------------------------------
              Reporter:  slyfox      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
-------------------------------------+-------------------------------------
 The original code snippet is taken from synthesizer-core-0.7.1 from
 hackage:
 http://code.haskell.org/synthesizer/core/src/Synthesizer/Causal/Class.hs

 Here is the minimal example:

 {{{#!hs
 {-# LANGUAGE TypeFamilies #-}
 module M where

 class ProcessOf (SignalOf process) ~ process => C process where
    type SignalOf process :: * -> *
    type ProcessOf (signal :: * -> *) :: * -> * -> *
 }}}

 {{{
 $ ghc -c M.hs

 M.hs:4:1:
     The associated type ‘ProcessOf’
     mentions none of the type or kind variables of the class ‘C process’
     In the class declaration for ‘C’
 }}}

 ghc-7.8.4 was able to compile this.
 Is it a known new restriction of ghc or a regression?

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10748
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler