[GHC] #4364: Template Haskell: Cycle in type synonym declarations

[GHC]

#4364: Template Haskell: Cycle in type synonym declarations
----------------------------------------+-----------------------------------
    Reporter:  igloo                    |        Owner:  simonpj     
        Type:  bug                      |       Status:  new         
    Priority:  high                     |    Milestone:  7.0.1       
   Component:  Compiler (Type checker)  |      Version:  7.1         
    Keywords:                           |     Testcase:              
   Blockedby:                           |   Difficulty:              
          Os:  Unknown/Multiple         |     Blocking:              
Architecture:  Unknown/Multiple         |      Failure:  None/Unknown
----------------------------------------+-----------------------------------
 `type-level-numbers-0.1` doesn't build with 7.0.1 RC 1. Here's the
 essence:

 {{{
 {-# LANGUAGE TemplateHaskell #-}
 module Q where

 data Z

 type N0 = $( [t| Z |] )
 type N1 = $( [t| Z |] )
 }}}

 {{{
 $ ghc --make m.hs
 [1 of 1] Compiling Q                ( m.hs, m.o )

 m.hs:7:1:
     Cycle in type synonym declarations:
       m.hs:7:1-23: type N0 = $([t| Z |])
       m.hs:8:1-23: type N1 = $([t| Z |])
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4364>
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