[GHC] #7220: Confusing error message in type checking related to type family, fundep, and higher-rank type

[GHC]

#7220: Confusing error message in type checking related to type family, fundep,
and higher-rank type
------------------------------+---------------------------------------------
 Reporter:  tsuyoshi          |          Owner:                         
     Type:  bug               |         Status:  new                    
 Priority:  normal            |      Component:  Compiler (Type checker)
  Version:  7.6.1-rc1         |       Keywords:                         
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple       
  Failure:  None/Unknown      |       Testcase:                         
Blockedby:                    |       Blocking:                         
  Related:                    |  
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Comment(by tsuyoshi):

 When I posted this report, I had been overlooking `TF` in the “actual
 type” part of the error message.  Now the error message at least makes
 some sense.

 (Although I do not fully understand why the code is rejected in the first
 place, I think that I have to understand the algorithm used by the type
 checker to understand this.)

 I am not sure whether this bug report still makes sense or not.  If not,
 please close it.  Sorry about this.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7220#comment:1>
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