[GHC] #14662: Partial type signatures + mutual recursion = confusion

[GHC]

#14662: Partial type signatures + mutual recursion = confusion
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Interestingly, this was changed '''three days ago'''.

 Now, in HEAD, Example 3 and Example 4 are rejected with

 {{{
     • Can't quantify over ‘b’
         bound by the partial type signature: g :: forall b. _ -> b -> b
 }}}

 I think this is an improvement in behavior, but it underscores how squishy
 this all is.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14662#comment:3>
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