[GHC] #12885: "too many iterations" causes constraint solving issue.

[GHC]

#12885: "too many iterations" causes constraint solving issue.
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        Reporter:  judahj            |                Owner:
            Type:  bug               |               Status:  merge
        Priority:  normal            |            Milestone:  8.0.3
       Component:  Compiler          |              Version:  8.0.2-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by judahj):

 Thanks for the quick response.  It's not critical to fix this in 8.0.2.
 In particular, Simon's diagnosis helped point me to the workaround of
 replacing `MyTypes` with a regular class:

 {{{
 class MyTypes (as :: [*]) where

 instance MyTypes '[] where
 instance (MyType a, MyTypes as) => MyTypes (a ': as) where
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12885#comment:4>
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