[GHC] #13035: GHC enters a loop when partial type signatures and advanced type level code mix

[GHC]

#13035: GHC enters a loop when partial type signatures and advanced type level code
mix
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        Reporter:  xcmw              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"3540d1e1a23926ce0a8a6ae83a36f5f6b2497ccf/ghc"
 3540d1e1/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="3540d1e1a23926ce0a8a6ae83a36f5f6b2497ccf"
 Avoid exponential blowup in FamInstEnv.normaliseType

 Trac #13035 showed up a nasty case where we took exponentially
 long to normalise a (actually rather simple) type.  Fortunately
 it was easy to fix: see Note [Normalisation and type synonyms].
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13035#comment:5>
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