[GHC] #9415: Superclass cycle with ambiguous type causes loop

[GHC]

#9415: Superclass cycle with ambiguous type causes loop
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              Reporter:  goldfire    |            Owner:  goldfire
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.9
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by Richard Eisenberg <eir@…>):

 In [changeset:"1b1388697e687154c2bf1943639e75f3ccf5bc59/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1b1388697e687154c2bf1943639e75f3ccf5bc59"
 Fix #9415.

 Abort typechecking when we detect a superclass cycle error, as
 ambiguity checking in the presence of superclass cycle errors can
 cause a loop.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9415#comment:1>
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