[GHC] #8137: Permited mega-polymorphic type

[GHC]

#8137: Permited  mega-polymorphic type
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        Reporter:  wvv                          |            Owner:
            Type:  bug                          |           Status:  closed
        Priority:  normal                       |        Milestone:
       Component:  Compiler (Type checker)      |          Version:  7.6.3
      Resolution:  invalid                      |         Keywords:
Operating System:  Unknown/Multiple             |     Architecture:
 Type of failure:  GHC accepts invalid program  |  Unknown/Multiple
       Test Case:                               |       Difficulty:
        Blocking:                               |  Unknown
                                                |       Blocked By:
                                                |  Related Tickets:
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Comment (by goldfire):

 In the scenario in your comment above, the type `t1` must be a sub-part of
 the type `t1`, which is only possible with infinite types. In the original
 case in the bug report, we get the equation `t = t`, where `t` is the type
 of `u`, which is satisfiable for any type.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8137#comment:3>
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