[GHC] #14450: GHCi spins forever

[GHC]

#14450: GHCi spins forever
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  TypeInType,
                                     |  PolyKinds
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"0a85190312a1de3d300912051309b94589c08683/ghc"
 0a851903/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0a85190312a1de3d300912051309b94589c08683"
 Fix a TyVar bug in the flattener

 A year ago I gave up on trying to rigorously separate TyVars
 from TcTyVars, and instead allowed TyVars to appear rather more
 freely in types examined by the constraint solver:

    commit 18d0bdd3848201882bae167e3b15fd797d217e93
    Author: Simon Peyton Jones <simonpj at microsoft.com>
    Date:   Wed Nov 23 16:00:00 2016 +0000

    Allow TyVars in TcTypes

 See Note [TcTyVars in the typechecker] in TcType.

 However, TcFlatten.flatten_tyvar1 turned out to treat
 a TyVar specially, and implicitly assumed that it could
 not have an equality constraint in the inert set.  Wrong!

 This caused Trac #14450.  Fortunately it is easily fixed,
 by deleting code.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14450#comment:7>
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