[GHC] #15629: "No skolem info" panic (GHC 8.6 only)

[GHC]

#15629: "No skolem info" panic (GHC 8.6 only)
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.6.1-beta1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Oh my, hand on.  Everything should work if the eager unifier does NOTHING.
 Indeed, I'd love to have a flag `-fno-eager-unifier` which switches off
 the eager unifier in order to stress the constraint solver.

 It'd b easy: in `TcUnify.uType`, test the flag and call `uType_defer`
 immediately if `-fno-eager-unifier` is set.

 I bet this shows up lots of bugs, so I partly fear to suggest it :-).  For
 this one, does the `No skolem` come back?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15629#comment:4>
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