[GHC] #10079: Coercible solver regression: Couldn't match rep of () with Const () b

[GHC]

#10079: Coercible solver regression: Couldn't match rep of () with Const () b
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        Reporter:  glguy             |                   Owner:  goldfire
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.1
       Component:  Compiler (Type    |                 Version:  7.10.1-rc1
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:                    |
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Comment (by goldfire):

 Yep. Fixed. Will validate and push later today.

 {{{
 try_decompose_repr_app :: CtEvidence
                        -> TcType -> TcType -> TcS (StopOrContinue Ct)
 -- Preconditions: like try_decompose_app, but also
 --                ev has a representational
 try_decompose_repr_app ev ty1 ty2
   | ty1 `eqType` ty2   -- See Note [AppTy reflexivity check]
   = canEqReflexive ev ReprEq ty1

   | AppTy {} <- ty1
   = canEqFailure ev ReprEq ty1 ty2

   | AppTy {} <- ty2
   = canEqFailure ev ReprEq ty1 ty2

   | otherwise  -- flattening in can_eq_wanted_app exposed some TyConApps!
   = ASSERT2( isJust (tcSplitTyConApp_maybe ty1) || isJust
 (tcSplitTyConApp_maybe ty2)
             , ppr ty1 $$ ppr ty2 )  -- If this assertion fails, we may
 fall
                                     -- into an infinite loop
     canEqNC ev ReprEq ty1 ty2
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10079#comment:6>
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