[GHC] #13601: GHC errors but hangs

[GHC]

#13601: GHC errors but hangs
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  TypeInType,
                                     |  LevityPolymorphism
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 I wondered about deferring the errors in `solveEqualities` by re-emitting
 them. Just jotting it down here; entirely untested.
 {{{
 +{-
 +       ; emitConstraints final_wc
 +       ; traceTc "End solveEqualities }" (ppr final_wc)
 +       ; when (anyErrorsWC final_wc) failM
 +       ; return result }
 +-}
 @@ -145,0 +153,8 @@ solveEqualities thing_inside
 +anyErrorsWC :: WantedConstraints -> Bool
 +anyErrorsWC (WC { wc_simple = wanteds, wc_insol = insols, wc_impl =
 implics })
 +  =   anyBag is_err wanteds
 +   || anyBag is_err insols
 +   || anyBag (anyErrorsWC . ic_wanted) implics
 +  where
 +    is_err ct = trulyInsoluble ct
 +
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13601#comment:4>
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