[GHC] #12033: [TypeApplications] GHC internal error

[GHC]

#12033: [TypeApplications] GHC internal error
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           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  TypeApplications                   |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Toying around, got

 {{{
 GHCi, version 8.1.20160503: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( /tmp/CatFail.hs, interpreted )

 /tmp/CatFail.hs:55:26: error:
     • GHC internal error: ‘a’ is not in scope during type checking, but it
 passed the renamer
       tcl_env of environment: [a1Ej :-> Type variable ‘i’ = i,
                                a1Ek :-> Type variable ‘p’ = p, a1Et :->
 Type variable ‘a’ = a,
                                a1Eu :-> Type variable ‘b’ = b]
     • In the first argument of ‘Vacuous’, namely ‘a’
       In the type ‘Vacuous a’
       In the expression: Dict @(Vacuous a)

 /tmp/CatFail.hs:66:10: error:
     • Couldn't match type ‘Fun p q’ with ‘Vacuous’
         arising from a use of ‘Main.$dmsrc’
     • In the expression: Main.$dmsrc
       In an equation for ‘src’: src = Main.$dmsrc
       In the instance declaration for ‘Category (Nat p q)’
     • Relevant bindings include
         src :: Nat p q a b -> Dict (Ob (Nat p q) a)
           (bound at /tmp/CatFail.hs:66:10)
 Failed, modules loaded: none.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12033>
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