[GHC] #15108: Panic: collectNBinders

[GHC]

#15108: Panic: collectNBinders
-------------------------------------+-------------------------------------
           Reporter:  cdisselkoen    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Profiling      |           Version:  8.4.2
           Keywords:  panic          |  Operating System:  Linux
  collectNBinders                    |
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 GHC 8.4.2 panics with the error message `collectNBinders`, when compiling
 with profiling.  This is a very similar bug to #15002, but although #15002
 is fixed in 8.4.2, this panic persists.

 Steps to reproduce:

 `stack.yaml`:
 {{{
 resolver: nightly-2018-04-30
 }}}

 `bug.cabal`:
 {{{
 name:                bug
 version:             0.1.0.0
 build-type:          Simple
 cabal-version:       >=1.10

 library
   build-depends:       base
   default-language:    Haskell2010

 executable bug
   main-is:             Main.hs
   build-depends:       base
                      , bug
   default-language:    Haskell2010
 }}}

 `Main.hs`:
 {{{
 module Main where

 main :: IO ()
 main = do
   _ <- return $ getInt Circle
   return ()

 newtype MyInt = MyInt Int

 data Shape = Circle
            | Square

 getInt :: Shape -> MyInt
 getInt sh =
   case sh of
     Circle ->
         let (MyInt i) = MyInt 3
         in myInt i
     Square ->
         let (MyInt i) = MyInt 2
         in myInt i
     where
       myInt = MyInt
 }}}

 Then run:
 {{{
 $ stack ghc -- --version
 The Glorious Glasgow Haskell Compilation System, version 8.4.2

 $ stack build --profile
 bug-0.1.0.0: build (lib + exe)
 Preprocessing library for bug-0.1.0.0..
 Building library for bug-0.1.0.0..
 Preprocessing executable 'bug' for bug-0.1.0.0..
 Building executable 'bug' for bug-0.1.0.0..
 [1 of 1] Compiling Main             ( Main.hs, .stack-work/dist/x86_64
 -linux-tinfo6-nopie/Cabal-2.2.0.1/build/bug/bug-tmp/Main.p_o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.4.2 for x86_64-unknown-linux):
         collectNBinders
   1
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/coreSyn/CoreSyn.hs:2025:25 in
 ghc:CoreSyn

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug


 --  While building custom Setup.hs for package bug-0.1.0.0 using:
       /usr/local/home/<USER>/.stack/setup-exe-cache/x86_64-linux-
 tinfo6-nopie/Cabal-simple_mPHDZzAJ_2.2.0.1_ghc-8.4.2 --builddir=.stack-
 work/dist/x86_64-linux-tinfo6-nopie/Cabal-2.2.0.1 build lib:bug exe:bug
 --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always"
     Process exited with code: ExitFailure 1
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15108>
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