[GHC] #13740: GHC panic with operator constructor of newtype

[GHC]

#13740: GHC panic with operator constructor of newtype
-------------------------------------+-------------------------------------
           Reporter:  codebje        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
  (Type checker)                     |
           Keywords:                 |  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:
-------------------------------------+-------------------------------------
 The following code causes a GHC panic:

 {{{
 newtype Cont r a = Cont { (>>-) :: (a -> r) -> r }
 x = \a b c -> c >>- a . b
 }}}

 This slight modification, however, is fine:

 {{{
 newtype Cont r a = Cont { (>>-) :: (a -> r) -> r }
 x = \a b c -> c >>- (a . b)
 }}}

 The presence or absence of a type signature for `x` makes no difference.
 Compiling with "-v" suggests the panic occurs during type checking:

 {{{
 Glasgow Haskell Compiler, Version 8.0.2, stage 2 booted by GHC version
 7.10.3
 Using binary package database:
 /Users/bje/.stack/programs/x86_64-osx/ghc-8.0.2/lib/ghc-8.0.2/package.conf.d/package.cache
 Using binary package database:
 /Users/bje/.stack/snapshots/x86_64-osx/lts-8.8/8.0.2/pkgdb/package.cache
 Using binary package database: /Users/bje/.stack/global/.stack-
 work/install/x86_64-osx/lts-8.8/8.0.2/pkgdb/package.cache
 loading package database
 /Users/bje/.stack/programs/x86_64-osx/ghc-8.0.2/lib/ghc-8.0.2/package.conf.d
 loading package database
 /Users/bje/.stack/snapshots/x86_64-osx/lts-8.8/8.0.2/pkgdb
 loading package database /Users/bje/.stack/global/.stack-
 work/install/x86_64-osx/lts-8.8/8.0.2/pkgdb
 wired-in package ghc-prim mapped to ghc-prim-0.5.0.0
 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1
 wired-in package base mapped to base-4.9.1.0
 wired-in package rts mapped to rts
 wired-in package template-haskell mapped to template-haskell-2.11.1.0
 wired-in package ghc mapped to ghc-8.0.2
 wired-in package dph-seq not found.
 wired-in package dph-par not found.
 Hsc static flags:
 loading package database
 /Users/bje/.stack/programs/x86_64-osx/ghc-8.0.2/lib/ghc-8.0.2/package.conf.d
 loading package database
 /Users/bje/.stack/snapshots/x86_64-osx/lts-8.8/8.0.2/pkgdb
 loading package database /Users/bje/.stack/global/.stack-
 work/install/x86_64-osx/lts-8.8/8.0.2/pkgdb
 wired-in package ghc-prim mapped to ghc-prim-0.5.0.0
 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1
 wired-in package base mapped to base-4.9.1.0
 wired-in package rts mapped to rts-1.0
 wired-in package template-haskell mapped to template-haskell-2.11.1.0
 wired-in package ghc mapped to ghc-8.0.2
 wired-in package dph-seq not found.
 wired-in package dph-par not found.
 *** Chasing dependencies:
 Chasing modules from: *panic.hs
 !!! Chasing dependencies: finished in 0.57 milliseconds, allocated 0.224
 megabytes
 Stable obj: []
 Stable BCO: []
 Ready for upsweep
   [NONREC
       ModSummary {
          ms_hs_date = 2017-05-22 07:07:41 UTC
          ms_mod = Main,
          ms_textual_imps = [(Nothing, Prelude)]
          ms_srcimps = []
       }]
 *** Deleting temp files:
 Deleting:
 compile: input file panic.hs
 *** Checking old interface for Main:
 [1 of 1] Compiling Main             ( panic.hs, panic.o )
 *** Parser [Main]:
 !!! Parser [Main]: finished in 0.38 milliseconds, allocated 0.209
 megabytes
 *** Renamer/typechecker [Main]:
 *** Deleting temp files:
 Deleting:
 *** Deleting temp dirs:
 Deleting:
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-apple-darwin):
         get_op >>-

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

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13740>
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