[GHC] #14568: Uncurried Parameter to n-ary Function in Type Signature Causes Crash

[GHC]

#14568: Uncurried Parameter to n-ary Function in Type Signature Causes Crash
-------------------------------------+-------------------------------------
           Reporter:  nixy           |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           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:
-------------------------------------+-------------------------------------
 If you uncomment the arrow, everything's fine; GHC crashes as-is.
 {{{#!hs
 f :: (a -> b) {- -> -} a -> c
 f = undefined
 }}}
 Apparently GHC incorrectly parses any n-ary function parameter followed by
 another uncurried parameter in type signatures.

 System Info:
 GHC v8.2.1
 GCC v5.4.0
 Linux Mint (Linux 4.8.0-53-generic #56~16.04.1-Ubuntu SMP x86_64)

 ghc -v -dcore-lint:
 {{{
 Glasgow Haskell Compiler, Version 8.2.1, stage 2 booted by GHC version
 8.0.2
 Using binary package database:
 /usr/local/haskell/ghc-8.2.1-x86_64/lib/ghc-8.2.1/package.conf.d/package.cache
 Using binary package database:
 /home/nic/.ghc/x86_64-linux-8.2.1/package.conf.d/package.cache
 package flags []
 loading package database
 /usr/local/haskell/ghc-8.2.1-x86_64/lib/ghc-8.2.1/package.conf.d
 loading package database /home/nic/.ghc/x86_64-linux-8.2.1/package.conf.d
 wired-in package ghc-prim mapped to ghc-prim-0.5.1.0
 wired-in package integer-gmp mapped to integer-gmp-1.0.1.0
 wired-in package base mapped to base-4.10.0.0
 wired-in package rts mapped to rts
 wired-in package template-haskell mapped to template-haskell-2.12.0.0
 wired-in package ghc mapped to ghc-8.2.1
 wired-in package dph-seq not found.
 wired-in package dph-par not found.
 package flags []
 loading package database
 /usr/local/haskell/ghc-8.2.1-x86_64/lib/ghc-8.2.1/package.conf.d
 loading package database /home/nic/.ghc/x86_64-linux-8.2.1/package.conf.d
 wired-in package ghc-prim mapped to ghc-prim-0.5.1.0
 wired-in package integer-gmp mapped to integer-gmp-1.0.1.0
 wired-in package base mapped to base-4.10.0.0
 wired-in package rts mapped to rts-1.0
 wired-in package template-haskell mapped to template-haskell-2.12.0.0
 wired-in package ghc mapped to ghc-8.2.1
 wired-in package dph-seq not found.
 wired-in package dph-par not found.
 *** Chasing dependencies:
 Chasing modules from: *bug.hs
 !!! Chasing dependencies: finished in 1.14 milliseconds, allocated 0.207
 megabytes
 Stable obj: []
 Stable BCO: []
 Ready for upsweep
   [NONREC
       ModSummary {
          ms_hs_date = 2017-12-08 23:11:58.321654412 UTC
          ms_mod = Main,
          ms_textual_imps = [(Nothing, Prelude)]
          ms_srcimps = []
       }]
 *** Deleting temp files:
 Deleting:
 compile: input file bug.hs
 *** Checking old interface for Main (use -ddump-hi-diffs for more
 details):
 [1 of 1] Compiling Main             ( bug.hs, bug.o )
 *** Parser [Main]:
 !!! Parser [Main]: finished in 0.13 milliseconds, allocated 0.090
 megabytes
 *** Renamer/typechecker [Main]:
 *** Deleting temp files:
 Deleting:
 *** Deleting temp dirs:
 Deleting:
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.1 for x86_64-unknown-linux):
         repSplitAppTys
   a_anL[sk:1]
   b_anM[sk:1]
   []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:808:9 in ghc:Type
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14568>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler