Re: [GHC] #11444: 8.0 rc1 panics in applyTypeToArgs

11 Jan 2017

      #11444: 8.0 rc1 panics in applyTypeToArgs
-------------------------------------+-------------------------------------
        Reporter:  osa1              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1-rc1
      Resolution:                    |             Keywords:
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 RyanGlScott):

 To be precise, here's the portion of `atomic-primops` that fails with a
 Core Lint error:

 {{{#!hs
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE MagicHash #-}
 module AtomicPrimops where

 import GHC.Exts

 {-# NOINLINE ptrEq #-}
 ptrEq :: a -> a -> Bool
 ptrEq !x !y = I# (reallyUnsafePtrEquality# x y) == 1
 }}}

 {{{
 $ ~/Software/ghc3/inplace/bin/ghc-stage2 -fforce-recomp -dcore-lint -O2
 Bug.hs[1 of 1] Compiling AtomicPrimops    ( Bug.hs, Bug.o )
 *** Core Lint errors : in result of Float out(FOS {Lam = Just 0,
                                                    Consts = True,
                                                    OverSatApps = False})
 ***
 <no location info>: warning:
     In the expression: I# (reallyUnsafePtrEquality# @ a x_a2OY y_a2OZ)
     This argument does not satisfy the let/app invariant:
       reallyUnsafePtrEquality# @ a x_a2OY y_a2OZ
 *** Offending Program ***
 lvl_s3TE :: Int
 [LclId]
 lvl_s3TE = I# 1#

 ptrEq [InlPrag=NOINLINE] :: forall a. a -> a -> Bool
 [LclIdX, Arity=2]
 ptrEq =
   \ (@ a_a3I6) (x_a2OY :: a) (y_a2OZ :: a) ->
     case x_a2OY of x_X2P2 { __DEFAULT ->
     case y_a2OZ of y_X2P4 { __DEFAULT ->
     eqInt (I# (reallyUnsafePtrEquality# @ a x_a2OY y_a2OZ)) lvl_s3TE
     }
     }

 $trModule_s3TA :: TrName
 [LclId]
 $trModule_s3TA = TrNameS "main"#

 $trModule_s3TB :: TrName
 [LclId]
 $trModule_s3TB = TrNameS "AtomicPrimops"#

 $trModule :: Module
 [LclIdX]
 $trModule = Module $trModule_s3TA $trModule_s3TB

 *** End of Offense ***

 <no location info>: error:
 Compilation had errors
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11444#comment:9
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