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[GHC] #14641: GHC panics in incomplete program
by GHC 08 Jan '18

08 Jan '18

#14641: GHC panics in incomplete program -------------------------------------+------------------------------------- Reporter: mmc | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- I misspell a variable and GHC panics. I have the following test1.hs file: {{{ foo :: Double -> Double -> Bool foo a b = c > b }}} Then I do ghc -c test1.hs and get: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): initTc: unsolved constraints WC {wc_insol = [W] x_a1LD :: t_a1LC[tau:1] (CHoleCan: x)} }}} If I add a "main" method to my test.hs, I get the expected {{{ test1.hs:2:11: error: Variable not in scope: c :: Double }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14641> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14042: Data type with type family in return kind spuriously rejected
by GHC 07 Jan '18

07 Jan '18

#14042: Data type with type family in return kind spuriously rejected -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: TypeInType, | Operating System: Unknown/Multiple TypeFamilies | Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This typechecks: {{{#!hs {-# LANGUAGE TypeInType #-} import Data.Kind type Id (a :: Type) = a data Foo :: Id Type }}} But changing the type synonym to a type family causes it to fail: {{{#!hs {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} import Data.Kind type family Id (a :: Type) :: Type where Id a = a data Foo :: Id Type }}} {{{ $ ghci Foo.hs GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Main ( Foo.hs, interpreted ) Foo.hs:9:1: error: • Kind signature on data type declaration has non-* return kind Id * • In the data declaration for ‘Foo’ | 9 | data Foo :: Id Type | ^^^^^^^^ }}} That error message is wrong, since `Id * = *`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14042> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10245: panic in new integer switch logic with "out-of-range" literals
by GHC 07 Jan '18

07 Jan '18

#10245: panic in new integer switch logic with "out-of-range" literals -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.11 (CodeGen) | Operating System: Unknown/Multiple Keywords: | Type of failure: Compile-time Architecture: x86_64 | crash (amd64) | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Compiling this module {{{ module D (f) where f :: Int -> String f n = case n of 0x8000000000000000 -> "yes" _ -> "no" }}} crashes with the error {{{ [1 of 1] Compiling D ( /tmp/D.hs, /tmp/D.o ) ghc-stage1: panic! (the 'impossible' happened) (GHC version 7.11.20150403 for x86_64-unknown-linux): Map.findMin: empty map has no minimal element }}} The constant does not have to be exactly `0x8000000000000000`, everything I tested from there up to `0xffffffffffffffff` yields the same crash. Also occurs with `Word` and negative literals. The bug seems to be tied to the target's word size somehow, though: a 64-bit compiler does not panic on `Int32` and `0x80000000`, but a 32-bit compiler does. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10245> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14642: ‘class C using’ fails to parse with MonadComprehensions
by GHC 07 Jan '18

07 Jan '18

#14642: ‘class C using’ fails to parse with MonadComprehensions -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `TransformListComp` / `MonadComprehensions` reserve `using` but should this not work? {{{#!hs {-# Language TransformListComp #-} class C using }}} gives {{{ $ ghci -ignore-dot-ghci /tmp/X.hs GHCi, version 8.5.20180105: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/X.hs, interpreted ) /tmp/X.hs:3:9: error: parse error on input ‘using’ | 3 | class C using | ^^^^^ Failed, no modules loaded. Prelude> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14642> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14639: "unresolved constraints" when import and main missing
by GHC 06 Jan '18

06 Jan '18

#14639: "unresolved constraints" when import and main missing -------------------------------------+------------------------------------- Reporter: bainewedlock | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I gut a weird error because I forgot an import and the main method. (the commented lines in the code below) GHCi told me to post a bug about this, so... :-) == Steps to reproduce: {{{ > ghci GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :l bug.hs [1 of 1] Compiling Main ( bug.hs, interpreted ) ghc.exe: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): initTc: unsolved constraints WC {wc_insol = [W] printf_a2MG :: t_a2MF[tau:1] (CHoleCan: printf)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} == File bug.hs: {{{#!hs module Main where import Test.Hspec import Test.QuickCheck -- import Text.Printf testMovie :: Int -> Int -> Double -> Int -> Spec testMovie card ticket perc s = it (printf "should return Movie for card: %d, ticket: %d perc %s " card ticket (show perc)) $ movie card ticket perc `shouldBe` s movie :: Int -> Int -> Double -> Int movie card ticket perc = 4 -- main :: IO () -- main = undefined }}} == Expected behavior: Useful error message. == Actual behavior: "panic" error message. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14639> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14638: Simplifier ticks exhausted on Ω lambda term
by GHC 05 Jan '18

05 Jan '18

#14638: Simplifier ticks exhausted on Ω lambda term -------------------------------------+------------------------------------- Reporter: merlynfry | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC panics when trying to compile the following program: {{{#!hs module Omega where newtype Mu a = Roll { unRoll :: Mu a -> a } omega = (\h -> $ Roll h) (\x -> unRoll x $ x) }}} However, GHC has no complaints about interpreting the module. ---- I've attached the most verbose output of GHC, should you so need it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14638> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14592: Totality checking
by GHC 05 Jan '18

05 Jan '18

#14592: Totality checking -------------------------------------+------------------------------------- Reporter: varosi | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Example of that is Idris totality checking (http://docs.idris- lang.org/en/latest/tutorial/theorems.html#sect-totality) This feature could be started as a very specific types of pure functions which could be found to be total for sure and improve it in time. I'm putting a ticket for discussion here, because I didn't find any ticket related to that in GHC Trac. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14592> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14507: Core Lint error with Type.Reflection and pattern synonyms
by GHC 05 Jan '18

05 Jan '18

#14507: Core Lint error with Type.Reflection and pattern synonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# Language PatternSynonyms, ViewPatterns, GADTs, ConstraintKinds, RankNTypes, KindSignatures, PolyKinds, ScopedTypeVariables, DataKinds, TypeInType, TypeOperators, TypeApplications, TypeFamilies, TypeFamilyDependencies #-} import Type.Reflection import Prelude import Data.Kind data Dict c where Dict :: c => Dict c data N = O | S N foo :: forall (kind::k') (a::k). TypeRep kind -> TypeRep a -> Maybe (kind :~~: k, TypeRep a) foo krep rep = do HRefl <- eqTypeRep krep (typeRepKind rep) pure (HRefl, rep) pattern Bloop' :: forall k' (a::k). Typeable k' => k':~~:k -> TypeRep (a::k) -> TypeRep (a::k) pattern Bloop' hrefl rep <- (foo (typeRep @k') -> Just (hrefl, rep)) where Bloop' HRefl rep = rep type family SING = (res :: k -> Type) | res -> k where -- Core Lint error disappears with this line: SING = (TypeRep :: N -> Type) pattern RepN :: forall (a::kk). Typeable a => N~kk => SING a -> TypeRep (a::kk) pattern RepN tr <- Bloop' (HRefl::N:~~:kk) (tr :: TypeRep (a::N)) where RepN tr = tr asTypeable :: TypeRep a -> Dict (Typeable a) asTypeable rep = withTypeable rep Dict pattern TypeRep :: () => Typeable a => TypeRep a pattern TypeRep <- (asTypeable -> Dict) where TypeRep = typeRep -- error pattern SO = RepN TypeRep }}} triggers “Core Lint errors” on 8.2.1, 8.3.20170920 when run with `ghci -ignore-dot-ghci -dcore-lint`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14507> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14608: Different GHCi error messages for similar scenarios
by GHC 04 Jan '18

04 Jan '18

#14608: Different GHCi error messages for similar scenarios -------------------------------------+------------------------------------- Reporter: mb64 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- With the following code: {{{#!hs {-# LANGUAGE UnboxedTuples #-} module Test where data UnboxedTupleData = MkUTD (# (),() #) doThings :: UnboxedTupleData -> () doThings (MkUTD t) = () }}} This is accepted and compiled with a simple `ghc --make Test.hs`. However, with `ghci Test.hs`, you get an ugly error message: {{{#!hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Test ( Test.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): bcIdPrimRep t_s1ro :: (# (), () #) 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/ghci/ByteCodeGen.hs:1582:5 in ghc:ByteCodeGen Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Replacing `(MkUTD t)` with just `t` obtains a different error, with a nicer message: {{{#!hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Test ( Test.hs, interpreted ) Error: bytecode compiler can't handle unboxed tuples and sums. Possibly due to foreign import/export decls in source. Workaround: use -fobject-code, or compile this module to .o separately. }}} True to its word, GHCi accepts it with `-fobject-code`, but it also accepts the unwrapping one, with the worse error message, with `-fobject- code`. It only happens with unboxed tuples in GHCi: if you replace the unboxed tuple with an unboxed int, GHCi will happily accept it. GHC cheerfully compiles everything. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14608> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10731: System.IO.openTempFile is not thread safe on Windows
by GHC 04 Jan '18

04 Jan '18

#10731: System.IO.openTempFile is not thread safe on Windows -------------------------------------+------------------------------------- Reporter: | Owner: NeilMitchell | Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.1 libraries/base | Keywords: | Operating System: Windows Architecture: | Type of failure: Runtime crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Given the test program: {{{#!hs import Control.Concurrent import System.IO import Control.Monad import System.Directory main = do putStrLn "Starting" var <- newEmptyMVar tdir <- getTemporaryDirectory xs <- replicateM 10 $ do var <- newEmptyMVar flip forkFinally (\s -> do print s; putMVar var ()) $ do replicateM_ 100000 $ do (file, h) <- openTempFile tdir "test.txt" hClose h removeFile file return var mapM_ takeMVar xs }}} If I compile and run that with {{{ghc --make TmpFile.hs -threaded && tmpfile +RTS -N5}}} I get: {{{ Starting Left C:\Users\NDMIT_~1\AppData\Local\Temp\: openTempFile: permission denied (Permission denied) Left C:\Users\NDMIT_~1\AppData\Local\Temp\: openTempFile: permission denied (Permission denied) ... }}} I've reproduced this on GHC 7.8 and 7.10.1. We hit this in production about twice a day. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10731> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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