December 2018 - ghc-tickets

[GHC] #15807: GHC panic with visible kind applications
by GHC 16 Jan '19

16 Jan '19

#15807: GHC panic with visible kind applications ----------------------------------------+--------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: TypeApplications | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- Using the https://phabricator.haskell.org/D5229 diff This is '''fine''' {{{#!hs {-# Language RankNTypes #-} {-# Language TypeApplications #-} {-# Language PolyKinds #-} {-# Language GADTs #-} import Data.Kind data App :: forall (f :: Type -> Type). Type -> Type where MkApp :: f a -> App @f a }}} Kind polymorphic is '''fine''' {{{#!hs {-# Language RankNTypes #-} {-# Language TypeApplications #-} {-# Language PolyKinds #-} {-# Language GADTs #-} import Data.Kind data App :: forall k (f :: k -> Type). k -> Type where MkApp :: f a -> App @k @(f :: k -> Type) (a :: k) }}} But offing the visibility of `k` '''fails''' {{{#!hs {-# Language RankNTypes #-} {-# Language TypeApplications #-} {-# Language PolyKinds #-} {-# Language GADTs #-} import Data.Kind data App :: forall (f :: k -> Type). k -> Type where MkApp :: f a -> App @(f :: k -> Type) (a :: k) }}} {{{#!hs {-# Language RankNTypes #-} {-# Language TypeApplications #-} {-# Language PolyKinds #-} {-# Language GADTs #-} import Data.Kind data App :: forall (f :: k -> Type). k -> Type where MkApp :: f a -> App @f a }}} {{{ $ ghci -ignore-dot-ghci 581_bug.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 581_bug.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): ASSERT failed! 2 1 f_a1yB[tau:1] f_a1yx[sk:1] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/utils/Outputable.hs:1219:5 in ghc:Outputable assertPprPanic, called at compiler/typecheck/TcMType.hs:778:54 in ghc:TcMType Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15807> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15797: GHC panic using visible kind application
by GHC 16 Jan '19

16 Jan '19

#15797: GHC panic using visible kind application -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: | Operating System: Unknown/Multiple TypeApplications | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# Language RankNTypes #-} {-# Language TypeFamilies #-} {-# Language ScopedTypeVariables #-} {-# Language TypeApplications #-} {-# Language DataKinds #-} {-# Language PolyKinds #-} {-# Language TypeOperators #-} {-# Language GADTs #-} {-# Options_GHC -dcore-lint #-} import Data.Kind class Ríki (obj :: Type) where type Obj :: obj -> Constraint type Obj = Bæ @obj class Bæ (a :: k) instance Bæ @k (a :: k) data EQ :: forall ob. ob -> ob -> Type where EQ :: EQ a a instance Ríki (EQ @ob) }}} {{{ $ ghci -dcore-lint 568_bug.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 568_bug.hs, interpreted ) WARNING: file compiler/types/TyCoRep.hs, line 2567 in_scope InScope {ob_a1zs co_a1zt} tenv [] cenv [a1zt :-> co_a1zt] tys [Bæ] cos [] needInScope [a1zn :-> co_a1zn, a1zs :-> ob_a1zs] ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): Core Lint error <no location info>: warning: In the type ‘Bæ’ Unfilled coercion hole: {co_a1zn} <no location info>: warning: In the type ‘Bæ’ co_a1zn :: (ob_a1zs -> ob_a1zs -> *) ~# * [LclId[CoVarId]] is out of scope Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/typecheck/FamInst.hs:171:31 in ghc:FamInst Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15797> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15798: Flag to warn when deriving strategy is not explicitly specified
by GHC 16 Jan '19

16 Jan '19

#15798: Flag to warn when deriving strategy is not explicitly specified -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- In my code, I aim to always specify deriving strategies. I would like to add a flag `-fwarn-unspecified-deriving` that would cause a warning to be emitted when someone wrote this: {{{ newtype Foo = Foo Int deriving (Show) }}} The user would be required to instead write: {{{ newtype Foo = Foo Int deriving newtype (Show) }}} Or they could use `stock` if that was the behavior they wanted. This flag would be off by default. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15798> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16031: Show instance for Data.Fixed does not show parentheses for negatives
by GHC 16 Jan '19

16 Jan '19

#16031: Show instance for Data.Fixed does not show parentheses for negatives -------------------------------------+------------------------------------- Reporter: skeuchel | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.7 libraries/base | Keywords: Data.Fixed, | Operating System: Unknown/Multiple Show | Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When showing negative numbers most types emit parentheses in precedence level 11 because the result is not atomic: {{{#!hs GHCi, version 8.7.20181015: http://www.haskell.org/ghc/ :? for help Prelude> show (Just (-1 :: Int)) "Just (-1)" Prelude> show (Just (-1 :: Float)) "Just (-1.0)" }}} However, the Show instance for Fixed does not {{{#!hs Prelude> :m Data.Fixed Prelude Data.Fixed> show (Just (-1 :: Fixed E2)) "Just -1.00" Prelude Data.Fixed> }}} I would expect it to, because of consistency and because the result "Just -1.00" is ill-typed when seen as an expression. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16031> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15779: Follow-ups to D5169
by GHC 16 Jan '19

16 Jan '19

#15779: Follow-ups to D5169 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- Simonmar points out that there are a few follow-up tasks after Phab:D5169: > > 1. We should build these at installation time, so they don't have to go into the binary distribution (the same goes for the vanilla way` libHSfoo.o` files) > 2. This also needs to be done in Hadrian > -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15779> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16063: ghc-8.6.3 + Mac OSX + FFI dependency causes 'impossible happened' compiler failure
by GHC 16 Jan '19

16 Jan '19

#16063: ghc-8.6.3 + Mac OSX + FFI dependency causes 'impossible happened' compiler failure -------------------------------------+------------------------------------- Reporter: benselfridge | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I am trying to build this library: https://github.com/GaloisInc/grift The build works perfectly on my Mac OS X system under ghc-8.4.4 via the README instructions. However, if I update to ghc-8.6.3, I get the following error: {{{ Building library for bv-sized-float-0.1.0.. [1 of 2] Compiling Data.BitVector.Sized.Float ( src/Data/BitVector/Sized/Float.hs, /Users/benselfridge/grift/dist- newstyle/build/x86_64-osx/ghc-8.6.3/bv-sized- float-0.1.0/build/Data/BitVector/Sized/Float.o ) [2 of 2] Compiling Data.BitVector.Sized.Float.App ( src/Data/BitVector/Sized/Float/App.hs, /Users/benselfridge/grift/dist- newstyle/build/x86_64-osx/ghc-8.6.3/bv-sized- float-0.1.0/build/Data/BitVector/Sized/Float/App.o ) ghc: loadArchive: Failed reading header from `/Users/benselfridge/grift /dist-newstyle/build/x86_64-osx/ghc-8.6.3/softfloat- hs-0.1.0/build/SoftFloat' ghc: panic! (the 'impossible' happened) (GHC version 8.6.3 for x86_64-apple-darwin): loadArchive "/Users/benselfridge/grift/dist- newstyle/build/x86_64-osx/ghc-8.6.3/softfloat-hs-0.1.0/build/SoftFloat": failed Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} The library "softfloat-hs" is a Haskell library that calls C functions that are dynamically linked. If I try to run it within this project via "cabal new-repl softfloat-hs", the dependency works fine. It's only when I try to build "bv-sized-float", which depends on softfloat-hs, that I get the above error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16063> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16069: Proposal to resolve some confusion about stages in Hadrian
by GHC 16 Jan '19

16 Jan '19

#16069: Proposal to resolve some confusion about stages in Hadrian -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- The current situation with hadrian is that 1. We build libraries required to build the stage2 compiler with stage1 and place them in `_build/stage1`. 2. The `stage2` compiler is built with `stage1` and then placed in `_build/stage1`. 3. Executables built using the `stage2` compiler such as haddock then also use the libraries built by the `stage1` compiler even though they are being built with the `stage2` compiler. However, this is problematic because when you want to build a `stage3` compiler, we want to actually build the libraries again using the `stage2` compiler and place them in `_build/stage2`. If we follow the existing logic for executables built using the `stage2` compiler then in order to build a `stage3` compiler we would just reuse all the libraries from `_build/stage1` which seems incorrect. The proposal is simply thus: 1. When building an executable at stageN, we use libraries also built at stageN. Concretely, if we want to build `haddock`, a stage2 executable, then we also have to build all the libraries it needs with the `stage2` compiler and install them into a package database in `_build/stage2`. 2. The definition of "build" can be configured. By default, in order to "build" a stage2 library we copy it from the stage1 database but it is configurable to rebuild it with the stage2 compiler as we would want to for stage3. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16069> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15360: Template Haskell splicing drops lots of type arguments
by GHC 16 Jan '19

16 Jan '19

#15360: Template Haskell splicing drops lots of type arguments -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Template | Version: 8.4.3 Haskell | 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: -------------------------------------+------------------------------------- The conversion functions (in the `Convert` module) drop type arguments in various places. Here are two examples: {{{ data T a b c = Mk a b c bar :: $( return $ AppT (InfixT (ConT ''Int) ''T (ConT ''Bool)) (ConT ''Double) ) bar = Mk 5 True 3.14 }}} This correct code leads to an error {{{ Expecting one more argument to ‘T Int Bool’ }}} because the `Double` is forgotten. Similarly, {{{ baz :: $( return $ AppT (ParensT (ConT ''Maybe)) (ConT ''Int) ) baz = Just 5 }}} fails because `baz :: (Maybe)` isn't valid. On the other hand, {{{ frob :: forall (a :: $( [t| * Int |] )). a -> a frob x = x }}} is spuriously accepted, because GHC has forgotten about the `Int` argument. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15360> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13648: ApplicativeDo selects "GHC.Base.Monad.return" when actions are used without patterns.
by GHC 15 Jan '19

15 Jan '19

#13648: ApplicativeDo selects "GHC.Base.Monad.return" when actions are used without patterns. -------------------------------------+------------------------------------- Reporter: AaronFriel | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 8.0.2 and 8.2.1-rc1 (rc2 not checked) have a bug where -XApplicativeDo causes "GHC.Base.Monad.return" to be used instead of the locally available "return", and a spurious "return ()" shows up. This desugaring is not adhering to the -XRebindableSyntax spec (see: #12490). Example: {{{#!hs {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE RebindableSyntax #-} -- Bug vanishes if this next line is removed: {-# LANGUAGE ApplicativeDo #-} module Main where import Prelude (String, print) class MyFunctor f where fmap :: (a -> b) -> f a -> f b class MyApplicative f where pure :: a -> f a (<*>) :: f (a -> b) -> f a -> f b class MyMonad m where return :: a -> m a (>>) :: m a -> m b -> m b (>>=) :: m a -> (a -> m b) -> m b fail :: String -> m a join :: m (m a) -> m a testCase1 m1 m2 = do m1 m2 return () testCase2 m1 m2 = do _ <- m1 _ <- m2 return () main = print "42" }}} {{{ :t testCase1 testCase1 :: (MyFunctor f, MyApplicative f, MyMonad f, Monad f) => f a2 -> f a1 -> f () :t testCase2 :: testCase2 :: (MyFunctor f, MyApplicative f) => f t -> f a -> f () }}} The desugaring for testCase1 shows the issue: {{{#!hs testCase1' m1 m2 = (<*>) (fmap (\() () -> ()) (m1 >> (GHC.Base.Monad.return ()))) (m2 >> (GHC.Base.Monad.return ())) -- or: testCase1' m1 m2 = (fmap (\() () -> () ) (m1 >> (return ()))) <*> (m2 >> (return ())) }}} I would be able to work on this if someone pointed me in the right direction. It looks like it would be in `compiler/rename/RnEnv` and `compiler/rename/RnExpr`, as with #12490? As a proposed fix, I would want to implement a limited-scope fix before the 8.2.1 release which would not address the thornier issue of #10892. The patch would: 1. Replace `GHC.Base.Monad.return` with local `pure`, removing the `Monad` constraint. 2. Replace `>>` with `*>`, removing the `MyMonad` constraint. This isn't a _complete_ fix, as this would still induce an unnecessary use of the local `fmap`, but it would reduce the desugaring bug in `testCase1` to only that local `fmap`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13648> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16093: mkPluginUsage: file not found
by GHC 14 Jan '19

14 Jan '19

#16093: mkPluginUsage: file not found -------------------------------------+------------------------------------- Reporter: lerkok | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- I've been trying to track down another plugin issue when I ran into this one. I have the following `TestPlugin.hs` file: {{{#!hs module TestPlugin (plugin) where import GhcPlugins plugin :: Plugin plugin = defaultPlugin {installCoreToDos = install} where install _ todos = return (test : todos) test = CoreDoPluginPass "Test" return }}} And the following `Test.hs` file: {{{#!hs {-# OPTIONS_GHC -fplugin TestPlugin #-} main :: IO () main = return () }}} They are both in the same directory. With ghc 8.4.2, I have: {{{ $ ghci-8.4.2 -package ghc Test.hs GHCi, version 8.4.2: http://www.haskell.org/ghc/ :? for help [1 of 2] Compiling TestPlugin ( TestPlugin.hs, interpreted ) [2 of 2] Compiling Main ( Test.hs, interpreted ) Ok, two modules loaded. }}} But with ghc 8.6.3, I get: {{{ $ ghci-8.6.3 -package ghc Test.hs GHCi, version 8.6.3: http://www.haskell.org/ghc/ :? for help [1 of 2] Compiling TestPlugin ( TestPlugin.hs, interpreted ) [2 of 2] Compiling Main ( Test.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.6.3 for x86_64-apple-darwin): mkPluginUsage: file not found TestPlugin ./TestPlugin.o Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/deSugar/DsUsage.hs:234:15 in ghc:DsUsage Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} My original problem was different actually, so if you can suggest at least a workaround for this without actually fixing it I can proceed to replicate the other one. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16093> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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