December 2014 - ghc-tickets

[GHC] #9845: GHC API evaluating some Cabal code fails with SegFault if executable is compiled statically
by GHC 19 Dec '14

19 Dec '14

#9845: GHC API evaluating some Cabal code fails with SegFault if executable is compiled statically -------------------------------------+------------------------------------- Reporter: | Owner: JeanPhilippeMoresmau | Status: new Type: bug | Milestone: Priority: normal | Version: 7.8.3 Component: GHC API | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Runtime Difficulty: Unknown | crash Blocked By: | Test Case: Related Tickets: 9480, 8935, 8376 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This is code from the dynamic-cabal project, but I've distilled it into an easier test case. Basically you load a module that calls the Cabal configure function, and we try to call a function and get the result. This works fine if the executable is compiled with -dynamic, but segfaults (on Ubuntu at least) if the executable is static. I've had that behavior since 7.8.1 and I've seen several similar bugs come and be fixed, but the issue is still present in 7.8.4 rc1 (ghc-7.8.3.20141119) I attach the full project, with the cabal file, the Main.hs module that loads the DynamicCabalQuery.hs module -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9845> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7473: getModificationTime gives only second-level resolution
by GHC 19 Dec '14

19 Dec '14

#7473: getModificationTime gives only second-level resolution -------------------------------------+------------------------------------- Reporter: duncan | Owner: ekmett Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Core | Version: 7.6.1 Libraries | Keywords: directory Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by redneb): I just posted a pull request for that on github: https://github.com/haskell/directory/pull/11. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7473#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9316: GHC 7.8.3 no longer infers correct type in presence of type families and constraints
by GHC 19 Dec '14

19 Dec '14

#9316: GHC 7.8.3 no longer infers correct type in presence of type families and constraints -------------------------------------+------------------------------------- Reporter: ocharles | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Differential Revisions: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: -------------------------------------+------------------------------------- The following code fails to compile under GHC 7.8.3: {{{ {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE QuasiQuotes #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE TypeFamilies #-} module SingletonsBug where import Control.Applicative import Data.Constraint (Dict(..)) import Data.Singletons import Data.Singletons.TH (singletons) import Data.Traversable (for) $(singletons [d| data SubscriptionChannel = BookingsChannel |]) type family T (c :: SubscriptionChannel) :: * type instance T 'BookingsChannel = Bool witnessC :: SSubscriptionChannel channel -> Dict (Show (T channel), SingI channel) witnessC SBookingsChannel = Dict forAllSubscriptionChannels :: forall m r. (Applicative m) => (forall channel. (SingI channel, Show (T channel)) => SSubscriptionChannel channel -> m r) -> m r forAllSubscriptionChannels f = withSomeSing BookingsChannel $ \(sChannel) -> case witnessC sChannel of Dict -> f sChannel }}} {{{ SingletonsBug.hs:38:15: Could not deduce (SingI channel0) arising from a use of ‘f’ from the context (Applicative m) bound by the type signature for forAllSubscriptionChannels :: Applicative m => (forall (channel :: SubscriptionChannel). (SingI channel, Show (T channel)) => SSubscriptionChannel channel -> m r) -> m r at SingletonsBug.hs:(32,6)-(34,8) or from ((Show (T a), SingI a)) bound by a pattern with constructor Dict :: forall (a :: Constraint). (a) => Dict a, in a case alternative at SingletonsBug.hs:38:7-10 The type variable ‘channel0’ is ambiguous Note: there is a potential instance available: instance SingI 'BookingsChannel -- Defined at SingletonsBug.hs:19:3 In the expression: f sChannel In a case alternative: Dict -> f sChannel In the expression: case witnessC sChannel of { Dict -> f sChannel } SingletonsBug.hs:38:17: Couldn't match type ‘channel0’ with ‘a’ because type variable ‘a’ would escape its scope This (rigid, skolem) type variable is bound by a type expected by the context: Sing a -> m r at SingletonsBug.hs:(36,3)-(38,24) Expected type: SSubscriptionChannel channel0 Actual type: Sing a Relevant bindings include sChannel :: Sing a (bound at SingletonsBug.hs:36:36) In the first argument of ‘f’, namely ‘sChannel’ In the expression: f sChannel }}} However, this works fine in GHC 7.8.2. If I change one line to this: {{{ withSomeSing BookingsChannel $ \(sChannel :: SSubscriptionChannel c) -> }}} The code compiles in GHC 7.8.3. Another change that doesn't require a type signature (but changes the program) is to change that constraint from: {{{ Show (T channel), SingI channel }}} to just {{{ SingI channel }}} It seems that the use of the type family breaks the inference, but this might be a bit of a red herring! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9316> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9860: Package flags not command line completable in 7.8
by GHC 19 Dec '14

19 Dec '14

#9860: Package flags not command line completable in 7.8 -------------------------------------+------------------------------------- Reporter: kolmodin | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.4 Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Incorrect Blocked By: | result at runtime Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Passing `--show-options` to ghc shows all the flags that ghc understands. Unfortunately `--show-options` does not list the package flags, `-package- db -package-id` etc. Requires a 1 line fix in `ghc/Main.hs`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9860> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9575: -XAutoDeriveTypeable fails to generate instances
by GHC 19 Dec '14

19 Dec '14

#9575: -XAutoDeriveTypeable fails to generate instances -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.4 Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following doesn't compile with GHC 7.8.3, but works with GHC HEAD. I couldn't find a matching ticket, so I don't know if this was fixed knowingly or not... {{{#!hs {-# LANGUAGE AutoDeriveTypeable #-} import Data.Typeable (Typeable) data T1 = C1 Int deriving (Eq,Ord) tvoid :: Typeable a => a -> IO () tvoid _ = return () main :: IO () main = tvoid (C1 0) }}} ...fails for GHC 7.8.3 with {{{ No instance for (Typeable T1) arising from a use of ‘tvoid’ In the expression: tvoid (C1 0) In an equation for ‘main’: main = tvoid (C1 0) }}} I'm marking this with high priority, as it makes `-XAutoDeriveTypeable` unusable on GHC 7.8.3 as it stands. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9575> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8984: Improve output of failed GeneralizedNewtypeDeriving coercion due to type roles
by GHC 19 Dec '14

19 Dec '14

#8984: Improve output of failed GeneralizedNewtypeDeriving coercion due to type roles -------------------------------------------+------------------------------- Reporter: haasn | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.8.1 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- When trying to build acme-schoenfinkel (as an example), I came across an error like this: {{{ Control/Category/Schoenfinkel.hs:66:48: Could not coerce from ‘cat (cat b c, b) c’ to ‘cat (WrappedSchoenfinkel cat b c, b) c’ because ‘cat (cat b c, b) c’ and ‘cat (WrappedSchoenfinkel cat b c, b) c’ are different types. arising from the coercion of the method ‘app’ from type ‘forall b c. cat (cat b c, b) c’ to type ‘forall b c. WrappedSchoenfinkel cat (WrappedSchoenfinkel cat b c, b) c’ Possible fix: use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (ArrowApply (WrappedSchoenfinkel cat)) }}} It was not immediately clear to me as a user that this was caused due to it wanting GNT which was now being blocked by type roles (rightfully so, as this instance allows UnsafeCoerce!), and beyond that, what the specific rule that triggered this was. In this case the failure is due to ‘WrappedSchoenfinkel cat b c’ not being nominally equal to ‘cat b c’, in the type ‘(WrappedSchoenfinkel cat b c, b)’, which is required to be nominally equal to ‘(cat b c, b)’ because it's used as a parameter to the variable ‘cat’. Printing a location breakdown and context information similar to this to the user would help understanding and debugging roles a lot. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8984> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6088: GeneralizedNewtypeDeriving + TypeFamilies + Equality constraints
by GHC 19 Dec '14

19 Dec '14

#6088: GeneralizedNewtypeDeriving + TypeFamilies + Equality constraints -------------------------------------------------+------------------------- Reporter: Lemming | Owner: Type: feature request | Status: Priority: normal | closed Component: Compiler (Type checker) | Milestone: Resolution: fixed | Version: 7.4.1 Operating System: Unknown/Multiple | Keywords: Type of failure: GHC rejects valid program | Architecture: Test Case: indexed- | Unknown/Multiple types/should_compile/T6088 | Difficulty: Blocking: | Unknown | Blocked By: | Related Tickets: 3046 -------------------------------------------------+------------------------- Comment (by Richard Eisenberg <eir@…>): In [changeset:"02b4845e07ef7110b2f735f323eb8748903330ff/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="02b4845e07ef7110b2f735f323eb8748903330ff" Consider equality contexts exotic, uninferrable by "deriving" See comments in #8984. This takes back the fix for #6088. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6088#comment:2> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2496: Invalid Eq/Ord instances in Data.Version
by GHC 19 Dec '14

19 Dec '14

#2496: Invalid Eq/Ord instances in Data.Version -------------------------------------+------------------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Core | Version: 6.8.3 Libraries | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D395 | -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel <hvr@…>): In [changeset:"5b8fa46ca37caa9ec83b217a697628135da34506/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="5b8fa46ca37caa9ec83b217a697628135da34506" Add Data.Version.makeVersion & `IsList Version` These two facilities provide some means to avoid the double-breakage caused by first by the deprecation (see #2496), and then again by the actual future field-removal. See also https://groups.google.com/d/msg/haskell-core-libraries/q9H- QlL_gnE/4lbb_mBjre8J for details about this library addition. Reviewed By: ekmett Differential Revision: https://phabricator.haskell.org/D577 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2496#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9902: Type family, pattern not matching
by GHC 18 Dec '14

18 Dec '14

#9902: Type family, pattern not matching -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.3 checker) | Operating System: MacOS X Keywords: | Type of failure: GHC Architecture: x86_64 (amd64) | rejects valid program Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- This is a follow up to issue #9898. The partially applied type families have been eliminated yet type checking is still failing. It is expected that 'test1' infer as `(Char, ())` but it does not. It seems that GHC is not matching the correct pattern on `:$:`. 'test3' and 'test4' indicate that GHC sometimes matches the correct pattern. 'test2' demonstrates an inconsistency between type checking with GHC and the type checking that occurs when the same expression is entered in GHCi. I do not know if this is a related problem. Enabling AllowAmbiguousTypes suggests it might be related because the compiler then complains `ApplyFilter (ToBool ((:.:) Not (Equal Char) Char)) (Char, ())` cannot be unified with `()` (With the second `:$:` rule enabled). Reported type of 'test1' with second rule removed {{{ test1 :: (Char, ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ())) }}} Reported type of 'test1' with second rule added {{{ test1 :: (Char, ApplyFilter (ToBool ((:.:) Not (Equal Char) Char)) (Char, ())) }}} test2 type check error {{{ ghc_bug3.hs:38:15: Couldn't match expected type ‘ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ())’ with actual type ‘ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ())’ NB: ‘ApplyFilter’ is a type function, and may not be injective The type variables ‘k0’, ‘k1’, ‘k2’ are ambiguous In the ambiguity check for: forall (k :: BOX) (k1 :: BOX) (k2 :: BOX). ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ()) To defer the ambiguity check to use sites, enable AllowAmbiguousTypes In an expression type signature: ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ()) In the expression: () :: ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ()) }}} {{{#!hs {-# LANGUAGE TypeFamilies, GADTs, DataKinds, UndecidableInstances, TypeOperators, PolyKinds #-} module Main where data Equal x y data Not x type family ToBool x where ToBool (Equal x x) = True ToBool (Equal x y) = False ToBool (Not True) = False ToBool (Not False) = True ToBool (Not p) = ToBool (Not (ToBool p)) data (:.:) g f x infixr 9 :.: type family f :$: x where (g :.: f) :$: x = g (f x) -- Uncomment to see change in 'test1' -- f :$: x = f x type family Filter f l where Filter f (x, xs) = ApplyFilter (ToBool (f :$: x)) (x, Filter f xs) Filter f () = () type family ApplyFilter p xs where ApplyFilter False (x, xs) = xs ApplyFilter p xs = xs type family xs :+: ys where (x, xs) :+: ys = (x, xs :+: Filter (Not :.: Equal x) ys) () :+: ys = ys infixl 5 :+: test1 = undefined :: (Char, ()) :+: (Char, ()) -- Typing this into GHCi works fine, but here does not type check. test2 = () :: ApplyFilter (ToBool ((Not :.: Equal Char) :$: Char)) (Char, ()) -- Type checks (with second rule added) test3 :: Maybe :$: Int test3 = Just 5 -- Type checks test4 :: (Maybe :.: Maybe) :$: Int test4 = Just (Just 5) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9902> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8749: Pattern synonyms crash GHCi
by GHC 18 Dec '14

18 Dec '14

#8749: Pattern synonyms crash GHCi ------------------------------------+------------------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- {{{ ghci -XPatternSynonyms > let pattern P x = x }}} causes a panic. I understand pattern synonyms are currently unsupported in GHCi, but we should give an error message, not a panic. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8749> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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