August 2015 - ghc-tickets

[GHC] #10318: Cycles in class declaration (via superclasses) sometimes make sense.
by GHC 13 Apr '16

13 Apr '16

#10318: Cycles in class declaration (via superclasses) sometimes make sense. -------------------------------------+------------------------------------- Reporter: ekmett | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.10.1 Component: Compiler | Operating System: Unknown/Multiple (Type checker) | Type of failure: GHC rejects Keywords: | valid program Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I'd like to be able to say the following, to describe the notion of an integral domain in Haskell: {{{ -- | Product of non-zero elements always non-zero. -- Every integral domain has a field of fractions. -- The field of fractions of any field is itself. class (Frac (Frac a) ~ Frac a, Fractional (Frac a), IntegralDomain (Frac a)) => IntegralDomain a where type Frac a :: * embed :: a -> Frac a instance IntegralDomain Integer where type Frac Integer = Rational embed = fromInteger instance IntegralDomain Rational where type Frac Rational = Rational embed = id }}} But GHC gets scared when it sees the cyclic reference that `IntegralDomain` instances depend on an IntegralDomain superclass, which really is cyclic in the (Frac a) case here, and that is kind of the point. =) Right now the best approximation of the correct answer that I have for this situation is to lie and claim the constraint is weaker: {{{ -- | Product of non-zero elements always non-zero class (Frac (Frac a) ~ Frac a, Fractional (Frac a)) => AlmostIntegralDomain a where type Frac a :: * embed :: a -> Frac a class (AlmostIntegralDomain a, AlmostIntegralDomain (Frac a)) => IntegralDomain a instance (AlmostIntegralDomain a, AlmostIntegralDomain (Frac a)) => IntegralDomain a instance AlmostIntegralDomain Integer where type Frac Integer = Rational embed = fromInteger instance AlmostIntegralDomain Rational where type Frac Rational = Rational embed = id }}} Now the user is stuck defining a different class than the one they consume. Alternately, with `ConstraintKinds`, I can encode: {{{ data Dict p where Dict :: p => Dict p class (Frac (Frac a) ~ Frac a, Fractional (Frac a)) => IntegralDomain a where type Frac a :: * embed :: a -> Frac a proofFracIsIntegral :: p a -> Dict (IntegralDomain (Frac a)) default proofFracIsIntegral :: IntegralDomain (Frac a) => p a -> Dict (IntegralDomain (Frac a)) proofFracIsIntegral _ = Dict }}} but now whenever I need to get from `IntegralDomain a` to `IntegralDomain (Frac a)` I need to explicitly open the `proofFracIsIntegral` with a rats' nest of `ScopedTypeVariables`. It would be really really nice if I could get GHC to deal with this for me as I currently have a few thousand lines of code hacking around this limitation. =/ -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10318> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10001: GHC crash trying to build a project within Nix-shell
by GHC 11 Apr '16

11 Apr '16

#10001: GHC crash trying to build a project within Nix-shell -------------------------------------+------------------------------------- Reporter: wolftune | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: 9825 Differential Revisions: | -------------------------------------+------------------------------------- {{{ <no location info>: ghc: panic! (the 'impossible' happened) (GHC version 7.8.4 for x86_64-unknown-linux): Loading temp shared object failed: /run/user/1000/ghc19915_0/ghc19915_20.so: failed to map segment from shared object Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug [20 of 99] Compiling Settings.StaticFiles ( Settings/StaticFiles.hs, dist/build/Settings/StaticFiles.o ) <no location info>: ghc: panic! (the 'impossible' happened) (GHC version 7.8.4 for x86_64-unknown-linux): Loading temp shared object failed: /run/user/1000/ghc19915_0/ghc19915_21.so: failed to map segment from shared object }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10001> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8468: ghc panic in deriving Generic1 on Array#
by GHC 07 Apr '16

07 Apr '16

#8468: ghc panic in deriving Generic1 on Array# -----------------------------------+--------------------------------------- Reporter: ghorn | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time crash Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -----------------------------------+--------------------------------------- Compiling the following code {{{ {-# Language DeriveGeneric, MagicHash #-} module Test where import GHC.Generics import GHC.Prim data Array a = Array (Array# a) newtype Vec a = MkVec {unVec :: Array a} deriving Generic1 }}} causes panic: {{{ [1 of 1] Compiling Test ( Test.hs, Test.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.6.3 for x86_64-unknown-linux): No match in record selector tyConTyVars Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} some comments from IRC: <monoidal> with deriving Generic1 we get "Can't make a derived instance of `Generic1 Array': Array must not have unlifted or polymorphic arguments" - so it seems the check is not done recursively on used types <monoidal> * deriving Generic1 on Array -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8468> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8416: GHC.Generics needs more documentation
by GHC 07 Apr '16

07 Apr '16

#8416: GHC.Generics needs more documentation -------------------------------------+------------------------------------- Reporter: tibbe | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries (other) | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- Recently I tried to used `GHC.Generics` "in anger" for the first time, to fix some code in hashable that wasn't originally written by me. After a while I just gave up (and the generics support in hashable is now somewhat broken). The documentation for `GHC.Generics` is too incomprehensible for mere mortals. In particular, I find the documentation for `M1` and `K1` not very helpful. The documentation needs examples, more in-depth explanations of what each of the data types/constructors is used for, and finally an explanation of the up to 4 type parameters! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8416> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8797: Generics instances for monoid and applicative newtypes
by GHC 07 Apr '16

07 Apr '16

#8797: Generics instances for monoid and applicative newtypes -------------------------------------------+------------------------------- Reporter: jcristovao | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.6.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 hour) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- Hi, Is there any particular reason why there aren't Generic instances for the newtypes under Data.Monoid and Control.Applicative (for example)? I've tried adding them to GHC/Generics.hs and base compiles without problems. Could this addition be considered? Best Regards, João -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8797> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8929: Deriving Generics broken
by GHC 07 Apr '16

07 Apr '16

#8929: Deriving Generics broken ----------------------------------+------------------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 (amd64) | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ----------------------------------+------------------------------------- I load the following code into ghci: == {-# LANGUAGE DeriveGeneric #-} import GHC.Generics import Data.Binary data Foo = Foo deriving (Show, Generic) instance Binary Foo == Then I execute: (decode . encode $ Foo) :: Foo In 7.6.3 (stage 2 booted 7.6.3), I get an error. In 7.6.3 (stage 2 booted 7.6.2), the desired result "Foo" is shown. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8929> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9523: Typo in GHC Generics documentation
by GHC 07 Apr '16

07 Apr '16

#9523: Typo in GHC Generics documentation -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.4 Component: Documentation | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- In `GHC.Generics`: The types `S`, `C` and `R` are once again type-level proxies, just used to create several variants of `M1`. The `R`, it seems, is supposed to be a `D`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9523> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9527: Add Generic instances for Language.Haskell.TH
by GHC 07 Apr '16

07 Apr '16

#9527: Add Generic instances for Language.Haskell.TH -------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less | Type of failure: than a day) | None/Unknown Blocked By: 9526 | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Template Haskell has a number of huge data types that would be much easier to work with if they had `Generic` instances. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9527> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9563: Support for deriving Generic1 for data families
by GHC 07 Apr '16

07 Apr '16

#9563: Support for deriving Generic1 for data families -------------------------------------+------------------------------------- Reporter: mnislaih | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: GHC Difficulty: Unknown | rejects valid program Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following code: {{{#!hs import GHC.Generics data family F typ :: * -> * data A data instance F A a = AData a deriving Generic1 }}} produces an error when run with ghc 7.8.2 or 7.8.3: {{{ Couldn't match type ‘Rep1 (F A)’ with ‘M1 t0 t1 (M1 t2 t3 (M1 t4 t5 Par1))’ The type variables ‘t0’, ‘t1’, ‘t2’, ‘t3’, ‘t4’, ‘t5’ are ambiguous Expected type: Rep1 (F A) a Actual type: M1 t0 t1 (M1 t2 t3 (M1 t4 t5 Par1)) a In the pattern: M1 (M1 (M1 g1)) In an equation for ‘to1’: to1 (M1 (M1 (M1 g1))) = AData (unPar1 g1) In the instance declaration for ‘Generic1 (F A)’ }}} whereas ghc 7.6.3 simply refuses to go ahead with the message: {{{ generic1.hs:14:40: Derived instance `Generic1 (F A)' requires illegal partial application of data type family F In the data instance declaration for `F' }}} Either a check has gone missing in 7.8.x, or a bug has crept up in the Generic1 support. I have gone through past tickets and https://ghc.haskell.org/trac/ghc/ticket/5936 suggests that it is the latter. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9563> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10513: ghc 7.6.3 Compiler panic with Generics
by GHC 07 Apr '16

07 Apr '16

#10513: ghc 7.6.3 Compiler panic with Generics -------------------------------------+------------------------------------- Reporter: | Owner: andreas.abel | Status: new Type: bug | Milestone: Priority: normal | Version: 7.6.3 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Currently, Agda only compiles with ghc 7.4, 7.8, and 7.10, see https://code.google.com/p/agda/issues/detail?id=1558 Here is a the relevant commit: https://github.com/agda/agda/commit/f7b47de0cb167514f6db859b204abd638887b76f Generics do not seem to work properly in ghc 7.6 {{{ [ 92 of 312] Compiling Agda.Syntax.Abstract.Name ( src/full/Agda/Syntax/Abstract/Name.hs, dist/build/Agda/Syntax/Abstract/Name.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.6.3 for x86_64-unknown-linux): tcIfaceGlobal (local): not found: Agda-2.4.3:Agda.Syntax.Fixity.D1PrecedenceLevel{tc a4mIV} [(rc0D, Type constructor `Agda-2.4.3:Agda.Syntax.Fixity.Fixity'{tc rc0D}'), (r4mFT, Type constructor `Agda-2.4.3:Agda.Syntax.Fixity.Precedence{tc r4mFT}'), […] (r4mKa, Identifier `Agda-2.4.3:Agda.Syntax.Fixity.$fTypeable1ThingWithFixity{v r4mKa}'), (r4mKb, Identifier `Agda-2.4.3:Agda.Syntax.Fixity.$fGenericThingWithFixity{v r4mKb}'), (r4mKc,ghc: panic! (the 'impossible' happened) (GHC version 7.6.3 for x86_64-unknown-linux): ghc: panic! (the 'impossible' happened) (GHC version 7.6.3 for x86_64-unknown-linux): tcIfaceGlobal (local): not found: <<details unavailable>> Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} I don't know whether you are maintaining old ghcs, but it seems we have to drop Generics until we drop support for ghc 7.6 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10513> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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