October 2015 - ghc-tickets

[GHC] #8524: GHC is inconsistent with the Haskell Report on which Unicode characters are allowed in string and character literals
by GHC 19 Apr '16

19 Apr '16

#8524: GHC is inconsistent with the Haskell Report on which Unicode characters are allowed in string and character literals ----------------------------+---------------------------------------------- Reporter: oerjan | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects valid program Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ----------------------------+---------------------------------------------- GHC is inconsistent with the Haskell Report on which Unicode characters are allowed in string and character literals. (And I don't like either option, why leave out any characters in strings unnecessarily?) Examples from ghci 7.6.3 (also tested in lambdabot on irc): {{{ Prelude> "" -- Unicode char \8203, Format class. <interactive>:10:2: lexical error in string/character literal at character '\8203' Prelude> " " -- Unicode char \8202, Space class. "\8202" Prelude> "t\ \est" -- Unicode char \8202 in a string gap. <interactive>:14:4: lexical error in string/character literal at character '\8202' }}} My reading of http://www.haskell.org/onlinereport/haskell2010/haskellch2.html (section 2.2 and 2.6): * The report BNF token "graphic", which can be used in literals, includes indirectly many Unicode classes, but uniWhite is not one of them. Thus the only Unicode whitespace allowed to represent itself in literals is ASCII space. * Unicode formatting characters are not mentioned in the BNF that I can see, so are not allowed in literals. * String gaps are made out of the report BNF token whitespace, which ''does'' include uniWhite. Who wants what: || ||= GHC =||= Report =||= Me =|| || Format in string || No || No || Yes || || Space/uniWhite in string || Yes || No || Yes || || Space/uniWhite in string gap || No || Yes || Dunno || In short, GHC's behavior is buggy and/or annoying in two opposite ways: * It leaves out some Unicode characters as allowable in strings and character literals, presumably because the report says so. * It allows some characters the report says it ''shouldn't'', and refuses some characters the report says it ''should''. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8524> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10914: Bad symbol resolution on Darwin when using DYLD_FORCE_FLAT_NAMESPACE=1
by GHC 17 Apr '16

17 Apr '16

#10914: Bad symbol resolution on Darwin when using DYLD_FORCE_FLAT_NAMESPACE=1 -----------------------------------------+------------------------------- Reporter: jacereda | Owner: Type: bug | Status: new Priority: high | Milestone: Component: GHCi | Version: 7.10.2 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -----------------------------------------+------------------------------- Starting ghci as: {{{ env DYLD_FORCE_FLAT_NAMESPACE=1 ghci }}} can cause symbol resolution to fail. I tried with Data.Hashable as follows: {{{ import Data.Hashable main = putStrLn $ show $ hashWithSalt 0 "foo" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10914> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[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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