April 2014 - ghc-tickets

[GHC] #8584: Pattern synonym type signatures
by GHC 17 Dec '14

17 Dec '14

#8584: Pattern synonym type signatures ------------------------------------+------------------------------------- Reporter: cactus | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: 5144 | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently, the only way to specify a type signature for a pattern synonym is by adding type annotations to the right-hand side, like this: {{{ {-# LANGUAGE PatternSynonyms, ScopedTypeVariables #-} pattern Single x = ([x] :: [Int]) }}} Bespoke syntax for adding type signatures for pattern synonyms would probably be useful. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8584> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8968: Pattern synonyms and GADTs
by GHC 17 Dec '14

17 Dec '14

#8968: Pattern synonyms and GADTs -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.1-rc2 checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects Architecture: Unknown/Multiple | valid program Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- I think this one is different from #8966, but feel free to close one as duplicate if it turns out to be the same problem. The following program (using GADTs and pattern synonyms, but not kind polymorphism or data kinds) fails to check with ghc-7.8.1-rc2, but I think it should: {{{ {-# LANGUAGE GADTs, KindSignatures, PatternSynonyms #-} data X :: (* -> *) -> * -> * where Y :: f Int -> X f Int pattern C x = Y (Just x) }}} The error I get is the following: {{{ PatKind.hs:6:18: Couldn't match type ‘t’ with ‘Maybe’ ‘t’ is untouchable inside the constraints (t1 ~ Int) bound by a pattern with constructor Y :: forall (f :: * -> *). f Int -> X f Int, in a pattern synonym declaration at PatKind.hs:6:15-24 ‘t’ is a rigid type variable bound by the inferred type of C :: X t t1 x :: Int at PatKind.hs:1:1 Expected type: t Int Actual type: Maybe Int In the pattern: Just x In the pattern: Y (Just x) PatKind.hs:6:18: Could not deduce (t ~ Maybe) from the context (t1 ~ Int) bound by the type signature for (Main.$WC) :: t1 ~ Int => Int -> X t t1 at PatKind.hs:6:9 ‘t’ is a rigid type variable bound by the type signature for (Main.$WC) :: t1 ~ Int => Int -> X t t1 at PatKind.hs:1:1 Expected type: t Int Actual type: Maybe Int Relevant bindings include ($WC) :: Int -> X t t1 (bound at PatKind.hs:6:9) In the first argument of ‘Y’, namely ‘(Just x)’ In the expression: Y (Just x) }}} Note that I'd be perfectly happy to provide a type signature for the pattern synonym, but I don't know of any syntax I could use. The Wiki page at https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms mentions I might be able to write {{{ pattern C :: Int -> X Maybe Int }}} but this triggers a parse error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8968> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8778: Typeable TypeNats
by GHC 15 Dec '14

15 Dec '14

#8778: Typeable TypeNats -------------------------------------------+------------------------------- Reporter: dmcclean | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler (Type checker) | Version: 7.8.1-rc1 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: 4385 | Test Case: | Blocking: -------------------------------------------+------------------------------- It would be useful (the case I have at hand is for some scenarios involving checking of physical dimensions) to be able to combine the Data.Dynamic story with the GHC.TypeLits story. A Typeable instance for every Nat is the sticking point. (I do not know if this is even theoretically possible.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8778> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8988: Documentation build fails if GHCi is unavailable
by GHC 15 Dec '14

15 Dec '14

#8988: Documentation build fails if GHCi is unavailable -------------------------------------+------------------------------------- Reporter: cjwatson | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.1 checker) | Operating System: Linux Keywords: | Type of failure: Building GHC Architecture: arm | failed Difficulty: Easy (less than 1 | Test Case: hour) | Blocking: Blocked By: | Related Tickets: | -------------------------------------+------------------------------------- Joachim Breitner [http://www.haskell.org/pipermail/glasgow-haskell- users/2014-March/024730.html reported] that the documentation fails to build on Debian armhf: {{{ 0% ( 0 / 5) in 'WwLib' 0% ( 0 / 2) in 'DmdAnal' 0% ( 0 / 2) in 'WorkWrap' compiler/typecheck/TcSplice.lhs-boot:29:1: TcSplice.tcTopSpliceExpr is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:37:1: TcSplice.runMetaE is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:38:1: TcSplice.runMetaP is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:39:1: TcSplice.runMetaT is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:40:1: TcSplice.runMetaD is exported by the hs-boot file, but not exported by the module 67% ( 2 / 3) in 'CmmPipeline' 0% ( 0 / 3) in 'StgCmmHpc' 0% ( 0 / 13) in 'PrelInfo' 0% ( 0 / 4) in 'StgCmmCon' 0% ( 0 / 2) in 'StgCmmExpr' 0% ( 0 / 6) in 'StgCmmBind' 0% ( 0 / 2) in 'CmmParse' 0% ( 0 / 2) in 'StgCmm' 5% ( 9 /175) in 'TcRnMonad' make[2]: *** [compiler/stage2/doc/html/ghc/ghc.haddock] Error 1 }}} The attached patch fixes this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8988> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8951: genSym uses atomic_inc but doesn't link arm_atomic_spin_lock
by GHC 15 Dec '14

15 Dec '14

#8951: genSym uses atomic_inc but doesn't link arm_atomic_spin_lock --------------------------------+---------------------------------------- Reporter: cjwatson | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 7.8.1-rc1 Keywords: | Operating System: Linux Architecture: arm | Type of failure: Building GHC failed Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | --------------------------------+---------------------------------------- On Debian armel, a snapshot of GHC 7.8 from 20140228 fails to build as follows: https://buildd.debian.org/status/fetch.php?pkg=ghc&arch=armel&ver=7.8.20140… {{{ "inplace/bin/ghc-stage2" -o utils/haddock/dist/build/tmp/haddock -hisuf hi -osuf o -hcsuf hc -static -H32m -O -lffi -optl-pthread -optc-mlong-calls -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/src -iutils/haddock/vendor/attoparsec-0.10.4.0 -iutils/haddock/dist/build -iutils/haddock/dist/build/autogen -Iutils/haddock/dist/build -Iutils/haddock/dist/build/autogen -optP-DIN_GHC_TREE -optP-include -optPutils/haddock/dist/build/autogen/cabal_macros.h -package Cabal-1.18.1.3 -package array-0.5.0.0 -package base-4.7.0.0 -package bytestring-0.10.4.0 -package containers-0.5.4.0 -package deepseq-1.3.0.2 -package directory-1.2.0.2 -package filepath-1.3.0.2 -package ghc-7.8.0.20140228 -package xhtml-3000.2.1 -funbox-strict-fields -Wall -fwarn-tabs -O2 -XHaskell2010 -no-user-package-db -rtsopts -odir utils/haddock/dist/build -hidir utils/haddock/dist/build -stubdir utils/haddock/dist/build utils/haddock/dist/build/Main.o utils/haddock/dist/build/Documentation/Haddock.o utils/haddock/dist/build/Data/Attoparsec.o utils/haddock/dist/build/Data/Attoparsec/ByteString.o utils/haddock/dist/build/Data/Attoparsec/ByteString/Char8.o utils/haddock/dist/build/Data/Attoparsec/Combinator.o utils/haddock/dist/build/Data/Attoparsec/Number.o utils/haddock/dist/build/Data/Attoparsec/ByteString/FastSet.o utils/haddock/dist/build/Data/Attoparsec/ByteString/Internal.o utils/haddock/dist/build/Data/Attoparsec/Internal.o utils/haddock/dist/build/Data/Attoparsec/Internal/Types.o utils/haddock/dist/build/Haddock.o utils/haddock/dist/build/Haddock/Interface.o utils/haddock/dist/build/Haddock/Interface/Rename.o utils/haddock/dist/build/Haddock/Interface/Create.o utils/haddock/dist/build/Haddock/Interface/AttachInstances.o utils/haddock/dist/build/Haddock/Interface/LexParseRn.o utils/haddock/dist/build/Haddock/Interface/ParseModuleHeader.o utils/haddock/dist/build/Haddock/Parser.o utils/haddock/dist/build/Haddock/Parser/Util.o utils/haddock/dist/build/Haddock/Utf8.o utils/haddock/dist/build/Haddock/Utils.o utils/haddock/dist/build/Haddock/Backends/Xhtml.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Decl.o utils/haddock/dist/build/Haddock/Backends/Xhtml/DocMarkup.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Layout.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Names.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Themes.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Types.o utils/haddock/dist/build/Haddock/Backends/Xhtml/Utils.o utils/haddock/dist/build/Haddock/Backends/LaTeX.o utils/haddock/dist/build/Haddock/Backends/HaddockDB.o utils/haddock/dist/build/Haddock/Backends/Hoogle.o utils/haddock/dist/build/Haddock/ModuleTree.o utils/haddock/dist/build/Haddock/Types.o utils/haddock/dist/build/Haddock/Doc.o utils/haddock/dist/build/Haddock/Version.o utils/haddock/dist/build/Haddock/InterfaceFile.o utils/haddock/dist/build/Haddock/Options.o utils/haddock/dist/build/Haddock/GhcUtils.o utils/haddock/dist/build/Haddock/Convert.o utils/haddock/dist/build/Paths_haddock.o /«PKGBUILDDIR»/compiler/stage2/build/libHSghc-7.8.0.20140228.a(genSym.o): In function `genSym': genSym.c:(.text+0x84): undefined reference to `arm_atomic_spin_lock' genSym.c:(.text+0x88): undefined reference to `arm_atomic_spin_unlock' collect2: error: ld returned 1 exit status make[2]: *** [utils/haddock/dist/build/tmp/haddock] Error 1 }}} Our armel architecture satisfies "arm_HOST_ARCH && defined(arm_HOST_ARCH_PRE_ARMv6)", so cas() in includes/stg/SMP.h will (uniquely among architectures) not be entirely inline: it calls arm_atomic_spin_lock and arm_atomic_spin_unlock, which are in libHSrts. 7.8 introduces compiler/cbits/genSym.c which uses atomic_inc. How should the linkage requirements be satisfied here? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8951> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8240: Better error messages for type family constraints
by GHC 11 Dec '14

11 Dec '14

#8240: Better error messages for type family constraints ------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- Consider this constraint {{{ F Int ~ Bool -- Arising (say) on line 5 F Int ~ Char -- Arising (say) on line 10 }}} At the moment we'll combine the two to {{{ F Int ~ Bool -- Arising on line 5 Bool ~ Char -- Arising on line 10 }}} The second of these errors is "insoluble" and is reported first. But it's totally misleading: nowhere in the program did we directly need `Int~Char`. Another variant of this came up in Trac #8227. There we get the constraint {{{ Scalar (V a) ~ t0 Scalar (V a) ~ t0 -> t0 }}} which leads to {{{ Scalar (V a) ~ t0 -> t0 t0 ~ t0 -> t0 -- Occurs check }}} which gives the confusing error {{{ T8227.hs:16:44: Occurs check: cannot construct the infinite type: t0 ~ t0 -> t0 Expected type: Scalar (V (t0 -> t0)) Actual type: Scalar (V a) }}} I think the solution is * Do not combine two Wanteds {{{ [W] F tys ~ t1 [W] F tys ~ t2 }}} unless t1 and t2 are both touchable unification variables. * Instead (perhaps) generate a Derived constraint {{{ [D] t1 ~ t2 }}} to express the fact that t1 and t2 had better end up equal. * To do this the inert set would need to contain many `CTyFunEq` constraints with the same LHS. I'm not very sure about this, and no time now, so I'm just making this ticket to record the issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8240> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8894: Clean up `Coercible` plumbing
by GHC 03 Dec '14

03 Dec '14

#8894: Clean up `Coercible` plumbing ------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently, the way `Coercible` is exported (with an data type in `GHC.Types` and a built-in !TyCon exported in `GHC.Prim`) works, but is confusing and should be cleaned up. Probably by exporting it directly from `GHC.Types`. Care needs to be taken that ghci and haddock display the data from modified built-in !TyCon; when I tried that a while ago it was displayed as a regular data type by one of them. If that is still the case and I didn't just do a mistake back then, this probably needs to be understood and fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8894> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8548: Coercible does not resolve type family application
by GHC 02 Dec '14

02 Dec '14

#8548: Coercible does not resolve type family application -------------------------------------------+------------------------------- Reporter: nomeata | Owner: nomeata Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.6.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: #8503 | Test Case: | Blocking: -------------------------------------------+------------------------------- With GND implemented using `Coercible` (See #8503) the test for #4185 fails. A minimal example is: {{{ {-# LANGUAGE TypeFamilies #-} module CoerceNewtypeFamily where import GHC.Exts data family Foo k newtype instance Foo Int = FooInt Int x :: Foo Int -> Int x = coerce }}} yielding {{{ [1 of 1] Compiling CoerceNewtypeFamily ( CoerceNewtypeFamily.hs, CoerceNewtypeFamily.o ) CoerceNewtypeFamily.hs:11:5: No instance for (Coercible (Foo Int) Int) because ‛Foo Int’ and ‛Int’ are different types. arising from a use of ‛coerce’ In the expression: coerce In an equation for ‛x’: x = coerce }}} I guess the `Coercible` finding code needs to simply type family equations if possible. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8548> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8304: more lenient operator sections (RelaxedSections extension)
by GHC 01 Dec '14

01 Dec '14

#8304: more lenient operator sections (RelaxedSections extension) -------------------------------------+------------------------------------- Reporter: aavogt | Owner: Type: feature request | Status: new Priority: lowest | Milestone: Component: Compiler (Parser) | 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: | -------------------------------------+------------------------------------- Some operator sections are rejected which could have some meaning. {{{ (a ++ b ++ ) could mean \x -> a ++ b ++ c (++ a ++) could mean \x y -> x ++ a ++ y }}} The attached quasiquoter implements this, but for various reasons it would be better if ghc supported this directly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8304> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8100: Standalone deriving using template haskell
by GHC 01 Dec '14

01 Dec '14

#8100: Standalone deriving using template haskell ------------------------------------+------------------------------------- Reporter: acube | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently, there seems to be no support for standalone deriving in TemplateHaskell: {{{ Prelude Data.Typeable Language.Haskell.TH> :set -XStandaloneDeriving Prelude Data.Typeable Language.Haskell.TH> data Weird a (b :: * -> * -> *) c = Weird Prelude Data.Typeable Language.Haskell.TH> runQ $ [d| deriving instance Typeable Weird |] [] }}} ''Use case'': The library [http://hackage.haskell.org/package/typeable-th typeable-th] can already generate Typeable instances using TH for GHC 7.4 and 7.6. To add support for GHC 7.8 in a way that the user doesn't have to care about the version, there has to be a way to make Typeable instances via TH in GHC 7.8. This is currently impossible, but with StandaloneDeriving support for TH, it would be possible. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8100> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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