January 2019 - ghc-tickets

[GHC] #8095: TypeFamilies painfully slow
by GHC 08 Mar '19

08 Mar '19

#8095: TypeFamilies painfully slow -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.6.3 checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: Compile-time Architecture: Unknown/Multiple | performance bug Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: 5321 | -------------------------------------+------------------------------------- I'm using the TypeFamilies extension to generate types that are quite large. GHC can handle these large types fine when they are created manually, but when type families get involved, GHC's performance dies. Unlike in ticket #5321, using tail recursion does not eliminate the problem, and the order of arguments greatly affects compile time. I've attached a file Types.hs that demonstrates the problems. This file generates another Haskell file which has the problems. It takes 3 flags. The first is the size of the type to generate, the second is which type family function to use, and the third is whether to call the type family or just use a manually generated type. Here are my performance results: Using non-tail recursion, I get these results. I have to increase the stack size based on the size of the type I want to generate. {{{ $ ./Types 200 a a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=250 real 0m2.973s $ ./Types 300 a a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=350 real 0m6.018s $ ./Types 400 a a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=450 real 0m9.995s $ ./Types 500 a a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=550 real 0m15.645s }}} Tail recursion generates much slower compile times for some reason, and I still need to adjust the stack size: {{{ $ ./Types 200 b a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=250 real 0m16.120s }}} Changing the order of arguments to the recursive type family greatly changes the run times: {{{ $ ./Types 200 c a > test.hs && time ghc test.hs > /dev/null -fcontext- stack=250 real 0m6.095s }}} Without the type family, I get MUCH better performance: {{{ $ ./Types 10000 a d > test.hs && time ghc test.hs > /dev/null real 0m2.271s }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8095> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16221: Core Lint error with a data type
by GHC 07 Mar '19

07 Mar '19

#16221: Core Lint error with a data type -------------------------------------+------------------------------------- Reporter: monoidal | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following data declaration fails `-dcore-lint` {{{ #!haskell {-# LANGUAGE PolyKinds, ExplicitForAll, ExistentialQuantification #-} module T16221 where data T0 a = forall k (b :: k). MkT0 (T0 b) !Int }}} The test case was extracted from T14066a, the bang is to force the data type to have a wrapper. This has been present at least since GHC 8.0. {{{ <no location info>: warning: In the type ‘T0 a_a1wY’ Kind application error in type ‘T0 a_a1wY’ Function kind = forall k. k -> * Arg kinds = [(k_X1x2, *), (a_a1wY, k_a1wZ)] Fun: k_X1x2 (a_a1wY, k_a1wZ) <no location info>: warning: In the expression: MkT0 @ k_X1x2 @ a_a1wY @ k_X1x2 @ b_a1x0 dt_a1xC dt_X1xK Kinds don't match in type application: Type variable: a_X1xw :: k_X1x2 Arg type: a_a1wY :: k_a1wZ Linted Arg kind: k_a1wZ <no location info>: warning: In the type ‘T0 a_a1wY’ Kind application error in type ‘T0 a_a1wY’ Function kind = forall k. k -> * Arg kinds = [(k_X1x2, *), (a_a1wY, k_a1wZ)] Fun: k_X1x2 (a_a1wY, k_a1wZ) <no location info>: warning: In the expression: MkT0 @ k_X1x2 @ a_a1wY @ k_X1x2 @ b_a1x0 dt_a1xC dt_X1xK Kinds don't match in type application: Type variable: a_X1xw :: k_X1x2 Arg type: a_a1wY :: k_a1wZ Linted Arg kind: k_a1wZ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16221> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16263: GHC accepts illegal constraint in kind
by GHC 07 Mar '19

07 Mar '19

#16263: GHC accepts illegal constraint in kind -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 8.6 accepts {{{#!hs data Q :: Eq a => Type }}} It shouldn't, as we can't have `Eq a` as a constraint in kinds. Note that writing a constructor for `Q` is rejected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16263> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11715: There's something fishy going on with Constraint
by GHC 07 Mar '19

07 Mar '19

#11715: There's something fishy going on with Constraint -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc1 (Type checker) | 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 first noticed something was a bit odd with `Constraint` when chasing #11334. Consider this testcase, {{{#!hs import Data.Typeable main = do print $ typeRep (Proxy :: Proxy Eq) print $ typeOf (Proxy :: Proxy Eq) }}} With `ghc-8.0` this will produce, {{{ Eq Proxy (* -> *) Eq }}} Notice the second line; GHC seems to be claiming that `Eq :: * -> *`, which is clearly nonsense. I believe this issue may be the cause of some of the testsuite failures that I'm seeing on #11011. Unfortunately I haven't the foggiest where this issue might originate. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11715> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15918: GHC panic from TypeApplications(?)
by GHC 07 Mar '19

07 Mar '19

#15918: GHC panic from TypeApplications(?) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 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: -------------------------------------+------------------------------------- Minimized from https://gist.github.com/Icelandjack/683bd4b79027695ffc31632645c9d58b, I don't expect `Build []` to kind check but ti shouldn't crash. {{{#!hs {-# Language PolyKinds #-} {-# Language TypeFamilies #-} {-# Language ConstraintKinds #-} {-# Language FlexibleContexts #-} {-# Language QuantifiedConstraints #-} {-# Language UndecidableInstances #-} import Data.Kind class Rev f where rev :: f a instance (forall xx. cls xx => Rev xx) => Rev (Build cls) where rev = undefined data Build :: ((k -> Type) -> Constraint) -> (k -> Type) uu = rev :: Build [] a }}} gives a panic {{{ $ ghc-stage2 --interactive -ignore-dot-ghci ~/hs/711_bug.hs GHCi, version 8.7.20181029: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( ~/hs/711_bug.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181029 for x86_64-unknown-linux): ASSERT failed! irred_a1zW :: [(xx_a1zV[sk:3] |> Sym {co_a1zu})] 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/TcType.hs:1826:53 in ghc:TcType Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15918> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15799: GHC panic (and warnings)
by GHC 07 Mar '19

07 Mar '19

#15799: GHC panic (and warnings) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | 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: -------------------------------------+------------------------------------- On the [https://phabricator.haskell.org/D5229 visible kind application] differential, {{{#!hs {-# Language CPP #-} {-# Language DataKinds #-} {-# Language RankNTypes #-} {-# Language PatternSynonyms #-} {-# Language TypeOperators #-} {-# Language PolyKinds #-} {-# Language GADTs #-} {-# Language TypeFamilies #-} {-# Language TypeApplications #-} {-# Language FlexibleContexts #-} {-# Language FlexibleInstances #-} {-# Language InstanceSigs #-} import qualified GHC.TypeLits as TypeLits import GHC.TypeLits (Nat, KnownNat) import Data.Kind data Op obj = Op obj type family UnOp (op_a :: Op obj) :: obj where UnOp ('Op obj) = obj class Ríki (obj :: Type) where type (-->) :: Op obj -> obj -> Type type (<--) :: obj -> Op obj -> Type unop :: forall (a :: obj) (b :: obj). (a <-- 'Op b) -> ('Op b --> a) data (<=) :: Op Nat -> Nat -> Type where LessThan :: (KnownNat (UnOp op_a), KnownNat b, UnOp op_a TypeLits.<= b) => (op_a <= b) newtype (>=) :: Nat -> Op Nat -> Type where Y :: (a <= b) -> (b >= a) instance Ríki Nat where type (-->) = (<=) type (<--) = (>=) unop :: (a >= b) -> (b <= a) unop GreaterThan = LessThan pattern GreaterThan :: () => (KnownNat (UnOp b), KnownNat a, UnOp b <= a) => a >= b pattern GreaterThan = Y LessThan }}} {{{ $ ghci -ignore-dot-ghci 573_bug.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 573_bug.hs, interpreted ) WARNING: file compiler/types/TyCoRep.hs, line 2567 in_scope InScope {b_a1Em a_a1En} tenv [a1Em :-> b_a1Em[sk:0], a1En :-> a_a1En[sk:0]] cenv [] tys [KnownNat (UnOp b_a1Em[sk:1]), KnownNat a_a1En[sk:1], (UnOp b_a1Em[sk:1] |> {co_a1HN}) <= a_a1En[sk:1]] cos [] needInScope [a1HN :-> co_a1HN] WARNING: file compiler/types/TyCoRep.hs, line 2567 in_scope InScope {b_a1Jo a_a1Jp} tenv [a1Em :-> b_a1Jo[tau:3], a1En :-> a_a1Jp[tau:3]] cenv [] tys [KnownNat (UnOp b_a1Em), KnownNat a_a1En, (UnOp b_a1Em |> {co_a1HN}) <= a_a1En] cos [] needInScope [a1HN :-> co_a1HN] ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): tcEvVarPred irred_a1Js (UnOp b_a1Jo[tau:3] |> {co_a1HN}) <= a_a1Jp[tau:3] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcType.hs:1998:20 in ghc:TcType Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15799> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16187: Hadrian: Build fails when using absolute path for build root
by GHC 06 Mar '19

06 Mar '19

#16187: Hadrian: Build fails when using absolute path for build root -------------------------------------+------------------------------------- Reporter: davide | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.6.3 (Hadrian) | Keywords: hadrian build | Operating System: Linux root relative absolute path | Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This fails: {{{ $ git clean -xdf $ ./boot && ./configure && ./hadrian/build.sh -o/tmp/build ... Error when running Shake build system: at src/Main.hs:58:30-42: * Depends on: test at src/Hadrian/Builder.hs:70:5-23: * Depends on: /tmp/build01/stage2/lib/platformConstants at src/Hadrian/Utilities.hs:292:5-18: * Depends on: /tmp/build01/generated/platformConstants at src/Hadrian/Builder.hs:70:5-23: * Depends on: /tmp/build01/stage0/bin/deriveConstants at src/Development/Shake/Internal/Rules/Oracle.hs:157:43-68: * Depends on: OracleQ (ContextDataKey (Context {stage = Stage0, package = Package {pkgType = Program, pkgName = "deriveConstants", pkgPath = "utils/deriveConstants"}, way = v})) at src/Hadrian/Haskell/Cabal/Parse.hs:214:5-36: * Depends on: /tmp/build01/stage0/utils/deriveConstants/setup-config * Raised the exception: Error, rule finished running but did not produce file: /tmp/build01/stage0/utils/deriveConstants/setup-config CallStack (from HasCallStack): error, called at src/Development/Shake/Internal/Rules/File.hs:180:58 in shake-0.17.4-5aa097213b9663d13b00fb582ca77bb18e6d60c3b0376f0fc60fdbf22a73c6f4:Development.Shake.Internal.Rules.File }}} but changing `/tmp/build` to the relative path succeeds (something like `-o../../../../tmp/build`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16187> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12509: ghci -XSafe fails in an inscrutable way
by GHC 06 Mar '19

06 Mar '19

#12509: ghci -XSafe fails in an inscrutable way -------------------------------------+------------------------------------- Reporter: int-e | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Trying to run `ghci -XSafe` produces the following output: {{{ GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help <interactive>:1:6: error: Not in scope: ‘System.IO.hSetBuffering’ No module named ‘System.IO’ is imported. <interactive>:1:30: error: Not in scope: ‘System.IO.stdin’ No module named ‘System.IO’ is imported. <interactive>:1:46: error: Not in scope: data constructor ‘System.IO.NoBuffering’ No module named ‘System.IO’ is imported. <interactive>:1:70: error: Not in scope: ‘System.IO.hSetBuffering’ No module named ‘System.IO’ is imported. <interactive>:1:94: error: Not in scope: ‘System.IO.stdout’ No module named ‘System.IO’ is imported. <interactive>:1:111: error: Not in scope: data constructor ‘System.IO.NoBuffering’ No module named ‘System.IO’ is imported. <interactive>:1:135: error: Not in scope: ‘System.IO.hSetBuffering’ No module named ‘System.IO’ is imported. <interactive>:1:159: error: Not in scope: ‘System.IO.stderr’ No module named ‘System.IO’ is imported. <interactive>:1:176: error: Not in scope: data constructor ‘System.IO.NoBuffering’ No module named ‘System.IO’ is imported. }}} I'm not sure whether this should work, but in any case the error message is horrible. I tried adding `-trust base` to no avail. For comparison, ghc-7.10.3 starts with no trouble: {{{ > ghci -XSafe GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help Prelude> }}} (Motivation: I'm using ghci in Safe mode to track down import problems with SafeHaskell. As a workaround, I can use `:set -XSafe` after ghci's startup is done.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12509> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15837: Hadrian should build dynamically linked ghc binary
by GHC 06 Mar '19

06 Mar '19

#15837: Hadrian should build dynamically linked ghc binary -------------------------------------+------------------------------------- Reporter: davide | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.6.1 (Hadrian) | 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 ghc binary is dynamically linked via make in various flavors (e.g. quick). Hadrian builds a static linked binary in these cases (this is a bug). Various change are needed to fix this: 1. Add new .cabal file field extra-dynamic-library-flavours (see [https://github.com/haskell/cabal/pull/5606 this PR]). 2. Use .cabal extra-dynamic-library-flavours for the RTS (see [https://github.com/snowleopard/hadrian/issues/695#issue-367436377 this comment], depends on 1.) 3. Hadrian: fix management of nontrivial dynamic flavours of libHSrts (see [https://github.com/snowleopard/hadrian/pull/698 this PR]). 4. Hadrian should build ghc with the `-fPIC -dynamic` options (see [https://github.com/DavidEichmann/ghc/commit/752021f69f577b678630302b567fd71… #diff-408bbe46d4afae11991cbadb2c531b78 this comment], depends on 3.). 5. Use the correct relative path to the dynamically linked libraries (see [https://phabricator.haskell.org/D5281 this change], depends on 3. and 4.). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15837> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12102: “Constraints in kinds” illegal family application in instance (+ documentation issues?)
by GHC 06 Mar '19

06 Mar '19

#12102: “Constraints in kinds” illegal family application in instance (+ documentation issues?) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 8.0.0.20160511. Example from the user guide: [https://downloads.haskell.org/~ghc/8.0.1/docs/html/users_guide/glasgow_exts… #constraints-in-kinds Constraints in kinds] {{{#!hs type family IsTypeLit a where IsTypeLit Nat = 'True IsTypeLit Symbol = 'True IsTypeLit a = 'False data T :: forall a. (IsTypeLit a ~ 'True) => a -> * where MkNat :: T 42 MkSymbol :: T "Don't panic!" }}} Deriving a standalone `Show` instance *without* the constraint works fine {{{#!hs deriving instance Show (T a) }}} but I couldn't define a `Show` instance given the constraints: {{{#!hs -- • Couldn't match expected kind ‘'True’ -- with actual kind ‘IsTypeLit a0’ -- The type variable ‘a0’ is ambiguous -- • In the first argument of ‘Show’, namely ‘T a’ -- In the stand-alone deriving instance for ‘Show (T a)’ deriving instance Show (T a) }}} let's add constraints {{{#!hs -- • Couldn't match expected kind ‘'True’ -- with actual kind ‘IsTypeLit lit’ -- • In the first argument of ‘Show’, namely ‘T (a :: lit)’ -- In the instance declaration for ‘Show (T (a :: lit))’ instance IsTypeLit lit ~ 'True => Show (T (a :: lit)) where }}} let's derive for a single literal {{{#!hs -- • Illegal type synonym family application in instance: -- T Nat -- ('Data.Type.Equality.C:~ -- Bool -- (IsTypeLit Nat) -- 'True -- ('GHC.Types.Eq# Bool Bool (IsTypeLit Nat) 'True <>)) -- 42 -- • In the stand-alone deriving instance for ‘Show (T (42 :: Nat))’ deriving instance Show (T (42 :: Nat)) }}} same happens with {{{#!hs instance Show (T 42) where }}} ---- The documentation > Note that explicitly quantifying with `forall a` is not necessary here. seems to be wrong since removing it results in {{{ tVDv.hs:10:17-18: error: … • Expected kind ‘a’, but ‘42’ has kind ‘Nat’ • In the first argument of ‘T’, namely ‘42’ In the type ‘T 42’ In the definition of data constructor ‘MkNat’ Compilation failed. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12102> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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