May 2016 - ghc-tickets

[GHC] #11357: Regression when deriving Generic1 on poly-kinded data family
by GHC 20 Jul '16

20 Jul '16

#11357: Regression when deriving Generic1 on poly-kinded data family -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.1 (CodeGen) | Keywords: Generics, | Operating System: Unknown/Multiple TypeInType | Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- On GHC 7.10.3, the following code compiles: {{{#!hs {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} module ProxyFam where import GHC.Generics (Generic1) data family ProxyFam (a :: k) data instance ProxyFam (a :: k) = ProxyCon deriving Generic1 }}} But on GHC 8.1, it fails: {{{ $ /opt/ghc/head/bin/ghc ProxyFam.hs [1 of 1] Compiling ProxyFam ( ProxyFam.hs, ProxyFam.o ) ProxyFam.hs:10:53: error: • Can't make a derived instance of ‘Generic1 ProxyFam’: ProxyFam must not be instantiated; try deriving `ProxyFam k a' instead • In the data instance declaration for ‘ProxyFam’ }}} I'm not sure what exactly is going on here, but I have a hunch. The `Generic1` typeclass is of kind `* -> *`, which means that in a `Generic1 ProxyFam` instance, the kind of `a` is instantiated to `*`. Curiously, though, the same error does ''not'' appear when `deriving Generic` for a normal datatype (e.g., `data ProxyFam (a :: k) = ProxyCon deriving Generic1`). Richard, I'm stuck as to how to fix this. I suspect this was triggered by `-XTypeInType`-related changes, specifically, [http://git.haskell.org/ghc.git/blobdiff/6e56ac58a6905197412d58e32792a04a63b… this change]: {{{#!diff diff --git a/compiler/typecheck/TcGenGenerics.hs b/compiler/typecheck/TcGenGenerics.hs index 2c5b80e..fb18517 100644 (file) --- a/compiler/typecheck/TcGenGenerics.hs +++ b/compiler/typecheck/TcGenGenerics.hs @@ -147,7 +146,7 @@ canDoGenerics tc tc_args -- -- Data family indices can be instantiated; the `tc_args` here are -- the representation tycon args - (if (all isTyVarTy (filterOut isKind tc_args)) + (if (all isTyVarTy (filterOutInvisibleTypes tc tc_args)) then IsValid else NotValid (tc_name <+> text "must not be instantiated;" <+> text "try deriving `" <> tc_name <+> tc_tys <> }}} What exactly does `filterOutInvisibleTypes` do? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11357> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11094: Cost-center heap profiler should be able to emit samples to eventlog
by GHC 20 Jul '16

20 Jul '16

#11094: Cost-center heap profiler should be able to emit samples to eventlog -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Often when looking at heap profiles I find myself wishing that I had better tools for aligning the heap behavior to various events in the lifetime of my program. The eventlog provides a nice facility for marking these events, why not record heap profile samples in the eventlog as well? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11094> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11348: Local open type families instances ignored during type checking
by GHC 20 Jul '16

20 Jul '16

#11348: Local open type families instances ignored during type checking -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeInType #-} import Data.Kind import Data.Proxy type family TrivialFamily t :: Type type instance TrivialFamily (t :: Type) = Bool data R where R :: Proxy Bool -> R type ProblemType t = 'R ('Proxy :: Proxy (TrivialFamily t)) }}} Compiling this program as-is, GHC rejects it! {{{#!sh error: • Expected kind ‘Proxy Bool’, but ‘'Proxy’ has kind ‘Proxy (TrivialFamily t)’ • In the first argument of ‘R’, namely ‘(Proxy :: Proxy (TrivialFamily t))’ In the type ‘R (Proxy :: Proxy (TrivialFamily t))’ In the type declaration for ‘ProblemType’ }}} But if we move `TrivialFamily` to another module and import it, GHC discovers that `TrivialFamily t = Bool` and the program is accepted. When compiling the rejected program (with the local family instance) I observe that the instance environments given by `FamInst.tcGetFamInstEnvs` contain no instances! The renamer processes the local instance, but no `FamInst` is created for it, and nothing enters the `TcGblEnv`'s family instance record. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11348> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12082: Typeable on RealWorld fails
by GHC 20 Jul '16

20 Jul '16

#12082: Typeable on RealWorld fails -------------------------------------+------------------------------------- Reporter: bgamari | 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: -------------------------------------+------------------------------------- This, {{{#!hs import GHC.Prim import Data.Typeable main = print $ typeRep (Proxy :: Proxy RealWorld) }}} fails with, {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.0.20160421 for x86_64-unknown-linux): tyConRep RealWorld Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12082> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12132: Type representations missing for promoted boxed tuples
by GHC 19 Jul '16

19 Jul '16

#12132: Type representations missing for promoted boxed tuples -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: 8.0.2 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: -------------------------------------+------------------------------------- This is a continuation of #11120. It seems there is something odd happening with type representations for boxed tuples, {{{ $ inplace/bin/ghc-stage2 --interactive GHCi, version 8.1.20160528: http://www.haskell.org/ghc/ :? for help Prelude> :set -XDataKinds Prelude> :m + Data.Typeable Data.Proxy Prelude Data.Typeable Data.Proxy> typeOf (Proxy :: Proxy (Int,Int)) Proxy * (Int,Int) Prelude Data.Typeable Data.Proxy> typeOf (Proxy :: Proxy '(Int,Int)) GHC error in desugarer lookup in Ghci2: Can't find interface-file declaration for variable $tc'(,) Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20160528 for x86_64-unknown-linux): initDs IOEnv failure Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Prelude Data.Typeable Data.Proxy> }}} This is odd since the `$tc'(,)` binding is present in the interface file for `GHC.Tuple`, {{{ $ inplace/bin/ghc-stage2 --show-iface libraries/ghc-prim/dist- install/build/GHC/Tuple.dyn_hi |less ... 14e44400752f4580e52ed2a760b9633f $tc'(,) :: TyCon {- HasNoCafRefs, Strictness: m, Unfolding: (TyCon 14407099369839560749## 10712746223293009168## $trModule $tc'(,)1) -} 543be63d698612591d2e75b0b60ad643 $tc'(,)1 :: TrName {- HasNoCafRefs, Strictness: m1, Unfolding: (TrNameS "'(,)"#) -} 469b4ffe716da12a5be1f5ab03864791 $tc'(,,) :: TyCon {- HasNoCafRefs, Strictness: m, Unfolding: (TyCon 3540448346642256323## 9150387332266490903## $trModule $tc'(,,)1) -} ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12132> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11717: Way to dump cmm only once
by GHC 18 Jul '16

18 Jul '16

#11717: Way to dump cmm only once -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (CodeGen) | Keywords: newcomer | 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 current way to dump Cmm output is `-ddump-cmm`, but that dumps Cmm repeatedly, of every stage, similar to `-ddump-verbose-core2core`. This is often confusing. I propose that `-ddump-cmm` dumps only the initial Cmm code, that the flag `-ddump-simpl-cmm` dumps the final Cmm code, and that `-ddump-verbose-cmm` dumps every stage. Shoudn’t be hard to do for a newcomer. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11717> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8732: Global big object heap allocator lock causes contention
by GHC 17 Jul '16

17 Jul '16

#8732: Global big object heap allocator lock causes contention ------------------------------------+------------------------------------- Reporter: tibbe | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | 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: | ------------------------------------+------------------------------------- The lock allocate() takes when allocating big objects hurts scalability of I/O bound application. Network.Socket.ByteString.recv is typically called with a buffer size of 4096, which causes a ByteString of that size to be allocate. The size of this ByteString causes it to be allocated from the big object space, which causes contention of the global lock that guards that space. See http://www.yesodweb.com/blog/2014/02/new-warp for a real world example. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8732> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12113: ghc-8.0.1-rc4: unification false positive?
by GHC 15 Jul '16

15 Jul '16

#12113: ghc-8.0.1-rc4: unification false positive? -------------------------------------+------------------------------------- Reporter: _deepfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE ExistentialQuantification #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE UnicodeSyntax #-} module Foo () where type family TF x ∷ * data ADT x type instance TF (ADT x) = x class (a ~ ADT (TF a)) ⇒ TC2 a b | a → b data Forget = ∀ a b. TC2 a b ⇒ Forget a -- ~ Forget (ADT (TF a)) data PhantomF a b = Constr Forget -- ~ Constr (Forget (ADT (TF a))) f ∷ ∀ a b. TC2 a b ⇒ ADT (TF a) → [Forget] f _ = case ((undefined) ∷ (PhantomF a b)) of Constr m → [Forget m] -- Here GHC 8.0.1-rc4 unifies, whereas GHC 7.10.3 (properly?) fails with: -- ghc8-unification-false-positive.hs:20:21: -- Couldn't match type ‘Forget’ with ‘ADT (TF Forget)’ -- In the expression: Forget m -- In the expression: [Forget m] -- In a case alternative: Constr m -> [Forget m] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12113> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12057: TypeFamilyDependencies on GHC.Generic's `Rep`
by GHC 14 Jul '16

14 Jul '16

#12057: TypeFamilyDependencies on GHC.Generic's `Rep` -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | Keywords: TypeFamilies, | Operating System: Unknown/Multiple Injective | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- With `TypeFamilyDependencies` (`InjectiveTypeFamilies`) can't `Rep` from `Generic` have a dependency? {{{#!hs class Generic a where type Rep a = (res :: Type -> Type) | res -> a ... }}} Assuming the meta data is always unique. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12057> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11835: ApplicativeDo failed to desugar last line with pure $ <expr>
by GHC 12 Jul '16

12 Jul '16

#11835: ApplicativeDo failed to desugar last line with pure $ <expr> -------------------------------------+------------------------------------- Reporter: Cosmia | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 Keywords: ApplicativeDo | Operating System: MacOS X Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: #11607 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE ApplicativeDo #-} f m = do x <- m 1 y <- m 2 return $ x + y }}} f should have type (Applicative f, Num a, Num b) => (a -> f b) -> f b but ghc considers f a monad maybe similar with #11607 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11835> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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