November 2018 - ghc-tickets

[GHC] #15881: GHC Panic: data A n (a :: n) :: a -> Type
by GHC 29 Nov '18

29 Nov '18

#15881: GHC Panic: data A n (a :: n) :: a -> Type -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 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: -------------------------------------+------------------------------------- {{{#!hs {-# Language KindSignatures #-} {-# Language PolyKinds #-} import Data.Kind data A n (a :: n) :: a -> Type }}} causes a panic on 8.7.20181017 {{{ $ ~/code/headghc/inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci 665_bug.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 665_bug.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): ASSERT failed! Type-correct unfilled coercion hole {co_a1xR} 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/TcHsSyn.hs:1805:99 in ghc:TcHsSyn Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} and an assertion failure in 8.7.20181029 {{{ $ ~/code/unmodifiedghc/inplace/bin/ghc-stage2 --interactive -ignore-dot- ghci 665_bug.hs GHCi, version 8.7.20181029: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 665_bug.hs, interpreted ) *** Exception: ASSERT failed! file compiler/types/TyCon.hs, line 420 > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15881> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15740: Type family with higher-rank result is too accepting
by GHC 29 Nov '18

29 Nov '18

#15740: Type family with higher-rank result is too accepting -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: TypeFamilies, | Operating System: Unknown/Multiple TypeInType | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC accepts this garbage: {{{ type family F2 :: forall k. k -> Type data SBool :: Bool -> Type data Nat data SNat :: Nat -> Type type instance F2 = SBool type instance F2 = SNat }}} The family `F2` should have an arity of 0, meaning that only one instance is possible -- and the RHS of that instance must have kind `forall k. k -> Type`. In other words, even accepting only one of the instances above is hogwash. This is from comment:15:ticket:11719, but you don't have to read that to understand this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15740> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15870: No skolem info panic
by GHC 29 Nov '18

29 Nov '18

#15870: No skolem info panic -------------------------------------+------------------------------------- Reporter: sheaf | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.2 (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: -------------------------------------+------------------------------------- I've been toying with some type-level lenses and running into some issues with kind unification, when I ran into a panic: {{{ bug.hs:30:34: error:ghc.exe: panic! (the 'impossible' happened) (GHC version 8.6.2 for x86_64-unknown-mingw32): No skolem info: [k_a1Hgj] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler\utils\Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler\\typecheck\\TcErrors.hs:2891:5 in ghc:TcErrors }}} Here's a boiled down version (with a bit of extraneous code left in for context, as it's so short): {{{#!hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} data Optic a where --Index :: Nat -> Optic a --Name :: Symbol -> Optic a (:.:) :: Optic a -> Optic b -> Optic a -- composition class Gettable a (optic :: Optic a) where type Get a (optic :: Optic a) {- some basic instances, e.g. instance Gettable (a,b) (Index 0) where type Get (a,b) (Index 0) = a ... -} instance forall a b (g1 :: Optic a) (g2 :: Optic b). ( Gettable a g1 , b ~ Get a g1 , Gettable b g2 ) => Gettable a (g1 :.: g2) where type Get a (g1 :.: g2) = Get a g2 }}} The program I am actually trying to write has the instance declaration changed to {{{#!hs instance forall a b (g1 :: Optic a) (g2 :: Optic (Get a g1)). ( Gettable a g1 , b ~ Get a g1 , Gettable b g2 ) => Gettable a (g1 :.: g2) where type Get a (g1 :.: g2) = Get (Get a g1) g2 }}} but GHC complains that it can't match kinds: {{{ • Expected kind ‘Optic b’, but ‘g2’ has kind ‘Optic (Get a g1)’ • In the second argument of ‘Gettable’, namely ‘g2’ In the instance declaration for ‘Gettable a (g1 :.: g2)’ | 20 | , Gettable b g2 | }}} I don't know if there is a way around that, and I'd be interested to hear any advice. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15870> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15789: GHC panic using visible kind applications and a higher-rank kind
by GHC 29 Nov '18

29 Nov '18

#15789: GHC panic using visible kind applications and a higher-rank kind -------------------------------------+------------------------------------- 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: -------------------------------------+------------------------------------- Using visible kind applications (#12045): {{{#!hs {-# Language LiberalTypeSynonyms #-} {-# Language PolyKinds #-} {-# Language RankNTypes #-} {-# Language DataKinds #-} import Data.Kind type Cat ob = ob -> ob -> Type data Zero :: forall (cat :: forall xx. xx -> Type) a. forall b. Cat (forall b. cat b u) }}} {{{ $ ghci -ignore-dot-ghci 546_bug.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 546_bug.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): ASSERT failed! Type-correct unfilled coercion hole {co_a1yl} 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/TcHsSyn.hs:1805:99 in ghc:TcHsSyn Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15789> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15764: GHC panic from PolyKinds + DataKinds
by GHC 29 Nov '18

29 Nov '18

#15764: GHC panic from PolyKinds + DataKinds -------------------------------------+------------------------------------- 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: -------------------------------------+------------------------------------- Playing around with GhcKinds/KindInference/Examples gives me a GHC panic {{{#!hs -- https://ghc.haskell.org/trac/ghc/wiki/GhcKinds/KindInference/Examples?versi… {-# Language PolyKinds #-} {-# Language KindSignatures #-} {-# Language DataKinds #-} import Data.Kind import Data.Proxy import GHC.TypeLits class C6 (k :: Type) (a :: k) (b :: Proxy (a :: k)) where type T6 (proxy :: Proxy '(k, b)) }}} on an out of date version of HEAD I get {{{ $ ghci -ignore-dot-ghci 519.hs GHCi, version 8.7.20180828: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 519.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20180828 for x86_64-unknown-linux): ASSERT failed! 1 0 k_a1FD[tau:0] Proxy a_a1EN[sk:1] 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/TcMType.hs:768:54 in ghc:TcMType Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15764> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15804: GHC panic (Visible kind application diff): data T :: (a :: k) -> *
by GHC 29 Nov '18

29 Nov '18

#15804: GHC panic (Visible kind application diff): data T :: (a :: k) -> * -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- (using [https://phabricator.haskell.org/D5229 Visual Kind Application (D5229)]) This might be the root cause of some of my previous {{{#!hs {-# Language PolyKinds #-} data T :: (a :: k) -> * }}} {{{ $ ghci -ignore-dot-ghci 580.hs GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 580.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181017 for x86_64-unknown-linux): ASSERT failed! Type-correct unfilled coercion hole {co_a1xI} 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/TcHsSyn.hs:1805:99 in ghc:TcHsSyn Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} on 8.6.1 this gives {{{ $ ~/.stack/programs/x86_64-linux/ghc-8.6.1/bin/ghci -ignore-dot-ghci 580.hs GHCi, version 8.6.1: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /home/baldur/hs/580.hs, interpreted ) /home/baldur/hs/580.hs:3:11: error: • Expected a type, but ‘(a :: k)’ has kind ‘k’ • In the kind ‘(a :: k) -> *’ | 3 | data T :: (a :: k) -> * | ^^^^^^^^ Failed, no modules loaded. Prelude> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15804> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15874: Data families with higher-rank kinds
by GHC 29 Nov '18

29 Nov '18

#15874: Data families with higher-rank kinds -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.2 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: -------------------------------------+------------------------------------- {{{#!hs {-# Language RankNTypes #-} {-# Language DataKinds #-} {-# Language PolyKinds #-} {-# Language GADTs #-} {-# Language TypeFamilies #-} import Data.Kind data Var where Op :: Var Id :: Var -- type family -- Flip (var :: Var) = (res :: Var) | res -> var where -- Flip Op = Id -- Flip Id = Op type Varianced = (forall (var :: Var). Type) -- data A :: Varianced where -- MkA :: Int -> A @Id -- data OpA :: Varianced where -- MkOpA :: Int -> OpA @Op -- data Exp :: Varianced -> Varianced where -- X :: forall (ext::Varianced) (var :: Var). Exp ext @var -- OpExp1 :: forall (var :: Varianced). var @op -> Exp var @(Flip op) data family Parser :: Varianced data instance Parser = P }}} {{{ $ ~/code/unmodifiedghc/inplace/bin/ghc-stage2 --interactive -ignore-dot- ghci 656.hs GHCi, version 8.7.20181029: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 656.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20181029 for x86_64-unknown-linux): ASSERT failed! kind axiom D:R:Parservar0 :: Parser = R:Parservar -- Defined at 656.hs:31:15 forall (var :: Var). * Var -> * 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/FamInst.hs:158:61 in ghc:FamInst Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15874> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14880: GHC panic: updateRole
by GHC 29 Nov '18

29 Nov '18

#14880: GHC panic: updateRole -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (Type checker) | Keywords: Roles | 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 program panics on GHC 8.0.2, 8.2.2, 8.4.1, and HEAD: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} module Bug where import Data.Kind import Data.Type.Equality ((:~:)(..)) type SameKind (a :: k) (b :: k) = (() :: Constraint) data TyFun :: Type -> Type -> Type type a ~> b = TyFun a b -> Type infixr 0 ~> type family Apply (f :: k1 ~> k2) (x :: k1) :: k2 type f @@ x = f `Apply` x infixl 9 @@ type family WhyCong (x :: Type) (y :: Type) (f :: x ~> y) (a :: x) (z :: x) (e :: a :~: z) :: Type where WhyCong _ _ f a z _ = f @@ a :~: f @@ z data WhyCongSym1 (x :: Type) :: forall (a :: x) (y :: Type) (z :: x). Type ~> (x ~> y) ~> x ~> x ~> a :~: z ~> Type data WhyCongSym0 :: forall (x :: Type) (a :: x) (y :: Type) (z :: x). Type ~> Type ~> (x ~> y) ~> x ~> x ~> a :~: z ~> Type where WhyCongSym0KindInference :: forall x arg. SameKind (Apply WhyCongSym0 arg) (WhyCongSym1 arg) => WhyCongSym0 x }}} {{{ $ /opt/ghc/8.2.2/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): updateRole WhyCongSym0 arg_aYV[sk:1] [aYU :-> 4, a22o :-> 0, a22p :-> 1, a22q :-> 2, a22r :-> 3] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcTyDecls.hs:656:23 in ghc:TcTyDecls }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15809: Use level numbers for generalisation
by GHC 29 Nov '18

29 Nov '18

#15809: Use level numbers for generalisation -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- GHC's type inference engine goes to quite a bit of effort to pin a ''level number'' on every type variable (both skolems and unification variables). '''Idea''': when generalising a type or kind, use those level numbers to decide which variables to generalise. This could completely replace the "global tyvars" field of the `TcLclEnv` (the `tcl_tyvars` field), which is very tiresome to maintain. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15809> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15414: Why both gen and gen_no in bdescr?
by GHC 29 Nov '18

29 Nov '18

#15414: Why both gen and gen_no in bdescr? -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Runtime | Version: 8.4.3 System | 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: -------------------------------------+------------------------------------- Block descriptors currently contain both `gen` (a `generation *`) and `gen_no` (a `uint16_t, which is `gen->no` cached). I wonder whether it would be worthwhile to drop the former and always use `generations[bd->gen_no]`. Afterall, this would save an entire word per descriptor which may improve our caches' coverage of the bdescr region appreciably. Presumably the `generations` array would be hot enough to stay in cache in such a scheme, so I would guess that the cost would be small-ish. Simon, have you measured this in the past? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15414> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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