June 2017 - ghc-tickets

Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 20 Jun '17

20 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I agree with nakaji-dayo here. Emitting a warning upon every use of `quux` feels like the wrong design choice. To address goldfire's point above: > We want to be able to have fields such as `quux` that are used only with some (but not all) constructors of a type I agree. I think a reasonable design would be: * Introduce a flag for this purpose (proposal: `-Wpartial-records`) * If the flag is enabled and you define a partial record selector (e.g., `data A = B1 { b :: Int } | B2 { b :: Int, wat :: Char }`, emit a warning of the definition site (and only the definition site). * One can disable this warning by prefixing the partial record selector with an underscore (e.g., `data A = B1 { b :: Int } | B2 { b :: Int, _wat :: Char }`). This should allow you to use the partial record for scenarios where it's handy, but it also gives a visual indication that something is fishy about that function. A separate question is if this flag should be implied by `-Wall`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13808: Bump Cabal submodule
by GHC 19 Jun '17

19 Jun '17

#13808: Bump Cabal submodule -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.2.1-rc2 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: -------------------------------------+------------------------------------- Cabal 2.0.0.1 will be released shortly -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13808> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13822: GHC not using injectivity?
by GHC 19 Jun '17

19 Jun '17

#13822: GHC not using injectivity? -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple InjectiveFamilies, TypeInType | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This may be normal behavior but.. (Example from [http://repository.brynmawr.edu/cgi/viewcontent.cgi?article=1014&context=com… System FC with Explicit Kind Equality]) {{{#!hs {-# LANGUAGE GADTs, TypeOperators, PolyKinds, DataKinds, TypeFamilyDependencies, TypeInType, RankNTypes, LambdaCase, EmptyCase #-} import Data.Kind data KIND = STAR | KIND :> KIND data Ty :: KIND -> Type where TInt :: Ty STAR TBool :: Ty STAR TMaybe :: Ty (STAR :> STAR) TApp :: Ty (a :> b) -> (Ty a -> Ty b) type family IK (k :: KIND) = (res :: Type) | res -> k where IK STAR = Type IK (a:>b) = IK a -> IK b type family I (t :: Ty k) = (res :: IK k) | res -> t where I TInt = Int I TBool = Bool I TMaybe = Maybe I (TApp f a) = (I f) (I a) data TyRep (k :: KIND) (t :: Ty k) where TyInt :: TyRep STAR TInt TyBool :: TyRep STAR TBool TyMaybe :: TyRep (STAR:>STAR) TMaybe TyApp :: TyRep (a:>b) f -> TyRep a x -> TyRep b (TApp f x) zero :: TyRep STAR a -> I a zero = \case TyInt -> 0 TyBool -> False TyApp TyMaybe _ -> Nothing }}} When I ask it to infer the representation for `Int` and `Bool` it does so with no surprises {{{#!hs -- Inferred type: -- -- int :: TyRep STAR TInt -> Int int rep = zero rep :: Int -- bool:: TyRep STAR TBool -> Bool bool rep = zero rep :: Bool }}} but inferring the representation for `Maybe Int` fails {{{#!hs -- v.hs:43:16: error: -- • Couldn't match kind ‘k’ with ‘'STAR’ -- ‘k’ is a rigid type variable bound by -- the inferred type of -- maybeInt :: (I 'TInt ~ Int, I 'TMaybe ~ Maybe) => -- TyRep 'STAR ('TApp 'TMaybe 'TInt) -> Maybe Int -- at v.hs:25:3 -- When matching the kind of ‘'TMaybe’ -- Expected type: Maybe Int -- Actual type: I ('TApp 'TMaybe 'TInt) -- • In the expression: zero rep :: Maybe Int -- In an equation for ‘maybeInt’: maybeInt rep = zero rep :: Maybe Int -- • Relevant bindings include -- rep :: TyRep 'STAR ('TApp 'TMaybe 'TInt) (bound at v.hs:43:10) -- maybeInt :: TyRep 'STAR ('TApp 'TMaybe 'TInt) -> Maybe Int -- (bound at v.hs:43:1) -- Failed, modules loaded: none. maybeInt rep = zero rep :: Maybe Int }}} even though `I` is injective and GHC knows that `I (TMaybe `TApp` TMaybe) = Maybe Int` {{{ >>> :kind! I (TMaybe `TApp` TInt) I (TMaybe `TApp` TInt) :: IK 'STAR = Maybe Int }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13822> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13832: No parameter-validation in Control.Concurrent.setNumCapabilities
by GHC 19 Jun '17

19 Jun '17

#13832: No parameter-validation in Control.Concurrent.setNumCapabilities -------------------------------------+------------------------------------- Reporter: AlistairWard | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Core | Version: 8.0.1 Libraries | Keywords: | Operating System: Linux setNumCapabilities | Architecture: x86 | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- > ghci GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude> Control.Concurrent.setNumCapabilities $ negate 1 malloc: failed on request for 18446744073709551104 bytes; message: moreCapabilities The parameter is forwarded to the underlying C-function without validation, the runtime then crashes; no exception is thrown. This behaviour also exists in ghc 8.0.2 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13832> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13821: bindings for unlifted types are allowed in .hs-boot files and .hsig files
by GHC 19 Jun '17

19 Jun '17

#13821: bindings for unlifted types are allowed in .hs-boot files and .hsig files -------------------------------------+------------------------------------- Reporter: duog | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 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: -------------------------------------+------------------------------------- The following module compiles without error. {{{ A.hs-boot --------- {-# LANGUAGE MagicHash -#} module A where import GHC.Prim x :: Int# === ghc -c A.hs-boot }}} I would expect to get a "Top-level unlifted bindings are not allowed." error, as I would with a .hs module. Similarly {{{ A.hsig ====== {-# LANGUAGE MagicHash #-} unit U where signature A where import GHC.Prim x :: Int# === ghc --backpack -fno-code -fwrite-interface A.hsig }}} succeeds, where I would expect the same error. This error is thrown during desugaring, and .hs-boot and .hsig files are not desugared. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13821> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7198: New codegen more than doubles compile time of T3294
by GHC 19 Jun '17

19 Jun '17

#7198: New codegen more than doubles compile time of T3294 -------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.4.2 (CodeGen) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #4258 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"6a2264d2bd47e993c43a592bd614ab7917184e22/ghc" 6a2264d/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="6a2264d2bd47e993c43a592bd614ab7917184e22" cmm/CmmLayoutStack: avoid generating unnecessary reloads This tries to be more precise when generating reloads of local registers in proc points. Previously we'd reload all local registers that were live. But we used liveness information that assumed local registers survive native calls. For the purpose of reloading registers this is an overapproximation and might lead to generating huge amounts of unnecessary reloads (in case there's another proc point before the register is used). This change takes the approach of moving the generation of reloads to a second pass over the Cmm, which allows to recompute the liveness and can use the knowledge that local registers do *not* survive calls. This leads to generating only useful reloads. For an extreme example where this helps a lot please see T3294. This should also fix #7198 Finally, this re-introduces the code to do Cmm rewriting using in `Dataflow` module (with the difference that we know operate on a whole block at a time). Signed-off-by: Michal Terepeta <michal.terepeta(a)gmail.com> Reviewers: austin, bgamari, simonmar Reviewed By: simonmar Subscribers: kavon, rwbarton, thomie GHC Trac Issues: #7198 Differential Revision: https://phabricator.haskell.org/D3586 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7198#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 19 Jun '17

19 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nakaji_dayo): > It would be great if GHC could produce a warning if I use quux as a function somewhere in my code Do you think should be warn at when **using quux** ? \\ I thought it might be necessary when defining `quux`. {{{ data Foo = Bar { frob :: Int } | Baz { frob :: Int, quux :: Bool } -- maybe here f :: Foo -> Bool f x = quux x -- here? }}} Because, I think simply, `quux` function is `quux (Baz _ x) = x` then it is non-exhaustive and should be warned. And, if it in "when use", is this warning done recursively? {{{ data Foo = ... f = quux g = f -- warn here also? }}} I'm sorry if I was wrong. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13813: DeriveFunctor spuriously rejects existential context with type synonym mentioning the last type variable
by GHC 19 Jun '17

19 Jun '17

#13813: DeriveFunctor spuriously rejects existential context with type synonym mentioning the last type variable -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | 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: -------------------------------------+------------------------------------- This code does not compile: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE DeriveFunctor #-} {-# LANGUAGE ExistentialQuantification #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE StandaloneDeriving #-} module Bug where import GHC.Exts (Constraint) type C (a :: Constraint) b = a data T a b = C (Show a) b => MkT b deriving instance Functor (T a) }}} {{{ GHCi, version 8.2.0.20170523: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:13:1: error: • Can't make a derived instance of ‘Functor (T a)’: Constructor ‘MkT’ must be truly polymorphic in the last argument of the data type • In the stand-alone deriving instance for ‘Functor (T a)’ | 13 | deriving instance Functor (T a) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} But it should, since if you expand `C (Show a) b`, you're left with `Show a`, which doesn't mention the last type variable `b` at all. Fix incoming. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13813> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13843: Expand type information collected (:set +c), used by :all-types, :type-at, ..
by GHC 18 Jun '17

18 Jun '17

#13843: Expand type information collected (:set +c), used by :all-types, :type-at, .. -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.3 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: -------------------------------------+------------------------------------- When [collecting type information https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html #ghci-cmd-:set%20+c] (`:set +c`) GHC does not collect type information from type variables in type synonyms {{{#!hs type Endo a = a -> a }}} data types and families {{{#!hs data List a = Nil | a ::: List a }}} fixity declarations {{{#!hs infixr 5 ::: }}} type class declarations {{{#!hs class A a where getA :: a }}} and type families.. probably other things: the feature appeared one GHC version ago so, has this just not been implemented yet? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13843> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13842: Is this output from :all-types correct
by GHC 18 Jun '17

18 Jun '17

#13842: Is this output from :all-types correct -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) 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: -------------------------------------+------------------------------------- Is this the expected outcome of loading {{{#!hs data B = F | T instance Eq B }}} with [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html #ghci-cmd-:set%20+c :set +c] and then running the `:all-types` command? {{{ λ> :all-types /tmp/test.hs:(3,10)-(3,14): GHC.Classes.Eq Main.B /tmp/test.hs:(3,10)-(3,14): (Main.B -> Main.B -> GHC.Types.Bool) -> GHC.Classes.Eq Main.B /tmp/test.hs:(3,10)-(3,14): (Main.B -> Main.B -> GHC.Types.Bool) -> (Main.B -> Main.B -> GHC.Types.Bool) -> GHC.Classes.Eq Main.B /tmp/test.hs:(3,10)-(3,14): Main.B -> Main.B -> GHC.Types.Bool /tmp/test.hs:(3,10)-(3,14): Main.B -> Main.B -> GHC.Types.Bool }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13842> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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