February 2017 - ghc-tickets

Re: [GHC] #4243: Make a proper options parser for the RTS
by GHC 16 Feb '17

16 Feb '17

#4243: Make a proper options parser for the RTS -------------------------------------+------------------------------------- Reporter: igloo | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 6.13 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: 7535 Related Tickets: #9839 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by AndreasK): 13287# is also an effect of difference in parsing between Windows and Linux which could be fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4243#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9432: IncoherentInstances are too restricted
by GHC 15 Feb '17

15 Feb '17

#9432: IncoherentInstances are too restricted -------------------------------------+------------------------------------- Reporter: danilo2 | Owner: Type: feature request | Status: new Priority: high | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Difficulty: Unknown | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Hello! The reason behind using `IncoherentInstances`is that we want GHC to commit to a specific instance even if after instantiation of some variables, other instance could be more specific (http://www.haskell.org/ghc/docs/7.0.4/html/users_guide/type-class- extensions.html). There is one problem though. Lets consider following example (which could not make much sense, but shows the problem well): {{{#!haskell {-# OPTIONS_GHC -fno-warn-missing-methods #-} {-# LANGUAGE NoMonomorphismRestriction #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE IncoherentInstances #-} {-# LANGUAGE ScopedTypeVariables #-} module Main where import Data.Typeable -------------------------------------------------------------------------------- -- Type classes -------------------------------------------------------------------------------- class InferType a where inferType :: Proxy a -> Proxy a inferType = undefined -------------------------------------------------------------------------------- -- Proxy datatypes -------------------------------------------------------------------------------- data Id0 = Id0 deriving (Show, Typeable) data Id1 t1 = Id1 deriving (Show, Typeable) data Id2 t1 t2 = Id2 deriving (Show, Typeable) data Id3 t1 t2 t3 = Id3 deriving (Show, Typeable) data Id4 t1 t2 t3 t4 = Id4 deriving (Show, Typeable) data Id5 t1 t2 t3 t4 t5 = Id5 deriving (Show, Typeable) -------------------------------------------------------------------------------- -- Instances -------------------------------------------------------------------------------- instance InferType Int instance (InferType m, InferType a) => InferType (m a) instance (a~Id0) => InferType (a :: *) instance (a~Id1) => InferType (a :: * -> *) instance (a~Id2) => InferType (a :: * -> * -> *) -------------------------------------------------------------------------------- -- Tests -------------------------------------------------------------------------------- toProxy :: a -> Proxy a toProxy _ = Proxy --inferTypeBase :: a -> Proxy a inferTypeBase a = inferType $ toProxy a instance InferType Foo1 instance InferType Foo2 tm _ = 5 data Foo1 a = Foo1 a deriving (Show, Typeable) data Foo2 a b = Foo2 a b deriving (Show, Typeable) instance Monad Id1 -- dummy instances just for tests instance Num Id0 main = do print $ typeOf $ inferType $ toProxy $ (return (5)) print $ typeOf $ inferType $ toProxy $ (5) print $ typeOf $ inferType $ toProxy $ (Foo1 (return 5)) print $ typeOf $ inferType $ toProxy $ (Foo2 (return 5) (return 5)) print "hello" ---- OUTPUT: -- Proxy (Id1 Id0) -- Proxy Id0 -- Proxy (Foo1 (Id1 Id0)) -- Proxy (Foo2 (Id1 Id0) (Id1 Id0)) -- "hello" }}} The idea is very simple - replace all unknown type variables with known ones. It works great, but the problem appears with the function `inferTypeBase`. It should have type of `a -> Proxy a`, but GHC claims it has got `Id0 -> Proxy Id0`. It is of course caused by enabled `-XIncoherentInstances` flag, but I think GHC should be more liberal here. If it really cannot pick any instance (causing an error using only `OverlappingInstances`), the `IncoherentInstances` should allow it to pick matching one even if more specific could be available after instantianization. But If no error would occur while using `OverlappingInstances`, `IncoherentInstances` should not affect the way it resolves the instances. I think this would make `IncoherentInstances` much more useful than now. Maybe it would be good to just add some options to the flag? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9432> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13284: Incoherent instance solving is over-eager
by GHC 15 Feb '17

15 Feb '17

#13284: Incoherent instance solving is over-eager -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- danilo2 writes (originally in #9432 comment:1) {{{ {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE OverlappingInstances #-} {-# LANGUAGE IncoherentInstances #-} -- the flag is niot needed by the example module Main where import Data.Typeable class CTest a b | a -> b where cTest :: a -> b -- this instance is choosen even if more specific is available! instance out~a => CTest a out where cTest = id instance CTest Int String where cTest _ = "test" main = do print $ typeOf $ cTest (5::Int) }}} The instance `CTest a out` even if more specific `(CTest Int String)` is in scope, which just breaks how `OverlappingInstances` work. If we disable the `IncoherentInstances` flag, the right one is selected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13284> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13277: When type classes are redefined in GHCi bindings that use old instances are still accessible
by GHC 15 Feb '17

15 Feb '17

#13277: When type classes are redefined in GHCi bindings that use old instances are still accessible -------------------------------------+------------------------------------- Reporter: deech | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I found the following behavior surprising: {{{#!hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /tmp/ghci7261/ghci-script Prelude> class Foo a where { foo :: a -> Int } Prelude> instance Foo () where { foo _ = 1 } Prelude> f = foo () Prelude> class Foo a where { foo :: a -> IO () } Prelude> f 1 }}} `Foo` is redefined but `f` which uses a now illegal instance of `Foo` is still accessible. I would have expected that any bindings that use the old `foo` (or have the old `foo` in their call graph) would be cleared. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13277> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13059: High memory usage during compilation
by GHC 15 Feb '17

15 Feb '17

#13059: High memory usage during compilation -------------------------------------+------------------------------------- Reporter: domenkozar | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: Compile-time (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm building stack using GHC 8.0.2-rc2 and noticed store uses 5.17GB of (RSS) memory during https://github.com/fpco/store/blob/master/src/Data/Store/Internal.hs compilation step. Using GHC 8.0.1 memory goes up to only 1.6GB. I haven't dug deeper, but something suspicious is going on. You should be able to reproduce using installed Nix and executing nix- build -A haskell.packages.ghc802.store '<nixpkgs>' using recent channel. Building haddock for store also goes up to 5.8GB. It'd be great if someone is able to reproduce this using plan GHC 8.0.2-rc2 See also https://github.com/fpco/store/issues/91 for upstream bug report. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13059> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5642: Deriving Generic of a big type takes a long time and lots of space
by GHC 15 Feb '17

15 Feb '17

#5642: Deriving Generic of a big type takes a long time and lots of space -------------------------------------+------------------------------------- Reporter: basvandijk | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.3 Resolution: | Keywords: deriving- | perf, Generics Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T5642 Blocked By: | Blocking: Related Tickets: #13059 | Differential Rev(s): Phab:D2304 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * related: => #13059 Comment: See also #13059 for an example of `GHC.Generics`-related memory blowup in the `store` library. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5642#comment:49> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] Trac password reset for user: bgamari-test
by GHC 14 Feb '17

14 Feb '17

Your Trac password has been reset. Here is your account information: Login URL: <http://ghc.haskell.org/trac/ghc/login> Username: bgamari-test Password: 3jbxNkmL -- GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] Trac password reset for user: ethercrow
by GHC 14 Feb '17

14 Feb '17

Your Trac password has been reset. Here is your account information: Login URL: <http://ghc.haskell.org/trac/ghc/login> Username: ethercrow Password: j00QxdHA -- GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4806: Make error message more user friendly when module is not found because package is unusable
by GHC 14 Feb '17

14 Feb '17

#4806: Make error message more user friendly when module is not found because package is unusable -------------------------------------+------------------------------------- Reporter: mitar | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.0.1 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bollu): * owner: bollu => (none) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4806#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11031: Record Pattern Synonym Cleanup
by GHC 14 Feb '17

14 Feb '17

#11031: Record Pattern Synonym Cleanup -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: task | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 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: -------------------------------------+------------------------------------- Ben comments that there are some loose ends with record pattern synonyms. * It's still not clear to me that the free variables produced in rnPatSynBind are correct * Perhaps in the future we want to refactor tc_single to use a function which extends the typechecking environment instead of using setGblEnv * @mpickering's suggested refactoring of RecSelId to RecSelId (Either PatSyn TyCon) Bool described in the comment in TcExpr.hs * There is a TODO in tc_patsyn_finish which should either be clarified so it can be considered actionable, removed, or just fixed The comment from TcExpr was: > I tried to refactor RecSelId to RecSelId [DataCon] Bool but this causes some pain when it comes to the interface files. Next try it is something like RecSelId (Either PatSyn TyCon) Bool with the aim for something better in the future. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11031> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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