September 2017 - ghc-tickets

[GHC] #13115: missing data instances for IntPtr and WordPtr in base
by GHC 13 Sep '17

13 Sep '17

#13115: missing data instances for IntPtr and WordPtr in base -------------------------------------+------------------------------------- Reporter: carter | 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: -------------------------------------+------------------------------------- as Defined in Foreign.Ptr -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13115> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14209: GHC 8.2.1 regression involving telescoping kind signature
by GHC 13 Sep '17

13 Sep '17

#14209: GHC 8.2.1 regression involving telescoping kind signature -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: TypeInType | 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: -------------------------------------+------------------------------------- The following program typechecks in GHC 8.0.1 and 8.0.2: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} module Bug where data MyProxy k (a :: k) = MyProxy data Foo (z :: MyProxy k (a :: k)) }}} But in GHC 8.2.1, it's rejected: {{{ GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:6:1: error: Kind variable ‘k’ is implicitly bound in datatype ‘Foo’, but does not appear as the kind of any of its type variables. Perhaps you meant to bind it explicitly somewhere? Type variables with inferred kinds: (k :: *) (a :: k) (z :: MyProxy k a) | 6 | data Foo (z :: MyProxy k (a :: k)) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14209> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14204: GHC bug - makeStatic: Unresolved static form at line 13, column 14.
by GHC 13 Sep '17

13 Sep '17

#14204: GHC bug - makeStatic: Unresolved static form at line 13, column 14. -------------------------------------+------------------------------------- Reporter: jchia | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- Building and running the attached code results in the above error mesage. Enabling StaticPointers in the code makes the error go away. GHC should either reject the code or generate code that works properly at run-time, depending on the fine points of how TH is supposed to interact with StaticPointers. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14204> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14140: Better treatment for dataToTag
by GHC 12 Sep '17

12 Sep '17

#14140: Better treatment for dataToTag -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- In `libraries/Cabal/Cabal/Distribution/System.hs` I found {{{ eqOS :: OS -> OS -> Bool eqOS (OtherOS s1) (OtherOS s2) = s1 == (s2 :: String) eqOs a b = dataToTag a == dataTag b }}} (actually it's not called `eqOS`; it's the derived equality for `OS`). By the time this gets to Core it looks something like this {{{ eqOS a b = case a of OtherOS s1 -> case b of OtherOS s2 -> eqString s1 s2 _ -> case dataToTag b of 16# -> True r -> False _ -> dataToTag a == dataToTag b }}} The `dataToTag` code has been duplicated; and in the `OtherOS s1` branch GHC can constant-fold the `dataToTag` on `a` to `16#`, the tag of `OtherOS`. But GHC is no so clever for the `dataToTag b`. We know that `b` is not `OtherOS`, so we know its tag is not `16#`, so the innermost case is entirely redundant. But we don't spot that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14140> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14186: CSE fails to CSE
by GHC 12 Sep '17

12 Sep '17

#14186: CSE fails to CSE -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: bug | Status: new 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: -------------------------------------+------------------------------------- Consider this code: {{{ module CSEBug where data Succs a = Succs a [a] instance Functor Succs where fmap f (Succs o s) = Succs (f o) (map f s) foo, bar :: (a -> b) -> (b -> c) -> Succs a -> Succs c foo f g x = fmap (g . f) x bar f g x = fmap (g . f) x }}} If I compile this with `-O`, `foo` and `bar` are not CSEd, which can be seen with `-ddump-cse`. Removing either the first or the second argument of `Succs` makes CSE work. Is there a size limit on CSE? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14186> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14219: Include source location information in -ddump-rule-rewrites
by GHC 12 Sep '17

12 Sep '17

#14219: Include source location information in -ddump-rule-rewrites -------------------------------------+------------------------------------- Reporter: harendra | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Debugging) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Debugging Unknown/Multiple | information is incorrect Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Inlining is one of the most common and powerful optimizations and it interacts with rewrite-rules which is also common the libraries including base. When debugging a performance problem we are interacting with the rewrite-rules written by others hidden somewhere in some library that we are using. When I use the `-ddump-rule-rewrites` option I get an output like this: {{{ Rule fired Rule: Class op >>= Module: (BUILTIN) Before: GHC.Base.>>= TyArg GHC.Types.IO ValArg GHC.Base.$fMonadIO After: GHC.Base.$fMonadIO1 }}} This does not say where exactly this rule is defined in the source. It is sort of ok if this is my code I would perhaps know where this rule is. But when it is in some dependency that I am using it is hard to find. It will be really helpful if the source location information can be provided in this dump information, so that one can go and examine the source. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14219> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14220: GeneralizedNewtypeDeriving and polymorphic arguments don't play nicely together
by GHC 12 Sep '17

12 Sep '17

#14220: GeneralizedNewtypeDeriving and polymorphic arguments don't play nicely together --------------------------------------+--------------------------------- Reporter: ivanm | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- I'm not sure if this is a bug per se, but ghci says to report it so here it is: test.hs: {{{#!hs {-# LANGUAGE GeneralizedNewtypeDeriving #-} class NameOf a where nameOf :: proxy a -> String instance NameOf Int where nameOf _ = "Int" newtype MyInt = MyInt Int deriving (NameOf) }}} {{{ $ ghci test.hs GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( test.hs, interpreted ) test.hs:10:13: warning: [-Wdeferred-type-errors] • Couldn't match representation of type ‘proxy1 Int’ with that of ‘proxy1 MyInt’ arising from a use of ‘GHC.Prim.coerce’ NB: We cannot know what roles the parameters to ‘proxy1’ have; we must assume that the role is nominal • In the expression: GHC.Prim.coerce @(forall (proxy :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). proxy Int -> String) @(forall (proxy :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). proxy MyInt -> String) nameOf In an equation for ‘nameOf’: nameOf = GHC.Prim.coerce @(forall (proxy :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). proxy Int -> String) @(forall (proxy :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). proxy MyInt -> String) nameOf When typechecking the code for ‘nameOf’ in a derived instance for ‘NameOf MyInt’: To see the code I am typechecking, use -ddump-deriv In the instance declaration for ‘NameOf MyInt’ ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-apple-darwin): opt_univ fell into a hole {a15j} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14220> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14216: Compare compiler performance of GHC 8.0.2 and 8.2.1 on Stackage
by GHC 11 Sep '17

11 Sep '17

#14216: Compare compiler performance of GHC 8.0.2 and 8.2.1 on Stackage -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- Simon M. suggests that we take a sample of Stackage packages (perhaps the top 200 by Hackage download count) and compare their compiler performance statistics with GHC 8.0.2 and 8.2.1. We'll want to collect overall GHC wall clock time, as well as the per-pass metrics produced by `-v`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14216> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8583: Associated pattern synonyms
by GHC 11 Sep '17

11 Sep '17

#8583: Associated pattern synonyms ------------------------------------+------------------------------------- Reporter: cactus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: 5144 | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The PatternSynonyms wiki page has a section on (typeclass-)associated pattern synonyms: {{{ class ListLike l where pattern Nil :: l a pattern Cons :: a -> l a -> a isNil :: l a -> Bool isNil Nil = True isNil (Cons _ _) = False append :: l a -> l a -> l a instance ListLike [] where pattern Nil = [] pattern Cons x xs = x:xs append = (++) headOf :: (ListLike l) => l a -> Maybe a headOf Nil = Nothing headOf (Cons x _) = Just x }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8583> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10818: GHC 7.10.2 takes much longer to compile some packages
by GHC 11 Sep '17

11 Sep '17

#10818: GHC 7.10.2 takes much longer to compile some packages -------------------------------------+------------------------------------- Reporter: kazu- | Owner: yamamoto | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- If we compile the iproute package by GHC, GHC 7.10.2 take much longer than GHC 7.8.4. See the report from Travis CI: https://travis-ci.org/kazu-yamamoto/iproute/builds/77427248 I can reproduce this on my local MacBookAir: - GHC 7.8.4: cabal build 8.81s user 0.94s system 103% cpu 9.430 total - GHC 7.10.2: cabal build 37.86s user 3.49s system 98% cpu 42.066 total -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10818> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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