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Re: [GHC] #2256: Incompleteness of type inference: must quantify over implication constraints
by GHC 29 Jun '16

29 Jun '16

#2256: Incompleteness of type inference: must quantify over implication constraints -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler (Type | Version: 6.8.2 checker) | Resolution: | 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: | -------------------------------------+------------------------------------- Changes (by Iceland_jack): * cc: Iceland_jack (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2256#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 29 Jun '16

29 Jun '16

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by Bartosz Nitka <niteria@…>): In [changeset:"9a645a1687aca21f965206f1d8c8bb23dd6410e5/ghc" 9a645a1/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="9a645a1687aca21f965206f1d8c8bb23dd6410e5" Refactor match to not use Unique order Unique order can introduce nondeterminism. As a step towards removing the Ord Unique instance I've refactored the code to use deterministic sets instead. Test Plan: ./validate Reviewers: simonmar, austin, bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2369 GHC Trac Issues: #4012 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:217> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2256: Incompleteness of type inference: must quantify over implication constraints
by GHC 29 Jun '16

29 Jun '16

#2256: Incompleteness of type inference: must quantify over implication constraints -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler (Type | Version: 6.8.2 checker) | Resolution: | 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: | -------------------------------------+------------------------------------- Comment (by goldfire): #12245 is further motivation for solving this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2256#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12244: Idea: Remove unused symbols in link-time for smaller binaries
by GHC 29 Jun '16

29 Jun '16

#12244: Idea: Remove unused symbols in link-time for smaller binaries -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: Compiler | Version: 8.1 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 caught my attention recently: https://github.com/ocaml/ocaml/pull/608 I think GHC could also benefit from this. I'm currently looking at an 8.0,1-generated executable, generated with -O2. In the code I defined some unused instances, just as an example, and I see code for those in text section in the binary. There is also lots of other unused stuff (I think mostly typeclass instances) imported from libraries and they're all unused because this is a "hello world" program that imports stuff and defines instances for no reason. There should be another ticket around here that reports some numbers on how big GHC-generated executables (and GHC itself) is (when compared with other compilers)... -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12244> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12185: Can't call rank-2 function with type family constraint
by GHC 29 Jun '16

29 Jun '16

#12185: Can't call rank-2 function with type family constraint -------------------------------------+------------------------------------- Reporter: crockeea | Owner: 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: -------------------------------------+------------------------------------- The following code compiles with 7.10.3: {{{ newtype Bar r = Pow r deriving (Eq) instance (Foo r) => Foo (Bar r) type family Ctx a where Ctx t = (Foo (Bar t), Eq (Bar t)) run :: (forall t . (Ctx t) => t -> Int) -> Int run g = undefined foo :: (Foo (Bar t)) => t -> Int foo = undefined main :: IO () main = print $ run foo }}} but fails in 8.0.1 with {{{ • Could not deduce (Foo t) arising from a use of ‘foo’ from the context: Ctx t bound by a type expected by the context: Ctx t => t -> Int at Main.hs:19:16-22 Possible fix: add (Foo t) to the context of a type expected by the context: Ctx t => t -> Int • In the first argument of ‘run’, namely ‘foo’ In the second argument of ‘($)’, namely ‘run foo’ In the expression: print $ run foo }}} This code seems valid to me: when I call `run foo`, `foo` is specialized to `(Foo (Bar t), Eq (Bar t)) => t -> Int)`, which meets the requirement of the argument to `run`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12185> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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freelance
by matthew＠wellquite.org 29 Jun '16

29 Jun '16

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[GHC] #12187: Clarify the scoping of existentials for pattern synonym signatures
by GHC 28 Jun '16

28 Jun '16

#12187: Clarify the scoping of existentials for pattern synonym signatures -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #12108 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- What are scoping rules for type variables in pattern synonym signatures? We said that existentials variables are scoped as follows: 1. Existentials scope over only the provided constraints and the arguments, not over the result type. {{{ type Disguised a b = b -> RP a pattern Q :: () => Eq b => Disguised a b }}} However, Simon argues that `Q` should be accepted as if we expand the type synonym then the existentially quantified `b` is no longer in the result type. Richard disagrees, he considers the result type to be `Disguised a b` and so `b` is in the result type and not in-scope. Therefore he wishes to reject this example. The purpose of this ticket is to decide the fate of `Q`. This kind of problem is related to #12108 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12187> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12207: CgStaticPointers fails with -O
by GHC 28 Jun '16

28 Jun '16

#12207: CgStaticPointers fails with -O -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (CodeGen) | Keywords: | Operating System: Unknown/Multiple StaticPointers | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: codeGen/should_run/CgStaticPointers| Blocking: | Related Tickets: #11656 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ $ make TEST=CgStaticPointers slow }}} {{{ Wrong exit code (expected 0 , actual 1 ) Stdout: Stderr: CgStaticPointers: couldn't find StaticPtrInfo {spInfoUnitId = "main", spInfoModuleName = "Main", spInfoSrcLoc = (13,21)} CallStack (from HasCallStack): error, called at CgStaticPointers.hs:25:14 in main:Main *** unexpected failure for CgStaticPointers(optasm) }}} This seems to be caused by the patch for #11656 (36d29f7ce332a2b1fbc36de831b0eef7a6405555). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12207> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11471: Note [The kind invariant] in TyCoRep needs to be updated
by GHC 28 Jun '16

28 Jun '16

#11471: Note [The kind invariant] in TyCoRep needs to be updated -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 (Type checker) | 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: -------------------------------------+------------------------------------- This Note, found in TyCoRep, needs to be updated to reflect `TypeInType`. It should not reference `OpenKind`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11471> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9078: Segfault with makeStableName
by GHC 28 Jun '16

28 Jun '16

#9078: Segfault with makeStableName ------------------------------------+------------------------------------- Reporter: robertce | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Calling `makeStableName` on the same object many times causes a segfault. The following triggers this behaviour on both OSX and Linux-x86_64, provided it is compiled (it doesn't seem to occur if the call to `makeStableName` is interpreted). {{{ module Main where import Control.Monad import System.Mem.StableName main :: IO () main = replicateM_ 100000 (makeStableName foo) foo :: Int foo = 1 }}} It seems to happen largely at random. The 100000 calls to `makeStableName` in the above example essentially guarantee its occurrence, but I have observed it happen with far fewer. The reason this bug was discovered is it is causing frequent failures in Accelerate on 7.8.2. See [https://github.com/AccelerateHS/accelerate/issues/162] In that case it seems to be causing more `strange closure type` errors than segfaults, but I assume it is the same root cause. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9078> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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