June 2018 - ghc-tickets

Re: [GHC] #6089: Allow declaration splices inside declaration brackets
by GHC 01 Jun '18

01 Jun '18

#6089: Allow declaration splices inside declaration brackets -------------------------------------+------------------------------------- Reporter: igloo | Owner: simonpj Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #11129 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by gbaz): * cc: gbaz (removed) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6089#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6089: Allow declaration splices inside declaration brackets
by GHC 01 Jun '18

01 Jun '18

#6089: Allow declaration splices inside declaration brackets -------------------------------------+------------------------------------- Reporter: igloo | Owner: simonpj Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #11129 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by gbaz): * cc: gbaz (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6089#comment:10> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13745: Investigate compile-time regressions in regex-tdfa-1.2.2
by GHC 01 Jun '18

01 Jun '18

#13745: Investigate compile-time regressions in regex-tdfa-1.2.2 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- hvr [[https://mail.haskell.org/pipermail/ghc- devs/2017-May/014208.html|points out]] that GHC 8.2 takes significantly longer to compile `regex-tdfa-1.2.2` than 8.0.2. Interestingly, it seems that compiler allocations fell dramatically while compilation time rose. {{{ GHC 8.0.2: <<ghc: 89544610040 bytes, 2301 GCs, 189183965/391103872 avg/max bytes residency (29 samples), 1075M in use, 0.001 INIT (0.001 elapsed), 55.747 MUT (61.520 elapsed), 23.276 GC (23.278 elapsed) :ghc>> GHC 8.2.1: <<ghc: 115210990008 bytes, 6383 GCs, 116487828/234031864 avg/max bytes residency (77 samples), 670M in use, 0.001 INIT (0.000 elapsed), 64.154 MUT (68.262 elapsed), 37.114 GC (37.077 elapsed) :ghc>> }}} == Reproducing == {{{ $ cabal unpack regex-tdfa-1.2.2 $ cd regex-tdfa-1.2.2 $ cabal install --only-dependencies $ cabal configure $ cabal build $ time ghc -idist/build/autogen -O2 Text/Regex/TDFA.hs \ -XMagicHash -XFlexibleInstances -XMultiParamTypeClasses \ -XRecursiveDo -XBangPatterns -XRankNTypes -XUnboxedTuples \ -XFlexibleContexts -XUnliftedFFITypes }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13745> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15177: Faulty instance termination check, with PolyKinds and/or TypeInType
by GHC 01 Jun '18

01 Jun '18

#15177: Faulty instance termination check, with PolyKinds and/or TypeInType -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- When checking the [http://downloads.haskell.org/~ghc/master/users- guide/glasgow_exts.html#instance-termination-rules Paterson conditions] for termination an instance declaration, we check for the number of "constructors and variables" in the instance head and constraints. '''Question''': Do we look at A. All the arguments, visible or invisible? B. Just the visible arguments? I think both will ensure termination, provided we are consistent. A current bug in GHC means that we are not consistent. In particular in `TcValidity.checkInstTermination` we see {{{ checkInstTermination tys theta = check_preds theta where ... head_size = sizeTypes tys ... check pred = case classifyPredType pred of ... -> check2 pred (sizeTypes $ filterOutInvisibleTypes (classTyCon cls) tys) }}} Notice the `filterOutInvisibleTypes` in the context predicate, but not for the `head_size`! I tried doing it both ways and fell into a swamp. Fails plan A: * `rebindable/T5908` has `instance (Category w, ...) => Monad (WriterT w m)`. With kind arguments this is actualy `instance (Category @(TYPE LiftedRep) w, ...) => Monad (WriterT w m)`, and now the predicate in the context and the head both ahve size 4. So under (B) this is OK but not under (A). * `deriving/should_compile/T11833` is similar * So is `overloadedrecflds/should_run/hasfieldrun02`. Fails plan B * `polykinds/T12718` has `instance Prelude.Num a => XNum a`, where `XNum` is poly-kinded. Under (A) this would be OK, but not under B. * `typecheck/should_compile/T14441` is tricky. Putting in explicit kinds we have {{{ type family Demote (k :: Type) :: Type -- Demote :: forall k -> Type type family DemoteX (a :: k) :: Demote k -- DemoteX :: forall k. k -> Demote k data Prox (a :: k) = P -- P :: forall k (a:k). Prox @k a type instance DemoteX P = P -- type instance DemoteX (Prox @k a) (P @k @a) -- = P @(Demote k) @(DemoteX @k a) }}} So the LHS has 2 visible constructors and variables, namely `DemoteX` and `P`. But the type-family applications in the RHS also each have two visible, e.g. `Demote` and `k` for `Demote k`. Confusingly, these applications are hidden inside the invisible argument of `P`; but we really must look at them to ensure termination. Aaargh. * `dependent/should_compile/T13910` is similar, but a lot more complicated. Currently, because of the bug, these all pass. But I think it should be possible to exploit the bug to defeat the termination check, so things are not good at all. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15177> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15163: non coercion variable in coVarKindsTypesRole
by GHC 01 Jun '18

01 Jun '18

#15163: non coercion variable in coVarKindsTypesRole -------------------------------------+------------------------------------- Reporter: alpmestan | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: T14732 | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It is triggered by T14732... in the `profasm` way, and only that one. {{{#!sh $ make fulltest TEST="T14732" THREADS=4 =====> T14732(profasm) 1 of 1 [0, 0, 0] cd "./typecheck/should_compile/T14732.run" && "/home/alp/WT/ghc-slow- validate/inplace/test spaces/ghc-stage2" -c T14732.hs -dcore-lint -dcmm- lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow- warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno- debug-output -fno-warn-incomplete-patterns -O -prof -static -fprof-auto Compile failed (exit code 1) errors were: ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.5.20180511 for x86_64-unknown-linux): coVarKindsTypesRole, non coercion variable as_atY Vector a_a2sO Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1162:37 in ghc:Outputable pprPanic, called at compiler/types/Coercion.hs:376:16 in ghc:Coercion Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug *** unexpected failure for T14732(profasm) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15163> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9724: reexport IsList class from a trustworthy module
by GHC 31 May '18

31 May '18

#9724: reexport IsList class from a trustworthy module -------------------------------------+------------------------------------- Reporter: int-e | Owner: ekmett Type: feature request | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- ==== Motivation GHC's Safe Haskell extension relies to a large extent on inferring safety of modules automatically. As a concrete example, [[http://hackage.haskell.org/package/data-default|data-default]] used to be inferred safe. This is no longer the case, because [[http://hackage.haskell.org/package/dlist-0.7.1|dlist-0.7.1]] added an {{{IsList}}} instance for difference lists. The only way to do that currently is to import the relevant parts of {{{GHC.Exts}}}, and that module is not safe. Of course the resulting non-safety of the {{{Data.DList}}} module can be fixed by adding a {{{TrustWorthy}}} pragma to the module and trusting the {{{dlist}}} package. But that is unsatisfactory, because there is nothing unsafe about providing an instance for the {{{IsList}}} class. This issue is bound to pop up in other packages as well. ==== Proposed Solution (this is one of many possibilities) Add a {{{GHC.Exts.Safe}}} module that is marked {{{TrustWorthy}}} and reexports the {{{IsList}}} class, and possibly other things from {{{GHC.Exts}}} that are safe to use. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9724> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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