December 2016 - ghc-tickets

[GHC] #13033: GHC Panics with "colorGraph: trivially colorable nodes didn't color!" on PPC
by GHC 03 Jan '17

03 Jan '17

#13033: GHC Panics with "colorGraph: trivially colorable nodes didn't color!" on PPC -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.2-rc2 Keywords: | Operating System: AIX Architecture: powerpc | Type of failure: Compile-time | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I was finally able to build GHC 8.0.2rc2 (or rather, c5f375c53671130c79713800b13a1da53d070b84 + a minor buildsys fix) on AIX/PPC; most packages seem to work as they did with GHC 8.0.1, however, `unordered-containers` now panics with: {{{ $ cabal get unordered-containers && cd unordered-containers-0.2.7.1/ $ cabal new-build -j1 Resolving dependencies... In order, the following will be built (use -v for more details): - unordered-containers-0.2.7.1 (lib) (first run) Configuring component lib from unordered-containers-0.2.7.1... Preprocessing library unordered-containers-0.2.7.1... [1 of 8] Compiling Data.HashMap.UnsafeShift ( Data/HashMap/UnsafeShift.hs, /home/hvr/unordered-containers-0.2.7.1/dist-newstyle/build/ppc- aix/ghc-8.0.1.20161223/unordered- containers-0.2.7.1/build/Data/HashMap/UnsafeShift.o ) [2 of 8] Compiling Data.HashMap.Unsafe ( Data/HashMap/Unsafe.hs, /home/hvr /unordered-containers-0.2.7.1/dist-newstyle/build/ppc- aix/ghc-8.0.1.20161223/unordered- containers-0.2.7.1/build/Data/HashMap/Unsafe.o ) [3 of 8] Compiling Data.HashMap.PopCount ( Data/HashMap/PopCount.hs, /home/hvr/unordered-containers-0.2.7.1/dist-newstyle/build/ppc- aix/ghc-8.0.1.20161223/unordered- containers-0.2.7.1/build/Data/HashMap/PopCount.o ) [4 of 8] Compiling Data.HashMap.Array ( Data/HashMap/Array.hs, /home/hvr /unordered-containers-0.2.7.1/dist-newstyle/build/ppc- aix/ghc-8.0.1.20161223/unordered- containers-0.2.7.1/build/Data/HashMap/Array.o ) [5 of 8] Compiling Data.HashMap.Base ( Data/HashMap/Base.hs, /home/hvr /unordered-containers-0.2.7.1/dist-newstyle/build/ppc- aix/ghc-8.0.1.20161223/unordered- containers-0.2.7.1/build/Data/HashMap/Base.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1.20161223 for powerpc-ibm-aix): colorGraph: trivially colorable nodes didn't color! ksTriv = [%vHi_HCRu, %vHi_HCRA, %vI_nGN7, %vI_nGNh, %vI_sCRp, %vI_sCRr, %vHi_HCRt, %vHi_HGNi, %vHi_HGNj, %vI_nGN3, %vI_nGN4, %vI_nGN5, %vI_nGN6, %vI_nGN8, %vI_nGN9, %vI_nGNa, %vI_nGNb, %vI_nGNc, %vI_nGNd, %vI_nGNe, %vI_nGNf, %vI_nGNi, %vI_nGNj, %vI_nGNk, %vI_nGNl, %vI_nGNm, %vI_nGNn, %vI_nGNo, %vI_nGNp, %vI_nGNq, %vI_nGNr, %vI_nGNs, %vI_nGNt, %vI_sCRH, %vI_sCRM] ksNoTriv = [%vI_sCRr] colors = [L0 :-> [R3 :-> %r3, R4 :-> %r4, R5 :-> %r5, R6 :-> %r6, R7 :-> %r7, R8 :-> %r8, R9 :-> %r9, Ra :-> %r10, Rb :-> %r11, Rc :-> %r12, Rn :-> %r23, Rq :-> %r26, Rs :-> %r28, Rt :-> %r29, Rv :-> %r31], L2 :-> [Rw :-> %r32, Rx :-> %r33, Ry :-> %r34, Rz :-> %r35, RA :-> %r36, RB :-> %r37, RC :-> %r38, RD :-> %r39, RE :-> %r40, RF :-> %r41, RG :-> %r42, RH :-> %r43, RI :-> %r44, RJ :-> %r45, RQ :-> %r52, RR :-> %r53, RS :-> %r54, RT :-> %r55, RU :-> %r56, RV :-> %r57, RW :-> %r58, RX :-> %r59, RY :-> %r60, RZ :-> %r61, R10 :-> %r62, R11 :-> %r63]] graph G { node [label="%vHi_HCRt :: I\n(%r3)" style=filled fillcolor="white"] "%vHi_HCRt"; node [label="%vHi_HCRu :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45 +%r3\n(%r23)" style=filled fillcolor="white"] "%vHi_HCRu"; node [label="%vHi_HCRA :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45 +%r5\n(%r26)" style=filled fillcolor="white"] "%vHi_HCRA"; node [label="%vHi_HGNi :: I\n+%r3\n(%r3)" style=filled fillcolor="white"] "%vHi_HGNi"; node [label="%vHi_HGNj :: I\n-%r3 -%r4 +%r5\n(%r5)" style=filled fillcolor="white"] "%vHi_HGNj"; node [label="%vI_nGN3 :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGN3"; node [label="%vI_nGN4 :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGN4"; node [label="%vI_nGN5 :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGN5"; node [label="%vI_nGN6 :: I\n(%r4)" style=filled fillcolor="white"] "%vI_nGN6"; node [label="%vI_nGN7 :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45 +%r4\n(%r28)" style=filled fillcolor="white"] "%vI_nGN7"; node [label="%vI_nGN8 :: I\n(%r5)" style=filled fillcolor="white"] "%vI_nGN8"; node [label="%vI_nGN9 :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGN9"; node [label="%vI_nGNa :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNa"; node [label="%vI_nGNb :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNb"; node [label="%vI_nGNc :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNc"; node [label="%vI_nGNd :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNd"; node [label="%vI_nGNe :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNe"; node [label="%vI_nGNf :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNf"; node [label="%vI_nGNh :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45 +%r6\n(%r29)" style=filled fillcolor="white"] "%vI_nGNh"; node [label="%vI_nGNi :: I\n-%r3 +%r4\n(%r4)" style=filled fillcolor="white"] "%vI_nGNi"; node [label="%vI_nGNj :: I\n-%r3 -%r4 -%r5 +%r6\n(%r6)" style=filled fillcolor="white"] "%vI_nGNj"; node [label="%vI_nGNk :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNk"; node [label="%vI_nGNl :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNl"; node [label="%vI_nGNm :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNm"; node [label="%vI_nGNn :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNn"; node [label="%vI_nGNo :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNo"; node [label="%vI_nGNp :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNp"; node [label="%vI_nGNq :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNq"; node [label="%vI_nGNr :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNr"; node [label="%vI_nGNs :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNs"; node [label="%vI_nGNt :: I\n(%r3)" style=filled fillcolor="white"] "%vI_nGNt"; node [label="%vI_sCRo :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45\n(spill?)" style=filled fillcolor=white] "%vI_sCRo"; node [label="%vI_sCRp :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45\n(%r31)" style=filled fillcolor="white"] "%vI_sCRp"; node [label="%vI_sCRr :: I\n-%r3 -%r4 -%r5 -%r6 -%r7 -%r8 -%r9 -%r10 -%r11 -%r12 -%r32 -%r33 -%r34 -%r35 -%r36 -%r37 -%r38 -%r39 -%r40 -%r41 -%r42 -%r43 -%r44 -%r45\n(spill?)" style=filled fillcolor=white] "%vI_sCRr"; node [label="%vI_sCRH :: I\n+%r3\n(%r3)" style=filled fillcolor="white"] "%vI_sCRH"; node [label="%vI_sCRM :: I\n+%r3\n(%r3)" style=filled fillcolor="white"] "%vI_sCRM"; "%vHi_HCRt" -- "%vHi_HCRu"; "%vHi_HCRt" -- "%vI_nGN6"; "%vHi_HCRt" -- "%vI_nGN7"; "%vHi_HCRt" -- "%vI_nGN8"; "%vHi_HCRu" -- "%vHi_HCRA"; "%vHi_HCRu" -- "%vHi_HGNi"; "%vHi_HCRu" -- "%vHi_HGNj"; "%vHi_HCRu" -- "%vI_nGN6"; "%vHi_HCRu" -- "%vI_nGN7"; "%vHi_HCRu" -- "%vI_nGN8"; "%vHi_HCRu" -- "%vI_nGNh"; "%vHi_HCRu" -- "%vI_nGNi"; "%vHi_HCRu" -- "%vI_nGNj"; "%vHi_HCRu" -- "%vI_sCRo"; "%vHi_HCRu" -- "%vI_sCRp"; "%vHi_HCRu" -- "%vI_sCRr"; "%vHi_HCRu" -- "%vI_sCRH"; "%vHi_HCRA" -- "%vHi_HGNi"; "%vHi_HCRA" -- "%vHi_HGNj"; "%vHi_HCRA" -- "%vI_nGN7"; "%vHi_HCRA" -- "%vI_nGNh"; "%vHi_HCRA" -- "%vI_nGNi"; "%vHi_HCRA" -- "%vI_nGNj"; "%vHi_HCRA" -- "%vI_sCRo"; "%vHi_HCRA" -- "%vI_sCRp"; "%vHi_HCRA" -- "%vI_sCRr"; "%vHi_HCRA" -- "%vI_sCRH"; "%vHi_HGNi" -- "%vI_nGN7"; "%vHi_HGNi" -- "%vI_nGNh"; "%vHi_HGNi" -- "%vI_nGNi"; "%vHi_HGNi" -- "%vI_sCRo"; "%vHi_HGNi" -- "%vI_sCRp"; "%vHi_HGNi" -- "%vI_sCRr"; "%vHi_HGNj" -- "%vI_nGN7"; "%vHi_HGNj" -- "%vI_nGNh"; "%vHi_HGNj" -- "%vI_nGNj"; "%vHi_HGNj" -- "%vI_sCRo"; "%vHi_HGNj" -- "%vI_sCRp"; "%vHi_HGNj" -- "%vI_sCRr"; "%vI_nGN6" -- "%vI_nGN7"; "%vI_nGN6" -- "%vI_nGN8"; "%vI_nGN7" -- "%vI_nGN8"; "%vI_nGN7" -- "%vI_nGNh"; "%vI_nGN7" -- "%vI_nGNi"; "%vI_nGN7" -- "%vI_nGNj"; "%vI_nGN7" -- "%vI_sCRo"; "%vI_nGN7" -- "%vI_sCRp"; "%vI_nGN7" -- "%vI_sCRr"; "%vI_nGN7" -- "%vI_sCRH"; "%vI_nGNh" -- "%vI_nGNi"; "%vI_nGNh" -- "%vI_nGNj"; "%vI_nGNh" -- "%vI_sCRo"; "%vI_nGNh" -- "%vI_sCRp"; "%vI_nGNh" -- "%vI_sCRr"; "%vI_nGNh" -- "%vI_sCRH"; "%vI_nGNi" -- "%vI_sCRo"; "%vI_nGNi" -- "%vI_sCRp"; "%vI_nGNi" -- "%vI_sCRr"; "%vI_nGNj" -- "%vI_sCRo"; "%vI_nGNj" -- "%vI_sCRp"; "%vI_nGNj" -- "%vI_sCRr"; "%vI_nGNo" -- "%vI_sCRo"; "%vI_nGNo" -- "%vI_sCRp"; "%vI_nGNo" -- "%vI_sCRr"; "%vI_nGNp" -- "%vI_sCRo"; "%vI_nGNp" -- "%vI_sCRp"; "%vI_nGNp" -- "%vI_sCRr"; "%vI_sCRo" -- "%vI_sCRp"; "%vI_sCRo" -- "%vI_sCRr"; "%vI_sCRo" -- "%vI_sCRH"; "%vI_sCRo" -- "%vI_sCRM"; "%vI_sCRp" -- "%vI_sCRr"; "%vI_sCRp" -- "%vI_sCRH"; "%vI_sCRp" -- "%vI_sCRM"; "%vI_sCRr" -- "%vI_sCRH"; "%vI_sCRr" -- "%vI_sCRM"; } Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13033> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12940: ghc-8.0.2 RC1 libs installed under package dirs vs Cabal installing packages under abi dir
by GHC 03 Jan '17

03 Jan '17

#12940: ghc-8.0.2 RC1 libs installed under package dirs vs Cabal installing packages under abi dir ----------------------------------------+--------------------------------- Reporter: juhpetersen | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Build System | Version: 8.0.2-rc1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- This may be more of an inconsistency than a bug: Under Linux, ghc-8.0.1.20161117 installs its dynlibs in package libdirs whereas Cabal-1.24.1.0 installs them under the abi dir: eg /usr/lib/ghc-8.0.2/pkg-version/libHSpkg-version-*.so vs /usr/lib/<arch>-linux-ghc-8.0.2/libHSpkg-version-*.so It would be more consistent for both to install in the same place. Personally I would even suggest just to install ghc dynlibs in /usr/lib itself but that is probably another discuss for Cabal... That would avoid the need for RPATH's entirely. :-) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12940> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13005: Mac OSX uses MAP_ANON in place of MAP_ANONYMOUS
by GHC 03 Jan '17

03 Jan '17

#13005: Mac OSX uses MAP_ANON in place of MAP_ANONYMOUS -------------------------------------+------------------------------------- Reporter: gracjan | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 (Linking) | Keywords: | Operating System: MacOS X Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Looks like Mac OS X has MAP_ANON instead of MAP_ANONYMOUS in /usr/include/sys/mman.h rts/linker/MachO.c needs fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13005> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12784: Typechecker regression in GHC 8.0.2 involving DefaultSignatures
by GHC 03 Jan '17

03 Jan '17

#12784: Typechecker regression in GHC 8.0.2 involving DefaultSignatures -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 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 compiles without issue on GHC 8.0.1 and earlier, but not with GHC 8.0.2 or HEAD. This was adapted from the [https://github.com/kazu- yamamoto/logger/blob/master/monad-logger/Control/Monad/Logger.hs monad- logger] library (which fails to build with GHC 8.0.2 and HEAD due to the same issue): {{{#!hs {-# LANGUAGE DefaultSignatures #-} {-# LANGUAGE GADTs #-} module MonadLogger where import Control.Monad.IO.Class import qualified Control.Monad.Trans.Class as Trans import Control.Monad.Trans.Identity data Loc data LogSource data LogLevel data LogStr class ToLogStr msg class Monad m => MonadLogger m class (MonadLogger m, MonadIO m) => MonadLoggerIO m where askLoggerIO :: m (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) default askLoggerIO :: (Trans.MonadTrans t, MonadLogger (t m), MonadIO (t m)) => t m (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) askLoggerIO = Trans.lift askLoggerIO instance MonadLogger m => MonadLogger (IdentityT m) instance MonadLoggerIO m => MonadLoggerIO (IdentityT m) }}} On GHC HEAD, this fails with: {{{ [1 of 1] Compiling MonadLogger ( MonadLogger.hs, interpreted ) MonadLogger.hs:23:10: error: • Couldn't match type ‘m’ with ‘IdentityT m’ ‘m’ is a rigid type variable bound by the instance declaration at MonadLogger.hs:23:10-55 Expected type: IdentityT m (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) Actual type: IdentityT (IdentityT m) (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) • In the expression: MonadLogger.$dmaskLoggerIO @IdentityT m In an equation for ‘askLoggerIO’: askLoggerIO = MonadLogger.$dmaskLoggerIO @IdentityT m In the instance declaration for ‘MonadLoggerIO (IdentityT m)’ • Relevant bindings include askLoggerIO :: IdentityT m (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) (bound at MonadLogger.hs:23:10) }}} This stopped typechecking after d2958bd08a049b61941f078e51809c7e63bc3354 (i.e, #12220). As a workaround, you can change the default signature to: {{{#!hs default askLoggerIO :: (Trans.MonadTrans t, MonadLoggerIO n, t n ~ m) => t n (Loc -> LogSource -> LogLevel -> LogStr -> IO ()) }}} And it'll work. Any thoughts on this, Simon? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12784> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13040: realToFrac into Complex Double has no specialization
by GHC 03 Jan '17

03 Jan '17

#13040: realToFrac into Complex Double has no specialization -------------------------------------+------------------------------------- Reporter: akio | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Example: {{{#!hs module Foo where import Data.Complex f :: Double -> Complex Double f x = realToFrac x }}} `ghc -O -ddump-simpl` gives: {{{ f = \ (w_s17v :: Double) -> case w_s17v of _ [Occ=Dead] { GHC.Types.D# ww1_s17y -> case GHC.Float.$w$ctoRational ww1_s17y of _ [Occ=Dead] { (# ww3_a152, ww4_a153 #) -> case GHC.Float.rationalToDouble ww3_a152 ww4_a153 of dt_a15c { GHC.Types.D# ipv_a15g -> Data.Complex.:+ @ Double dt_a15c Data.Complex.$fFloatingComplex1 } } } }}} This means the conversion goes through Rational. However, in this case, the conversion could be done much more efficiently with `(:+0)`. It would be nice if this happened automatically. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13040> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12879: (xs -> xs) wrongly suggests TypeApplications
by GHC 02 Jan '17

02 Jan '17

#12879: (xs -> xs) wrongly suggests TypeApplications -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `(xs -> xs)` and `map (xs -> xs)` wrongly suggest `TypeApplications` {{{ > map (xs -> xs) <interactive>:38:6: error: Pattern syntax in expression context: xs -> xs Did you mean to enable TypeApplications? }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12879> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12534: GHC 8.0 accepts recursive kind signature that GHC 7.10 rejects
by GHC 02 Jan '17

02 Jan '17

#12534: GHC 8.0 accepts recursive kind signature that GHC 7.10 rejects -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: TypeInType | 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: -------------------------------------+------------------------------------- GHC 7.10 rejects this datatype: {{{#!hs {-# LANGUAGE KindSignatures #-} {-# LANGUAGE PolyKinds #-} module Bug where data T (a :: a) }}} {{{ $ /opt/ghc/7.10.3/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:5:1: Kind variable also used as type variable: ‘a’ In the data type declaration for ‘T’ }}} But GHC 8.0 accepts the above code! It appears that GHC implicitly freshens the kind-level `a` so as to have a different name, since the following modification to `T`: {{{#!hs data T a (a :: a) }}} Results in this error: {{{ $ /opt/ghc/8.0.1/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:5:8: error: Conflicting definitions for ‘a’ Bound at: Bug.hs:5:8 Bug.hs:5:11 Bug.hs:5:16: error: Type variable ‘a’ used in a kind. Did you mean to use TypeInType? the data type declaration for ‘T’ }}} But with this modification: {{{#!hs data T (a :: a) a }}} You won't get an error message about `a` being used as both a kind and type: {{{ $ /opt/ghc/8.0.1/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:5:9: error: Conflicting definitions for ‘a’ Bound at: Bug.hs:5:9 Bug.hs:5:17 }}} To make things even more confusing, this behavior doesn't seem to carry over to typeclass instances. For example: GHC 8.0 will (rightfully) reject this code: {{{#!hs {-# LANGUAGE KindSignatures #-} {-# LANGUAGE PolyKinds #-} module Bug where data T (a :: a) class C x instance C (T (a :: a)) }}} {{{ $ /opt/ghc/8.0.1/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:8:16: error: Variable ‘a’ used as both a kind and a type Did you intend to use TypeInType? }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12534> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12837: KnownNat and KnownSymbol should be abstract
by GHC 02 Jan '17

02 Jan '17

#12837: KnownNat and KnownSymbol should be abstract -------------------------------------+------------------------------------- Reporter: adamgundry | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: newcomer | 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: -------------------------------------+------------------------------------- Consider the following patent nonsense: {{{#!hs {-# LANGUAGE FlexibleInstances #-} import GHC.TypeLits instance KnownNat n }}} This is accepted (albeit with a warning about the missing `natSing` method). I think it should be rejected, as should an instance of `KnownSymbol`. Compare doing the same thing with `Typeable`, which says: {{{ Class ‘Typeable’ does not support user-specified instances }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12837> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13003: improve documentation for typed TH and make it more discoverable
by GHC 02 Jan '17

02 Jan '17

#13003: improve documentation for typed TH and make it more discoverable -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Documentation | 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: -------------------------------------+------------------------------------- theres quite a sparsity of documentation and dearth of discoverability for typed TH in the Template Haskell Library haddocks and the GHC manual, this probably wouldn't be much work to make it vastly better. one specific two course of action might be a) adding to the template haskell library a module `Language.Haskell.TH.Typed` that only exports the stuff in `Language.Haskell.TH` that is needed for typed TH (namely the newtype `TExp` but not its constructor), plus perhaps the function `unTypeQ :: Q (TExp a) -> Q Exp` and additionally documents how to use typed TH splices and quotations. b) add a clear section to the manual that perhaps touches on some of this too? (its not clear if theres any real docs in the ghc manual on this :( ) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13003> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13042: Allow type annotations / visible type application in pattern synonyms
by GHC 02 Jan '17

02 Jan '17

#13042: Allow type annotations / visible type application in pattern synonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple TypeApplications, PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs data Lift f a = Pure a | Other (f a) data V0 a }}} To make a pattern synonym for `a -> Lift V0 a` I would like to be able to write either {{{#!hs pattern A a = Pure @V0 a }}} or {{{#!hs pattern B a = (Pure :: _ -> _ V0 _) a }}} to be equivalent to {{{#!hs pattern C :: a -> Lift V0 a pattern C a = Pure a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13042> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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