October 2018 - ghc-tickets

[GHC] #14088: Allow users to omit`forall`
by GHC 15 Oct '18

15 Oct '18

#14088: Allow users to omit`forall` -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- Just an idea I wanted to get out there, I don't think it causes parsing ambiguity {{{#!hs -- id :: forall a. a -> a id :: a. a -> a -- everywhere :: (forall b. Term b => b -> b) -> (forall a. Term a => a -> a) everywhere :: (b. Term b => b -> b) -> (a. Term a => a -> a) }}} I think it looks beautiful but clearly more difficult to Google or grep for. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14088> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15488: GHC takes up huge amount of memory when compiling accelerate 1.2.0
by GHC 15 Oct '18

15 Oct '18

#15488: GHC takes up huge amount of memory when compiling accelerate 1.2.0 -------------------------------------+------------------------------------- Reporter: noah | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Linux accelerate,memory,compile | Architecture: x86_64 | Type of failure: Compile-time (amd64) | performance bug Test Case: accelerate | Blocked By: 1.2.0 | Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Every time I try to run {{{ cabal install accelerate }}} the compiler take up nearly all 4GB of memory. Stracing it reveals that it seems to be spending nearly all of the time it runs checking a timer file descriptor, and occasionally checking its memory usage without actually doing anything about the problem. This makes installing accelerate nearly impossible. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15488> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15745: Panicking typechecker plugins
by GHC 15 Oct '18

15 Oct '18

#15745: Panicking typechecker plugins -------------------------------------+------------------------------------- Reporter: philderbeast | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- If I use a typechecker plugin that fails then ghc panics and I'm asked to report a bug with GHC; {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-apple-darwin): Prelude.undefined CallStack (from HasCallStack): error, called at libraries/base/GHC/Err.hs:79:14 in base:GHC.Err undefined, called at plugin/Undefined/Solve/Plugin.hs:14:39 in undefined-solve- plugin-1.0.0.0-56evBabJYBHHTUlrE3HO5m:Undefined.Solve.Plugin Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Could we please say that it is the typechecker plugin that is panicking and ask for a bug report for the faulty typechecker, giving the issues URL for the plugin if we know it? The following [https://github.com/BlockScope/undefined-plugin undefined plugins] fail for init, solve and stop functions. {{{ #!haskell module Undefined.Init.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult(..), Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-init-plugin" $ TcPlugin { tcPluginInit = undefined , tcPluginSolve = \_ _ _ _ -> return $ TcPluginOk [] [] , tcPluginStop = const $ return () } }}} {{{ #!haskell module Undefined.Solve.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult, Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-solve-plugin" $ TcPlugin { tcPluginInit = return () , tcPluginSolve = \_ _ _ _ -> undefined , tcPluginStop = const $ return () } }}} {{{ #!haskell module Undefined.Stop.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult(..), Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-stop-plugin" $ TcPlugin { tcPluginInit = return () , tcPluginSolve = \_ _ _ _ -> return $ TcPluginOk [] [] , tcPluginStop = const $ undefined } }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15745> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15749: Long Harbormaster builds
by GHC 14 Oct '18

14 Oct '18

#15749: Long Harbormaster builds -------------------------------------+------------------------------------- Reporter: monoidal | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: Component: Continuous | Version: 8.6.1 Integration | 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: -------------------------------------+------------------------------------- Harbormaster builds sometimes take too long and are not terminated. For example, the following builds have been running for over 2 days: https://phabricator.haskell.org/harbormaster/build/54452/ https://phabricator.haskell.org/harbormaster/build/54477/ https://phabricator.haskell.org/harbormaster/build/54485/ We should have some timeout (or lower the threshold if it's already present). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15749> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4306: UNPACK can lead to unnecessary copying and wasted stack space
by GHC 14 Oct '18

14 Oct '18

#4306: UNPACK can lead to unnecessary copying and wasted stack space -------------------------------------+------------------------------------- Reporter: Olathe | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 6.12.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: Runtime | Test Case: performance bug | simplCore/should_compile/T4306 Blocked By: | Blocking: -------------------------------------+------------------------------------- Comment (by Krzysztof Gogolewski <krz.gogolewski@…>): In [changeset:"448b77b93b369745e9bfbc8b46a5b87bb73dd379/ghc" 448b77b9/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="448b77b93b369745e9bfbc8b46a5b87bb73dd379" Add RubbishLit for absent bindings of UnliftedRep Summary: Trac #9279 reminded us that the worker wrapper transformation copes really badly with absent unlifted boxed bindings. As `Note [Absent errors]` in WwLib.hs points out, we can't just use `absentError` for unlifted bindings because there is no bottom to hide the error in. So instead, we synthesise a new `RubbishLit` of type `forall (a :: TYPE 'UnliftedRep). a`, which code-gen may subsitute for any boxed value. We choose `()`, so that there is a good chance that the program crashes instead instead of leading to corrupt data, should absence analysis have been too optimistic (#11126). Reviewers: simonpj, hvr, goldfire, bgamari, simonmar Reviewed By: simonpj Subscribers: osa1, rwbarton, carter GHC Trac Issues: #15627, #9279, #4306, #11126 Differential Revision: https://phabricator.haskell.org/D5153 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4306#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15746: Memory leak in print when RTS option -N is >= 2
by GHC 14 Oct '18

14 Oct '18

#15746: Memory leak in print when RTS option -N is >= 2 -------------------------------------+------------------------------------- Reporter: nmattia | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 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 GHC 802 the code below runs with constant memory. In GHC 822, 843 and 861 the code below runs with constant memory only if at most one core is used. If the RTS option -N is set to anything greater than 1, the memory usage grows with the size of "big_file". {{{#!hs import Data.ByteString.Builder.Extra (defaultChunkSize) import Data.Function import System.IO import qualified Data.ByteString as BS main :: IO () main = do h <- openFile "big_file" ReadMode fix $ \loop -> do bs <- BS.hGetSome h defaultChunkSize if BS.null bs then pure () else do print bs loop }}} You can reproduce this by cloning https://github.com/nmattia/ghc-print- leak and running "nix-shell". Alternatively save the code above to "Main.hs" and run "ghc ./Main.hs -threaded -rtsopts" and then "./Main +RTS -M2M -N[1|2] > /dev/null". Side note: the memory does not grow as quickly if the _size_ of the bytestring is printed, i.e. it seems to be a problem specific to hPutStrLn/print as opposed to the actual file content/bytestring being retained. I first encountered this issue when using conduit for the loop. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15746> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15695: Core Lint error, from -fobject-code + defer type errors + pattern synonyms + other stuff
by GHC 14 Oct '18

14 Oct '18

#15695: Core Lint error, from -fobject-code + defer type errors + pattern synonyms + other stuff -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Try running this (`-fobject-code` is required) with '''and''' without `-dcore-lint`. I tried to minimize it but it is still hefty. This is showing it without `-dcore-lint`: {{{#!hs {-# Language RankNTypes, PatternSynonyms, DataKinds, PolyKinds, GADTs, TypeOperators, MultiParamTypeClasses, TypeFamilies, TypeSynonymInstances, FlexibleInstances, InstanceSigs, FlexibleContexts #-} {-# Options_GHC -fdefer-type-errors #-} import Data.Kind import Data.Type.Equality data TyVar :: Type -> Type -> Type where VO :: TyVar (a -> as) a VS :: TyVar as a -> TyVar (b -> as) a data NP :: (k -> Type) -> ([k] -> Type) where Nil :: NP f '[] (:*) :: f a -> NP f as -> NP f (a:as) data NS :: (k -> Type) -> ([k] -> Type) where Here :: f a -> NS f (a:as) There :: NS f as -> NS f (a:as) infixr 6 :&: data Ctx :: Type -> Type where E :: Ctx(Type) (:&:) :: a -> Ctx(as) -> Ctx(a -> as) data NA a type SOP(kind::Type) code = NS (NP NA) code data ApplyT(kind::Type) :: kind -> Ctx(kind) -> Type where AO :: a -> ApplyT(Type) a E AS :: ApplyT(ks) (f a) ctx -> ApplyT(k -> ks) f (a:&:ctx) from' :: ApplyT(Type -> Type -> Type) Either ctx -> NS (NP NA) '[ '[VO] ] from' (ASSO (Left a)) = Here (a :* Nil) from' (ASSO (Right b)) = There (Here undefined) pattern ASSO :: () => forall (ks :: Type) k (f :: k -> ks) (a1 :: k) (ks1 :: Type) k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> Type), a ~~ f, b ~~ (a1 :&: a2 :&: E), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b pattern ASSO a = AS (AS (AO a)) }}} {{{ $ latestbug -fobject-code 466.hs GHCi, version 8.7.20180828: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 466.hs, 466.o ) 466.hs:35:14: warning: [-Wdeferred-type-errors] • Could not deduce: a2 ~ NA 'VO from the context: ((* -> * -> *) ~ (k1 -> k2 -> *), Either ~~ f, ctx ~~ (a2 ':&: (a3 ':&: 'E)), f a2 ~~ f1, f1 a3 ~~ a4) bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> *), a ~~ f, b ~~ (a1 ':&: (a2 ':&: 'E)), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b, in an equation for ‘from'’ at 466.hs:35:8-21 ‘a2’ is a rigid type variable bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> *), a ~~ f, b ~~ (a1 ':&: (a2 ':&: 'E)), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b, in an equation for ‘from'’ at 466.hs:35:8-21 Expected type: a4 Actual type: Either (NA 'VO) a3 • In the pattern: Left a In the pattern: ASSO (Left a) In an equation for ‘from'’: from' (ASSO (Left a)) = Here (a :* Nil) • Relevant bindings include from' :: ApplyT (* -> * -> *) Either ctx -> NS (NP NA) '[ '[ 'VO]] (bound at 466.hs:35:1) | 35 | from' (ASSO (Left a)) = Here (a :* Nil) | ^^^^^^^ 466.hs:36:26: warning: [-Wdeferred-type-errors] • Couldn't match type ‘a0 : as0’ with ‘'[]’ Expected type: NS (NP NA) '[ '[ 'VO]] Actual type: NS (NP NA) ('[ 'VO] : a0 : as0) • In the expression: There (Here undefined) In an equation for ‘from'’: from' (ASSO (Right b)) = There (Here undefined) • Relevant bindings include from' :: ApplyT (* -> * -> *) Either ctx -> NS (NP NA) '[ '[ 'VO]] (bound at 466.hs:35:1) | 36 | from' (ASSO (Right b)) = There (Here undefined) | ^^^^^^^^^^^^^^^^^^^^^^ WARNING: file compiler/types/TyCoRep.hs, line 2378 in_scope InScope {wild_00 wild_Xl wild_Xv wild_X1m a_a1Gv ks_a1Ou k_a1Ov f_a1Ow a_a1Ox ctx_a1Oy co_a1Oz co_a1OA co_a1OB ks_a1OC k_a1OD f_a1OE a_a1OF ctx_a1OG co_a1OH co_a1OI co_a1OJ a_a1OK co_a1OL co_a1OM co_a1ON as_a1Q3 a_a1Q4 ctx_a1Q5 $krep_a2XW $krep_a2XX $krep_a2XY $krep_a2XZ $krep_a2Y0 $krep_a2Y1 $krep_a2Y2 $krep_a2Y3 $krep_a2Y4 $krep_a2Y5 $krep_a2Y6 $krep_a2Y7 $krep_a2Y8 $krep_a2Y9 $krep_a2Ya $krep_a2Yb $krep_a2Yc $krep_a2Yd $krep_a2Ye $krep_a2Yf $krep_a2Yg $krep_a2Yh $krep_a2Yi $krep_a2Yj $krep_a2Yk $krep_a2Yl $krep_a2Ym $krep_a2Yn $krep_a2Yo $krep_a2Yp $krep_a2Yq $krep_a2Yr $krep_a2Ys $krep_a2Yt $krep_a2Yu $krep_a2Yv $krep_a2Yw $krep_a2Yx $krep_a2Yy $krep_a2Yz $krep_a2YA $krep_a2YB $krep_a2YC $krep_a2YD $krep_a2YE $krep_a2YF $krep_a2YG $krep_a2YH $krep_a2YI $krep_a2YJ $krep_a2YK $krep_a2YL ds_d2YO ds_d2YP ds_d2YV fail_d2Z2 from' $bASSO $mASSO $tc':&: $tc':* $tc'AO $tc'AS $tc'E $tc'Here $tc'Nil $tc'There $tc'VO $tc'VS $tcApplyT $tcCtx $tcNA $tcNP $tcNS $tcTyVar $trModule $trModule_s2ZM $trModule_s2ZN $trModule_s2ZO $trModule_s2ZP $krep_s2ZQ $krep_s2ZR $krep_s2ZS $krep_s2ZT $krep_s2ZU $krep_s2ZV $krep_s2ZW $krep_s2ZX $tcTyVar_s2ZY $tcTyVar_s2ZZ $krep_s300 $krep_s301 $krep_s302 $krep_s303 $tc'VO_s304 $tc'VO_s305 $krep_s306 $krep_s307 $tc'VS_s308 $tc'VS_s309 $tcNP_s30a $tcNP_s30b $krep_s30c $krep_s30d $krep_s30e $krep_s30f $krep_s30g $krep_s30h $tc':*_s30i $tc':*_s30j $krep_s30k $krep_s30l $krep_s30m $tc'Nil_s30n $tc'Nil_s30o $tcNS_s30p $tcNS_s30q $krep_s30r $krep_s30s $krep_s30t $krep_s30u $krep_s30v $krep_s30w $tc'Here_s30x $tc'Here_s30y $krep_s30z $krep_s30A $krep_s30B $tc'There_s30C $tc'There_s30D $tcCtx_s30E $tcCtx_s30F $krep_s30G $krep_s30H $krep_s30I $tc':&:_s30J $tc':&:_s30K $krep_s30L $krep_s30M $krep_s30N $krep_s30O $krep_s30P $tc'E_s30Q $tc'E_s30R $tcNA_s30S $tcNA_s30T $tcApplyT_s30U $tcApplyT_s30V $krep_s30W $krep_s30X $krep_s30Y $krep_s30Z $krep_s310 $krep_s311 $tc'AS_s312 $tc'AS_s313 $krep_s314 $krep_s315 $krep_s316 $tc'AO_s317 $tc'AO_s318} tenv [a1Ow :-> f_a1Ow, a1Ox :-> a_a1Ox, a1Oy :-> ctx_a1Oy, a1OE :-> f_a1OE, a1OF :-> a_a1OF, a1OG :-> ctx_a1OG] cenv [a1Oz :-> co_a1Oz, a1OA :-> co_a1OA, a1OB :-> co_a1OB, a1OH :-> co_a1OH, a1OI :-> co_a1OI, a1OJ :-> co_a1OJ, a1OL :-> co_a1OL, a1OM :-> co_a1OM, a1ON :-> co_a1ON] tys [a_a1Ox ~# (NA 'VO |> Sym (Nth:2 (Sym co_a2U0)))] cos [] needInScope [a1Ov :-> k_a1Ov, a1OD :-> k_a1OD, a1Q3 :-> as_a1Q3, a1Q4 :-> a_a1Q4, a2U0 :-> co_a2U0] WARNING: file compiler/types/TyCoRep.hs, line 2378 in_scope InScope {wild_00 wild_Xl wild_Xv wild_X1m a_a1Gv ks_a1Ou k_a1Ov f_a1Ow a_a1Ox ctx_a1Oy co_a1Oz co_a1OA co_a1OB ks_a1OC k_a1OD f_a1OE a_a1OF ctx_a1OG co_a1OH co_a1OI co_a1OJ a_a1OK co_a1OL co_a1OM co_a1ON as_a1Q3 a_a1Q4 ctx_a1Q5 $krep_a2XW $krep_a2XX $krep_a2XY $krep_a2XZ $krep_a2Y0 $krep_a2Y1 $krep_a2Y2 $krep_a2Y3 $krep_a2Y4 $krep_a2Y5 $krep_a2Y6 $krep_a2Y7 $krep_a2Y8 $krep_a2Y9 $krep_a2Ya $krep_a2Yb $krep_a2Yc $krep_a2Yd $krep_a2Ye $krep_a2Yf $krep_a2Yg $krep_a2Yh $krep_a2Yi $krep_a2Yj $krep_a2Yk $krep_a2Yl $krep_a2Ym $krep_a2Yn $krep_a2Yo $krep_a2Yp $krep_a2Yq $krep_a2Yr $krep_a2Ys $krep_a2Yt $krep_a2Yu $krep_a2Yv $krep_a2Yw $krep_a2Yx $krep_a2Yy $krep_a2Yz $krep_a2YA $krep_a2YB $krep_a2YC $krep_a2YD $krep_a2YE $krep_a2YF $krep_a2YG $krep_a2YH $krep_a2YI $krep_a2YJ $krep_a2YK $krep_a2YL ds_d2YO ds_d2YP ds_d2YV fail_d2Z2 from' $bASSO $mASSO $tc':&: $tc':* $tc'AO $tc'AS $tc'E $tc'Here $tc'Nil $tc'There $tc'VO $tc'VS $tcApplyT $tcCtx $tcNA $tcNP $tcNS $tcTyVar $trModule $trModule_s2ZM $trModule_s2ZN $trModule_s2ZO $trModule_s2ZP $krep_s2ZQ $krep_s2ZR $krep_s2ZS $krep_s2ZT $krep_s2ZU $krep_s2ZV $krep_s2ZW $krep_s2ZX $tcTyVar_s2ZY $tcTyVar_s2ZZ $krep_s300 $krep_s301 $krep_s302 $krep_s303 $tc'VO_s304 $tc'VO_s305 $krep_s306 $krep_s307 $tc'VS_s308 $tc'VS_s309 $tcNP_s30a $tcNP_s30b $krep_s30c $krep_s30d $krep_s30e $krep_s30f $krep_s30g $krep_s30h $tc':*_s30i $tc':*_s30j $krep_s30k $krep_s30l $krep_s30m $tc'Nil_s30n $tc'Nil_s30o $tcNS_s30p $tcNS_s30q $krep_s30r $krep_s30s $krep_s30t $krep_s30u $krep_s30v $krep_s30w $tc'Here_s30x $tc'Here_s30y $krep_s30z $krep_s30A $krep_s30B $tc'There_s30C $tc'There_s30D $tcCtx_s30E $tcCtx_s30F $krep_s30G $krep_s30H $krep_s30I $tc':&:_s30J $tc':&:_s30K $krep_s30L $krep_s30M $krep_s30N $krep_s30O $krep_s30P $tc'E_s30Q $tc'E_s30R $tcNA_s30S $tcNA_s30T $tcApplyT_s30U $tcApplyT_s30V $krep_s30W $krep_s30X $krep_s30Y $krep_s30Z $krep_s310 $krep_s311 $tc'AS_s312 $tc'AS_s313 $krep_s314 $krep_s315 $krep_s316 $tc'AO_s317 $tc'AO_s318} tenv [a1Ow :-> f_a1Ow, a1Ox :-> a_a1Ox, a1Oy :-> ctx_a1Oy, a1OE :-> f_a1OE, a1OF :-> a_a1OF, a1OG :-> ctx_a1OG] cenv [a1Oz :-> co_a1Oz, a1OA :-> co_a1OA, a1OB :-> co_a1OB, a1OH :-> co_a1OH, a1OI :-> co_a1OI, a1OJ :-> co_a1OJ, a1OL :-> co_a1OL, a1OM :-> co_a1OM, a1ON :-> co_a1ON] tys [a_a1Ox ~# (NA 'VO |> Sym (Nth:2 (Sym co_a2U0)))] cos [] needInScope [a1Ov :-> k_a1Ov, a1OD :-> k_a1OD, a1Q3 :-> as_a1Q3, a1Q4 :-> a_a1Q4, a2U0 :-> co_a2U0] Ok, one module loaded. Prelude Main> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15695> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15481: TH fails to recover from reifyFixity with -fexternal-interpreter
by GHC 14 Oct '18

14 Oct '18

#15481: TH fails to recover from reifyFixity with -fexternal-interpreter -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Template | Version: 8.4.3 Haskell | Keywords: RemoteGHCi | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (Originally reported at https://github.com/glguy/th- abstraction/issues/53.) If you compile the following program: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Language.Haskell.TH main :: IO () main = putStrLn $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) }}} It will work fine without the use of `-fexternal-interpreter`. However, using `-fexternal-interpreter` will result in an error: {{{ $ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) $ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp -fexternal-interpreter [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:7:19: error: • The exact Name ‘foo_a3MT’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) | 7 | main = putStrLn $(recover (stringE "reifyFixity failed") | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Bug.hs:7:19: error: • The exact Name ‘foo_a3MT’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) | 7 | main = putStrLn $(recover (stringE "reifyFixity failed") | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15481> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12005: Constraint instances not shown in `:info`
by GHC 13 Oct '18

13 Oct '18

#12005: Constraint instances not shown in `:info` -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- {{{ $ ghci -ignore-dot-ghci -XKindSignatures -XRank2Types -XConstraintKinds -XAllowAmbiguousTypes -XInstanceSigs GHCi, version 8.1.20160428: http://www.haskell.org/ghc/ :? for help Prelude> import Data.Kind Prelude Data.Kind> class Defer (p :: Constraint) where defer :: (p => r) -> r Prelude Data.Kind> instance Defer () where defer :: r -> r; defer = id Prelude Data.Kind> :i Defer class Defer (p :: Constraint) where defer :: (p => r) -> r {-# MINIMAL defer #-} -- Defined at <interactive>:2:1 }}} Same happens with the [https://github.com/ekmett/constraints/blob/master/src/Data/Constraint/Defer… Data.Constraint.Deferrable] which defines: {{{#!hs instance (Typeable a, Typeable b) => Deferrable (a ~ b) instance (Deferrable a, Deferrable b) => Deferrable (a, b) instance (Deferrable a, Deferrable b, Deferrable c) => Deferrable (a, b, c) }}} but no instances are shown: {{{ ghci> import Data.Constraint.Deferrable ghci> :i Deferrable class Deferrable (p :: Constraint) where deferEither :: proxy p -> (p => r) -> Either String r {-# MINIMAL deferEither #-} -- Defined in ‘Data.Constraint.Deferrable’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12005> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15722: Add -Wstar-is-type to the User's Guide
by GHC 13 Oct '18

13 Oct '18

#15722: Add -Wstar-is-type to the User's Guide -------------------------------------+------------------------------------- Reporter: int-index | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.2 Component: Documentation | Version: 8.6.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): Phab:D5203 | Wiki Page: -------------------------------------+------------------------------------- Documentation for `-Wstar-is-type` is missing in the 8.6.1 release. Creating this ticket with a milestone as a reminder to cherry-pick the patch to 8.6.2 (right now it's merged to `master`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15722> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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