June 2018 - ghc-tickets

[GHC] #15318: Core Lint error involving newtype family instances with wrappers
by GHC 12 Jul '18

12 Jul '18

#15318: Core Lint error involving newtype family instances with wrappers -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 (Type checker) | Keywords: TypeFamilies | 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: -------------------------------------+------------------------------------- The following program gives a Core Lint error on GHC 8.4 and later: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} module Bug where data family Sn a newtype instance Sn (Either a b) where SnC :: forall b a. Char -> Sn (Either a b) }}} {{{ $ /opt/ghc/8.4.3/bin/ghc -dcore-lint Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) *** Core Lint errors : in result of Tidy Core *** <no location info>: warning: [in body of lambda with binder dt_aZm :: Char] From-type of Cast differs from type of enclosed expression From-type: R:SnEither a_auS b_auR Type of enclosed expr: Sn (Either a_auS b_auR) Actual enclosed expr: dt_aZm `cast` (Sym (N:R:SnEither[0] <a_auS>_N <b_auR>_N) ; Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (Char :: *) ~R# (Sn (Either a_auS b_auR) :: *)) Coercion used in cast: Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) *** Offending Program *** $WSnC [InlPrag=INLINE[2]] :: forall b a. Char -> Sn (Either a b) [GblId[DataConWrapper], Arity=1, Caf=NoCafRefs, Str=<L,U>, Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=True) Tmpl= \ (@ b_auR) (@ a_auS) (dt_aZm [Occ=Once] :: Char) -> (dt_aZm `cast` (Sym (N:R:SnEither[0] <a_auS>_N <b_auR>_N) ; Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (Char :: *) ~R# (Sn (Either a_auS b_auR) :: *))) `cast` (Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (R:SnEither a_auS b_auR :: *) ~R# (Sn (Either a_auS b_auR) :: *))}] $WSnC = \ (@ b_auR) (@ a_auS) (dt_aZm [Occ=Once] :: Char) -> (dt_aZm `cast` (Sym (N:R:SnEither[0] <a_auS>_N <b_auR>_N) ; Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (Char :: *) ~R# (Sn (Either a_auS b_auR) :: *))) `cast` (Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (R:SnEither a_auS b_auR :: *) ~R# (Sn (Either a_auS b_auR) :: *)) $trModule1_r10g :: Addr# [GblId, Caf=NoCafRefs] $trModule1_r10g = "main"# $trModule2_r10D :: TrName [GblId, Caf=NoCafRefs] $trModule2_r10D = TrNameS $trModule1_r10g $trModule3_r10E :: Addr# [GblId, Caf=NoCafRefs] $trModule3_r10E = "Bug"# $trModule4_r10F :: TrName [GblId, Caf=NoCafRefs] $trModule4_r10F = TrNameS $trModule3_r10E $trModule :: Module [GblId, Caf=NoCafRefs] $trModule = Module $trModule2_r10D $trModule4_r10F $krep_r10G :: KindRep [GblId] $krep_r10G = KindRepTyConApp $tcChar ([] @ KindRep) $krep1_r10H :: KindRep [GblId, Caf=NoCafRefs] $krep1_r10H = KindRepVar 1# $krep2_r10I :: KindRep [GblId, Caf=NoCafRefs] $krep2_r10I = KindRepVar 0# $krep3_r10J :: [KindRep] [GblId, Caf=NoCafRefs] $krep3_r10J = : @ KindRep $krep2_r10I ([] @ KindRep) $krep4_r10K :: [KindRep] [GblId, Caf=NoCafRefs] $krep4_r10K = : @ KindRep $krep1_r10H $krep3_r10J $krep5_r10L :: KindRep [GblId] $krep5_r10L = KindRepTyConApp $tcEither $krep4_r10K $tcSn1_r10M :: Addr# [GblId, Caf=NoCafRefs] $tcSn1_r10M = "Sn"# $tcSn2_r10N :: TrName [GblId, Caf=NoCafRefs] $tcSn2_r10N = TrNameS $tcSn1_r10M $tcSn :: TyCon [GblId] $tcSn = TyCon 461968091845555535## 16320521938866097056## $trModule $tcSn2_r10N 0# krep$*Arr* $krep6_r10O :: [KindRep] [GblId] $krep6_r10O = : @ KindRep $krep5_r10L ([] @ KindRep) $krep7_r10P :: KindRep [GblId] $krep7_r10P = KindRepTyConApp $tcSn $krep6_r10O $krep8_r10Q :: KindRep [GblId] $krep8_r10Q = KindRepFun $krep_r10G $krep7_r10P $tc'SnC1_r10R :: Addr# [GblId, Caf=NoCafRefs] $tc'SnC1_r10R = "'SnC"# $tc'SnC2_r10S :: TrName [GblId, Caf=NoCafRefs] $tc'SnC2_r10S = TrNameS $tc'SnC1_r10R $tc'SnC :: TyCon [GblId] $tc'SnC = TyCon 3818830880305712792## 17484539998814842835## $trModule $tc'SnC2_r10S 2# $krep8_r10Q *** End of Offense *** <no location info>: error: Compilation had errors }}} If we look at the Core for `$WSnC`, we see the culprit: {{{ $WSnC = \ (@ b_auR) (@ a_auS) (dt_aZm [Occ=Once] :: Char) -> (dt_aZm `cast` (Sym (N:R:SnEither[0] <a_auS>_N <b_auR>_N) ; Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (Char :: *) ~R# (Sn (Either a_auS b_auR) :: *))) `cast` (Sym (D:R:SnEither0[0] <a_auS>_N <b_auR>_N) :: (R:SnEither a_auS b_auR :: *) ~R# (Sn (Either a_auS b_auR) :: *)) }}} The inner cast goes from `Char` to `Sn (Either a b)`, but then the outer cast goes from `R:SnEither a b` to `Sn (Either a b)`, which is not transitive. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15318> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 5

[GHC] #15323: mkGadtDecl does not set con_forall correctly
by GHC 12 Jul '18

12 Jul '18

#15323: mkGadtDecl does not set con_forall correctly -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- A GADT declaration surrounded in parens does not det the `con_forall` field correctly. e.g. {{{#!hs data MaybeDefault v where TestParens :: (forall v . (Eq v) => MaybeDefault v) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15323> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #15324: -ddump-splices does not parenthesize rank-n contexts correctly
by GHC 12 Jul '18

12 Jul '18

#15324: -ddump-splices does not parenthesize rank-n contexts correctly -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Template | Version: 8.4.3 Haskell | 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: -------------------------------------+------------------------------------- Ryan discovers another `-ddump-splices` bug—news at 11: {{{#!hs {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TemplateHaskell #-} {-# OPTIONS_GHC -ddump-splices #-} module Bug where $([d| f :: forall a. (Show a => a) -> a f _ = undefined |]) }}} {{{ $ /opt/ghc/8.4.3/bin/ghci Bug.hs -dsuppress-uniques GHCi, version 8.4.3: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:(6,3)-(8,6): Splicing declarations [d| f :: forall a. (Show a => a) -> a f _ = undefined |] ======> f :: forall a. Show a => a -> a f _ = undefined }}} Notice that `f`'s type signature is pretty-printed as `forall a. Show a => a -> a`, which is just wrong. Patch incoming. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15324> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #15301: Regression in Natural desugaring
by GHC 12 Jul '18

12 Jul '18

#15301: Regression in Natural desugaring -------------------------------------+------------------------------------- Reporter: hsyl20 | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- My recent merged patch "Built-in Natural literals in Core" https://phabricator.haskell.org/rGHCfe770c211631e7b4c9b0b1e88ef9b6046c6585ef introduced a regression when desugaring large numbers. Patch coming. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15301> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #15289: isUnliftedType GHC panic on pattern with True :: Maybe
by GHC 12 Jul '18

12 Jul '18

#15289: isUnliftedType GHC panic on pattern with True :: Maybe -------------------------------------+------------------------------------- Reporter: Remi | Owner: (none) Type: bug | Status: new Priority: low | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: aarch64 | Type of failure: Compile-time | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE ScopedTypeVariables #-} module Oops where pattern What = True :: Maybe }}} Fails on 8.4.3 with: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.4.3 for x86_64-unknown-linux): isUnliftedType (Maybe |> {co_a1Dg3}) :: TYPE t_a1Dg9[tau:1] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1939:10 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} I'm currently cloning from git, and will try to get around to check it with HEAD over the next days. BTW, it's not a show-stopper for me. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15289> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 9

[GHC] #15303: API Annotations lost when parsing tyapp
by GHC 12 Jul '18

12 Jul '18

#15303: API Annotations lost when parsing tyapp -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect API Unknown/Multiple | annotation Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In `Parser.y`, the `typapp` production has {{{#!hs | SIMPLEQUOTE qconop {% ams (sLL $1 $> $ TyElOpr (unLoc $2)) [mj AnnSimpleQuote $1] } | SIMPLEQUOTE varop {% ams (sLL $1 $> $ TyElOpr (unLoc $2)) [mj AnnSimpleQuote $1] } }}} By using `unLoc $2` we are discarding any annotations attached to the `qconop` or `qvarop`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15303> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #14808: GHC HEAD regression: GADT constructors no longer quantify tyvars in topological order
by GHC 12 Jul '18

12 Jul '18

#14808: GHC HEAD regression: GADT constructors no longer quantify tyvars in topological order -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.5 (Type checker) | Keywords: GADTs | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #14529, #14796 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally noticed in #14796. This program: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeApplications #-} module Bug where import Data.Kind data ECC ctx f a where ECC :: ctx => f a -> ECC ctx f a f :: [()] -> ECC () [] () f = ECC @() @[] @() }}} Typechecks in GHC 8.2.2 and 8.4.1, but not in GHC HEAD: {{{ $ ~/Software/ghc2/inplace/bin/ghc-stage2 Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:12:5: error: • Couldn't match type ‘()’ with ‘[]’ Expected type: [()] -> ECC (() :: Constraint) [] () Actual type: () [] -> ECC (() :: Constraint) () [] • In the expression: ECC @() @[] @() In an equation for ‘f’: f = ECC @() @[] @() | 12 | f = ECC @() @[] @() | ^^^^^^^^^^^^^^^ Bug.hs:12:10: error: • Expected kind ‘* -> *’, but ‘()’ has kind ‘*’ • In the type ‘()’ In the expression: ECC @() @[] @() In an equation for ‘f’: f = ECC @() @[] @() | 12 | f = ECC @() @[] @() | ^^ Bug.hs:12:14: error: • Expecting one more argument to ‘[]’ Expected a type, but ‘[]’ has kind ‘* -> *’ • In the type ‘[]’ In the expression: ECC @() @[] @() In an equation for ‘f’: f = ECC @() @[] @() | 12 | f = ECC @() @[] @() | ^^ }}} This is because the order of type variables for `ECC` has changed between GHC 8.4.1 and HEAD. In 8.4.1, it's {{{ $ /opt/ghc/8.4.1/bin/ghci Bug.hs -XTypeApplications -fprint-explicit- foralls GHCi, version 8.4.0.20180209: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Ok, one module loaded. λ> :type +v ECC ECC :: forall (ctx :: Constraint) (f :: * -> *) a. ctx => f a -> ECC ctx f a }}} In GHC HEAD, however, it's: {{{ $ ~/Software/ghc2/inplace/bin/ghc-stage2 --interactive Bug.hs -XTypeApplications -fprint-explicit-foralls GHCi, version 8.5.20180213: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Ok, one module loaded. λ> :type +v ECC ECC :: forall (f :: * -> *) a (ctx :: Constraint). ctx => f a -> ECC ctx f a }}} This regression was introduced in fa29df02a1b0b926afb2525a258172dcbf0ea460 (Refactor ConDecl: Trac #14529). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14808> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 10

[GHC] #8581: Add support for explicitly-bidirectional pattern synonyms
by GHC 12 Jul '18

12 Jul '18

#8581: Add support for explicitly-bidirectional pattern synonyms ------------------------------------+------------------------------------- Reporter: cactus | Owner: cactus Type: feature request | 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: | ------------------------------------+------------------------------------- Some patterns cannot, by themselves, be turned over into an expression, so they have to be defined as unidirectional. Maybe the most trivial example would be {{{ pattern P -> _ }}} Sometimes, however, it would be desirable to give an explicit way of turning these pattern synonyms into expressions. The PatternSynonyms wiki page has this example: {{{ import qualified Data.Sequence as Seq pattern Empty -> (Seq.viewl -> Seq.EmptyL) pattern x :< xs -> (Seq.viewl -> x Seq.:< xs) pattern xs :> x -> (Seq.viewr -> xs Seq.:> x) }}} It would make a ton of sense to be able to use this cons/snoc notation as "constructors" for `Seq`s. The proposed syntax for this {{{ pattern x :< xs -> (Seq.viewl -> x Seq.:< xs) where x :< xs = x Seq.<| xs }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8581> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 52

[GHC] #14164: GHC hangs on type family dependency
by GHC 12 Jul '18

12 Jul '18

#14164: GHC hangs on type family dependency -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- {{{#!hs {-# Language TypeOperators, DataKinds, PolyKinds, KindSignatures, TypeInType, GADTs, TypeFamilyDependencies #-} import Data.Kind type Cat a = a -> a -> Type data SubList :: Cat [a] where SubNil :: SubList '[] '[] Keep :: SubList xs ys -> SubList (x:xs) (x:ys) Drop :: SubList xs ys -> SubList xs (x:ys) type family UpdateWith (ys'::[a]) (xs::[a]) (pf::SubList ys xs) = (res :: [a]) | res -> pf ys' xs where UpdateWith '[] '[] SubNil = '[] UpdateWith (y:ys) '[] SubNil = y:ys -- UpdateWith '[] (_:_) (Keep _) = '[] UpdateWith (y:ys) (_:xs) (Keep rest) = y:UpdateWith ys xs rest -- UpdateWith ys (x:xs) (Drop rest) = x:UpdateWith ys xs rest }}} seems to loop forever on the "`Renamer/typechecker`" {{{ $ ghci -ignore-dot-ghci -v /tmp/u.hs GHCi, version 8.3.20170605: http://www.haskell.org/ghc/ :? for help Glasgow Haskell Compiler, Version 8.3.20170605, stage 2 booted by GHC version 8.0.2 [...] *** Parser [Main]: !!! Parser [Main]: finished in 1.31 milliseconds, allocated 0.651 megabytes *** Renamer/typechecker [Main]: [hangs] }}} while {{{#!hs type family UpdateWith (ys'::[a]) (xs::[a]) (pf::SubList ys xs) = (res :: [a]) | res -> pf ys' xs where UpdateWith '[] '[] SubNil = '[] UpdateWith (y:ys) '[] SubNil = y:ys UpdateWith '[] (_:_) (Keep _) = '[] }}} immediately gives {{{ $ ghc -ignore-dot-ghci /tmp/u.hs [1 of 1] Compiling Main ( /tmp/u.hs, /tmp/u.o ) /tmp/u.hs:14:3: error: • Type family equations violate injectivity annotation: UpdateWith '[] '[] 'SubNil = '[] -- Defined at /tmp/u.hs:14:3 forall a (xs :: [a]) (_1 :: [a]) (_2 :: a) (_3 :: SubList xs _1). UpdateWith '[] (_2 : _1) ('Keep _3) = '[] -- Defined at /tmp/u.hs:16:3 • In the equations for closed type family ‘UpdateWith’ In the type family declaration for ‘UpdateWith’ | 14 | UpdateWith '[] '[] SubNil = '[] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /tmp/u.hs:16:3: error: • Type family equation violates injectivity annotation. Type and kind variables ‘_2’, ‘_1’, ‘xs’, ‘_3’ cannot be inferred from the right-hand side. Use -fprint-explicit-kinds to see the kind arguments In the type family equation: forall a (xs :: [a]) (_1 :: [a]) (_2 :: a) (_3 :: SubList xs _1). UpdateWith '[] (_2 : _1) ('Keep _3) = '[] -- Defined at /tmp/u.hs:16:3 • In the equations for closed type family ‘UpdateWith’ In the type family declaration for ‘UpdateWith’ | 16 | UpdateWith '[] (_:_) (Keep _) = '[] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14164> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 16

[GHC] #14929: Program compiled with -O2 exhibits much worse performance
by GHC 10 Jul '18

10 Jul '18

#14929: Program compiled with -O2 exhibits much worse performance -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 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: -------------------------------------+------------------------------------- A user on reddit reports that compiling the program with `-O2` makes his program use a lot more memory. https://www.reddit.com/r/haskell/comments/84qovv/an_example_of_code_where_g… It runs in constant memory without `-O2` and leaks memory with `-O2. It seems worth investigating as the example is quite small (< 1000 lines) and self-contained. https://github.com/luispedro/TestingNGLESS -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14929> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4