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[GHC] #12358: Read1/Read2 don't have methods defined in terms of ReadPrec
by GHC 31 Aug '16

31 Aug '16

#12358: Read1/Read2 don't have methods defined in terms of ReadPrec -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: | Version: 8.0.1 libraries/base | 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: -------------------------------------+------------------------------------- Original Haskell libraries mailing list discussion: https://mail.haskell.org/pipermail/libraries/2016-June/027102.html > GHC 8.0 added the [http://hackage.haskell.org/package/base-4.9.0.0/docs /Data-Functor-Classes.html Data.Functor.Classes] module to `base`, and with it the `Read1` and `Read2` typeclasses. The current definition of `Read1` is this: > > {{{#!hs > class Read1 f where > liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) > liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [f a] > }}} > > There's a pretty big problem with this definition: it uses `ReadS` (a synonym for `String -> [(a, String)]`). This sort of parser is very slow (the docs even [http://hackage.haskell.org/package/base-4.9.0.0/docs/Text- ParserCombinators-ReadP.html#t:ReadS admit as such]), and moreover, the actual `Read` typeclass on which Read1 is based tries to avoid using it whenever possible. > > The `Read` typeclass has this definition currently: > > {{{#!hs > class Read a where > readsPrec :: Int -> ReadS a > readList :: ReadS [a] > readPrec :: ReadPrec a > readListPrec :: ReadPrec [a] > }}} > > Where `ReadPrec` is a much more efficient parser datatype. When deriving `Read` instances, GHC defines them in terms of `readPrec`, and gives the other methods default definitions that leverage `readPrec`. > > For the sake of consistency, I propose adding analogous methods to `Read1` and `Read2` that use the `ReadPrec` datatype. For example, here is how I would change `Read1`: > > {{{#!hs > class Read1 f where > liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) > liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [f a] > liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (f a) > liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [f a] > }}} > > And similarly for `Read2`. Here is a [https://gist.github.com/RyanGlScott/7cdd11d6aa878e4229acf1a682beb1fc full gist] with a sketch of what the new `Read1`/`Read2` definitions would look like, including what the default definitions of the other methods would be. Diff coming soon. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12358> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7259: Eta expansion of products in System FC
by GHC 31 Aug '16

31 Aug '16

#7259: Eta expansion of products in System FC -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | 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/7259#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12460: Solaris linker does not recognize option --gc-sections
by GHC 30 Aug '16

30 Aug '16

#12460: Solaris linker does not recognize option --gc-sections ------------------------------------------+---------------------------- Reporter: herzen | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Linking) | Version: 8.0.1 Keywords: | Operating System: Solaris Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ------------------------------------------+---------------------------- Linking helloworld.hs fails with the error ld: fatal: unrecognized option '--' If gcc is called by hand to link with "-Wl,--gc-sections" removed, the link succeeds. $ ghc --version The Glorious Glasgow Haskell Compilation System, version 8.0.1 $ uname -a SunOS diotima 5.11 11.3 i86pc i386 i86pc $ gcc --version gcc (GCC) 4.9.3 $ cat helloworld.hs main = putStrLn "hello, world" $ ghc -c helloworld.hs $ ghc -v -keep-tmp-files -o helloworld helloworld.o Glasgow Haskell Compiler, Version 8.0.1, stage 2 booted by GHC version 7.10.1 Using binary package database: /usr/lib/ghc-8.0.1/package.conf.d/package.cache loading package database /usr/lib/ghc-8.0.1/package.conf.d wired-in package ghc-prim mapped to ghc-prim-0.5.0.0 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1 wired-in package base mapped to base-4.9.0.0 wired-in package rts mapped to rts wired-in package template-haskell mapped to template-haskell-2.11.0.0 wired-in package ghc mapped to ghc-8.0.1 wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: Created temporary directory: /tmp/ghc5103_0 *** C Compiler: gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc5103_0/ghc_1.c -o /tmp/ghc5103_0/ghc_2.o -I/usr/lib/ghc-8.0.1/include *** Linker: gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -o helloworld -Wl ,--gc-sections helloworld.o -L/usr/lib/ghc-8.0.1/base-4.9.0.0 -L/usr/lib/ghc-8.0.1/integer-gmp-1.0.0.1 -L/usr/lib/ -L/usr/lib/ghc-8.0.1 /ghc-prim-0.5.0.0 -L/usr/lib/ghc-8.0.1/rts /tmp/ghc5103_0/ghc_2.o -Wl,-u,ghczmprim_GHCziTypes_Izh_static_info -Wl,-u,ghczmprim_GHCziTypes_Czh_static_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_static_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_static_info -Wl,-u,base_GHCziPtr_Ptr_static_info -Wl,-u,ghczmprim_GHCziTypes_Wzh_static_info -Wl,-u,base_GHCziInt_I8zh_static_info -Wl,-u,base_GHCziInt_I16zh_static_info -Wl,-u,base_GHCziInt_I32zh_static_info -Wl,-u,base_GHCziInt_I64zh_static_info -Wl,-u,base_GHCziWord_W8zh_static_info -Wl,-u,base_GHCziWord_W16zh_static_info -Wl,-u,base_GHCziWord_W32zh_static_info -Wl,-u,base_GHCziWord_W64zh_static_info -Wl,-u,base_GHCziStable_StablePtr_static_info -Wl,-u,ghczmprim_GHCziTypes_Izh_con_info -Wl,-u,ghczmprim_GHCziTypes_Czh_con_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_con_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_con_info -Wl,-u,base_GHCziPtr_Ptr_con_info -Wl,-u,base_GHCziPtr_FunPtr_con_info -Wl,-u,base_GHCziStable_StablePtr_con_info -Wl,-u,ghczmprim_GHCziTypes_False_closure -Wl,-u,ghczmprim_GHCziTypes_True_closure -Wl,-u,base_GHCziPack_unpackCString_closure -Wl,-u,base_GHCziIOziException_stackOverflow_closure -Wl,-u,base_GHCziIOziException_heapOverflow_closure -Wl,-u,base_ControlziExceptionziBase_nonTermination_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -Wl,-u,base_GHCziIOziException_allocationLimitExceeded_closure -Wl,-u,base_ControlziExceptionziBase_nestedAtomically_closure -Wl,-u,base_GHCziEventziThread_blockedOnBadFD_closure -Wl,-u,base_GHCziWeak_runFinalizzerBatch_closure -Wl,-u,base_GHCziTopHandler_flushStdHandles_closure -Wl,-u,base_GHCziTopHandler_runIO_closure -Wl,-u,base_GHCziTopHandler_runNonIO_closure -Wl,-u,base_GHCziConcziIO_ensureIOManagerIsRunning_closure -Wl,-u,base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -Wl,-u,base_GHCziConcziSync_runSparks_closure -Wl,-u,base_GHCziConcziSignal_runHandlersPtr_closure -lHSbase-4.9.0.0 -lHSinteger-gmp-1.0.0.1 -lHSghc-prim-0.5.0.0 -lHSrts -lCffi -lgmp -lm -lrt -ldl ld: fatal: unrecognized option '--' ld: fatal: use the '-z help' option for usage information collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) $ gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -o helloworld helloworld.o -L/usr/lib/ghc-8.0.1/base-4.9.0.0 -L/usr/lib/ghc-8.0.1 /integer-gmp-1.0.0.1 -L/usr/lib/ -L/usr/lib/ghc-8.0.1/ghc-prim-0.5.0.0 -L/usr/lib/ghc-8.0.1/rts /tmp/ghc5103_0/ghc_2.o -Wl,-u,ghczmprim_GHCziTypes_Izh_static_info -Wl,-u,ghczmprim_GHCziTypes_Czh_static_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_static_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_static_info -Wl,-u,base_GHCziPtr_Ptr_static_info -Wl,-u,ghczmprim_GHCziTypes_Wzh_static_info -Wl,-u,base_GHCziInt_I8zh_static_info -Wl,-u,base_GHCziInt_I16zh_static_info -Wl,-u,base_GHCziInt_I32zh_static_info -Wl,-u,base_GHCziInt_I64zh_static_info -Wl,-u,base_GHCziWord_W8zh_static_info -Wl,-u,base_GHCziWord_W16zh_static_info -Wl,-u,base_GHCziWord_W32zh_static_info -Wl,-u,base_GHCziWord_W64zh_static_info -Wl,-u,base_GHCziStable_StablePtr_static_info -Wl,-u,ghczmprim_GHCziTypes_Izh_con_info -Wl,-u,ghczmprim_GHCziTypes_Czh_con_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_con_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_con_info -Wl,-u,base_GHCziPtr_Ptr_con_info -Wl,-u,base_GHCziPtr_FunPtr_con_info -Wl,-u,base_GHCziStable_StablePtr_con_info -Wl,-u,ghczmprim_GHCziTypes_False_closure -Wl,-u,ghczmprim_GHCziTypes_True_closure -Wl,-u,base_GHCziPack_unpackCString_closure -Wl,-u,base_GHCziIOziException_stackOverflow_closure -Wl,-u,base_GHCziIOziException_heapOverflow_closure -Wl,-u,base_ControlziExceptionziBase_nonTermination_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -Wl,-u,base_GHCziIOziException_allocationLimitExceeded_closure -Wl,-u,base_ControlziExceptionziBase_nestedAtomically_closure -Wl,-u,base_GHCziEventziThread_blockedOnBadFD_closure -Wl,-u,base_GHCziWeak_runFinalizzerBatch_closure -Wl,-u,base_GHCziTopHandler_flushStdHandles_closure -Wl,-u,base_GHCziTopHandler_runIO_closure -Wl,-u,base_GHCziTopHandler_runNonIO_closure -Wl,-u,base_GHCziConcziIO_ensureIOManagerIsRunning_closure -Wl,-u,base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -Wl,-u,base_GHCziConcziSync_runSparks_closure -Wl,-u,base_GHCziConcziSignal_runHandlersPtr_closure -lHSbase-4.9.0.0 -lHSinteger-gmp-1.0.0.1 -lHSghc-prim-0.5.0.0 -lHSrts -lCffi -lgmp -lm -lrt -ldl $ ./helloworld hello, world -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12460> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12552: Merge OpenBSD linking fix
by GHC 30 Aug '16

30 Aug '16

#12552: Merge OpenBSD linking fix -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | 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: -------------------------------------+------------------------------------- Merge f9aa996f0af59f32dc7b1528ff78be41413a9c27 to `ghc-8.0`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12552> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12531: Holes should be kind-polymorphic
by GHC 30 Aug '16

30 Aug '16

#12531: Holes should be kind-polymorphic -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I often use holes while writing long expressions out in GHCi in order to let the typechecker assist me with type inference. Sometimes though I find myself in a situation where I want to use holes near unlifted types and results in kind check messages obscuring the holes or having hole errors not show up at all: {{{#!hs > I# (_ +# 1#) <interactive>:5:5: error: • Couldn't match a lifted type with an unlifted type When matching the kind of ‘Int#’ • In the first argument of ‘(+#)’, namely ‘_’ In the first argument of ‘I#’, namely ‘(_ +# 1#)’ In the expression: I# (_ +# 1#) <interactive>:5:5: error: • Found hole: _ :: Int# • In the first argument of ‘(+#)’, namely ‘_’ In the first argument of ‘I#’, namely ‘(_ +# 1#)’ In the expression: I# (_ +# 1#) • Relevant bindings include it :: Int (bound at <interactive>:5:1) }}} (Don't be deceived, the type of `_` there is actually `Int# |> (TYPE U(hole:{a1qG}, 'IntRep, 'PtrRepLifted)_N)_N`) Perhaps the type of `_` should be `forall r (a :: TYPE r). a` or even `forall k (a :: k). a` instead? This might lead to issues with `-fdefer-typed-holes` but maybe we could at first disallow deferred unlifted-kinded holes? But in theory a hole is just a call to `error` which is representation-polymorphic already. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12531> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12458: Segfault in GHCi runtime type reconstruction
by GHC 30 Aug '16

30 Aug '16

#12458: Segfault in GHCi runtime type reconstruction -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHCi crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> data D a = D Prelude> d = D Prelude> :print d d = (_t1::D a) Prelude> d `seq` () () Segmentation fault (core dumped) }}} This is unrelated to #12449 because we're evaluating `d` which has a proper type and not `_t1`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12458> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12177: Relevant bindings includes shadowed bindings
by GHC 30 Aug '16

30 Aug '16

#12177: Relevant bindings includes shadowed bindings -------------------------------------+------------------------------------- Reporter: ezyang | 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: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ ezyang@sabre:~$ ghc-8.0 --interactive GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> \x -> \x -> _ <interactive>:1:13: error: • Found hole: _ :: t2 Where: ‘t2’ is a rigid type variable bound by the inferred type of it :: t -> t1 -> t2 at <interactive>:1:1 • In the expression: _ In the expression: \ x -> _ In the expression: \ x -> \ x -> _ • Relevant bindings include x :: t1 (bound at <interactive>:1:8) x :: t (bound at <interactive>:1:2) it :: t -> t1 -> t2 (bound at <interactive>:1:1) }}} GHC should not report bindings which are shadowed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12177> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12551: Make type indices take local constraints into account in type instance declaration
by GHC 30 Aug '16

30 Aug '16

#12551: Make type indices take local constraints into account in type instance declaration -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: TypeFamilies | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given {{{#!hs infixl 1 :$ infixr :-> data Sig x where Full :: a -> Sig a (:->) :: a -> b -> Sig a data AST dom a where Sym :: dom a -> AST dom a (:$) :: AST dom (a:->b) -> AST dom (Full a) -> AST dom b class Syntactic a dom | a -> dom where type Rep a desugar :: a -> AST dom (Full (Rep a)) sugar :: AST dom (Full (Rep a)) -> a }}} I want to be able to define the trivial instance for `Syntactic (AST dom (Full a))`: {{{#!hs instance Syntactic (AST dom (Full a)) dom where type Rep (AST dom (Full a)) = a desugar, sugar :: AST dom (Full a) -> AST dom (Full a) desugar = id sugar = id }}} This should be the only `Syntactic` instance for `AST _ _` so I would like to apply the [http://chrisdone.com/posts/haskell-constraint-trick ‘constraint’ trick] ([https://gist.github.com/Icelandjack/5afdaa32f41adf3204ef9025d9da2a70 #blog-reddit-constraint-trick-for-instances link]) but I cannot use the `Rep` instance as before: {{{#!hs -- • Type indexes must match class instance head -- Found ‘AST dom ('Full a)’ but expected ‘AST dom full_a’ -- • In the type instance declaration for ‘Rep’ -- In the instance declaration for ‘Syntactic (AST dom full_a) dom’ instance full_a ~ Full a => Syntactic (AST dom full_a) dom where type Rep (AST dom (Full a)) = a }}} Maybe this could be accepted, given that `full_a ~ Full a`, therefore the instance head is equal to `AST dom (Full a)`? My current workaround is using a type family {{{#!hs type family Edrú a where Edrú (Full a) = a instance full_a ~ Full a => Syntactic (AST dom full_a) dom where type Rep (AST dom full_a) = Edrú full_a desugar, sugar :: AST dom (Full a) -> AST dom (Full a) desugar = id sugar = id }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12551> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12446: Doesn't suggest TypeApplications when `~` used prefix
by GHC 30 Aug '16

30 Aug '16

#12446: Doesn't suggest TypeApplications when `~` used prefix -------------------------------------+------------------------------------- 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: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ $ ghci -ignore-dot-ghci GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> :t undefined @(_ ~ _) <interactive>:1:1: error: Pattern syntax in expression context: undefined@(_ (~(_))) Did you mean to enable TypeApplications? }}} It is suggested with non-`~` type operators {{{ Prelude> :t undefined @((+) _ _) <interactive>:1:1: error: Pattern syntax in expression context: undefined@((+) (_) (_)) Did you mean to enable TypeApplications? }}} but not with {{{ Prelude> :t undefined @((~) _ _) <interactive>:1:15: error: parse error on input ‘)’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12446> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12483: Improve parse error message on indentation mistake
by GHC 29 Aug '16

29 Aug '16

#12483: Improve parse error message on indentation mistake -------------------------------------+------------------------------------- Reporter: harendra | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider the following code fragment: {{{#!hs (ExecGhc, args) -> execCompiler "" args -- NOTE: this won't currently work for GHCJS, because it doesn't have -- a runghcjs binary. It probably will someday, though. (ExecRunGhc, args) -> }}} The last line is indented by one space but it is hard to notice esp when we looking at this along with a screenful of code and there are many comments between the two lines. When this code is compiled ghc throws the following error: {{{ Main.hs:745:40: error: parse error on input ‘->’ }}} I look at the error and then the code and wonder what is wrong with this code, there is nothing noticeably wrong. If ghc can provide some context I can easily make out where the problem is. ghc can perhaps tell me how the current expression is being parsed e.g. `(ExecRunGhc, args) ->` is being considered as a continuation of the expression on the previous line. I have run into this many times. The first time it was really frustrating. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12483> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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