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[GHC] #14232: Invalid type signature prokoves error in GHCi
by GHC 03 Oct '17

03 Oct '17

#14232: Invalid type signature prokoves error in GHCi -------------------------------------+------------------------------------- Reporter: walling | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.1 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Poor/confusing (amd64) | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When I create and save a file with the following content (notice the missing arrow `->`): {{{#!hs f :: (String -> a) String -> a f g s = g s }}} ... it outputs this snippet in GHCi (copy-pasted from terminal): {{{ $ ghci bug.hs GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( Playground/bug.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-apple-darwin): repSplitAppTys String a_a1pl[sk:1] [] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:808:9 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > Leaving GHCi. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14232> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14306: pretty-printer missing parens for infix class declaration
by GHC 03 Oct '17

03 Oct '17

#14306: pretty-printer missing parens for infix class declaration -------------------------------------+------------------------------------- Reporter: alanz | 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: #14289 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs class (a `C` b) c }}} Is pretty printed as {{{#!hs class a `C` b c }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14306> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12759: Latest Debian GCC breajs GHC
by GHC 03 Oct '17

03 Oct '17

#12759: Latest Debian GCC breajs GHC ----------------------------------------+-------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+-------------------------- Just got `gcc (Debian 6.2.0-9) 6.2.0 20161019` in a recent upgrade (Debian Testing) and now: {{{ > cat hello.hs main :: IO () main = putStrLn "Hello" > ghc hello.hs -o hello [1 of 1] Compiling Main ( hello.hs, hello.o ) Linking hello ... /usr/bin/ld: hello.o: relocation R_X86_64_32S against symbol `stg_bh_upd_frame_info' \ can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: /usr/lib/ghc-8.0/lib/base-4.9.0.0/libHSbase-4.9.0.0.a(Base__166.o): \ relocation R_X86_64_32S against symbol `stg_bh_upd_frame_info' can not be used when \ making a shared object; recompile with -fPIC .... }}} The previous version of gcc in Debian Testing (gcc (Debian 6.2.0-6) 6.2.0 20161010) is fine. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12759> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13884: To an automatic compilation of file-header LANGUAGE pragmas in GHC.
by GHC 02 Oct '17

02 Oct '17

#13884: To an automatic compilation of file-header LANGUAGE pragmas in GHC. -------------------------------------+------------------------------------- Reporter: vanto | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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 wrote this little piece of code to show that the compiler could very well execute the pragma by itself without being ordered to do so.\\ {{{ module Testfoo where import Language.Haskell.TH.Lib import Data.Kind tup = $(tupE $ take 4 $ cycle [ [| "hi" |] , [| 5 |] ]) data T = MkT (forall a. [a] -> [a]) answer_read = show (read @Int "3") data Foo (a :: Type) (b :: Type) where MkFoo :: (a ~ Int, b ~ Char) => Foo a b data family Song (a :: k) }}} By compiling the code without the Pragmas, GHC responds:\\ * 1) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:13:7: error: parse error on input `$' Perhaps you intended to use TemplateHaskell\\ * 2) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:15:23: error: Illegal symbol '.' in type Perhaps you intended to use {{{RankNTypes}}} or a similar language extension to enable explicit-forall syntax: forall <tvs>.<type>\\ * 3) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:19:16: error: Illegal kind signature: `Type' Perhaps you intended to use KindSignatures In the data type declaration for `Foo' testfoo.hs:19:28: error: Illegal kind signature: `Type' Perhaps you intended to use KindSignatures In the data type declaration for `Foo' testfoo.hs:22:1: error: Unexpected kind variable `k' Perhaps you intended to use {{{PolyKinds}}} In the declaration for type family `Song' testfoo.hs:22:24: error: Illegal kind signature: `k' Perhaps you intended to use KindSignatures In the declaration for type family `Song'\\ * 4) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:18:21: error: Pattern syntax in expression context: read@Int Did you mean to enable {{{TypeApplications}}}?\\ * 5) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:20:1: error: * Illegal generalised algebraic data declaration for `Foo' (Use {{{GADTs}}} to allow GADTs) * In the data declaration for `Foo'\\ * 6) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) testfoo.hs:23:1: error: * Illegal family declaration for `Song' Use {{{TypeFamilies}}} to allow indexed type families * In the data family declaration for `Song'\\ * 7) c:\Testghc>ghc testfoo.hs [1 of 1] Compiling Testfoo ( testfoo.hs, testfoo.o ) c:\Testghc>\\ Here is the code once completed. {{{ {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeFamilies #-} module Testfoo where import Language.Haskell.TH.Lib import Data.Kind tup = $(tupE $ take 4 $ cycle [ [| "hi" |] , [| 5 |] ]) data T = MkT (forall a. [a] -> [a]) answer_read = show (read @Int "3") data Foo (a :: Type) (b :: Type) where MkFoo :: (a ~ Int, b ~ Char) => Foo a b data family Song (a :: k) }}} As you may notice, GHC suggests the appropriate pragma.\\ If we add manually in the code the Pragmas one after the other and we arrive at the end, the code is fully compiled without error.\\ The compiler could do this alone.\\ We could test it using a "-auto" option on the compiler command line.\\ This is a start to the compiler automation technology, what do you think of that? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13884> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9198: large performance regression in type checker speed in 7.8
by GHC 02 Oct '17

02 Oct '17

#9198: large performance regression in type checker speed in 7.8 -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: Compile-time Architecture: Unknown/Multiple | performance bug Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- it was recently demonstrated on the haskell-cafe mailing list that the following code takes measurably longer to type check in GHC 7.8.2 than in GHC 7.6. http://www.haskell.org/pipermail/haskell-cafe/2014-June/114562.html the program example is as follows {{{ begin cont = cont (return ()) a m =cont (m >> putstrn "a") end m = m main = begin a a a a a a a a a a a a a a a a a end }}} takes about a second to type check in ghc 7.8, and is "instant" in 7.6 () each additional a doubles the time to type check the program {{{ main = begin a a a a a a a a a a a a a a a a a a a a a a a a end }}} takes longer than I have the patience to wait :) (so more than 5 seconds) the author of the email notes that a related program {{{ main = id id id id id id id id id id id id id id id id id id id id id id (return ()) }}} has the exponential complexity in both 7.8.2 and 7.6.2 This It could very well be that some of the type checker changes between 7.8 and 7.6 enlarged the space of programs that trip up exponential worst case behavior, but one way or another understanding *why* this happened -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9198> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13397: Optimise calls to tagToEnum#
by GHC 02 Oct '17

02 Oct '17

#13397: Optimise calls to tagToEnum# -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) 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: -------------------------------------+------------------------------------- Ever since we started using `Int#` to represent booleans unboxed (see [wiki:PrimBool]) we have had lots of code looking like {{{ case tagToEnum# (a ># b) of False -> e1 True -> e2 }}} It would be better (less code to optimise, more straightforward, more direct) to optimise this to {{{ case a ># b of DEFAULT -> e1 1# -> e2 }}} Happily, we already have a nice spot to do so: the `caseRules` function in `SimplUtils`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13397> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11771: ghc.exe: `panic'! (the 'impossible' happened); thread blocked indefinitely in an MVar operation
by GHC 02 Oct '17

02 Oct '17

#11771: ghc.exe: `panic'! (the 'impossible' happened); thread blocked indefinitely in an MVar operation ----------------------------------------+------------------------------- Reporter: YoYoYonnY | Owner: Type: bug | Status: new Priority: low | Milestone: Component: GHCi | Version: 7.10.3 Keywords: | Operating System: Windows Architecture: Unknown/Multiple | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+------------------------------- Here's a "fun" one: {{{#!hs *Main> main Interrupted. *Main> *Main> !cl ghc.exe: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-mingw32): thread blocked indefinitely in an MVar operation Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > > ghci --version The Glorious Glasgow Haskell Compilation System, version 7.10.3 }}} Don't mind the {{{!cl}}}, GHC crashed as soon as the interupt was registered, I usually {{{:!cls}}} after I execute main. I will backup the code in case someone wants to see if it's a bug in my program, but I didn't use multithreading myself, and I don't think the vector, unordered-containers, bytestring and parsec packages use threading either (all heavily at work, though)... The interupt was nececairy because my code was generating a infinite (oops) collection of these bad boys, using all sorts of folds, maps, etc.: {{{#!hs newtype ParserData = ParserData { unpackParserData :: HashMap ByteString (ParserData -> Either ByteString (Parser ())) } }}} I am wondering if this could be a problem with Windows, because the system was running slow at the time of the interupt; The {{{Alt+Tab}}} screen didn't appear until after the interupt. I don't think I can manage to reproduce this bug, which is unfortunate aswell (low priority because of that :c). Either way, it crashed, that's all I can tell you for sure. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11771> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14299: GHCi for GHC 8.2.1 crashed with simple function?
by GHC 02 Oct '17

02 Oct '17

#14299: GHCi for GHC 8.2.1 crashed with simple function? --------------------------------------+------------------------------- Reporter: mathiassm | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.1 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+------------------------------- I'm a newbie here, but I'm following your instructions! I started GHCi, defined a simple factorial function and then called it and... it crashed. {{{#!hs let f 0 = 0 f n = n * f (n-1) f 0 }}} That is what I introduced in the console... After that computer hanged and gave me the following error: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-apple-darwin): thread blocked indefinitely in an MVar operation Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14299> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11963: GHC introduces kind equality without TypeInType
by GHC 02 Oct '17

02 Oct '17

#11963: GHC introduces kind equality without TypeInType -------------------------------------+------------------------------------- Reporter: ezyang | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 (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: -------------------------------------+------------------------------------- The following program is accepted by GHC 8.0 rc2 {{{ {-# LANGUAGE GADTs, PolyKinds, RankNTypes #-} data Typ k t where Typ :: (forall (a :: k -> *). a t -> a t) -> Typ k t }}} This probably shouldn't be accepted, because this is a circuitous way of saying: {{{ {-# LANGUAGE TypeInType #-} data Typ k (t :: k) = Typ }}} which does not work without `TypeInType`. Or perhaps both should be accepted without `TypeInType`? Printing with explicit kinds makes it clear why the obvious check didn't fire: {{{ ezyang@sabre:~$ ghc-8.0 --interactive B.hs -fprint-explicit-kinds GHCi, version 8.0.0.20160204: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( B.hs, interpreted ) Ok, modules loaded: Main. *Main> :info Typ type role Typ nominal nominal nominal data Typ k k1 (t :: k) where Typ :: forall k (t :: k). (forall (a :: k -> *). a t -> a t) -> Typ k k t -- Defined at B.hs:2:1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11963> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14303: HasField ambiguity error
by GHC 02 Oct '17

02 Oct '17

#14303: HasField ambiguity error -------------------------------------+------------------------------------- Reporter: cloudhead | 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: -------------------------------------+------------------------------------- Both of these functions fail to compile with the error below: {{{#!haskell {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeApplications #-} import Control.Monad.Reader import GHC.Records import Data.Proxy askField :: forall x a m r. (HasField x r a, MonadReader r m) => m a askField = asks (getField @x) askField' :: forall x a m r. (HasField x r a, MonadReader r m) => m a askField' = asks (getFieldWithProxy (Proxy :: Proxy x)) where getFieldWithProxy :: forall proxy. proxy x -> r -> a getFieldWithProxy = const getField }}} {{{ Test.hs:12:14: error: • Could not deduce (HasField x0 r a) from the context: (HasField x r a, MonadReader r m) bound by the type signature for: askField' :: forall x a (m :: * -> *) r. (HasField x r a, MonadReader r m) => m a at Test.hs:12:14-69 The type variable ‘x0’ is ambiguous • In the ambiguity check for ‘askField'’ To defer the ambiguity check to use sites, enable AllowAmbiguousTypes In the type signature: askField' :: forall x a m r. (HasField x r a, MonadReader r m) => m a | 12 | askField' :: forall x a m r. (HasField x r a, MonadReader r m) => m a | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} I hope I'm not missing something, but one of these should compile. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14303> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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