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[GHC] #11392: Decide and document how semicolons are supposed to work in GHCi
by GHC 18 Nov '17

18 Nov '17

#11392: Decide and document how semicolons are supposed to work in GHCi -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: GHCi | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #10663 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Currently there is a fair bit of confusion surrounding the intended function of semicolons in GHCi (see #10663 and Phab:D1726), * the users guide doesn't discuss the matter at all * sometimes the content after semicolons work as expected {{{ λ> let x=2; y=5 λ> x+y 7 }}} * other times it is silently ignored (see #10663), {{{ λ> import Data.List; 684 λ> }}} * other times it works but the parser state is subtly wrong, resulting in (arguably) incorrect line numbers later in the session, {{{ λ> data Infix a b = a :@: b; infixl 4 :@: λ> a <interactive>:3:1: error: Variable not in scope: a }}} * some times the only way to accomplish a given task is with a semicolon, {{{ Prelude> data Infix a b = a :@: b; infixl 4 :@: -- this is OK, but: Prelude> data Infix a b = a :@: b Prelude> infixl 4 :@: <interactive>:12:10: error: The fixity signature for `:@:' lacks an accompanying binding (The fixity signature must be given where `:@:' is declared) }}} This inconsistency is surprising and at times frustrating. Let's decide how we want semicolons to work and stick with it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11392> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14484: GHC rejects use of mulit-param type class.
by GHC 18 Nov '17

18 Nov '17

#14484: GHC rejects use of mulit-param type class. -------------------------------------+------------------------------------- Reporter: trinithis | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 (Type checker) | Keywords: | Operating System: Windows Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In the following example, I instantiate a few small typeclasses. The last instantiation provided does not compile, despite it being virtually identical the prior instantiation. {{{#!hs {-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE MultiParamTypeClasses #-} -------------------------------------------------------------------------------- class Collection collection handle | collection -> handle, handle -> collection where getHandles :: collection -> [handle] -------------------------------------------------------------------------------- data HandleX = HandleX Int data CollectionX = CollectionX [HandleX] instance Collection CollectionX HandleX where getHandles (CollectionX handles) = handles -------------------------------------------------------------------------------- newtype HandleY = HandleY HandleX newtype CollectionY = CollectionY CollectionX instance Collection CollectionY HandleY where getHandles (CollectionY collectionX) = map HandleY $ getHandles collectionX -- Good, this compiles! -------------------------------------------------------------------------------- newtype HandleZ = HandleZ HandleY newtype CollectionZ = CollectionZ CollectionY instance Collection CollectionZ HandleZ where getHandle (CollectionZ collectionY) = map HandleZ $ getHandles collectionY -- Error: `getHandle' is not a (visible) method of class `Collection' }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14484> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14481: Mutually dependent modules with orphan instances causes missing symbols with single-shot compilation
by GHC 18 Nov '17

18 Nov '17

#14481: Mutually dependent modules with orphan instances causes missing symbols with single-shot compilation -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 (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: -------------------------------------+------------------------------------- Alan Zimmerman encountered this nasty bug in his Trees That Grow branch: Consider we have the following types, {{{#!hs module Types where data Expr p = Var String | App (Expr p) (Expr p) | ADecl (Decl p) data Decl p = Bind String (Expr p) }}} Now imagine that for some reason we want to define orphan instances for some class (`Show`, for instance) for these types in two separate modules. We would have: {{{#!hs -- Instances1.hs module Instances1 where import {-# SOURCE #-} Instances2 () import Types deriving instance Show (Decl p) -- Instances1.hs-boot module Instances1 where import Types instance Show (Decl p) -- Instances2.hs module Instances2 where import {-# SOURCE #-} Instances1 () import Types deriving instance Show (Expr p) -- Instances2.hs-boot module Instances2 where import Types instance Show (Expr p) }}} Now, for instance, say we have some program that uses this whole mess, {{{#!hs -- Main.hs module Main where import Types -- Use SOURCE import to ensure GHC doesn't grab dictionary from unfolding in -- interface file import {-# SOURCE #-} Instances2 main = putStrLn $ show $ (Var "hi" :: Expr Int) }}} With `--make` mode we can compile `Main.hs` with no trouble: {{{ $ ghc --make Main.hs [1 of 6] Compiling Types ( Types.hs, Types.o ) [2 of 6] Compiling Instances2[boot] ( Instances2.hs-boot, Instances2.o-boot ) [3 of 6] Compiling Main ( Main.hs, Main.o ) [4 of 6] Compiling Instances1[boot] ( Instances1.hs-boot, Instances1.o-boot ) [5 of 6] Compiling Instances2 ( Instances2.hs, Instances2.o ) [6 of 6] Compiling Instances1 ( Instances1.hs, Instances1.o ) Linking Main ... $ ./Main Var "hi" }}} However, if we instead use single-shot mode, we end up never producing object code for one of the boot DFuns, {{{ $ ghc -c Types.hs $ ghc -c Instances1.hs-boot $ ghc -c Instances2.hs $ ghc -c Instances2.hs-boot $ ghc -c Instances1.hs $ ghc -c Main.hs $ ghc -o test Types.o Instances1.o Instances2.o Main.o Main.o:s1lN_info: error: undefined reference to 'Instances2_zdfxShowExpr_closure' Main.o(.data.rel.ro+0x8): error: undefined reference to 'Instances2_zdfxShowExpr_closure' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) }}} In the case of `--make` mode the symbol in question is emitted in the object code for `Instances2`. However, when we use single-shot mode the `hi-boot` file for `Instances2` doesn't exist when the `hs` file is compiled. It seems that this makes the DFun impedance matching logic in `TcRnDriver.checkBootIface'` not fire. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14481> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14255: Type-indexed type fingerprints
by GHC 17 Nov '17

17 Nov '17

#14255: Type-indexed type fingerprints -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Core | Version: 8.2.1 Libraries | Keywords: Typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I have the feeling that it might well be possible to reduce the size of the trusted codebase somewhat by introducing type-indexed fingerprints. Imagine {{{#!hs data TypeRep (a :: k) where TrTyCon :: {-# UNPACK #-} !FingerprintIx a -> !TyCon -> [SomeTypeRep] -> TypeRep (a :: k) TrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1). {-# UNPACK #-} !FingerprintIx (a b) -> TypeRep (a :: k1 -> k2) -> TypeRep (b :: k1) -> TypeRep (a b) TrFun :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (a :: TYPE r1) (b :: TYPE r2). {-# UNPACK #-} !FingerprintIx (a -> b) -> TypeRep a -> TypeRep b -> TypeRep (a -> b) }}} We could have some primitive operations like {{{#!hs mkFunFP :: FingerPrintIx a -> FingerPrintIx b -> FingerPrintIx (a -> b) mkAppFP :: FingerPrintIx (a -> b) -> FingerPrintIx a -> FingerPrintIx b eq :: FingerPrintIx a -> FingerPrintIx b -> Maybe (a :~~: b) eqE :: FingerPrintIx a -> FingerPrintIx b -> Either (a :~~: b -> c) (a :~~: b) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14255> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14476: Keep source locations in Core (optionally)
by GHC 17 Nov '17

17 Nov '17

#14476: Keep source locations in Core (optionally) -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.3 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: -------------------------------------+------------------------------------- The people working on liquid haskell have to maintain their own copy of the desugarer because of one little change they have to do: Add lots and lots of `CC`s to keep source spans around. Their current patch is {{{ diff --git a/src/Language/Haskell/Liquid/Desugar/DsExpr.hs b/src/Language/Haskell/Liquid/Desugar/DsExpr.hs index 396095e9a..9ba60c56f 100644 --- a/src/Language/Haskell/Liquid/Desugar/DsExpr.hs +++ b/src/Language/Haskell/Liquid/Desugar/DsExpr.hs @@ -221,14 +221,13 @@ dsUnliftedBind bind body = pprPanic "dsLet: unlifted" (ppr bind $$ ppr body) dsLExpr :: LHsExpr Id -> DsM CoreExpr dsLExpr (L loc e) - = putSrcSpanDs loc $ - do { core_expr <- dsExpr e - -- uncomment this check to test the hsExprType function in TcHsSyn - -- ; MASSERT2( exprType core_expr `eqType` hsExprType e - -- , ppr e <+> dcolon <+> ppr (hsExprType e) $$ - -- ppr core_expr <+> dcolon <+> ppr (exprType core_expr) ) - ; return core_expr } + = do ce <- putSrcSpanDs loc $ dsExpr e + m <- getModule + return $ Tick (srcSpanTick m loc) ce +srcSpanTick :: Module -> SrcSpan -> Tickish a +srcSpanTick m loc + = ProfNote (AllCafsCC m loc) False True -- | Variant of 'dsLExpr' that ensures that the result is not levity -- polymorphic. This should be used when the resulting expression will -- be an argument to some other function. }}} It would make their live easier if they could just use GHC’s desugarer, and it might open the path to making Liquid Haskell a proper GHC plugin instead of a separate program, which could facilitate adoption. Would it be ok to add a flag to GHC that enables this behaviour? Or is there another way of doing this? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14476> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14480: Clean up tyConTYPE
by GHC 17 Nov '17

17 Nov '17

#14480: Clean up tyConTYPE -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Core | Version: 8.2.1 Libraries | Keywords: Typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Phab:4085 builds a `TyCon` representing `TYPE` by hand in `Data.Typeable.Internal`. This is pretty disgusting, but it was the only way I managed to smash the last of the mysterious loops. It would be very nice to find a cleaner way, but we want to get that merged. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14480> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14477: the 'impossible' happened, initTc: unsolved constraints
by GHC 16 Nov '17

16 Nov '17

#14477: the 'impossible' happened, initTc: unsolved constraints --------------------------------------+--------------------------------- Reporter: bmusin | Owner: (none) Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14477> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14474: reify RHS of "value" variable
by GHC 16 Nov '17

16 Nov '17

#14474: reify RHS of "value" variable -------------------------------------+------------------------------------- Reporter: dailectic | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Template | Version: 8.2.1 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: -------------------------------------+------------------------------------- According to the [https://hackage.haskell.org/package/template- haskell-2.12.0.0/docs/Language-Haskell-TH-Syntax.html#t:Info documentation], when reifying value variables "returning the RHS has not yet been implemented because of lack of interest". I'd like to formally request interest since I don't see a ticket here (may have missed it). My motivating example is to make source available for documentation and better error messages. Something like: {{{#!hs printSource :: Name -> Q Exp printSource n = do VarI _ _ (Just dec) <- reify n lift $ pprint dec foo x = x * 2 fooSource = $(printSource 'foo) -- === "\x_0 -> x_0 GHC.Num.* 2" }}} How significant of a change is this? I could take a pass at it if pointed to the relevant bits, having not contributed to GHC before. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14474> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14472: error __STDC_VERSION__ does not advertise C99 or later
by GHC 16 Nov '17

16 Nov '17

#14472: error __STDC_VERSION__ does not advertise C99 or later -------------------------------------+------------------------------------- Reporter: kaldiroglu | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: GHC rejects (amd64) | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hi, I am using Mac OS highSierra 10.13.1 and downloaded and installed Haskell Platform 8.2.1 Full 64bit-signed.pkg. Then as a first program I created a file called Selam.hs that includes followng one line: "main = putStrLn "Hello, world!"" When I compiled the code using ghc -o Selam Selam.hs at the linking phase I am having "error __STDC_VERSION__ does not advertise C99 or later" error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14472> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #452: +RTS -xc and SIGINT handler gives seg fault
by GHC 15 Nov '17

15 Nov '17

#452: +RTS -xc and SIGINT handler gives seg fault --------------------------------+-------------------- Reporter: fergus | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: Profiling | Version: None Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Andrey Mokhov <andrey.mokhov@…>): * failure: => None/Unknown Comment: In [changeset:"c1fcd9b3f60e8420dd228cd4e3efeb9cfa793aa5/ghc" c1fcd9b/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c1fcd9b3f60e8420dd228cd4e3efeb9cfa793aa5" Squashed 'hadrian/' changes from 5ebb69a..fa3771f fa3771f hadrian: Disable -Wno-undef in files which include ffi.h (#459) f15e851 Do not run configure by default (#458) 5baa8db Fix AppVeyor cache failure (#456) 94dbe9d Fix ghc-cabal build (#455) a679764 Fix CI scripts (#454) 06ec241 Widen bounds on Cabal (#452) git-subtree-dir: hadrian git-subtree-split: fa3771fe6baf5008a8506fec48220f8347ac59af }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/452#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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