February 2016 - ghc-tickets

[GHC] #11418: Suggest correct spelling when module is not found because of typo
by GHC 17 Feb '16

17 Feb '16

#11418: Suggest correct spelling when module is not found because of typo -------------------------------------+------------------------------------- Reporter: syd | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: Compiler | Version: 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: -------------------------------------+------------------------------------- Given these two modules: Aaa.hs: {{{#!hs module Aaa where import BBb main :: IO () main = putStrLn myString }}} Bbb.hs: {{{#!hs module Bbb where myString :: String myString = "hi" }}} There's a typo in `Aaa.hs`, the import should be `Bbb` instead of `BBb`. Running `runhaskell Aaa.hs` results in this error: {{{ Aaa.hs:3:18: Could not find module ‘BBb’ Use -v to see a list of the files searched for. }}} The request is to have the compiler suggest that this is a typo and that it should be `Bbb` instead. It already does this for misspelled functions, if I recall correctly. Because the compiler will not continue when finding an error like this, it won't be harmful to spend a little extra time looking for possible misspellings. How typo's should be recognized is something that should be fleshed out later. For example, a hamming distance of 2 or less could indicate a typo. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11418> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9637: Type level programming needs an error function
by GHC 17 Feb '16

17 Feb '16

#9637: Type level programming needs an error function -------------------------------------+------------------------------------- Reporter: augustss | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- When doing type level programming you often need a way to report errors. I suggest a closed type family called Error with special semantics. It is kinded like this Error :: Symbol -> k1 -> k2 If this function has to be reduced during constraint solving it will simply generate a type error with the given string and printing the type as extra information (this kind can be generalized a lot if we want to). I've found that having this function gives more accurate and earlier error messages. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9637> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11582: Redundant constraints warning complains that (a ~ b) is redundant
by GHC 17 Feb '16

17 Feb '16

#11582: Redundant constraints warning complains that (a ~ b) is redundant -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc2 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Lemming came up with an interesting example where the redundant constraints warning is arguable a bit too trigger-happy in #10635. Consider, {{{#!hs asTypeOf :: a -> a -> a asTypeOf x _ = x }}} We could equivalently rewrite this with an equality constraint, {{{#!hs asTypeOf1 :: (a ~ b) => a -> b -> a asTypeOf1 x _ = x }}} If compiled with GHC 8.0 with `-Wredundant-constraints` we see a warning, {{{ hi.hs:4:1: warning: • Redundant constraint: a ~ b • In the type signature for: asTypeOf1 :: (a ~ b) => a -> b -> a }}} But is this really unused? We may not have referenced the constraint in the RHS, but surely the typechecker has gleaned something from it. Perhaps we should simply ignore equality constraints when generating redundant constraint warnings? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11582> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8927: Multiple case match at once
by GHC 16 Feb '16

16 Feb '16

#8927: Multiple case match at once -------------------------------------------+------------------------------- Reporter: vxanica | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Parser) | Version: 7.6.3 Keywords: case, multiple | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 hour) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- In F# we can do {{{ #!div style="font-size: 120%" {{{#!haskell match x with | 1 | 2 | 3 -> "123" | 4 | 5 | 6 -> "456" }}} }}} It will be nice if we have an extension which allows us to do {{{ #!div style="font-size: 120%" {{{#!haskell case x of 1 | 2 | 3 -> "123" 4 | 5 | 6 -> "456" }}} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8927> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11273: PowerPC NCG: Assign all STG float and double regs to PowerPC registers
by GHC 16 Feb '16

16 Feb '16

#11273: PowerPC NCG: Assign all STG float and double regs to PowerPC registers -------------------------------------+------------------------------------- Reporter: trommler | Owner: trommler Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.11 (CodeGen) | Keywords: | Operating System: Linux Architecture: powerpc | Type of failure: Runtime | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Currently only `F1` through `F4` and `D1` and `D2` are assigned to registers in the PowerPC backend. Assign `F5` and `F6` and `D3` through `D6` to registers too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11273> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8022: Outdated documentation for the -fwarn-lazy-unlifted-bindings warning
by GHC 16 Feb '16

16 Feb '16

#8022: Outdated documentation for the -fwarn-lazy-unlifted-bindings warning -------------------------------------+--------------------------------- Reporter: asr | Owner: thoughtpolice Type: bug | Status: closed Priority: highest | Milestone: 7.10.1 Component: Documentation | Version: 7.6.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+--------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"ad30c760f55205174b3b3472bbcd85fc51fb65d0/ghc" ad30c760/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="ad30c760f55205174b3b3472bbcd85fc51fb65d0" Remove documentation for -Wlazy-unlifted-bindings This flag was supposed to be removed in 7.10. This finally resolves Trac #8022. Test Plan: Read it Reviewers: austin Reviewed By: austin Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1922 GHC Trac Issues: #8022 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8022#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11586: GHC 8.0 can't be bootstrapped with GHC 8.0
by GHC 16 Feb '16

16 Feb '16

#11586: GHC 8.0 can't be bootstrapped with GHC 8.0 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Build System | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It seems that GHC 8.0 can't bootstrap itself. With a clean `ghc-8.0` tree and `ghc` from the 8.0.1-rc2 release in `PATH` on x86-64 Debian things fall apart quite quickly, {{{ $ ghc -V The Glorious Glasgow Haskell Compilation System, version 8.0.0.20160204 $ ./boot $ ./configure $ make -j2 + test -f mk/config.mk.old + cmp -s mk/config.mk mk/config.mk.old + cp -p mk/config.mk mk/config.mk.old touch -r mk/config.mk.old mk/config.mk + test -f mk/project.mk.old + cmp -s mk/project.mk mk/project.mk.old touch -r mk/project.mk.old mk/project.mk + test -f compiler/ghc.cabal.old + cmp -s compiler/ghc.cabal compiler/ghc.cabal.old touch -r compiler/ghc.cabal.old compiler/ghc.cabal ===--- building phase 0 make --no-print-directory -f ghc.mk phase=0 phase_0_builds "rm" -f compiler/stage1/build/Config.hs "inplace/bin/ghc-cabal" configure libraries/ghc-boot dist-boot "" --with- ghc="/opt/exp/ghc/roots/8.0.1-rc2/bin/ghc" --with-ghc- pkg="/opt/exp/ghc/roots/8.0.1-rc2/bin/ghc-pkg" --package- db=/opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf --disable-library- for-ghci --enable-library-vanilla --disable-library-profiling --disable- shared --with-hscolour="/home/ben/.cabal/bin/HsColour" --configure- option=CFLAGS="-Wall -fno-stack-protector -Werror=unused-but-set- variable -Wno-error=inline" --configure-option=LDFLAGS=" " --configure- option=CPPFLAGS=" " --gcc-options="-Wall -fno-stack-protector -Werror =unused-but-set-variable -Wno-error=inline " --constraint "binary == 0.8.2.0" --constraint "Cabal == 1.23.1.0" --constraint "hpc == 0.6.0.3" --constraint "ghc-boot == 8.0.0.20160211" --constraint "hoopl == 3.10.2.1" --constraint "transformers == 0.5.1.0" --constraint "template-haskell == 2.11.0.0" --constraint "terminfo == 0.4.0.2" --with-gcc="/usr/bin/gcc" --with-ar="/usr/bin/ar" --with- alex="/home/ben/.cabal/bin/alex" --with-happy="/home/ben/.cabal/bin/happy" Creating compiler/stage1/build/Config.hs ... Configuring ghc-boot-8.0.0.20160211... done. ghc-cabal: ghc-pkg dump failed libraries/ghc-boot/ghc.mk:3: recipe for target 'libraries/ghc-boot/dist- boot/package-data.mk' failed make[1]: *** [libraries/ghc-boot/dist-boot/package-data.mk] Error 1 Makefile:129: recipe for target 'all' failed make: *** [all] Error 2 }}} In particular the failing command is {{{ $ /opt/exp/ghc/roots/8.0.1-rc2/bin/ghc-pkg dump --package- db=/opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf -v2 GHC package manager version 8.0.0.20160204 Timestamp 2016-02-12 09:21:06.076187903 UTC for /opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf/package.cache Timestamp 2016-02-12 09:21:06.076187903 UTC for /opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf (same as cache) using cache: /opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf/package.cache ghc-pkg: /opt/exp/ghc/ghc-8.0/libraries/bootstrapping.conf/package.cache: GHC.PackageDb.readPackageDb: inappropriate type (Not a valid Unicode code point!) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11586> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7414: plugins always trigger recompilation
by GHC 16 Feb '16

16 Feb '16

#7414: plugins always trigger recompilation -------------------------------------+------------------------------------- Reporter: jwlato | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: plugin, | recompilation Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by conal): * cc: conal@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7414#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11361: Test tc253 doesn't pass with reversed uniques
by GHC 15 Feb '16

15 Feb '16

#11361: Test tc253 doesn't pass with reversed uniques -------------------------------------+------------------------------------- Reporter: niteria | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It fails with: {{{ tc253.hs:23:7: error: • Couldn't match type ‘Maybe Int’ with ‘(String, Bool)’ Expected type: Maybe Int -> (String, Int) -> Maybe Int Actual type: Fam Int Bool -> Fam Int Int -> Fam Int Bool • In the expression: inc (undefined :: Int) In an equation for ‘foo’: foo = inc (undefined :: Int) }}} Steps to reproduce: 1. Add line `TEST_HC_OPTS += -dinitial-unique=16777000 -dunique-increment=-1` after line `TEST_HC_OPTS = -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-$(GhcPackageDbFlag) -rtsopts $(EXTRA_HC_OPTS)` in `mk/test.mk` 2. `make TESTS=tc253` I suspect this is related to #11148 since the symptoms are similar. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11361> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11416: GHC mistakenly believes datatype with type synonym in its type can't be eta-reduced
by GHC 15 Feb '16

15 Feb '16

#11416: GHC mistakenly believes datatype with type synonym in its type can't be eta-reduced -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I uncovered this when playing around with `-XTypeInType`: {{{#!hs {-# LANGUAGE DeriveFunctor, TypeInType #-} module CantEtaReduce1 where import Data.Kind type ConstantT a b = a newtype T (f :: * -> *) (a :: ConstantT * f) = T (f a) deriving Functor }}} This fails because it thinks that you can't reduce the last type variable of `T`, since it mentions another type variable (`f`): {{{ • Cannot eta-reduce to an instance of form instance (...) => Functor (T f) • In the newtype declaration for ‘T }}} But it ''should'' be able to, since `ConstantT * f` reduces to `*`, and the equivalent declaration `newtype T (f :: * -> *) (a :: *) = ...` eta- reduces just fine. I marked this as appearing in GHC 8.1 since you need `-XTypeInType` to have kind synonyms, but this can also happen in earlier GHC versions with data families: {{{#!hs {-# LANGUAGE DeriveFunctor, PolyKinds, TypeFamilies #-} module CantEtaReduce2 where type ConstantT a b = a data family T (f :: * -> *) (a :: *) newtype instance T f (ConstantT a f) = T (f a) deriving Functor }}} I believe the fix will be to apply `coreView` with precision to parts of the code which typecheck `deriving` statements so that these type synonyms are peeled off. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11416> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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