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[GHC] #11333: GHCi does not discharge satisfied constraints
by GHC 03 May '17

03 May '17

#11333: GHCi does not discharge satisfied constraints ----------------------------------------+-------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+-------------------------- Don't know if this is the intended behaviour (GHCi, version 8.1.20151231), with the new extension TypeApplications. For the function [https://hackage.haskell.org/package/base-4.8.1.0/docs /Text-Show.html#v:show show]: {{{#!hs Prelude> :set -XTypeApplications Prelude> :t show show :: Show a => a -> String Prelude> :t show @Int show @Int :: Show Int => Int -> String }}} And the function [https://hackage.haskell.org/package/base/docs/Data- Typeable.html#v:eqT eqT] (`:: forall a b. (Typeable a, Typeable b) => Maybe (a :~: b)`): {{{#!hs Prelude> :set -XTypeApplications Prelude> import Data.Typeable Prelude Data.Typeable> :t eqT eqT :: forall k1 (a :: k1) (b :: k1). (Typeable a, Typeable b) => Maybe (a :~: b) Prelude Data.Typeable> :t eqT eqT :: forall k1 (a :: k1) (b :: k1). (Typeable a, Typeable b) => Maybe (a :~: b) Prelude Data.Typeable> :t eqT @Int eqT @Int :: (Typeable Int, Typeable b) => Maybe (Int :~: b) }}} Should the types of `show @Int` and `eqT @Int` not be `Int -> String` and `(Typeable b) => Maybe (Int :~: b)` respectively? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11333> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13585: ala from Control.Lens.Wrapped panics
by GHC 03 May '17

03 May '17

#13585: ala from Control.Lens.Wrapped panics -------------------------------------+------------------------------------- Reporter: fumieval | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: (Type checker) | Keywords: | Operating System: Linux Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Panic.hs: {{{ module Panic where import Control.Lens.Wrapped import Data.Monoid foo :: Maybe String foo = ala Last foldMap [Just "foo"] }}} main.hs: {{{ module Main where import Panic (foo) main :: IO () main = print foo }}} {{{ $ ghc -c -O2 Panic.hs $ ghc -c -O2 main.hs ghc: panic! (the 'impossible' happened) (GHC version 8.2.0.20170404 for x86_64-unknown-linux): splitTyConApp (Exchange (Unwrapped (Last String)) (Unwrapped (Last String)) |> <* -> * -> *>_N) (Maybe [Char]) ((Identity |> <* -> *>_N) (Maybe [Char])) Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1134:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1105:34 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} The GHC version is 8134f7d4ba2c14b2f24d2f4c1f5260fcaff3304a. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13585> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13333: Typeable regression in GHC HEAD
by GHC 03 May '17

03 May '17

#13333: Typeable regression in GHC HEAD -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 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: -------------------------------------+------------------------------------- I recently wrote some code while exploring a fix for #13327 that heavily uses poly-kinded `Typeable`. This compiles without issue on GHC 8.0.1 and 8.0.2: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} module DataCast where import Data.Data import GHC.Exts (Constraint) data T (phantom :: k) = T data D (p :: k -> Constraint) (x :: j) where D :: forall (p :: k -> Constraint) (x :: k). p x => D p x class Possibly p x where possibly :: proxy1 p -> proxy2 x -> Maybe (D p x) dataCast1T :: forall k c t (phantom :: k). (Typeable k, Typeable t, Typeable phantom, Possibly Data phantom) => (forall d. Data d => c (t d)) -> Maybe (c (T phantom)) dataCast1T f = case possibly (Proxy :: Proxy Data) (Proxy :: Proxy phantom) of Nothing -> Nothing Just D -> gcast1 f }}} But on GHC HEAD, it barfs this error: {{{ Bug.hs:28:29: error: • Could not deduce (Typeable T) arising from a use of ‘gcast1’ GHC can't yet do polykinded Typeable (T :: * -> *) from the context: (Typeable k, Typeable t, Typeable phantom, Possibly Data phantom) bound by the type signature for: dataCast1T :: (Typeable k, Typeable t, Typeable phantom, Possibly Data phantom) => (forall d. Data d => c (t d)) -> Maybe (c (T phantom)) at Bug.hs:(22,1)-(25,35) or from: (k ~ *, (phantom :: k) ~~ (x :: *), Data x) bound by a pattern with constructor: D :: forall k (p :: k -> Constraint) (x :: k). p x => D p x, in a case alternative at Bug.hs:28:23 • In the expression: gcast1 f In a case alternative: Just D -> gcast1 f In the expression: case possibly (Proxy :: Proxy Data) (Proxy :: Proxy phantom) of Nothing -> Nothing Just D -> gcast1 f | 28 | Just D -> gcast1 f | ^^^^^^^^ }}} That error message itself is hilariously strange, since GHC certainly has the power to do polykinded `Typeable` nowadays. Marking as high priority since this is a regression—feel free to lower the priority if you disagree. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13333> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11669: Incorrectly suggests RankNTypes for ill-formed type "forall a. Eq a. Int"
by GHC 03 May '17

03 May '17

#11669: Incorrectly suggests RankNTypes for ill-formed type "forall a. Eq a. Int" -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- {{{ baldur@Loki:~$ ghci -ignore-dot-ghci GHCi, version 8.1.20160117: http://www.haskell.org/ghc/ :? for help Prelude> let foo :: forall a. Eq a. Int; foo = undefined <interactive>:1:20: error: Illegal symbol '.' in type Perhaps you intended to use RankNTypes or a similar language extension to enable explicit-forall syntax: forall <tvs>. <type> Prelude> :set -XRankNTypes Prelude> let foo :: forall a. Eq a. Int; foo = undefined <interactive>:3:26: error: Illegal symbol '.' in type Perhaps you intended to use RankNTypes or a similar language extension to enable explicit-forall syntax: forall <tvs>. <type> Prelude> }}} also {{{ Prelude> :kind forall a. Eq a. Int <interactive>:1:15: error: Illegal symbol '.' in type Perhaps you intended to use RankNTypes or a similar language extension to enable explicit-forall syntax: forall <tvs>. <type> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11669> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13578: Incorrect Record Pattern Synonym example in users guide
by GHC 03 May '17

03 May '17

#13578: Incorrect Record Pattern Synonym example in users guide -------------------------------------+------------------------------------- Reporter: cjholdbrooks | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Documentation | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The first example in section 9.7.1 of the users guide provides the example {{{#!hs pattern Point :: (Int, Int) pattern Point{x, y} = (x, y) }}} which results in the error {{{ • Pattern synonym ‘Point’ has two arguments but its type signature has none • In the declaration for pattern synonym ‘Point’ }}} upon load. I believe the correct code is as follows. {{{#!hs pattern Point :: Int -> Int -> (Int, Int) pattern Point{x, y} = (x, y) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13578> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13641: Compile error while performing stack upgrade
by GHC 03 May '17

03 May '17

#13641: Compile error while performing stack upgrade -------------------------------------+------------------------------------- Reporter: pisomojado | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hello, I'm a very green user of this ticket system, as well as GHC, so apologies if I have not given useful details. I'm complying with the request of stack/ghc, as you can see down towards the bottom of my attempt to upgrade stack on my host. Any help would be appreciated. {{{ pisomojado@host:~$ stack upgrade Fetching package index ...remote: Counting objects: 1, done. remote: Total 1 (delta 0), reused 1 (delta 0), pack-reused 0 Unpacking objects: 100% (1/1), done. Fetched package index. aeson-1.0.2.1: configure aeson-1.0.2.1: build Cabal-1.24.2.0: configure Cabal-1.24.2.0: build ed25519-0.0.5.0: configure ed25519-0.0.5.0: build cryptohash-sha256-0.11.100.1: configure cryptohash-sha256-0.11.100.1: build cryptohash-sha256-0.11.100.1: copy/register http-client-0.5.3.3: configure http-client-0.5.3.3: build ed25519-0.0.5.0: copy/register optparse-applicative-0.13.0.0: configure optparse-applicative-0.13.0.0: build optparse-applicative-0.13.0.0: copy/register optparse-simple-0.0.3: configure optparse-simple-0.0.3: build optparse-simple-0.0.3: copy/register pid1-0.1.0.0: configure pid1-0.1.0.0: build http-client-0.5.3.3: copy/register http-client-tls-0.3.4: configure pid1-0.1.0.0: copy/register http-client-tls-0.3.4: build store-core-0.3: configure store-core-0.3: build http-client-tls-0.3.4: copy/register text-metrics-0.1.0: configure store-core-0.3: copy/register text-metrics-0.1.0: build th-orphans-0.13.1: configure th-orphans-0.13.1: build text-metrics-0.1.0: copy/register th-orphans-0.13.1: copy/register th-utilities-0.2.0.1: configure th-utilities-0.2.0.1: build th-utilities-0.2.0.1: copy/register store-0.3: configure store-0.3: build store-0.3: copy/register aeson-1.0.2.1: copy/register aeson-compat-0.3.6: configure aeson-compat-0.3.6: build binary-tagged-0.1.4.1: configure binary-tagged-0.1.4.1: build http-conduit-2.2.3: configure http-conduit-2.2.3: build aeson-compat-0.3.6: copy/register path-0.5.9: configure path-0.5.9: build http-conduit-2.2.3: copy/register persistent-2.6: configure persistent-2.6: build path-0.5.9: copy/register path-io-1.1.0: configure path-io-1.1.0: build binary-tagged-0.1.4.1: copy/register yaml-0.8.20: configure yaml-0.8.20: build path-io-1.1.0: copy/register yaml-0.8.20: copy/register hpack-0.17.0: configure hpack-0.17.0: build persistent-2.6: copy/register persistent-template-2.5.1.6: configure persistent-template-2.5.1.6: build persistent-sqlite-2.6: configure persistent-sqlite-2.6: build Cabal-1.24.2.0: copy/register hpack-0.17.0: copy/register hackage-security-0.5.2.2: configure hackage-security-0.5.2.2: build persistent-template-2.5.1.6: copy/register hackage-security-0.5.2.2: copy/register persistent-sqlite-2.6: copy/register stack-1.4.0: configure [1 of 1] Compiling Main ( /private/var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/stack- upgrade4706/stack-1.4.0/Setup.hs, /private/var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/stack- upgrade4706/stack-1.4.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/Main.o ) Linking /private/var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/stack- upgrade4706/stack-1.4.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/setup ... Configuring stack-1.4.0... stack-1.4.0: build Preprocessing library stack-1.4.0... [ 1 of 124] Compiling Text.PrettyPrint.Leijen.Extended ( src/Text/PrettyPrint/Leijen/Extended.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Text/PrettyPrint/Leijen/Extended.o ) [ 2 of 124] Compiling Hackage.Security.Client.Repository.HttpLib.HttpClient ( src/Hackage/Security/Client/Repository/HttpLib/HttpClient.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Hackage/Security/Client/Repository/HttpLib/HttpClient.o ) [ 3 of 124] Compiling Stack.Options.ScriptParser ( src/Stack/Options/ScriptParser.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Stack/Options/ScriptParser.o ) [ 4 of 124] Compiling Stack.Ghci.Script ( src/Stack/Ghci/Script.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Stack/Ghci/Script.o ) [ 5 of 124] Compiling Stack.FileWatch ( src/Stack/FileWatch.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Stack/FileWatch.o ) [ 6 of 124] Compiling System.Process.PagerEditor ( src/System/Process/PagerEditor.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Process/PagerEditor.o ) [ 7 of 124] Compiling System.Process.Log ( src/System/Process/Log.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Process/Log.o ) [ 8 of 124] Compiling Paths_stack ( .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/autogen/Paths_stack.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Paths_stack.o ) [ 9 of 124] Compiling Path.Find ( src/Path/Find.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Path/Find.o ) [ 10 of 124] Compiling Path.Extra ( src/Path/Extra.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Path/Extra.o ) [ 11 of 124] Compiling System.Process.Read ( src/System/Process/Read.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Process/Read.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-apple-darwin): Loading temp shared object failed: dlopen(/var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/ghc7482_0/libghc_68.dylib, 5): no suitable image found. Did find: /var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/ghc7482_0/libghc_68.dylib: malformed mach-o: load commands size (49672) > 32768 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Completed 26 action(s). -- While building package stack-1.4.0 using: /private/var/folders/vy/td7mc44s36g6b_wvdz7258rw0000gn/T/stack- upgrade4706/stack-1.4.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/setup --builddir=.stack- work/dist/x86_64-osx/Cabal-1.22.5.0 build lib:stack exe:stack --ghc- options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13641> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10230: multiline literals doesn't work with CPP extension.
by GHC 02 May '17

02 May '17

#10230: multiline literals doesn't work with CPP extension. -------------------------------------+------------------------------------- Reporter: qnikst | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- If LANGUAGE CPP is enabled then multiline literals stops working. Steps to reproduce. 1. write a program with multiline literal: cat 1.hs {{{#!hs test = "mutli\ \line" main = putStrLn test }}} 2. it should compile without CPP: ghc 1.hs [1 of 1] Compiling Main ( 1.hs, 1.o ) Linking 1 ... 3. compile it with CPP extension Expected result: program compiles {{{ ghc 1.hs [1 of 1] Compiling Main ( 1.hs, 1.o ) Linking 1 ... }}} Actual result: compilation breaks {{{ ghc -XCPP 1.hs [1 of 1] Compiling Main ( 1.hs, 1.o ) [flags changed] 1.hs:1:18: lexical error in string/character literal at character 'l' }}} At least ghc-7.8.4 and ghc-7.10 are affected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10230> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13635: Incorrect result at runtime with list comprehensions in that case
by GHC 02 May '17

02 May '17

#13635: Incorrect result at runtime with list comprehensions in that case -------------------------------------+------------------------------------- Reporter: vanto | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- 1. With GHC 8.0.2\\ {{{ Prelude> [x | x <- [_, _], False] <interactive>:1:12: error: * Found hole: _ :: t Where: `t' is a rigid type variable bound by the inferred type of it :: [t] at <interactive>:1:1 * In the expression: _ In the expression: [_, _] In a stmt of a list comprehension: x <- [_, _] * Relevant bindings include it :: [t] (bound at <interactive>:1:1) <interactive>:1:15: error: * Found hole: _ :: t Where: `t' is a rigid type variable bound by the inferred type of it :: [t] at <interactive>:1:1 * In the expression: _ In the expression: [_, _] In a stmt of a list comprehension: x <- [_, _] * Relevant bindings include it :: [t] (bound at <interactive>:1:1) Prelude>\\ }}} This result makes no sense here.\\ The result will always be the empty list [].\\ 2. With GHC 7.6.3\\ {{{ Prelude> [x | x <- [_, _], False] <interactive>:2:12: Pattern syntax in expression context: _ <interactive>:2:12: Pattern syntax in expression context: _ Prelude> }}} This result also makes no sense here.\\ Similarly this result will always be the empty list []. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13635> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13357: Check demand signatures for catchRetry# and catchSTM#
by GHC 02 May '17

02 May '17

#13357: Check demand signatures for catchRetry# and catchSTM# -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) 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: -------------------------------------+------------------------------------- #13330 was fixed by giving `catch#` a different (simpler and more honest) demand signature. Are the signatures for `catchRetry#` and `catchSTM#` similarly problematic? We need to check. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13357> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2893: Implement "Quantified contexts" proposal
by GHC 02 May '17

02 May '17

#2893: Implement "Quantified contexts" proposal -------------------------------------+------------------------------------- Reporter: porges | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.10.1 Resolution: | Keywords: proposal 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 baramoglo): * cc: baramoglo (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2893#comment:25> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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