August 2015 - ghc-tickets

[GHC] #10815: Need more kind inference in associated type instances
by GHC 22 Oct '15

22 Oct '15

#10815: Need more kind inference in associated type instances -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When I say {{{ {-# LANGUAGE DataKinds, PolyKinds, TypeFamilies #-} module Bug where import Data.Proxy class kproxy ~ 'KProxy => C (kproxy :: KProxy k) where type F (a :: k) instance C ('KProxy :: KProxy Bool) where type F a = Int }}} I get {{{ Type indexes must match class instance head Found ‘k’ but expected ‘Bool’ In the type instance declaration for ‘F’ In the instance declaration for ‘C (KProxy :: KProxy Bool)’ }}} But the kind of `a` should really be known to be `Bool`. This ticket is broken out from comment:3:ticket:9063, which was evidently not addressed when fixing that ticket. Patch coming soon. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10815> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10769: Yet another crash from type holes
by GHC 22 Oct '15

22 Oct '15

#10769: Yet another crash from type holes -----------------------------------------+------------------------------- Reporter: rpglover64 | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.3 Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -----------------------------------------+------------------------------- {{{#!hs {-# OPTIONS_GHC -fdefer-typed-holes #-} hylo a b = h where h = b . fmap h . a foo a b = hylo a' b' where a' x = _ b' = _ bar :: [Int] bar = [] main = print bar }}} Loading this up in ghci and attempting to run main prints: {{{ GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help unknown option: 'c' [1 of 1] Compiling Main ( bad.hs, interpreted ) bad.hs:6:16: Warning: Found hole ‘_’ with type: t4 Where: ‘t4’ is a rigid type variable bound by the inferred type of a' :: t3 -> t4 at bad.hs:6:9 Relevant bindings include x :: t3 (bound at bad.hs:6:12) a' :: t3 -> t4 (bound at bad.hs:6:9) b' :: forall t. t (bound at bad.hs:7:9) b :: t1 (bound at bad.hs:5:7) a :: t (bound at bad.hs:5:5) foo :: t -> t1 -> t2 -> b (bound at bad.hs:5:1) In the expression: _ In an equation for ‘a'’: a' x = _ In an equation for ‘foo’: foo a b = hylo a' b' where a' x = _ b' = _ bad.hs:7:14: Warning: Found hole ‘_’ with type: t3 Where: ‘t3’ is a rigid type variable bound by the inferred type of b' :: t3 at bad.hs:7:9 Relevant bindings include b' :: t3 (bound at bad.hs:7:9) b :: t1 (bound at bad.hs:5:7) a :: t (bound at bad.hs:5:5) foo :: t -> t1 -> t2 -> b (bound at bad.hs:5:1) In the expression: _ In an equation for ‘b'’: b' = _ In an equation for ‘foo’: foo a b = hylo a' b' where a' x = _ b' = _ Ok, modules loaded: Main. *Main> main ghc: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-linux): nameModule $dFunctor_aKj Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Compiling with ghc and then running the resulting binary works. Attempting to replicate with a recent version of GHC HEAD gives {{{ GHCi, version 7.11.20150812: http://www.haskell.org/ghc/ :? for help unknown option: 'c' [1 of 1] Compiling Main ( bad.hs, interpreted ) bad.hs:5:11: error: No instance for (Functor f0) arising from a use of ‘hylo’ The type variable ‘f0’ is ambiguous Note: there are several potential instances: instance Functor Maybe -- Defined in ‘GHC.Base’ instance Functor IO -- Defined in ‘GHC.Base’ instance Functor ((->) r) -- Defined in ‘GHC.Base’ ...plus two others In the expression: hylo a' b' In an equation for ‘foo’: foo a b = hylo a' b' where a' x = _ b' = _ Failed, modules loaded: none. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10769> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10416: GHC 7.10.1 User Guide profiling section 5.4 missing images
by GHC 22 Oct '15

22 Oct '15

#10416: GHC 7.10.1 User Guide profiling section 5.4 missing images -------------------------------------+------------------------------------- Reporter: alanz | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.2 Component: | Version: 7.10.1 Documentation | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The page https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/prof- heap.html References an image https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/prof_scc which does not render. This URL does render though: https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/prof_scc.png -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10416> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10409: Binary compiled with ghc-7.10 amd64/linux to aarch64/linux cross compiler segfaults.
by GHC 22 Oct '15

22 Oct '15

#10409: Binary compiled with ghc-7.10 amd64/linux to aarch64/linux cross compiler segfaults. -------------------------------------+------------------------------------- Reporter: erikd | Owner: erikd Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: cross- | Operating System: Linux compiling | Type of failure: Runtime crash Architecture: aarch64 | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Compiling a simple "hello-world" program with an amd64/linux to aarch64/linux cross compiler built from the current `ghc-7.10` branch results in a binary that segfaults as soon as it is run. A cross compiler build from the master branch works and I thought it also worked for `ghc-7.10`. A native aarch64/linux compiler built from the `ghc-7.10` branch works correctly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10409> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10549: floatExpr tick break<2>
by GHC 22 Oct '15

22 Oct '15

#10549: floatExpr tick break<2> -------------------------------------+------------------------------------- Reporter: | Owner: NeilMitchell | Status: new Type: bug | Milestone: Priority: normal | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When running the Shake test suite against GHC HEAD I get: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.11.20150615 for x86_64-unknown-linux): floatExpr tick break<2>() }}} Full log at https://travis-ci.org/ndmitchell/shake/jobs/67636563. The command line that produced it is: {{{ runhaskell -ignore-package=hashmap -ioutput/docs/ -isrc output/docs/Main.hs }}} If this seems like a legitimate bug that you don't already know about and are interested in tracking down, I'll try and grab the output/docs directory (it's on a remote machine I don't have access to on a different OS with a compiler I don't have installed, so it's not trivial to find it, but should be possible). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10549> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10493: Inaccessible code might be accessible with newtypes and Coercible
by GHC 22 Oct '15

22 Oct '15

#10493: Inaccessible code might be accessible with newtypes and Coercible -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- If I say {{{ module A (Age, ageCo) where import Data.Type.Coercion newtype Age = MkAge Int ageCo :: Coercion Age Int ageCo = Coercion }}} {{{ {-# LANGUAGE FlexibleContexts #-} module B where import Data.Coerce import A foo :: Coercible Age Int => () foo = () }}} I get {{{ B.hs:8:8: error: Couldn't match representation of type ‘Age’ with that of ‘Int’ Inaccessible code in the type signature for: foo :: Coercible Age Int => () In the ambiguity check for the type signature for ‘foo’: foo :: Coercible Age Int => () To defer the ambiguity check to use sites, enable AllowAmbiguousTypes In the type signature for ‘foo’: foo :: Coercible Age Int => () }}} I agree that module `B` can't directly prove `Coercible Age Int`. But `ageCo` is in scope which proves exactly this! So it is provable, albeit directly. GHC should not claim that the code is inaccessible. Proposed fix: in `canDecomposableTyConApp`, only call `canEqHardFailure` for a representational equality when both tycons involved say `True` to `isDistinctTyCon`. I'm happy to put the fix in, once someone seconds this idea. Getting this right has proved harder than I thought! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10493> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9297: Packages linked against certain Windows .dll files give warnings at runtime
by GHC 22 Oct '15

22 Oct '15

#9297: Packages linked against certain Windows .dll files give warnings at runtime ----------------------------------+--------------------------------- Reporter: RyanGlScott | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.8.2 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ----------------------------------+--------------------------------- I am using GHC 7.8.3 on Windows 7, x86_64. When GHC loads certain packages at runtime, it gives some interesting warnings: {{{ > ghci -package haskeline GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package array-0.5.0.0 ... linking ... done. Loading package deepseq-1.3.0.2 ... linking ... done. Loading package bytestring-0.10.4.0 ... linking ... done. Loading package Win32-2.3.0.2 ... linking ... done. Loading package containers-0.5.5.1 ... linking ... done. Loading package filepath-1.3.0.2 ... linking ... done. Loading package old-locale-1.0.0.6 ... linking ... done. Loading package time-1.4.2 ... linking ... done. Loading package directory-1.2.1.0 ... linking ... done. Loading package transformers-0.3.0.0 ... linking ... done. Loading package haskeline-0.7.1.2 ... linking ... ghc.exe: warning: SetConsoleCursorPosition from kernel32 is linked instead of __imp_SetConsoleCursorPosition ghc.exe: warning: FillConsoleOutputCharacterA from kernel32 is linked instead of __imp_FillConsoleOutputCharacterA ghc.exe: warning: FillConsoleOutputAttribute from kernel32 is linked instead of __imp_FillConsoleOutputAttribute done. Prelude> }}} Besides {{{haskeline}}}, other packages with similar problems include {{{unix-compat}}}, {{{network}}}, and {{{regex-posix}}}. To see them all at once, you can run the [{{{hermit-web}}} https://github.com/ku-fpg /hermit-web] executable: {{{ > hermit-web Last.hs [starting HERMIT-Web v0.1.0.0 on Last.hs] [starting HERMIT v0.5.0.0 on Last.hs] % ghc Last.hs -fforce-recomp -O2 -dcore-lint -fsimple-list-literals -fexpose-all-unfoldings -fplugin=HERMIT.Web -fplugin-opt=HERMIT.Web:*: [1 of 1] Compiling Main ( Last.hs, Last.o ) Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package array-0.5.0.0 ... linking ... done. Loading package deepseq-1.3.0.2 ... linking ... done. Loading package bytestring-0.10.4.0 ... linking ... done. Loading package containers-0.5.5.1 ... linking ... done. Loading package Win32-2.3.0.2 ... linking ... done. Loading package filepath-1.3.0.2 ... linking ... done. Loading package old-locale-1.0.0.6 ... linking ... done. Loading package time-1.4.2 ... linking ... done. Loading package directory-1.2.1.0 ... linking ... done. Loading package pretty-1.1.1.1 ... linking ... done. Loading package process-1.2.0.0 ... linking ... done. Loading package Cabal-1.18.1.3 ... linking ... done. Loading package binary-0.7.1.0 ... linking ... done. Loading package bin-package-db-0.0.0.0 ... linking ... done. Loading package hoopl-3.10.0.1 ... linking ... done. Loading package hpc-0.6.0.1 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package transformers-0.3.0.0 ... linking ... done. Loading package ghc-7.8.3 ... linking ... done. Loading package haskeline-0.7.1.2 ... linking ... ghc: warning: SetConsoleCursorPosition from kernel32 is linked instead of __imp_SetConsoleCursorPosition ghc: warning: FillConsoleOutputCharacterA from kernel32 is linked instead of __imp_FillConsoleOutputCharacterA ghc: warning: FillConsoleOutputAttribute from kernel32 is linked instead of __imp_FillConsoleOutputAttribute done. Loading package text-1.1.1.3 ... linking ... done. Loading package hashable-1.2.2.0 ... linking ... done. Loading package scientific-0.3.2.2 ... linking ... done. Loading package attoparsec-0.12.1.0 ... linking ... done. Loading package dlist-0.7.1 ... linking ... done. Loading package mtl-2.1.3.1 ... linking ... done. Loading package syb-0.4.2 ... linking ... done. Loading package unordered-containers-0.2.5.0 ... linking ... done. Loading package primitive-0.5.3.0 ... linking ... done. Loading package vector-0.10.11.0 ... linking ... done. Loading package aeson-0.7.0.6 ... linking ... done. Loading package blaze-builder-0.3.3.2 ... linking ... done. Loading package data-default-class-0.0.1 ... linking ... done. Loading package data-default-instances-base-0.0.1 ... linking ... done. Loading package data-default-instances-containers-0.0.1 ... linking ... done. Loading package data-default-instances-dlist-0.0.1 ... linking ... done. Loading package data-default-instances-old-locale-0.0.1 ... linking ... done. Loading package data-default-0.5.3 ... linking ... done. Loading package ansi-terminal-0.6.1.1 ... linking ... done. Loading package kure-2.16.2 ... linking ... done. Loading package marked-pretty-0.1 ... linking ... done. Loading package random-1.0.1.1 ... linking ... done. Loading package operational-0.2.3.2 ... linking ... done. Loading package stm-2.4.3 ... linking ... done. Loading package exceptions-0.6.1 ... linking ... done. Loading package temporary-1.2.0.3 ... linking ... done. Loading package hermit-0.5.0.0 ... linking ... done. Loading package case-insensitive-1.2.0.0 ... linking ... done. Loading package http-types-0.8.5 ... linking ... done. Loading package transformers-base-0.4.2 ... linking ... done. Loading package monad-control-0.3.3.0 ... linking ... done. Loading package lifted-base-0.2.3.0 ... linking ... done. Loading package mmorph-1.0.3 ... linking ... done. Loading package resourcet-1.1.2.2 ... linking ... done. Loading package nats-0.2 ... linking ... done. Loading package semigroups-0.15.1 ... linking ... done. Loading package void-0.6.1 ... linking ... done. Loading package conduit-1.1.6 ... linking ... done. Loading package regex-base-0.93.2 ... linking ... done. Loading package regex-posix-0.95.2 ... linking ... ghc: warning: isupper from msvcrt is linked instead of __imp_isupper ghc: warning: toupper from msvcrt is linked instead of __imp_toupper ghc: warning: tolower from msvcrt is linked instead of __imp_tolower ghc: warning: isalpha from msvcrt is linked instead of __imp_isalpha ghc: warning: isalpha from msvcrt is linked instead of __imp_isalpha ghc: warning: isalpha from msvcrt is linked instead of __imp_isalpha ghc: warning: iscntrl from msvcrt is linked instead of __imp_iscntrl ghc: warning: isupper from msvcrt is linked instead of __imp_isupper ghc: warning: isgraph from msvcrt is linked instead of __imp_isgraph ghc: warning: isprint from msvcrt is linked instead of __imp_isprint ghc: warning: ispunct from msvcrt is linked instead of __imp_ispunct ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalpha from msvcrt is linked instead of __imp_isalpha ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum ghc: warning: isalnum from msvcrt is linked instead of __imp_isalnum done. Loading package regex-compat-0.95.1 ... linking ... done. Loading package parsec-3.1.5 ... linking ... done. Loading package network-2.5.0.0 ... linking ... ghc: warning: WSACleanup from ws2_32 is linked instead of __imp_WSACleanup ghc: warning: WSAStartup from ws2_32 is linked instead of __imp_WSAStartup ghc: warning: WSACleanup from ws2_32 is linked instead of __imp_WSACleanup ghc: warning: accept from ws2_32 is linked instead of __imp_accept ghc: warning: inet_ntoa from ws2_32 is linked instead of __imp_inet_ntoa ghc: warning: getnameinfo from ws2_32 is linked instead of __imp_getnameinfo ghc: warning: getaddrinfo from ws2_32 is linked instead of __imp_getaddrinfo ghc: warning: freeaddrinfo from ws2_32 is linked instead of __imp_freeaddrinfo done. Loading package vault-0.3.0.3 ... linking ... done. Loading package wai-3.0.0.2 ... linking ... done. Loading package base64-bytestring-1.0.0.1 ... linking ... done. Loading package fast-logger-2.1.5 ... linking ... done. Loading package zlib-0.5.4.1 ... linking ... done. Loading package streaming-commons-0.1.3.1 ... linking ... done. Loading package stringsearch-0.3.6.5 ... linking ... done. Loading package byteorder-1.0.4 ... linking ... done. Loading package wai-logger-2.1.1 ... linking ... done. Loading package word8-0.0.4 ... linking ... done. Loading package wai-extra-3.0.1 ... linking ... done. Loading package conduit-extra-1.1.1 ... linking ... done. Loading package simple-sendfile-0.2.15 ... linking ... done. Loading package unix-compat-0.4.1.3 ... linking ... ghc: warning: GetVersionExA from kernel32 is linked instead of __imp_GetVersionExA ghc: warning: GetModuleHandleA from kernel32 is linked instead of __imp_GetModuleHandleA ghc: warning: GetProcAddress from kernel32 is linked instead of __imp_GetProcAddress ghc: warning: _snprintf from msvcrt is linked instead of __imp__snprintf ghc: warning: GetSystemInfo from kernel32 is linked instead of __imp_GetSystemInfo ghc: warning: GetSystemMetrics from user32 is linked instead of __imp_GetSystemMetrics ghc: warning: GetVersionExA from kernel32 is linked instead of __imp_GetVersionExA ghc: warning: _snprintf from msvcrt is linked instead of __imp__snprintf ghc: warning: GetSystemInfo from kernel32 is linked instead of __imp_GetSystemInfo ghc: warning: GetComputerNameA from kernel32 is linked instead of __imp_GetComputerNameA ghc: warning: CryptAcquireContextA from advapi32 is linked instead of __imp_CryptAcquireContextA ghc: warning: CryptGenRandom from advapi32 is linked instead of __imp_CryptGenRandom ghc: warning: _stat64 from msvcrt is linked instead of __imp__stat64 ghc: warning: _open from msvcrt is linked instead of __imp__open ghc: warning: _stat64 from msvcrt is linked instead of __imp__stat64 done. Loading package warp-3.0.0.4 ... linking ... done. Loading package scotty-0.8.1 ... linking ... done. Loading package hermit-web-0.1.0.0 ... linking ... done. Setting phasers to stun... (port 3000) (ctrl-c to quit) }}} These warnings seem to be related to Windows-specific {{{.dll}}} files, including {{{kernel32.dll}}}, {{{user32.dll}}}, {{{msvcrt.dll}}}, {{{advapi32.dll}}}, and {{{ws2_32.dll}}}. As far as I can tell, there are no problems other than the warnings themselves, but I can't be sure. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9297> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9878: Static pointers in GHCi cause panic
by GHC 22 Oct '15

22 Oct '15

#9878: Static pointers in GHCi cause panic -------------------------------------+------------------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: GHCi crash Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I load this module into ghci {{{#!hs {-# LANGUAGE StaticPointers #-} module Static where import GHC.StaticPtr f = deRefStaticPtr (static True) }}} and get a panic upon evaluating `f` {{{ > f ghc: panic! (the 'impossible' happened) (GHC version 7.9.20141210 for x86_64-unknown-linux): Loading temp shared object failed: /tmp/ghc30486_0/ghc30486_5.so: undefined symbol: Static_sptEntryZC0_closure Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Am I doing static pointers right? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9878> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10747: Infix pattern synonyms fail to parse (regression)
by GHC 22 Oct '15

22 Oct '15

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE PatternSynonyms #-} pattern head `Cons` tail = head : tail }}} In v7.11 I get: {{{ [1 of 1] Compiling Main ( pat.hs, interpreted ) pat.hs:2:14: parse error on input ?`? }}} In v7.10 I get: {{{ *Main> :set -XPatternSynonyms *Main> let h `Cons` t = "ht" *Main> h 'h' *Main> t "t" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10747> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10149: The argument of mask does not always restore the masking state
by GHC 22 Oct '15

22 Oct '15

#10149: The argument of mask does not always restore the masking state -------------------------------------+------------------------------------- Reporter: | Owner: facundo.dominguez | Status: new Type: bug | Milestone: Priority: normal | Version: 7.8.4 Component: | Operating System: Unknown/Multiple libraries/base | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- In the documentation of `mask` and `uninterruptibleMask` it is claimed that the `restore` argument restores the masking state. However this is not true in the following programs: {{{#!hs mask_ $ -- start with exceptions masked mask $ \restore -> forkIOWithUnmask $ \unmask -> unmask $ restore $ getMaskingState >>= print }}} {{{#!hs uninterruptibleMask_ $ -- start with exceptions uninterruptibly masked uninterruptibleMask $ \restore -> forkIOWithUnmask $ \unmask -> unmask $ restore $ getMaskingState >>= print }}} The expected state is that `getMaskingState` would produce `MaskedInterruptible` and `MaskedUninterruptible`, however, in both cases it gives Unmasked. Either the documentation needs to be changed, or the implementation must really restore the masking state in these cases. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10149> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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