July 2017 - ghc-tickets

[GHC] #13830: '+RTS -s' gives incorrect value for work balance in some cases
by GHC 11 Jul '17

11 Jul '17

#13830: '+RTS -s' gives incorrect value for work balance in some cases -------------------------------------+------------------------------------- Reporter: duog | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 8.0.1 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Debugging Unknown/Multiple | information is incorrect Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The formula for work balance as printed by the rts -s flag does not account for the possibility of the number of capabilities changing. Nor does it account for the number of garbage collection threads being other than n_capabilities. The attached program demonstrates the first problem, with instructions for replication in comments. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13830> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13919: Incorrect unused top binding warning when interacting with GHC.Generics
by GHC 11 Jul '17

11 Jul '17

#13919: Incorrect unused top binding warning when interacting with GHC.Generics -------------------------------------+------------------------------------- Reporter: Taneb | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The program {{{#!hs {-# LANGUAGE DeriveGeneric #-} module Main (main) where import Data.Aeson import GHC.Generics data Foo = Foo {bar :: String} deriving Generic instance ToJSON Foo where toJSON = genericToJSON defaultOptions main :: IO () main = print (toJSON (Foo "hello")) }}} emits the warning {{{ UTB.hs:7:17: warning: [-Wunused-top-binds] Defined but not used: ‘bar’ }}} but removing that binding changes the behaviour of the program, as the above prints {{{ Object (fromList [("bar",String "hello")]) }}} but {{{#!hs {-# LANGUAGE DeriveGeneric #-} module Main (main) where import Data.Aeson import GHC.Generics data Foo = Foo String deriving Generic instance ToJSON Foo where toJSON = genericToJSON defaultOptions main :: IO () main = print (toJSON (Foo "hello")) }}} prints {{{ String "hello" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13919> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1: Implicit parameters cause strange behavi
by GHC 11 Jul '17

11 Jul '17

#1: Implicit parameters cause strange behavi --------------------------------+-------------------- Reporter: nobody | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 5.0 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"b8f33bc6b738b0378976e42b79369f0e53b680c7/ghc" b8f33bc6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="b8f33bc6b738b0378976e42b79369f0e53b680c7" Always allow -staticlib the `-staticlib` flag is currently only supported on apple platforms, due to the avaiablity of libtool (the apple version, which is unlike the gnu version). This however prevents the use of -staticlib in cases where it would be beneficial as well. The functionality that `-staticlib` uses from `libtool` can be stubbed with a small script like the following: ``` #!/bin/bash # This script pretends to be libtool. And supports # only a limited set of flags. # # It is supposed to be a stand in for libtool -static, whic # creates a static archive. This is done by locating all -l<lib> # libs in the provied -L<lib path> library paths, and building an # MRI script to create the final archive from all the libraries, and # other provided inputs. # name=${0##*/} target=${name%-*} set -e ldflags_L=() ldflags_l=() output="" inputs=() STATIC=0 DYNAMIC=1 mode=$DYNAMIC verbose=0 # find_lib <name> path path path path function find_lib () { lib=$1; shift 1; for dir in $@; do if [ -f "$dir/$lib" ]; then echo "$dir/$lib" break fi done } while [ "$#" -gt 0 ]; do case "$1" in -v|--verbose) verbose=1; shift 1;; -o) output="$2"; shift 2;; -L*) ldflags_L+=("${1:2:${#1}-2}"); shift 1;; -l*) ldflags_l+=("lib${1:2:${#1}-2}.a"); shift 1;; -static) mode=$STATIC; shift 1;; -dynamic) mode=$DYNAMIC; shift 1;; -Wl,*) ldflags+=("${1#*,}"); shift 1;; -*) echo "unknown option: $1" >&2; exit 1;; *) inputs+=("$1"); shift 1;; esac done if [ ! $mode == $STATIC ]; then echo "-dynamic not supported!" >&2; exit 1; fi MRI="create ${output}\n" for input in "${ldflags_l[@]}"; do lib=$(find_lib $input ${ldflags_L[@]}) if [ -z $lib ]; then echo "Failed to find lib $input" >&2 exit 1 else MRI+="addlib $lib\n" continue fi done for input in "${inputs[@]}"; do MRI+="addmod $input\n" done MRI+="save\nend\n" echo -e "$MRI" | $target-ar -M $target-ranlib $output ``` if `ar` supports MRI scripts. Reviewers: austin, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3706 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10150: Suppress orphan instance warning per instance
by GHC 11 Jul '17

11 Jul '17

#10150: Suppress orphan instance warning per instance -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: feature | Status: new request | Milestone: Priority: low | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple (Type checker) | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- In the same way we have overlapping/incoherent instance pragmas which can be applied on a per instance basis, it would be good to have a `-fno-warn- orphan-instance` pragma which can be applied on a per-instance basis. Annoyingly, there is not an obvious syntax to use for this case, since SOP for a module with orphan instances is `{-# GHC_OPTIONS -fno-warn-orphans #-}` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10150> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2515: Flag to suppress orphan instance warnings
by GHC 11 Jul '17

11 Jul '17

#2515: Flag to suppress orphan instance warnings -------------------------------------+------------------------------------- Reporter: tim | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Documentation | Version: 6.8.3 Resolution: fixed | Keywords: 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 buecking): * cc: buecking (added) * failure: => None/Unknown -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2515#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12921: initTc: unsolved constraints
by GHC 10 Jul '17

10 Jul '17

#12921: initTc: unsolved constraints -------------------------------------+------------------------------------- Reporter: jlp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | 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: -------------------------------------+------------------------------------- While working on a small project of mine, GHC panicked with the following error: {{{ lua-types-0.1.0.0: build Preprocessing executable 'lua-types' for lua-types-0.1.0.0... [2 of 3] Compiling Lua.Parser ( src/Lua/Parser.hs, .stack- work/dist/x86_64-osx/Cabal-1.24.1.0/build/lua-types/lua-types- tmp/Lua/Parser.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1.20161117 for x86_64-apple-darwin): initTc: unsolved constraints WC {wc_insol = [W] explist_a3nf :: t_a3ne[tau:1] (CHoleCan: explist) [W] funccall_a4dv :: t_a4du[tau:1] (CHoleCan: funccall)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} From a quick google search, it seems like this is a bug in the type checker. I'm not willing nor able to dive any further into the GHC code myself, though. I'll attach the code as it is, before looking for a workaround. I'm using stack, GHC version 8.0.1.20161117 for x86_64-apple-darwin. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12921> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13954: Source tarballs are missing from the GHC downloads page for older releases.
by GHC 10 Jul '17

10 Jul '17

#13954: Source tarballs are missing from the GHC downloads page for older releases. -------------------------------------+------------------------------------- Reporter: maxf130 | Owner: (none) Type: bug | Status: new Priority: normal | 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: -------------------------------------+------------------------------------- I'm trying to download the source tarballs for some old GHC releases (7.4 onwards) and they appear to be missing. There is a link to sources, but no corresponding section: https://www.haskell.org/ghc/download_ghc_7_4_2.html#sources IRC advised me to post a bug report. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13954> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13952: Liberal coverage condition fails if TypeInType is enabled
by GHC 10 Jul '17

10 Jul '17

#13952: Liberal coverage condition fails if TypeInType is enabled -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 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 compiles with 8.0.2 but fails with 8.2.1-rc2. It succeeds if the `TypeInType` extension is disabled. {{{#!hs {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE DataKinds, FlexibleContexts, FlexibleInstances, FunctionalDependencies, MultiParamTypeClasses, TypeFamilies, TypeOperators #-} -- Removing TypeInType causes compilation to succeed {-# LANGUAGE TypeInType #-} module Bookkeeper.Internal where import GHC.Generics import GHC.TypeLits (Symbol, KnownSymbol, TypeError, ErrorMessage(..)) class FromGeneric a book | a -> book where fromGeneric :: a x -> book type family Expected a where Expected (l :+: r) = TypeError ('Text "Cannot convert sum types into Books") Expected U1 = TypeError ('Text "Cannot convert non-record types into Books") instance (book ~ Expected U1) => FromGeneric U1 book where fromGeneric = error "impossible" }}} {{{ src/Bookkeeper/Internal.hs:18:10: error: • Illegal instance declaration for ‘FromGeneric U1 book’ The coverage condition fails in class ‘FromGeneric’ for functional dependency: ‘a -> book’ Reason: lhs type ‘U1’ does not determine rhs type ‘book’ Un-determined variable: book • In the instance declaration for ‘FromGeneric U1 book’ | 18 | instance (book ~ Expected U1) => FromGeneric U1 book where | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} Perhaps this is related to #12803 but I made another ticket so that it can be diagnosed separately. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13952> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13920: 自動選擇實例
by GHC 10 Jul '17

10 Jul '17

#13920: 自動選擇實例 -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- https://github.com/zaoqi/U.hs/blob/master/Data/U.hs:{{{#!hs --Copyright (C) 2017 Zaoqi --This program is free software: you can redistribute it and/or modify --it under the terms of the GNU Affero General Public License as published --by the Free Software Foundation, either version 3 of the License, or --(at your option) any later version. --This program is distributed in the hope that it will be useful, --but WITHOUT ANY WARRANTY; without even the implied warranty of --MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --GNU Affero General Public License for more details. --You should have received a copy of the GNU Affero General Public License --along with this program. If not, see <http://www.gnu.org/licenses/>. {-# LANGUAGE DataKinds, TypeOperators, KindSignatures, GADTs, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, AllowAmbiguousTypes, UndecidableInstances, IncoherentInstances, NoMonomorphismRestriction #-} module Data.U ( U(), t, u ) where data U :: [*] -> * where UOne :: x -> U (x : xs) USucc :: U xs -> U (x : xs) class T1 a b where t1 :: (U a) -> (U b) instance T1 a a where t1 = id instance T1 xs (x : xs) where t1 = USucc instance T1 (x : y : xs) (y : x : xs) where t1 (UOne x) = USucc (UOne x) t1 (USucc (UOne x)) = UOne x t1 (USucc (USucc xs)) = USucc (USucc xs) instance T1 xs ys => T1 (x : xs) (x : ys) where t1 (UOne x) = UOne x t1 (USucc xs) = USucc (t1 xs) t = t1 . t1 . t1 . t1 . t1 . t1 . t1 . t1 uone :: a -> U '[a] uone = UOne u x = t (uone x) instance Show x => Show (U '[x]) where show (UOne x) = "(u " ++ showsPrec 11 x ")" instance (Show x, Show (U xs)) => Show (U (x : xs)) where show (UOne x) = "(u " ++ showsPrec 11 x ")" show (USucc xs) = show xs }}} {{{#!hs *Data.U> (u 'c') :: U [Int,Char] <interactive>:12:2: error: • No instance for (T1 a30 '[Int, Char]) arising from a use of ‘u’ • In the expression: (u 'c') :: U '[Int, Char] In an equation for ‘it’: it = (u 'c') :: U '[Int, Char] *Data.U> t1 (uone 'c') :: U [Int,Char] (u 'c') }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13920> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13950: IncoherentInstances
by GHC 10 Jul '17

10 Jul '17

#13950: IncoherentInstances -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple IncoherentInstances | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs --Copyright (C) 2017 Zaoqi --This program is free software: you can redistribute it and/or modify --it under the terms of the GNU Affero General Public License as published --by the Free Software Foundation, either version 3 of the License, or --(at your option) any later version. --This program is distributed in the hope that it will be useful, --but WITHOUT ANY WARRANTY; without even the implied warranty of --MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --GNU Affero General Public License for more details. --You should have received a copy of the GNU Affero General Public License --along with this program. If not, see <http://www.gnu.org/licenses/>. {-# LANGUAGE DataKinds, TypeOperators, KindSignatures, GADTs, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, AllowAmbiguousTypes, UndecidableInstances, NoMonomorphismRestriction #-} module Data.U where data U :: [*] -> * where UOne :: x -> U (x : xs) USucc :: U xs -> U (x : xs) class Usuccs a b where usuccs :: U a -> U b instance Usuccs a a where usuccs = id instance Usuccs xs ys => Usuccs xs (y : ys) where usuccs xs = USucc (usuccs xs) u x = usuccs (UOne x) }}} {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :load U.hs [1 of 1] Compiling Data.U ( U.hs, interpreted ) Ok, modules loaded: Data.U. *Data.U> :set -XDataKinds *Data.U> (u 'c')::U [String, Char, Int] <interactive>:3:2: error: • Overlapping instances for Usuccs (Char : xs0) '[Char, Int] arising from a use of ‘u’ Matching instances: instance [safe] Usuccs a a -- Defined at U.hs:25:10 ...plus one instance involving out-of-scope types (use -fprint-potential-instances to see them all) (The choice depends on the instantiation of ‘xs0’ To pick the first instance above, use IncoherentInstances when compiling the other instance declarations) • In the expression: (u 'c') :: U '[String, Char, Int] In an equation for ‘it’: it = (u 'c') :: U '[String, Char, Int] }}} {{{#!hs --Copyright (C) 2017 Zaoqi --This program is free software: you can redistribute it and/or modify --it under the terms of the GNU Affero General Public License as published --by the Free Software Foundation, either version 3 of the License, or --(at your option) any later version. --This program is distributed in the hope that it will be useful, --but WITHOUT ANY WARRANTY; without even the implied warranty of --MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --GNU Affero General Public License for more details. --You should have received a copy of the GNU Affero General Public License --along with this program. If not, see <http://www.gnu.org/licenses/>. {-# LANGUAGE DataKinds, TypeOperators, KindSignatures, GADTs, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, AllowAmbiguousTypes, UndecidableInstances, IncoherentInstances, NoMonomorphismRestriction #-} module Data.U where data U :: [*] -> * where UOne :: x -> U (x : xs) USucc :: U xs -> U (x : xs) class Usuccs a b where usuccs :: U a -> U b instance Usuccs a a where usuccs = id instance Usuccs xs ys => Usuccs xs (y : ys) where usuccs xs = USucc (usuccs xs) u x = usuccs (UOne x) }}} {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :load U.hs [1 of 1] Compiling Data.U ( U.hs, interpreted ) Ok, modules loaded: Data.U. *Data.U> :set -XDataKinds *Data.U> (u 'c')::U [String, Char, Int] <interactive>:3:2: error: • No instance for (Usuccs (Char : xs0) '[]) arising from a use of ‘u’ • In the expression: (u 'c') :: U '[String, Char, Int] In an equation for ‘it’: it = (u 'c') :: U '[String, Char, Int] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13950> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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