April 2018 - ghc-tickets

[GHC] #15048: Fix mirroring of terminfo and haskeline
by GHC 19 Apr '18

19 Apr '18

#15048: Fix mirroring of terminfo and haskeline -------------------------------------+------------------------------------- Reporter: bgamari | Owner: hvr Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Trac & Git | Version: 8.2.2 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: -------------------------------------+------------------------------------- These seem not to mirror from GitHub to git.haskell.org automatically, unlike most of the boot libraries. Looking at the mirroring configuration it appears that it was never configured for these packages, but there is no indication as to why. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15048> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14997: mut_list_size calculation is off
by GHC 19 Apr '18

19 Apr '18

#14997: mut_list_size calculation is off -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: bug | Status: new Priority: lowest | Milestone: Component: Runtime | Version: 8.5 System | 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: -------------------------------------+------------------------------------- Program: {{{ main = print (foldr (+) 0 [ 0 .. 10000 ] :: Int) }}} Compile: {{{ $ ghc-stage2 Main.hs -debug -rtsopts -O0 }}} Run: {{{ $ ./Main +RTS -Dg }}} It prints something like {{{ mut_list_size: 16 (0 vars, 0 arrays, 0 MVARs, 0 TVARs, 0 TVAR_WATCH_QUEUEs, 0 TREC_CHUNKs, 0 TREC_HEADERs, 0 ATOMIC_INVARIANTs, 0 INVARIANT_CHECK_QUEUEs, 0 others) }}} So there are two objects in the mut list, but `scavenge_mutable_list` wasn't able to find anything. This is curious, and it seems like a bug. Pretty much any program has this bug, `mut_list_size` and sum of objects found in the mut list never match. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14997> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15018: Bump base's version number to 4.12.0.0 in HEAD
by GHC 19 Apr '18

19 Apr '18

#15018: Bump base's version number to 4.12.0.0 in HEAD -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: libraries | Version: 8.5 (other) | 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: -------------------------------------+------------------------------------- Currently, `base` sits at version `4.11.0.0` in HEAD (which is the same version of `base` as shipped with GHC 8.4.1). This is making it difficult to adapt certain Hackage libraries to recent changes in `base`, such as moving `Data.Functor.Contravariant` into `base` (see the discussion [https://github.com/ekmett/contravariant/issues/44 here]). Before we can do this, here is a list of libraries that will need to have their upper version bounds on `base` bumped from `< 4.12` to `< 4.13`: * `array` * `deepseq` * `directory` * `filepath` * `ghc-boot-th` * `ghc-compat` * `ghci` * `haddock` * `haskeline` * `hpc` * `parallel` * `parsec` * `primitive` * `process` * `stm` * `template-haskell` * `terminfo` Some of these can be changed in-place, while others will require downstream changes. I'll update this ticket as I progress. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15018> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13450: Better parse error for empy character literal
by GHC 19 Apr '18

19 Apr '18

#13450: Better parse error for empy character literal -------------------------------------+------------------------------------- Reporter: parsonsmatt | 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: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Empty character literals give an obscure error message. As an example, this code: {{{#!hs example = foo : bar where foo = '' bar = "asdf" }}} gives the following error when loaded in GHCi: {{{ err.hs:4:6: parse error (possibly incorrect indentation or mismatched brackets) }}} This has affected me once, as a beginner. I've seen it affect a few other beginners, and the error message isn't very helpful to figuring out what's wrong. It would be nice if a better error message could be reported. If there's a parse error on `''`, then GHC could report something like: {{{ err.hs:3:11: parse error on `''`. Note: Character literals may not be empty. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13450> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10037: Several profiling tests give different results optimised vs. unoptimised
by GHC 19 Apr '18

19 Apr '18

#10037: Several profiling tests give different results optimised vs. unoptimised -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Profiling | Version: 7.10.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Most of the differences are relatively harmless (mostly CAF attribution), but it would be nice to get this right. In the meantime I'll mark them expect_broken and point to this ticket. The following tests in `tests/profiling/should_run` are affected: {{{ scc001 T2552 ioprof callstack001 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10037> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14944: Compile speed regression
by GHC 19 Apr '18

19 Apr '18

#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Keywords: | 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: -------------------------------------+------------------------------------- Compile time went from 5 seconds in 7.6.1 to 12 seconds in 8.2.2 and then down to 10 seconds in 8.4.1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14944> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15042: Bump unix's version number to 2.8.0.0 in HEAD
by GHC 19 Apr '18

19 Apr '18

#15042: Bump unix's version number to 2.8.0.0 in HEAD -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: libraries | Version: 8.5 (other) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #15018 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In order to perform a `unix` submodule bump (as requested in #15018), we'll need to deal with the fact that its major version number was bumped upstream to 2.8.0.0. As a result, the following boot libraries will need to be adjusted: * `Cabal` and `cabal-install` * `directory` * `haskeline` * `iserv-bin` (ready, in-place) * `process` Some of these can be changed in-place, while others will require downstream changes. I'll update this ticket as I progress. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15042> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14710: GHC 8.4.1-alpha allows the use of kind polymorphism without PolyKinds
by GHC 19 Apr '18

19 Apr '18

#14710: GHC 8.4.1-alpha allows the use of kind polymorphism without PolyKinds -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 8.4.1-alpha1 (Type checker) | Keywords: PolyKinds | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This program: {{{#!hs {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ImpredicativeTypes #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeApplications #-} {-# OPTIONS_GHC -ddump-deriv #-} module Bug where import Data.Coerce import Data.Proxy class C a b where c :: Proxy (x :: a) -> b newtype I a = MkI a instance C x a => C x (Bug.I a) where c = coerce @(forall (z :: x). Proxy z -> a) @(forall (z :: x). Proxy z -> I a) c }}} is rightfully rejected by GHC 8.2.2: {{{ $ /opt/ghc/8.2.2/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:20:16: error: Unexpected kind variables Perhaps you intended to use PolyKinds In a type argument | 20 | c = coerce @(forall (z :: x). Proxy z -> a) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Bug.hs:21:16: error: Unexpected kind variables Perhaps you intended to use PolyKinds In a type argument | 21 | @(forall (z :: x). Proxy z -> I a) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} But GHC 8.4.1-alpha2 actually //accepts// this program! {{{ $ /opt/ghc/8.4.1/bin/ghci Bug.hs GHCi, version 8.4.0.20180118: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Ok, one module loaded. }}} This is almost certainly bogus. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14710> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14689: Load order of .ghci config files is counterintuitive
by GHC 19 Apr '18

19 Apr '18

#14689: Load order of .ghci config files is counterintuitive -------------------------------------+------------------------------------- Reporter: hal9zillion | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #14250, #6017 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Basically ghci seems to give precedence to global .ghci conguration settings by applying them after any local/project specific .ghci files: https://github.com/ghc/ghc/blob/314bc31489f1f4cd69e913c3b1e33236b2bdf553/gh… OTOH there are a couple of open issues where people dont like the idea of local ghci evaluation for security reasons: #6017 #14250 I suggest the following resolution: - Change the order or evaluation from global first to local - include a new ghci setting that prevents/enables the evaluation of local/project specific .ghci files for people who wish to avoid the security concerns some people have - This flag can then be set in the global .ghci file I believe this would both address the counterintuitive loading strategy implied currently (i was convinced local .ghci files didnt work because when i changed the prompt it was always overwritten by my global config) and the security question. The only question then would be if evaluation of project/local .ghci files would be on or off by default. I would favour the former but that is just personal preference. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14689> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15020: PatternSynonyms: Problems with quantified constraints / foralls
by GHC 18 Apr '18

18 Apr '18

#15020: PatternSynonyms: Problems with quantified constraints / foralls -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.5 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I couldn't find a way to implement `PLam2` as a simply bidirectional pattern synonym, I expected it to work but I recall a similar ticket. I couldn't find it though. {{{#!hs {-# Language RankNTypes, PatternSynonyms, ViewPatterns #-} newtype Lam1 = Lam1 (forall xx mm. Monad mm => mm xx) pattern PLam1 :: (forall xx mm. Monad mm => mm xx) -> Lam1 pattern PLam1 a = Lam1 a -- newtype Lam2 a = Lam2 (forall mm. Monad mm => mm a) newtype Forall f = Forall (forall xx. f xx) -- · FAILS · -- pattern PLam2 :: (forall xx mm. Monad mm => mm xx) -> Forall Lam2 -- pattern PLam2 lam = Forall (Lam2 lam) -- get :: Forall Lam2 -> forall xx mm. Monad mm => mm xx get (Forall (Lam2 lam)) = lam pattern PLam3 :: (forall xx mm. Monad mm => mm xx) -> Forall Lam2 pattern PLam3 lam <- (get -> lam) where PLam3 lam = Forall (Lam2 lam) }}} The complaint is and I wonder if this is a limitation of PatternSynonyms {{{ • Couldn't match type ‘xx0’ with ‘xx’ because type variable ‘xx’ would escape its scope This (rigid, skolem) type variable is bound by a type expected by the context: forall xx (mm :: * -> *). Monad mm => mm xx at Test.hs:16:34-36 Expected type: mm xx Actual type: mm xx0 • In the declaration for pattern synonym ‘PLam2’ • Relevant bindings include lam :: forall (mm :: * -> *). Monad mm => mm xx0 (bound at Test.hs:16:34) | 16 | pattern PLam2 lam = Forall (Lam2 lam) | ^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15020> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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