January 2016 - ghc-tickets

[GHC] #11424: "Occurs check" not considered when reducing closed type families
by GHC 18 Jan '16

18 Jan '16

#11424: "Occurs check" not considered when reducing closed type families -------------------------------------+------------------------------------- Reporter: diatchki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | 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: -------------------------------------+------------------------------------- Hello, consider the following example: {{{#!hs {-# LANGUAGE TypeFamilies #-} type family Same a b where Same a a = Int Same a b = Char example :: Same a [a] -> a example = undefined bad :: a bad = example 'c' }}} This program should type check, using the following reasoning: `a` and `[a]` can never be equal, therefore the first equation for `Same` does not apply, and so we can fall trough to the second one, thus reducing `Same` to `Char`. Therefore, `bad` should be accept. GHC rejects this program with the following error: {{{ • Couldn't match expected type ‘Same a [a]’ with actual type ‘Char’ • In the first argument of ‘example’, namely ‘'c'’ In the expression: example 'c' In an equation for ‘bad’: bad = example 'c' • Relevant bindings include bad :: a (bound at tmp/test.hs:11:1) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11424> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11058: selected processor does not support ARM mode
by GHC 18 Jan '16

18 Jan '16

#11058: selected processor does not support ARM mode --------------------------------+---------------------------------------- Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: arm | Type of failure: Building GHC failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------+---------------------------------------- Building GHC-7.10.3-rc1 on Debian armel produces: {{{ "inplace/bin/ghc-stage1" -static -H32m -O -lffi -optl-pthread -optl-B/usr/bin/ld.gold -Iincludes -Iincludes/dist -Iincludes/dist- derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -this-package-key rts -dcmm-lint -i -irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build -Irts/dist/build/autogen -O2 -c rts/StgStartup.cmm -o rts/dist/build/StgStartup.o /tmp/ghcd0b9_0/ghc_7.s: Assembler messages: /tmp/ghcd0b9_0/ghc_7.s:96:0: Error: selected processor does not support ARM mode `ldrd r0,r1,[r3,#64]' /tmp/ghcd0b9_0/ghc_7.s:99:0: Error: selected processor does not support ARM mode `strd r0,r1,[r3,#64]' /tmp/ghcd0b9_0/ghc_7.s:210:0: Error: selected processor does not support ARM mode `ldrd r0,r1,[r7,#64]' /tmp/ghcd0b9_0/ghc_7.s:214:0: Error: selected processor does not support ARM mode `strd r0,r1,[r7,#64]' rts/ghc.mk:236: recipe for target 'rts/dist/build/StgStartup.o' failed make[3]: *** [rts/dist/build/StgStartup.o] Error 1 Makefile:71: recipe for target 'all' failed make[2]: *** [all] Error 2 }}} According to Austin, this is fallout from changeset:933adc0f31164cb651d11ecfcfe612ac429f714f/ghc / #10375. But it is also a regression from GHC-7.10.2. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11058> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2374: MutableByteArray# is slower than Addr#
by GHC 18 Jan '16

18 Jan '16

#2374: MutableByteArray# is slower than Addr# -------------------------------------+------------------------------------- Reporter: dolio | Owner: Type: bug | Status: new Priority: lowest | Milestone: 8.0.1 Component: Compiler (NCG) | Version: 6.8.2 Resolution: | Keywords: performance | array Operating System: Linux | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Hmm, indeed there still seems to be a bit of a difference here ([[https://github.com/bgamari/T2374-benchmark|benchmark]] {{{ benchmarking ptr time 949.1 ms (945.9 ms .. 953.2 ms) 1.000 R² (1.000 R² .. 1.000 R²) mean 954.2 ms (952.3 ms .. 955.7 ms) std dev 2.470 ms (0.0 s .. 2.710 ms) variance introduced by outliers: 19% (moderately inflated) benchmarking bytearr time 989.2 ms (979.9 ms .. 997.8 ms) 1.000 R² (1.000 R² .. 1.000 R²) mean 984.2 ms (981.2 ms .. 986.3 ms) std dev 3.125 ms (0.0 s .. 3.602 ms) variance introduced by outliers: 19% (moderately inflated) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2374#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11351: Scoped type variables in pattern synonyms
by GHC 18 Jan '16

18 Jan '16

#11351: Scoped type variables in pattern synonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Linux Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Unsure of pattern synonym scoping rules. I want to be able to refer to a type in the signature (assuming `symbol` from #11349): {{{#!hs symbol :: forall s. KnownSymbol s => String symbol = symbolVal @s Proxy -- Not in scope: type variable ‘s’ -- Not in scope: type variable ‘s’ pattern Symbol :: forall s. KnownSymbol s => String pattern Symbol <- ((== symbol @s) -> True) where Symbol = symbol @s }}} Without `TypeApplications`: {{{#!hs -- • Could not deduce (KnownSymbol n0) -- arising from a use of ‘symbolVal’ -- from the context: KnownSymbol s -- bound by the type signature for pattern synonym ‘Symbol’: -- String pattern Symbol :: forall s. KnownSymbol s => String pattern Symbol <- ((== symbolVal (Proxy :: Proxy s)) -> True) }}} but it (GHCi, version 8.1.20160102) says the type variable `s` is not in scope. The desired outcome would be something like (this touches on ticket #11350): {{{#!hs >>> Symbol @"blessed duck" "blessed duck" isDuck :: String -> Bool isDuck (Symbol @"duck") = True isDuck _ = False }}} With a nudge and a wink to #9671. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11351> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11331: panic! TEST=tc198: lookupVers2 GHC.Stack.Types CallStack
by GHC 18 Jan '16

18 Jan '16

#11331: panic! TEST=tc198: lookupVers2 GHC.Stack.Types CallStack -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 7.11 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: -------------------------------------+------------------------------------- {{{ $ ghc-head --info | grep Project [("Project name","The Glorious Glasgow Haskell Compilation System") ,("Project version","8.1.20151231") ,("Project Git commit id","8afeaad919dc67643b4eff14efafb48b59039b2b") }}} {{{ $ make slowtest TEST=tc198 TEST_HC=ghc-head VERBOSE=2 =====> tc198(normal) 1 of 1 [0, 0, 0] =====> tc198(hpc) 1 of 1 [0, 0, 0] Compile failed (status 256) errors were: ghc: panic! (the 'impossible' happened) (GHC version 8.1.20151231 for x86_64-unknown-linux): lookupVers2 GHC.Stack.Types CallStack Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug *** unexpected failure for tc198(hpc) =====> tc198(optasm) 1 of 1 [0, 1, 0] Compile failed (status 256) errors were: ghc: panic! (the 'impossible' happened) (GHC version 8.1.20151231 for x86_64-unknown-linux): lookupVers2 GHC.Stack.Types CallStack Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug *** unexpected failure for tc198(optasm) Unexpected results from: TEST="tc198" }}} Test was added in 2005. Seems like a release blocker. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11331> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5063: unix package has untracked dependency on libbsd
by GHC 18 Jan '16

18 Jan '16

#5063: unix package has untracked dependency on libbsd -------------------------------------+------------------------------------- Reporter: duncan | Owner: trommler Type: bug | Status: upstream Priority: low | Milestone: 8.2.1 Component: Core Libraries | Version: 7.0.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * milestone: 8.0.1 => 8.2.1 Comment: What is the status of this? It seems like there have been no patches submitted upstream to resolve this. Punting to 8.2.1 unless informed otherwise. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5063#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11408: Delicate solve order
by GHC 18 Jan '16

18 Jan '16

#11408: Delicate solve order -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Should we successfully infer a type for `f`: {{{ f x = [h x, [x]] }}} assuming `h :: forall b. F b -> b`? Assuming `(x::alpha)` and we instantiate `h` at `beta`, we get the constraints {{{ (1) beta ~ [alpha] from the list [h x, [x]] (2) alpha ~ F beta from the call of h }}} Now if we happen to unify the constraint (1) first, `beta := [alpha`], then we successfully infer {{{ f :: forall a. (a ~ F [a]) => a -> [[a]] }}} But if we unify the constraint (2) first, `alpha := F beta`, we get {{{ f :: forall b. (b ~ [F b]) => F b -> [[F b]] }}} which is ambiguous. Eeek! This actually shows up in type inference for `indexed- types/should_compile/IndTypesPerfMerge`, where the function `merge` has (a slightly more complicated form of) this delicately-balanced situation. But see `Note [Orientation of equalities with fmvs]` in `TcFlatten` for why we don't defer solving (2). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11408> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11422: outofmem RTS testcase fails on Windows
by GHC 18 Jan '16

18 Jan '16

#11422: outofmem RTS testcase fails on Windows ----------------------------------------+--------------------------------- Reporter: Phyx- | Owner: Phyx- Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Windows Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: outpfmem | Blocked By: Blocking: | Related Tickets: #11300 Differential Rev(s): Phab:D1753 | Wiki Page: ----------------------------------------+--------------------------------- The `outofmem` test case fails on Windows `x86` and `x86_64` with the wrong exit code. Expected `251` but gotten `1`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11422> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11367: [Regression] Pattern synonyms
by GHC 18 Jan '16

18 Jan '16

#11367: [Regression] Pattern synonyms -------------------------------------+------------------------------------- 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: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Regression. This worked in 7.10.2: {{{#!hs {-# LANGUAGE PatternSynonyms, ViewPatterns #-} pattern A :: Int -> String pattern A n <- (read -> n) where A 0 = "hi" A 1 = "bye" }}} Removing the final clause works in GHC head but given the same code it claims the clause is empty: {{{ % ghci -ignore-dot-ghci /tmp/tmp.t0h0pMgwWb.hs GHCi, version 8.1.20160105: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/tmp.t0h0pMgwWb.hs, interpreted ) /tmp/tmp.t0h0pMgwWb.hs:4:9: error: pattern synonym 'where' clause cannot be empty In the pattern synonym declaration for: A Failed, modules loaded: none. Prelude> }}} The where clause is certainly not empty — ironically seems to be caused by my very own #10426 ([https://phabricator.haskell.org/D1665 D1665]) :--) hoist by my own ticket as we say: {{{#!hs ; when (length matches /= 1) (wrongNumberErr loc) }}} Personally a trailing `where` is quite alright and handy when quickly checking if a declaration is otherwise OK. It works for data/newtype declarations as well as type classes. A workaround is to pattern match in other ways: {{{#!hs pattern A n <- ... where A = \case 0 -> "hi" 1 -> "bye" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11367> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11252: :kind command hides the explicit kind
by GHC 18 Jan '16

18 Jan '16

#11252: :kind command hides the explicit kind ----------------------------------------+-------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.11 Keywords: TypeInType | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+-------------------------- {{{#!hs -- /tmp/test.hs {-# LANGUAGE TypeInType #-} data Proxy1 k (a :: k) = P1 data Proxy2 (a :: k) = P2 }}} if I load the following into ghci (head) the `:kind` command gives the same result {{{#!haskell % ghci -ignore-dot-ghci /tmp/test.hs GHCi, version 7.11.20151216: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( test.hs, interpreted ) Ok, modules loaded: Main. *Main> :kind Proxy1 :kind Proxy1 Proxy1 :: k -> * *Main> :kind Proxy2 :kind Proxy2 Proxy2 :: k -> * }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11252> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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