June 2016 - ghc-tickets

[GHC] #12235: Wrong compilation of bang patterns
by GHC 27 Jun '16

27 Jun '16

#12235: Wrong compilation of bang patterns -------------------------------------+------------------------------------- Reporter: osa1 | 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: -------------------------------------+------------------------------------- I have this function: {{{#!haskell fn5 :: Int -> [T] -> Int fn5 i [] = i fn5 i (A : ts) = fn5 (i + 1) ts fn5 !i (B : ts) = fn5 (i + 2) ts fn5 i (C : ts) = fn5 0 ts }}} This function should only `seq` the int after seeing that head of the list is `B`. But this is the generated code: (desugar) {{{#!haskell Rec { -- RHS size: {terms: 64, types: 33, coercions: 0} fn5 [Occ=LoopBreaker] :: Int -> [T] -> Int [LclIdX, Str=DmdType] fn5 = \ (i_ayA :: Int) (ds_d1Zb :: [T]) -> let { fail_d1Zn :: GHC.Prim.Void# -> Int [LclId, Str=DmdType] fail_d1Zn = \ _ [Occ=Dead, OS=OneShot] -> Control.Exception.Base.patError @ 'GHC.Types.PtrRepLifted @ Int "Main.hs:(41,1)-(44,25)|function fn5"# } in case ds_d1Zb of _ [Occ=Dead] { [] -> i_ayA; : ds_d1Zk ts_ayC -> case ds_d1Zk of _ [Occ=Dead] { __DEFAULT -> (\ _ [Occ=Dead, OS=OneShot] -> let { fail_d1Zp :: GHC.Prim.Void# -> Int [LclId, Str=DmdType] fail_d1Zp = \ _ [Occ=Dead, OS=OneShot] -> case ds_d1Zb of _ [Occ=Dead] { __DEFAULT -> fail_d1Zn GHC.Prim.void#; : ds_d1Zm ts_ayG -> case ds_d1Zm of _ [Occ=Dead] { __DEFAULT -> fail_d1Zn GHC.Prim.void#; C -> fn5 (GHC.Types.I# 0#) ts_ayG } } } in case i_ayA of i_XyO { __DEFAULT -> case ds_d1Zb of _ [Occ=Dead] { __DEFAULT -> fail_d1Zp GHC.Prim.void#; : ds_d1Zl ts_ayE -> case ds_d1Zl of _ [Occ=Dead] { __DEFAULT -> fail_d1Zp GHC.Prim.void#; B -> fn5 (+ @ Int GHC.Num.$fNumInt i_XyO (GHC.Types.I# 2#)) ts_ayE } } }) GHC.Prim.void#; A -> fn5 (+ @ Int GHC.Num.$fNumInt i_ayA (GHC.Types.I# 1#)) ts_ayC } } end Rec } }}} This code evaluates the list, and evaluates the int unless head of the list is `A`. I don't know why there's special case in A? In any case, this is wrong behavior as it forces the int in wrong times. As an example, this fails: {{{#!haskell fn5 :: Int -> [T] -> Int fn5 i [] = i fn5 i (A : ts) = fn5 (i + 1) ts fn5 !i (B : ts) = fn5 (i + 2) ts fn5 i (C : ts) = fn5 0 ts main = print (fn5 undefined [C]) }}} Tried with: GHC HEAD, 8.0.1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12235> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1965: Allow unconstrained existential contexts in newtypes
by GHC 24 Jun '16

24 Jun '16

#1965: Allow unconstrained existential contexts in newtypes -------------------------------------+------------------------------------- Reporter: guest | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 6.8.1 Resolution: | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Possible example from [http://www.cl.cam.ac.uk/~mpf23/papers/Types/gadtif.pdf A Foundation for GADTs and Inductive Families], encoding GADTs as left Kan extensions can be reworked to: {{{#!hs data N = O | S N data LanO j where LanO :: LanO (S i) data LanS j where LanS :: Fin i -> LanS (S i) }}} `Fin` defined as {{{#!hs data Fin a where FinO :: LanO i -> Fin i FinS :: LanS i -> Fin i pattern FinO' = FinO LanO pattern FinS' n = FinS (LanS n) }}} Do `LanO`, `LanS` satisfy the conditions to be newtypes? === Original code=== {{{#!hs data Fin :: * -> * where NZero :: Lan S One j -> Fin j NSucc :: Lan S Fin j -> Fin j data One j = One data Lan h _X j = forall i. Lan (Eql j (h i), _X i) data Eql i j where Refl :: Eql i i }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1965#comment:31> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12184: unsafeCoerce# causing invalid assembly generation
by GHC 24 Jun '16

24 Jun '16

#12184: unsafeCoerce# causing invalid assembly generation -------------------------------------+------------------------------------- Reporter: osa1 | 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: -------------------------------------+------------------------------------- Discovered by MichaelBurge on IRC: {{{#!haskell {-# LANGUAGE MagicHash #-} import GHC.Prim import GHC.Types x = D# ((unsafeCoerce# (5# :: Int#) :: Double#) +## 5.0##) main = putStrLn $ show x }}} Compile with GHC 7.8, 8.0.1 or HEAD: {{{ [1 of 1] Compiling Main ( weird.hs, weird.o ) /tmp/ghc23262_0/ghc_2.s: Assembler messages: /tmp/ghc23262_0/ghc_2.s:43:0: error: Error: junk `naughty x86_64 register' after expression `gcc' failed in phase `Assembler'. (Exit code: 1) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12184> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12183: Display all relevant local bindings
by GHC 24 Jun '16

24 Jun '16

#12183: Display all relevant local bindings -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (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: -------------------------------------+------------------------------------- Presently, "Relevant bindings" messages (e.g., from holes) will attempt to report all local bindings, and relevant global bindings (by some heuristic), up to the number of bindings specified by `-fmax-relevant- binds=N`. For example, here is an error I recently had with a small number of relevant bindings: {{{ Productive.hs:162:16: error: • Found hole: _ :: Par (D k0 (Stream k0 b)) Where: ‘k0’ is an ambiguous type variable ‘b’ is a rigid type variable bound by the type signature for: maapM :: forall a b. (a -> Par b) -> (forall (k :: Clock). Stream k a) -> Par (Forall1 Stream b) at Productive.hs:155:10 • In the second argument of ‘(<$>)’, namely ‘_’ In a stmt of a 'do' block: Cons b <$> _ In the expression: do { (a, s') <- deStreamCons s; b <- f a; b' <- f (scar (unForall1 s')); Cons b <$> _ } • Relevant bindings include b' :: b (bound at Productive.hs:159:5) b :: b (bound at Productive.hs:158:5) s' :: Forall1 Stream a (bound at Productive.hs:157:9) (Some bindings suppressed; use -fmax-relevant-binds=N or -fno-max- relevant-binds) }}} When I set `-fno-max-relevant-binds)`, this extends with: {{{ a :: a (bound at Productive.hs:157:6) s :: forall (k :: Clock). Stream k a (bound at Productive.hs:156:9) f :: a -> Par b (bound at Productive.hs:156:7) maapM :: (a -> Par b) -> (forall (k :: Clock). Stream k a) -> Par (Forall1 Stream b) (bound at Productive.hs:156:1) take :: forall a. Int -> (forall (k :: Clock). Stream k a) -> Par [a] (bound at Productive.hs:143:1) ...and a pile more global binds... }}} I think this is not really the behavior we want. If I'm doing an Agda/Coq development, what I want is for the compiler to tell me all LOCAL bindings. Heuristically picked global bindings might be nice, but it's not a priority (after all, I probably have explicit type signatures for all of these anyway.) Thus, I propose that `-fmax-relevant-binds=N` be changed to apply to GLOBAL bindings only, and that GHC should unconditionally print all local bindings. Furthermore, I suggest that by default `-fmax-relevant-binds=0`. As a minor addendum, I don't find the context information `In the second argument of ‘(<$>)’, namely ‘_’`, etc. very useful. Just makes the message longer and harder to view. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12183> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12179: Incorrect parsing of a pattern synonym type
by GHC 24 Jun '16

24 Jun '16

#12179: Incorrect parsing of a pattern synonym type -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #12108 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following definition is accepted by GHC. {{{ pattern Q :: a -> forall. (Bool -> a) pattern Q v <- (($ True) -> v) }}} What does this type signature mean? Who knows. It should be rejected for being an invalid form. Maybe see #12108 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12179> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12219: TH test failures with -fexternal-interpreter
by GHC 24 Jun '16

24 Jun '16

#12219: TH test failures with -fexternal-interpreter -------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: high | Milestone: 8.0.2 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: -------------------------------------+------------------------------------- These TH tests are currently failing with -fexternal-interpreter. I need to fix these before I can enable testing of all TH tests with -fexternal- interpreter. {{{ Unexpected failures: T10697_decided_1.run T10697_decided_1 [exit code non-0] (ext-interp) T10697_decided_2.run T10697_decided_2 [exit code non-0] (ext-interp) T10697_decided_3.run T10697_decided_3 [exit code non-0] (ext-interp) T8761.run T8761 [stderr mismatch] (ext-interp) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12219> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12112: Testsuite driver links from /tmp directory to .hi and .o files in source directory
by GHC 24 Jun '16

24 Jun '16

#12112: Testsuite driver links from /tmp directory to .hi and .o files in source directory -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Test Suite | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #11980 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is a clear bug, but only shows up when the source directory is not clean. Perhaps from a validate run from before the `/tmp` testsuite patch. A user might also have been running some small sample programs in the source directory manually. The testsuite driver currently matches `<testname>*`. I'm not sure if a whitelist or blacklist solution is more future proof. These are all existing filetypes in the testsuite: {{{ $ find . -name tests | xargs dir | grep -v stderr | grep -v stdout Extension Files ==================================== .def (1) .tix (1) .hspp (2) .ghci (1) .primops (1) .mix (1) .gnp (2) .so (1) .md (2) .hx (1) .sh (1) .test (1) .cpp (2) .mm (1) .gitignore (7) .m (2) .asm (4) .conf (2) .h (19) .hsc (10) .lib (2) .pkg (14) .hs-boot (49) .txt (5) .hsig (14) .cabal (37) .gml (1) .cmm (46) .sample (14) .c (66) .dat (3) .pgn (1) .stdin (8) .lhs (23) .script (318) .plt (2) .T (311) (370) . (438) .hs (5343) Total: (10370) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12112> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 23 Jun '16

23 Jun '16

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by niteria): That's definitely a nice idea, but as you said we need the bootstrapping compiler to catch up. I'm few changes away from removing `Ord Unique` and I plan to put a note where it used to be, explaining why it was removed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:216> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 23 Jun '16

23 Jun '16

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by Iceland_jack): We can add the recent Proposal/CustomTypeErrors instead of removing the `Ord` instances {{{#!hs instance TypeError (Text "Implemented in terms of ‘Uniques’.") => Ord (CoAxiom br) instance TypeError (Text "Implemented in terms of unique comparison, which is nondeterministic.") => Ord TyCon ... }}} although it may need to wait a few releases it could be added as comments, thoughts? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:215> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 23 Jun '16

23 Jun '16

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by ryantrinkle): Thanks so much, Bartosz and all the others working on this! This looks like a ton of work, and I know it will improve things for me and many more people I've spoken to about it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:214> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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