May 2018 - ghc-tickets

[GHC] #11452: Typed Template Haskell sneakily allows impredicativity
by GHC 11 Jan '19

11 Jan '19

#11452: Typed Template Haskell sneakily allows impredicativity -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire 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: -------------------------------------+------------------------------------- The following module is accepted: {{{#!hs {-# LANGUAGE ExplicitForAll, TemplateHaskell #-} module Bug where impred :: forall a. a -> a impred = $$( [|| \x -> x ||] ) }}} But that requires an intermediate `TExp (forall a. a -> a)`. Will fix in ongoing work. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11452> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 6

[GHC] #10949: Document typed Template Haskell
by GHC 11 Jan '19

11 Jan '19

#10949: Document typed Template Haskell -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Template | Version: 7.10.2 Haskell | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | -------------------------------------+------------------------------------- As far as I can tell, typed Template Haskell is completely missing from the manual. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10949> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #14838: missing "incomplete-patterns" warning for TH-generated functions
by GHC 11 Jan '19

11 Jan '19

#14838: missing "incomplete-patterns" warning for TH-generated functions -------------------------------------+------------------------------------- Reporter: gelisam | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.2.2 Haskell | 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: -------------------------------------+------------------------------------- "incomplete-patterns" warnings are generated for TH-generated case expressions, but not for TH-generated functions, so the behaviour is inconsistent. For example: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Lib where import Language.Haskell.TH qIncompleteCase :: Q [Dec] qIncompleteCase = [d| incompleteCase :: Bool -> () incompleteCase b = case b of True -> () |] qIncompleteFunction :: Q [Dec] qIncompleteFunction =[d| incompleteFunction :: Bool -> () incompleteFunction True = () |] }}} {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Lib $qIncompleteCase $qIncompleteFunction incompleteCase' :: Bool -> () incompleteCase' b = case b of True -> () incompleteFunction' :: Bool -> () incompleteFunction' True = () }}} When compiling the above two files with `-Wall`, GHC 8.2.2 produces an "incomplete-patterns" warning for `qIncompleteCase`, `incompleteCase'`, and `incompleteFunction'`, but not for `qIncompleteFunction`. I would prefer to get a warning for `qIncompleteFunction` as well. My use case is the [https://hackage.haskell.org/package/surjective surjective] package, in which I intentionally generate code which produces warnings in order to warn the user about corresponding issues in their code. I could generate [https://github.com/gelisam/surjective/blob/master/src/Surjective.hs#L158-L1… better error messages] if GHC generated warnings for TH-generated functions as well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14838> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 13

[GHC] #14271: ghci hangs with -fexternal-interpreter -prof
by GHC 09 Jan '19

09 Jan '19

#14271: ghci hangs with -fexternal-interpreter -prof ----------------------------------------+------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.1 Keywords: | Operating System: Windows Architecture: Unknown/Multiple | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+------------------------------- {{{ ghci -fexternal-interpreter -prof GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Access violation in generated code when reading 00000001001e0418 }}} * The address remains the same between reruns (and reinstalls) of ghc. * Closing the hanging process leaves the launched ghc active in the background. * The directory I launch ghci from doesn't seem to matter. * I have only tried it on my desktop so far (Win10/Skylake) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14271> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 13

[GHC] #14576: Internal error when compiling TH code with profiling on Windows
by GHC 09 Jan '19

09 Jan '19

#14576: Internal error when compiling TH code with profiling on Windows -------------------------------------+------------------------------------- Reporter: lazac | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When using the GHC API with this minimal example, compiled with profiling enabled: {{{#!hs module Main where import GHC import GHC.Paths ( libdir ) main = runGhc (Just libdir) $ do env <- getSession dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget "A.hs" Nothing setTargets [target] load LoadAllTargets }}} Invoking the main executable: {{{ testprof }}} While A.hs contains a TH splice: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module A where $(return []) }}} The compiler crashes: {{{ testprof.exe: internal error: IMAGE_REL_AMD64_ADDR32[NB]: High bits are set in 10e6109d0 for .text (GHC version 8.2.1 for x86_64_unknown_mingw32) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. }}} The walkaround is to use -fexternal-interpreter, in that case, the crash does not happen. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14576> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 5

[GHC] #13962: GHCi allows unsaturated type family
by GHC 08 Jan '19

08 Jan '19

#13962: GHCi allows unsaturated type family -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new 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: -------------------------------------+------------------------------------- Taken from [http://ics.p.lodz.pl/~stolarek/_media/pl:research:promotion- haskell14-slides.pdf Promoting Functions to Type Families in Haskell] {{{#!hs {-# Language TypeFamilies, PolyKinds, DataKinds, TypeOperators #-} type family Map (f :: a -> b) (xs :: [a]) :: [b] where Map f '[] = '[] Map f (x ': xs) = f x ': Map f xs data N = O | S N type family Pred (n :: N) :: N where Pred O = O Pred (S n) = n -- The type family ‘Map’ should have 2 arguments, but has been given 1 type MapPred = Map Pred }}} fails as expected, but it works in GHCi {{{ ghci> :kind Map Pred Map Pred :: [N] -> [N] ghci> :kind! Map Pred '[S (S O), S O, O] Map Pred '[S (S O), S O, O] :: [N] = '['S 'O, 'O, 'O] }}} I can only test this in GHC 7.8, 8 now. I know GHCi has weird rules for unsaturated type families but I figured I'd write a ticket because the slides say "But it is invalid to write: `Map Pred '[O, S O]`". -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13962> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 7

[GHC] #14677: Code generator does not correctly tag a pointer
by GHC 08 Jan '19

08 Jan '19

#14677: Code generator does not correctly tag a pointer -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: -------------------------------------+------------------------------------- Consider {{{ data T a = MkT ![a] }}} The pointer stored in a `MkT` constructor should always be correctly tagged, never tagged with un-evaluated 00. C.f. [wiki:Commentary/Rts/HaskellExecution/PointerTagging] But this invariant is broken. Example taken from #14626, comment:37-39. Trac14626_1.hs {{{ module Trac14626_1 where data Style = UserStyle Int | PprDebug data SDC = SDC !Style !Int defaultUserStyle :: Bool -> Style defaultUserStyle True = UserStyle 123 defaultUserStyle False = PprDebug }}} Trac14626_2.hs {{{ module Trac14626_2 where import Trac14626_1 f :: Int -> SDC f x = SDC (defaultUserStyle (x > 1)) x }}} Compiling with `ghc Trac14626_1 Trac14626_2 -ddump-simpl -O` results in a similar scenario than the one described by Heisenbug: {{{ -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0} defaultUserStyle2 defaultUserStyle2 = I# 123# -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0} defaultUserStyle1 defaultUserStyle1 = UserStyle defaultUserStyle2 -- RHS size: {terms: 7, types: 2, coercions: 0, joins: 0/0} defaultUserStyle defaultUserStyle = \ ds_dZ7 -> case ds_dZ7 of { False -> PprDebug; True -> defaultUserStyle1 } }}} Our `UserStyle 123` constant has been lifted to top-level, just like in Heisenbugs example. Now looking at the Core of `f` {{{ f f = \ x_a1dk -> case x_a1dk of { I# x1_a2gV -> case ># x1_a2gV 1# of { __DEFAULT -> SDC PprDebug x1_a2gV; 1# -> SDC defaultUserStyle1 x1_a2gV } } }}} (Note how `f` doesn't scrutinise defaultUserStyle1) Looking at the CMM for `f` we can see {{{ ... if (%MO_S_Le_W64(_s2hT::I64, 1)) goto c2ip; else goto c2is; c2ip: I64[Hp - 16] = SDC_con_info; P64[Hp - 8] = PprDebug_closure+2; I64[Hp] = _s2hT::I64; R1 = Hp - 15; Sp = Sp + 8; call (P64[Sp])(R1) args: 8, res: 0, upd: 8; c2is: I64[Hp - 16] = SDC_con_info; P64[Hp - 8] = defaultUserStyle1_closure; -- defaultUserStyle1 isn't tagged! I64[Hp] = _s2hT::I64; R1 = Hp - 15; Sp = Sp + 8; call (P64[Sp])(R1) args: 8, res: 0, upd: 8; }}} When generating code for f the code generator wants to know the `LambdaFormInfo` (the closure type) of `defaultUserStyle1`. Since `defaultUserStyle1` is defined in another module we end up calling `mkLFImported` in `StgCmmClosure` which ultimatively gives an `LFUnknown` which always gets a `DynTag` 0 from `lfDynTag`. I think we lack a bit of information here to give defaultUserStyle1 the correct `LFCon` lambda form. Maybe top-level binders should know its `LambdaForm` and include them in their interfaces. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14677> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 33

[GHC] #13742: Code using ConstraintKinds needs explicit kind signature with GHC 8.2.1
by GHC 08 Jan '19

08 Jan '19

#13742: Code using ConstraintKinds needs explicit kind signature with GHC 8.2.1 -------------------------------------+------------------------------------- Reporter: albertov | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 (Type checker) | Keywords: | Operating System: Unknown/Multiple ConstraintKinds, KindSignatures | Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The attached module compiles without errors with GHC 8.0.1 but needs an explicit kind signature with GHC 8.2.1-rc2. Mentioned in this [https://mail.haskell.org/pipermail/ghc- devs/2017-May/014222.html ghc-dev thread]. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13742> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 13

[GHC] #11621: GHC doesn't see () as a Constraint in type family
by GHC 08 Jan '19

08 Jan '19

#11621: GHC doesn't see () as a Constraint in type family -------------------------------------+------------------------------------- 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: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE DataKinds, TypeOperators, KindSignatures, MultiParamTypeClasses, TypeFamilies #-} import Data.Kind class NotFound type family F b where F 'False = (NotFound :: Constraint) F 'True = (() :: Constraint) }}} works fine. Removing all constraints and final line it works without any annotations and infers the type of `F :: Bool -> Constraint`: {{{#!hs type family F b where F 'False = NotFound }}} GHC seems determined that `() :: Type` unless explicitly told otherwise, I would like to be able to write: {{{#!hs type family F b where F 'False = NotFound F 'True = () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11621> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 11

[GHC] #14331: Overzealous free-floating kind check causes deriving clause to be rejected
by GHC 07 Jan '19

07 Jan '19

#14331: Overzealous free-floating kind check causes deriving clause to be rejected -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: deriving | 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: -------------------------------------+------------------------------------- GHC rejects this program: {{{#!hs {-# LANGUAGE DeriveAnyClass #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} module Bug where class C a b data D = D deriving (C (a :: k)) }}} {{{ GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:8:1: error: Kind variable ‘k’ is implicitly bound in datatype ‘D’, but does not appear as the kind of any of its type variables. Perhaps you meant to bind it (with TypeInType) explicitly somewhere? | 8 | data D = D deriving (C (a :: k)) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} But it really shouldn't, since it's quite possible to write the code that is should generate: {{{#!hs instance C (a :: k) D }}} Curiously, this does not appear to happen for data family instances, as this typechecks: {{{#!hs {-# LANGUAGE DeriveAnyClass #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} module Bug where class C a b data family D1 data instance D1 = D1 deriving (C (a :: k)) class E where data D2 instance E where data D2 = D2 deriving (C (a :: k)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14331> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 64