September 2017 - ghc-tickets

[GHC] #13738: TypeApplications-related GHC internal error
by GHC 11 Sep '17

11 Sep '17

#13738: TypeApplications-related GHC internal error -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple TypeApplications | Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is reproducible with GHC 8.0.1, 8.0.2, 8.2.1, and HEAD: {{{#!hs {-# LANGUAGE PolyKinds #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeApplications #-} module Bug where import Data.Coerce class MFunctor t where hoist :: (Monad m) => (forall a . m a -> n a) -> t m b -> t n b newtype TaggedTrans tag trans m a = TaggedTrans (trans m a) instance MFunctor trans => MFunctor (TaggedTrans tag trans) where hoist = coerce @(forall (m :: * -> *) (n :: * -> *) (b :: k). Monad m => (forall (a :: *). m a -> n a) -> trans m b -> trans n b) @(forall (m :: * -> *) (n :: * -> *) (b :: k). Monad m => (forall (a :: *). m a -> n a) -> TaggedTrans tag trans m b -> TaggedTrans tag trans n b) hoist }}} {{{ GHCi, version 8.3.20170516: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:18:26: error: • GHC internal error: ‘k’ is not in scope during type checking, but it passed the renamer tcl_env of environment: [a1tR :-> Type variable ‘m’ = m, a1tS :-> Type variable ‘n’ = n, a1tT :-> Type variable ‘b’ = b, a1tV :-> Type variable ‘trans’ = trans, a1tW :-> Type variable ‘tag’ = tag, a1tX :-> Type variable ‘m’ = m, a1tY :-> Type variable ‘n’ = n, a1KE :-> Type variable ‘k’ = k, a1KF :-> Type variable ‘k’ = k] • In the kind ‘k’ In the type ‘(forall (m :: * -> *) (n :: * -> *) (b :: k). Monad m => (forall (a :: *). m a -> n a) -> trans m b -> trans n b)’ In the expression: coerce @(forall (m :: * -> *) (n :: * -> *) (b :: k). Monad m => (forall (a :: *). m a -> n a) -> trans m b -> trans n b) @(forall (m :: * -> *) (n :: * -> *) (b :: k). Monad m => (forall (a :: *). m a -> n a) -> TaggedTrans tag trans m b -> TaggedTrans tag trans n b) hoist | 18 | (b :: k). | ^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13738> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12025: Order of constraints forced (in pattern synonyms, type classes in comments)
by GHC 10 Sep '17

10 Sep '17

#12025: Order of constraints forced (in pattern synonyms, type classes in comments) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple TypeApplications PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: 11513, 10928 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Ever since `TypeApplications` the order of quantification matters. It seems there are some places where the user has no control over the order: {{{#!hs data A a where X :: A [xxx] pattern X' :: forall t. () => forall xxx. t ~ [xxx] => A t pattern X' = X }}} This quantifies the universal `t` and the existential `xxx`.. but in this case `t` is constrained to equal `[xxx]` so when we supply our first type (the universal `t`) it is forced to be of the form `[a]`. Then the existential is forced to equal `a` (there is currently no way to express this without a type annotation `X' @[t] @t :: A [t]`, see ticket #11385 to allow `X' @[_t] @_t`, for this ticket the equality is inherent in `X` so it's no big deal). This means that the first argument really doesn't give any further information but it seems impossible to reorder the existential type before the universal. This either forces the user to supply a dummy type: {{{#!hs X' @_ @ActualType }}} or to write `[ActualType]` explicitly {{{#!hs X' @[ActualType] X' @[ActualType] @ActualType X' @[_] @ActualType }}} This may be a bigger inconvenience than it may seem: the return type can be more complicated `A (B (C a))` and it requires the user to look it up. `X' @_ @ActualType` feels like bad library design, especially as the number of existential variables grows and the user has to remember how many underscores to provide. See also ticket:10928#comment:5 Keep in mind that this usage will be common, since the more obvious (see ticket:10928#comment:16) {{{#!hs pattern X'' :: forall xxx. A [xxx] pattern X'' = X }}} cannot match against a type `A a` {{{#!hs -- Works foo :: A a -> ... foo X' = ... -- Doesn't bar :: A a -> ... bar X'' = ... }}} Thoughts? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12025> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14212: Give better error message with non-supported Backpack/TH use
by GHC 10 Sep '17

10 Sep '17

#14212: Give better error message with non-supported Backpack/TH use -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.2.1 Haskell | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is something of a follow up to #13268. Suppose you have an indefinite package. If you use TemplateHaskell with a splice that was defined in the indefinite package itself, there is no reasonable way to expect this to work, since in general you can't have compiled the the imported module before you need to run the splice (and the splice needs to be run before you know how the holes are instantiated.) But say you try and do it anyway. GHC will give an error like this: {{{ ghc: ^^ Could not load 'qzm0zi1zminplacezmENEL5G3hx7IK2t0f6HloyH_A_f_closure', dependency unresolved. See top entry above. ByteCodeLink.lookupCE During interactive linking, GHCi couldn't find the following symbol: qzm0zi1zminplacezmENEL5G3hx7IK2t0f6HloyH_A_f_closure This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-bugs(a)haskell.org }}} This is not a good error message. A good error message would be to say that you can't use in a splice a function defined in an indefinite package (as per the current library.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14212> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13268: Backpack doesn't work with Template Haskell, even when it should
by GHC 10 Sep '17

10 Sep '17

#13268: Backpack doesn't work with Template Haskell, even when it should -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.0.1 Haskell | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Obviously, we can't run Template Haskell from an indefinite package when we are (solely) typechecking the indefinite package itself. But in principle, Template Haskell code from other packages should be fair game. Alas, this not the case, because GHC attempts to dynamic link in libraries for ALL dependencies, including the ones we don't have code for. Quick fix should be to not link those in? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13268> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14210: bkp files cannot find TemplateHaskell symbols (even without Backpack features)
by GHC 10 Sep '17

10 Sep '17

#14210: bkp files cannot find TemplateHaskell symbols (even without Backpack features) -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: feature | Status: new request | Priority: low | Milestone: Component: Compiler | Version: 8.2.1 (Linking) | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ {-# LANGUAGE TemplateHaskell #-} unit th where module TH where f = [d| x = True |] unit p where dependency th module B where import TH $(f) }}} When run, this gives: {{{ ghc: ^^ Could not load 'th_TH_f_closure', dependency unresolved. See top entry above. ByteCodeLink.lookupCE During interactive linking, GHCi couldn't find the following symbol: th_TH_f_closure This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-bugs(a)haskell.org }}} I am not sure how easy or hard the fix is. We should bump this priority up if we get more serious about supporting Template Haskell with Backpack. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14210> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14207: Levity polymorphic GADT requires extra type signatures
by GHC 10 Sep '17

10 Sep '17

#14207: Levity polymorphic GADT requires extra type signatures -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple LevityPolymorphism | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This does not compile: {{{#!hs data Foo s (a :: TYPE k) where FooC :: Foo s Int# }}} However, this does: {{{#!hs data Foo (s :: Type) (a :: TYPE k) where FooC :: Foo s Int# }}} This also works: {{{#!hs data Foo (s :: j) (a :: TYPE k) where FooC :: Foo s Int# }}} These are all of the language pragmas I have enabled: {{{#!hs {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE BangPatterns #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE UnboxedSums #-} {-# LANGUAGE UnboxedTuples #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE UndecidableInstances #-} }}} This is pretty easy to work around, but I think it's an incorrect behavior. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14207> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14205: GHCI freaked out when I tryed to load a program and told me to report it as a bug.
by GHC 10 Sep '17

10 Sep '17

#14205: GHCI freaked out when I tryed to load a program and told me to report it as a bug. -------------------------------------+------------------------------------- Reporter: Ebanflo | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): initTc: unsolved constraints WC {wc_insol = [W] %_a2g7 :: t_a2g6[tau:1] (CHoleCan: %)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14205> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6132: Can't use both shebang line and #ifdef declarations in the same file.
by GHC 09 Sep '17

09 Sep '17

#6132: Can't use both shebang line and #ifdef declarations in the same file. -------------------------------------+------------------------------------- Reporter: gfxmonk | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 7.0.4 (Parser) | Resolution: | Keywords: cpp Operating System: MacOS X | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: runghc/T6132 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by lelf): * cc: lelf (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6132#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14090: Static pointers are not being registered under certain conditions
by GHC 09 Sep '17

09 Sep '17

#14090: Static pointers are not being registered under certain conditions -------------------------------------+------------------------------------- Reporter: mnislaih | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- It seems that if the module is compiled with -O2 only the static pointers in the module export list survive the Simplifier. This is a regression. {{{ {-# LANGUAGE StaticPointers #-} import GHC.StaticPtr staticHello :: StaticPtr String staticHello = static "hello" main = do keys <- staticPtrKeys if null keys then error "static ptrs are not being registered" else putStrLn "Everything is fine" }}} {{{ pepe:~/scratch$ stack --resolver ghc-8.2.1 script --optimize bug-spt.hs Using resolver: ghc-8.2.1 specified on command line bug-spt: static ptrs are not being registered CallStack (from HasCallStack): error, called at bug-spt.hs:11:10 in main:Main pepe:~/scratch$ stack --resolver ghc-8.0.2 script --optimize bug-spt.hs Using resolver: ghc-8.0.2 specified on command line Everything is fine }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14090> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9661: Branchless ==# is compiled to branchy code
by GHC 08 Sep '17

08 Sep '17

#9661: Branchless ==# is compiled to branchy code -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This started as a comment on #6135, but Jan Stolarek requested that I file a separate report. The branchless tests `<#`, `>#`, `<=#`, and `>=#`, and their wordy cousins, seem to work properly, but `==#` and `eqWord#` don't. If I write {{{#!hs foo x = tagToEnum# ((x <# 3#) `orI#` (x ># 100#) `orI#` (x ==# 12#) `orI#` (x ==# 15#)) }}} I get (in 7.8.3 and in 7.9) {{{#!hs IsDigit.foo :: GHC.Prim.Int# -> GHC.Types.Bool [GblId, Arity=1, Caf=NoCafRefs, Str=DmdType <S,1*U>, Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False) Tmpl= \ (x3_a2if [Occ=Once!] :: GHC.Prim.Int#) -> case x3_a2if of wild_Xe { __DEFAULT -> GHC.Prim.tagToEnum# @ GHC.Types.Bool (GHC.Prim.orI# (GHC.Prim.<# wild_Xe 3) (GHC.Prim.># wild_Xe 100)); 12 -> GHC.Types.True; 15 -> GHC.Types.True }}] IsDigit.foo = \ (x3_a2if :: GHC.Prim.Int#) -> case x3_a2if of wild_Xe { __DEFAULT -> GHC.Prim.tagToEnum# @ GHC.Types.Bool (GHC.Prim.orI# (GHC.Prim.<# wild_Xe 3) (GHC.Prim.># wild_Xe 100)); 12 -> GHC.Types.True; 15 -> GHC.Types.True }}} and branching assembly to match. Jan Stolarek indicates this is probably a problem with constant folding. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9661> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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