February 2016 - ghc-tickets

[GHC] #11410: Quantification over unlifted type variable
by GHC 07 Mar '16

07 Mar '16

#11410: Quantification over unlifted type variable -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: TypeInType | 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 silliness is accepted: {{{ data X (a :: TYPE 'Unlifted) = X }}} I will fix. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11410> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9699: TH function to list names in scope
by GHC 07 Mar '16

07 Mar '16

#9699: TH function to list names in scope -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I [asked about this on stackoverflow](http://stackoverflow.com/questions/26394199/using- templatehaskell-to-list-all-names-in-a-namespace), and apparently it doesn't exist yet. I want a TemplateHaskell function `variablesInScope :: Q [Name]` that returns a list of the `Name`'s of all the variables in scope. TemplateHaskell obviously has this information available in order to implement functions like `reify :: Name -> Q Info` and `lookupValueName :: String -> Q (Maybe Name)`. So it seems like this might be a pretty simple function to add. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9699> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11516: Panic, "falls into a hole"
by GHC 05 Mar '16

05 Mar '16

#11516: Panic, "falls into a hole" -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- {{{#!hs {-# language PolyKinds #-} {-# language FlexibleContexts #-} {-# language ConstraintKinds #-} {-# language FlexibleInstances #-} {-# language FunctionalDependencies #-} import GHC.Types (Constraint) class Ríki (p :: i -> i -> *) class (Ríki p) => Varpi p q f | f -> p q instance Varpi () () f => Varpi (->) (->) (Either f) where }}} causes {{{ % ghci -ignore-dot-ghci /tmp/testing.hs GHCi, version 8.1.20160117: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/testing.hs, interpreted ) /tmp/testing.hs:11:10: error:ghc: panic! (the 'impossible' happened) (GHC version 8.1.20160117 for x86_64-unknown-linux): fvProv falls into a hole {a13R} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > Leaving GHCi. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11516> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11524: Something is amiss with quantification in pattern synonym type signatures
by GHC 05 Mar '16

05 Mar '16

#11524: Something is amiss with quantification in pattern synonym type signatures -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc1 (Type checker) | 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: -------------------------------------+------------------------------------- Consider this program, {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ExplicitForAll #-} {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE TypeInType #-} module Test where data AType (a :: k) where AMaybe :: AType Maybe AInt :: AType Int AApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1). AType a -> AType b -> AType (a b) pattern PApp :: () => (fun ~ a b) => AType a -> AType b -> AType fun --pattern PApp :: forall k (fun :: k) k1 (a :: k1 -> k) (b :: k1). -- () => (fun ~ a b) => AType a -> AType b -> AType fun pattern PApp fun arg <- AApp fun arg }}} I would have thought that the two type signatures would be equivalent. However, when I use the quantified signature GHC complains with, {{{ hi.hs:14:34: error: • Expected kind ‘AType a’, but ‘fun’ has kind ‘AType a1’ • In the declaration for pattern synonym ‘PApp’ • Relevant bindings include arg :: AType b1 (bound at hi.hs:14:34) fun :: AType a1 (bound at hi.hs:14:30) }}} Moreover, if I use the un-quantified signature and ask GHCi for the full type signature, it gives me the precisely the quantified type that it rejected previously, {{{ λ> :info PApp pattern PApp :: forall k (fun :: k) k1 (a :: k1 -> k) (b :: k1). () => fun ~ a b => AType a -> AType b -> AType fun -- Defined at hi.hs:14:1 }}} Very odd. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11524> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11558: Using Cabal 1.22 against GHC 8.0 results in terrible errors
by GHC 05 Mar '16

05 Mar '16

#11558: Using Cabal 1.22 against GHC 8.0 results in terrible errors -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Package | Version: 8.0.1-rc1 system | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 8.0 will require Cabal >1.22 due to a variety of interface changes (see #10714, Phab:D1780, https://mail.haskell.org/pipermail/ghc- devs/2016-January/010978.html). Unfortunately things currently blow up late in compilation with a seemingly unrelated error when this requirement isn't met. Namely, we complain about missing interface files for dependencies. For instance, {{{ Text/Parsec/Prim.hs:85:1: error: Bad interface file: /root/.cabal/lib/x86_64-linux- ghc-8.0.0.20160204/mtl-2.2.1-9wMhzcfsAXi7cNtl9n7svO/Control/Monad/Cont/Class.hi Something is amiss; requested module mtl-2.2.1@mtl-2.2.1-1af5dabd2d7abb688f2145aec87badc4:Control.Monad.Cont.Class differs from name found in the interface file mtl_9wMhzcfsAXi7cNtl9n7svO:Control.Monad.Cont.Class }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11558> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10472: SigOf tests fail following renamer tidy-up
by GHC 01 Mar '16

01 Mar '16

#10472: SigOf tests fail following renamer tidy-up -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I'm about to commit a patch that fixes #7672. Sadly, though, it causes these failures {{{ driver/sigof02 sigof02dmt [bad stderr] (normal) driver/sigof02 sigof02dt [bad stderr] (normal) driver/sigof02 sigof02mt [bad exit code] (normal) driver/sigof02 sigof02t [bad exit code] (normal) }}} with errors like {{{ Main.hs:8:13: error: Can't find interface-file declaration for variable empty Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error In the second argument of ‘($)’, namely ‘empty’ In the expression: insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty In an equation for ‘x’: x = insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty Main.hs:10:12: error: Can't find interface-file declaration for variable toList Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error In the first argument of ‘print’, namely ‘(toList x)’ In a stmt of a 'do' block: print (toList x) In the expression: do { let x = insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty; print (member 1 x); print (toList x); print x } }}} Clearly there is only one bug here, and it's in the signature-handling code, which I do not fully understand. Happily, it's Edward's territory, and he is also involved in #7672. So I plan to mark these tests as broken on this ticket, and hope that Edward can adapt the signature stuff (which in any case is in-flight) to the new code. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10472> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11596: ghci gets confused if a file is deleted
by GHC 29 Feb '16

29 Feb '16

#11596: ghci gets confused if a file is deleted -------------------------------------+------------------------------------- Reporter: NeilMitchell | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.0.1-rc2 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: -------------------------------------+------------------------------------- With GHC 8.0 RC2 if a currently loaded .hs file is deleted then {{{:reload}}} works, but actual execution of anything is broken. In previous versions this situation resulted in an error at {{{:reload}}} time. Below is a session that demonstrate the bug: {{{ $ ghci A.hs GHCi, version 8.0.0.20160205: http://www.haskell.org/ghc/ :? for help [1 of 2] Compiling B ( B.hs, interpreted ) [2 of 2] Compiling A ( A.hs, interpreted ) Ok, modules loaded: A, B. *A> :!cat A.hs module A where import B a = b + 1 *A> :!cat B.hs module B where b = 41 *A> :!mv B.hs B.txt *A> :r Ok, modules loaded: A. *A> :show modules A ( A.hs, interpreted ) *A> a <interactive>: fatal: cannot find object file for module `B' while linking an interpreted expression *A> :r Ok, modules loaded: A. }}} Specifically, I load A.hs, which depends on B.hs. I move B.hs away (or delete it). I reload and it says everything is fine. I try to run and it fails. Putting the B.hs file back solves it. This sequence worked fine in all previous versions of GHC, and is caught by the [https://github.com/ndmitchell/ghcid ghcid] test suite. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11596> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11650: Default definitions for Alternative(some, many) can easily blow up
by GHC 29 Feb '16

29 Feb '16

#11650: Default definitions for Alternative(some, many) can easily blow up -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | 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: -------------------------------------+------------------------------------- Consider this case (taken from #11649) {{{#!hs import Control.Applicative data U1 p = U1 instance Functor U1 where fmap f U1 = U1 instance Applicative U1 where pure _ = U1 U1 <*> U1 = U1 instance Alternative U1 where empty = U1 U1 <|> U1 = U1 instance Show (U1 p) where show U1 = "U1" main = print (some U1) }}} This looks fine, right? Wrong, {{{ $ ./Main Main: <<loop>> }}} It seems that the default definitions of `some` and `many` will produce looping code in these cases (although it's not entirely clear to me which cases "these" cases are). I suppose this is due to the fact that `U1` will always "succeed". We should ensure that this is noted in the documentation to ensure that users don't end up with accidentally bottoming instances. Well, consider what happens -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11650> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6113: Profiling with -p not written if killed with SIGTERM
by GHC 29 Feb '16

29 Feb '16

#6113: Profiling with -p not written if killed with SIGTERM -------------------------------------+------------------------------------- Reporter: Veinor | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Profiling | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by Thomas Miedema <thomasmiedema@…>): In [changeset:"e3b9dbf48c7b7b1ac4a5d6ecf1411469b5f7666c/ghc" e3b9dbf4/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="e3b9dbf48c7b7b1ac4a5d6ecf1411469b5f7666c" Testsuite: check actual_prof_file only when needed Might be a little faster. Avoids testing for #6113 (.prof file not written when process is killed with any signal but SIGINT) for tests that don't have a .prof.sample file (which is almost all of them) when running the profiling ways. Tests that were failing because of #6113: T8089, overflow1, overflow2 and overflow3. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6113#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10873: Bad error message for incorrect pattern synonym signature
by GHC 29 Feb '16

29 Feb '16

#10873: Bad error message for incorrect pattern synonym signature -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 (Type checker) | Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Consider the following program {{{ {-# LANGUAGE PatternSynonyms #-} pattern Pat :: Show a => () => a -> Maybe a pattern Pat a = Just a }}} GHC complains that {{{ test.hs:4:9: No instance for (Show a) arising from a pattern }}} I think this is quite difficult to understand. The problem is that matching on `Just a` doesn't provide the show constraint (it provides no constraints). A better error message here would explain this fact and maybe a short explanation of the difference between prov/req in a pattern synonym signature. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10873> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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