May 2013 - ghc-tickets

Re: [GHC] #7268: Explicit type signatures for top level record pattern matches polymorphism fail
by GHC 16 May '13

16 May '13

#7268: Explicit type signatures for top level record pattern matches polymorphism fail ---------------------------------------------+------------------------------ Reporter: TristanAllwood | Owner: simonpj Type: bug | Status: closed Priority: normal | Milestone: 7.8.1 Component: Compiler (Type checker) | Version: 7.4.1 Resolution: fixed | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC rejects valid program | Difficulty: Unknown Testcase: typecheck/should_compile/T7268 | Blockedby: Blocking: | Related: ---------------------------------------------+------------------------------ Comment(by MartijnVanSteenbergen): I'm really happy with this fix, thank you very much! -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7268#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7892: GHC accepts multiple conflicting kind signatures in type class declarations
by GHC 16 May '13

16 May '13

#7892: GHC accepts multiple conflicting kind signatures in type class declarations ----------------------------------------+----------------------------------- Reporter: MartijnVanSteenbergen | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC accepts invalid program | Blockedby: Blocking: | Related: ----------------------------------------+----------------------------------- Hi, Consider this suspicious looking program: {{{ {-# LANGUAGE TypeFamilies #-} class C (f :: * -> *) where type F (f :: *) :: * }}} I use the same type argument name `f` but specify different kinds. Now I can never define an instance anymore: {{{ instance C [] where -- Error: Type indexes must match class instance head -- type F () = () -- Error: Expecting one more argument to `[]' -- type F [] = () }}} I think GHC should verify, if the same type argument name is used multiple times in a type class definition, that their kinds match. In that case the type class above would be rejected. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7892> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #781: GHCi on x86_64, cannot link to static data in shared libs
by GHC 16 May '13

16 May '13

#781: GHCi on x86_64, cannot link to static data in shared libs -------------------------------+-------------------------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 6.5 Resolution: | Keywords: getEnvironment Os: Linux | Architecture: x86_64 (amd64) Failure: GHCi crash | Difficulty: Unknown Testcase: getEnvironment01 | Blockedby: 3658 Blocking: | Related: -------------------------------+-------------------------------------------- Changes (by jimstutt): * cc: jims@… (added) -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/781#comment:24> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7903: Failure to find class instance specified with extra parentheses
by GHC 15 May '13

15 May '13

#7903: Failure to find class instance specified with extra parentheses -----------------------------+---------------------------------------------- Reporter: conal | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- The following two-line program fails to compile under GHC 7.6.3 and compiles fine with GHC 7.4.1: {{{ instance Eq (((->) a) b) instance (Ord b) => Ord (((->) a) b) }}} Error message: {{{ Could not deduce (Eq (a -> b)) arising from the superclasses of an instance declaration from the context (Ord b) }}} Compilation goes through if I tweak the {{{Eq}}} instance to use "{{{((->) a b)}}}" or "{{{(a -> b)}}}" in place of "{{{(((->) a) b)}}}". -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7903> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7906: INLINEABLE on class method triggers the error for INLINE
by GHC 15 May '13

15 May '13

#7906: INLINEABLE on class method triggers the error for INLINE ----------------------------------------------+----------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- {{{ class Foo f where foo :: f {-# INLINEABLE foo #-} }}} causes the following error {{{ The INLINE pragma for `foo' lacks an accompanying binding (You cannot give a INLINE pragma for a record selector or class method) }}} Which incorrectly refers to INLINE and not the used INLINEABLE. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7906> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7268: Explicit type signatures for top level record pattern matches polymorphism fail
by GHC 15 May '13

15 May '13

#7268: Explicit type signatures for top level record pattern matches polymorphism fail ---------------------------------------------+------------------------------ Reporter: TristanAllwood | Owner: simonpj Type: bug | Status: closed Priority: normal | Milestone: 7.8.1 Component: Compiler (Type checker) | Version: 7.4.1 Resolution: fixed | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC rejects valid program | Difficulty: Unknown Testcase: typecheck/should_compile/T7268 | Blockedby: Blocking: | Related: ---------------------------------------------+------------------------------ Changes (by simonpj): * status: new => closed * testcase: => typecheck/should_compile/T7268 * resolution: => fixed Comment: Excellent point thank you. Pattern bindings are devilish tricky. Fixed now. I added a regression test for #7891 as well. Simon -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7268#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7891: Can't write type signature for top-level polymorphic pattern binding
by GHC 15 May '13

15 May '13

#7891: Can't write type signature for top-level polymorphic pattern binding --------------------------------------+------------------------------------- Reporter: MartijnVanSteenbergen | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC rejects valid program | Blockedby: Blocking: | Related: --------------------------------------+------------------------------------- Hi, In GHC 7.4.1 and 7.6.3 I can't write a type signature for a top-level polymorphic pattern binding. Consider this program: {{{ {-# LANGUAGE RankNTypes #-} newtype T = T (forall t. t -> t) tf :: T tf = T id -- Can't write this type signature: -- f :: t -> t T f = tf -- But with an indirection we can: g :: t -> t g = f -- We can still use f as it were fully polymorphic (which is good): a :: () a = f () b :: Char b = f 'b' }}} I expect to be able to specify a type for f. The same applies for a data family constructor, which is my original use case. I don't think it matters much, but here is an similar test case that uses a data family: {{{ {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeFamilies #-} class C t where data F t :: * mkF :: t -> F t instance C () where data F () = FUnit (forall t. t -> t) mkF () = FUnit id -- Can't write a type for f here either: FUnit f = mkF () }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7891> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7910: ConstraintKinds and reifyInstances
by GHC 15 May '13

15 May '13

#7910: ConstraintKinds and reifyInstances ----------------------------------------+----------------------------------- Reporter: elliottt | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.3 | Keywords: ConstraintKinds, TemplateHaskell Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Blockedby: Blocking: | Related: ----------------------------------------+----------------------------------- reifyInstances doesn't appear to know how to deal with a constraint that is just an alias. For example, the following prints (True,False): {{{ {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TemplateHaskell #-} import Language.Haskell.TH import Language.Haskell.TH.Syntax class C a instance C Int type D a = C a main = print $( do isCInst <- isInstance ''C [ConT ''Int] isDInst <- isInstance ''D [ConT ''Int] lift (isCInst,isDInst)) }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7910> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7888: Impredicativity flag needed more often
by GHC 15 May '13

15 May '13

#7888: Impredicativity flag needed more often ----------------------------------------------+----------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- I don't know if this is a bug or a deliberate change, but HEAD requires -XImpredicativeTypes for this program while 7.6.3 does not. {{{ {-# LANGUAGE RankNTypes #-} f :: (forall a. a) -> b f = undefined }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7888> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7268: Explicit type signatures for top level record pattern matches polymorphism fail
by GHC 15 May '13

15 May '13

#7268: Explicit type signatures for top level record pattern matches polymorphism fail ----------------------------------------+----------------------------------- Reporter: TristanAllwood | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler (Type checker) | Version: 7.4.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: GHC rejects valid program Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ----------------------------------------+----------------------------------- Comment(by simonpj@…): commit 0452021e726ab44f3866faacf7817ac116bb58db {{{ Author: Simon Peyton Jones <simonpj(a)microsoft.com> Date: Wed May 15 10:15:47 2013 +0100 Fix typechecking of pattern bindings that have type signatures (Trac #7268) Pattern bindings are jolly tricky to typecheck, especially if there are also type signatures involved. Trac #7268 pointed out that I'd got it wrong; this fixes it. See Note [Typing patterns in pattern bindings] in TcPat. compiler/typecheck/TcBinds.lhs | 21 ++++------ compiler/typecheck/TcPat.lhs | 81 +++++++++++++++++++++------------------ 2 files changed, 52 insertions(+), 50 deletions(-) }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7268#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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