April 2013 - ghc-tickets

[GHC] #7869: GHC complains about applying a function to one argument
by GHC 30 Apr '13

30 Apr '13

#7869: GHC complains about applying a function to one argument -----------------------------+---------------------------------------------- Reporter: Mortchek | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.4.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- When this function is compiled: {{{ let f = (\x -> f x) :: [a] -> b }}} GHC gives this error message: {{{ Foo.hs:1:12: Couldn't match type `b' with `b1' `b' is a rigid type variable bound by the inferred type of f :: [a] -> b at Foo.hs:1:1 `b1' is a rigid type variable bound by an expression type signature: [a1] -> b1 at Foo.hs:1:5 Expected type: [a1] -> b1 Actual type: [a] -> b The function `f' is applied to one argument, but its type `[a] -> b' has only one In the expression: f x In the expression: (\ x -> f x) :: [a] -> b Foo.hs:1:12: Couldn't match type `a' with `a1' `a' is a rigid type variable bound by the inferred type of f :: [a] -> b at Foo.hs:1:1 `a1' is a rigid type variable bound by an expression type signature: [a1] -> b1 at Foo.hs:1:5 Expected type: [a1] -> b1 Actual type: [a] -> b The function `f' is applied to one argument, but its type `[a] -> b' has only one In the expression: f x In the expression: (\ x -> f x) :: [a] -> b }}} The erroneous part is: {{{ The function `f' is applied to one argument, but its type `[a] -> b' has only one In the expression: f x In the expression: (\ x -> f x) :: [a] -> b }}} This error message should not be present, as applying a function to one argument is not a problem. This happens in GHCi as well. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7869> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7473: getModificationTime gives only second-level resolution
by GHC 30 Apr '13

30 Apr '13

#7473: getModificationTime gives only second-level resolution ----------------------------------+----------------------------------------- Reporter: duncan | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: libraries/directory | Version: 7.6.1 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: ----------------------------------+----------------------------------------- Comment(by refold): I've added a version of Neil's code to Cabal: https://github.com/haskell/cabal/blob/master/cabal- install/Distribution/Compat/Time.hs#L58 Perhaps it can be reused for `directory`. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7473#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7856: Wrong error message for unknown Instance
by GHC 30 Apr '13

30 Apr '13

#7856: Wrong error message for unknown Instance ----------------------------------------------+----------------------------- Reporter: bas | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.3 | Keywords: Instance Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- This type-incorrect program gives a wrong error message: {{{ main = tmp "hello" where tmp :: String -> IO () tmp = sequence_ lst lst = [putStrLn "hi"] }}} Namely: {{{ Couldn't match expected type `IO ()' with actual type `()' Expected type: String -> IO () Actual type: String -> () In the return type of a call of `sequence_' In the expression: sequence_ lst }}} I would not expect the "actual type" to be "String -> ()", but rather "IO ()". Note: GHC expects that "(->) String" is a monad. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7856> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7851: Give better diagnostic when arguments are omitted to a function call in do-notation
by GHC 30 Apr '13

30 Apr '13

#7851: Give better diagnostic when arguments are omitted to a function call in do- notation ----------------------------------------------+----------------------------- Reporter: JohnWiegley | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler (Parser) Version: 7.4.2 | Keywords: Os: MacOS X | Architecture: x86_64 (amd64) Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- When using any Monad other than (->) e, it is almost always an error for a function call to yield another function, rather than a monadic value. For example: import Control.Monad.Trans.State main = flip runStateT 10 $ do print print "Hello" The error you get from this code is (with GHC 7.4.2): Couldn't match expected type `StateT b0 m0 a0' with actual type `a1 -> IO ()' While this is fully correct, I think the compiler could do much better. The fact that the naked call to "print" doesn't return an IO value, but rather a function type, could be immediately detected as an error, allowing GHC to say something like: Detected function type (a -> IO ()) returned when IO () was expected, perhaps missing an argument in call to "print"? My example with StateT, IO and print is rather trivial, but when you start getting into nested monad transformers, in polymorphic functions where the transformer and underlying monad types are parameterized, the errors from GHC become downright mysterious. Only through experience have I become able to read them as saying "You've forgotten an argument in your call to f". Since I can't think of a case (outside the function monad), where statements within a do-notation block should yield a function type rather than a monadic value appropriate to that Monad, perhaps we could do better here in guiding the user to the real source of the problem. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7851> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7778: kindFunResult panic with => inside a constraint
by GHC 30 Apr '13

30 Apr '13

#7778: kindFunResult panic with => inside a constraint -----------------------------+---------------------------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- Following type (found by arkeet on #haskell) causes kindFunResult panic in 7.6 and HEAD: {{{ v :: ((Num Int => Num) ()) => () v = v }}} In a probably related issue, {{{ Prelude> :set -XFlexibleContexts -XRankNTypes Prelude> type T = Num Int => Num Bool Prelude> :k T T :: Constraint Prelude> :k Num Int => Num Bool Num Int => Num Bool :: * }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7778> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7473: getModificationTime gives only second-level resolution
by GHC 29 Apr '13

29 Apr '13

#7473: getModificationTime gives only second-level resolution ----------------------------------+----------------------------------------- Reporter: duncan | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: libraries/directory | Version: 7.6.1 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: ----------------------------------+----------------------------------------- Changes (by refold): * cc: the.dead.shall.rise@… (added) -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7473#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7863: Verbosity level for quieter Template Haskell
by GHC 29 Apr '13

29 Apr '13

#7863: Verbosity level for quieter Template Haskell -----------------------------+---------------------------------------------- Reporter: dolio | Owner: Type: feature request | Status: new Priority: normal | Component: Template Haskell Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- In projects with large numbers of dependencies, use of template haskell can cause very large amounts of output that aren't particularly interesting. However, it seems that the only verbosity level that quiets template haskell output is -v0, which also turns off normal indications of build progress. It would be pleasant to have a way to turn off template haskell loading messages while retaining the rest of -v1 output. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7863> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7439: Include dynamic-by-default support in Cabal with GHC 7.6.2
by GHC 28 Apr '13

28 Apr '13

#7439: Include dynamic-by-default support in Cabal with GHC 7.6.2 -------------------------------+-------------------------------------------- Reporter: igloo | Owner: igloo Type: bug | Status: closed Priority: highest | Milestone: 7.6.2 Component: Compiler | Version: 7.6.1 Resolution: invalid | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: -------------------------------+-------------------------------------------- Changes (by igloo): * status: new => closed * resolution: => invalid Comment: We went a different route in the end; Cabal HEAD now has support for `-dynamic-too`, which GHC 7.8 will use. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7439#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7465: ./configure --with--ffi-libraries: ld cannot find libffi in a non-standard location
by GHC 28 Apr '13

28 Apr '13

#7465: ./configure --with--ffi-libraries: ld cannot find libffi in a non-standard location ----------------------------------+----------------------------------------- Reporter: trommler | Owner: trommler Type: bug | Status: closed Priority: normal | Milestone: 7.8.1 Component: Build System | Version: 7.7 Resolution: fixed | Keywords: Os: Linux | Architecture: Unknown/Multiple Failure: Building GHC failed | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: #5743 ----------------------------------+----------------------------------------- Changes (by igloo): * status: patch => closed * resolution: => fixed Comment: OK, variation on the second patch applied too (I've changed ghc-pkg to give us something closer to what we want, to simplify the build system code). Thanks for sending the patches! -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7465#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7465: ./configure --with--ffi-libraries: ld cannot find libffi in a non-standard location
by GHC 28 Apr '13

28 Apr '13

#7465: ./configure --with--ffi-libraries: ld cannot find libffi in a non-standard location ---------------------------------+------------------------------------------ Reporter: trommler | Owner: trommler Type: bug | Status: patch Priority: normal | Milestone: 7.8.1 Component: Build System | Version: 7.7 Keywords: | Os: Linux Architecture: Unknown/Multiple | Failure: Building GHC failed Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: #5743 | ---------------------------------+------------------------------------------ Comment(by ian@…): commit 23f5080ceb2e6809430a6ffc40f612b23aa86327 {{{ Author: Ian Lynagh <ian(a)well-typed.com> Date: Sun Apr 28 22:04:04 2013 +0100 Add -L flags to libs.depend (fixes #7465) Based on a patch from Peter Trommler rts/ghc.mk | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7465#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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