January 2015 - ghc-tickets

[GHC] #9563: Support for deriving Generic1 for data families
by GHC 07 Apr '16

07 Apr '16

#9563: Support for deriving Generic1 for data families -------------------------------------+------------------------------------- Reporter: mnislaih | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: GHC Difficulty: Unknown | rejects valid program Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following code: {{{#!hs import GHC.Generics data family F typ :: * -> * data A data instance F A a = AData a deriving Generic1 }}} produces an error when run with ghc 7.8.2 or 7.8.3: {{{ Couldn't match type ‘Rep1 (F A)’ with ‘M1 t0 t1 (M1 t2 t3 (M1 t4 t5 Par1))’ The type variables ‘t0’, ‘t1’, ‘t2’, ‘t3’, ‘t4’, ‘t5’ are ambiguous Expected type: Rep1 (F A) a Actual type: M1 t0 t1 (M1 t2 t3 (M1 t4 t5 Par1)) a In the pattern: M1 (M1 (M1 g1)) In an equation for ‘to1’: to1 (M1 (M1 (M1 g1))) = AData (unPar1 g1) In the instance declaration for ‘Generic1 (F A)’ }}} whereas ghc 7.6.3 simply refuses to go ahead with the message: {{{ generic1.hs:14:40: Derived instance `Generic1 (F A)' requires illegal partial application of data type family F In the data instance declaration for `F' }}} Either a check has gone missing in 7.8.x, or a bug has crept up in the Generic1 support. I have gone through past tickets and https://ghc.haskell.org/trac/ghc/ticket/5936 suggests that it is the latter. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9563> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10030: packageName for GHC.Generics.Datatype
by GHC 07 Apr '16

07 Apr '16

#10030: packageName for GHC.Generics.Datatype -------------------------------------+------------------------------------- Reporter: phadej | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.4 Component: | Operating System: Unknown/Multiple libraries/base | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Seems it's perfectly ok to have the data type of the same name in the same module, but different packages. Yet used in the same module: {{{ {-# LANGUAGE PackageImports #-} {-# LANGUAGE RankNTypes #-} module Data.Foo where import "void" Data.Void as A import Data.Void as B foo :: A.Void -> a foo = absurd bar :: B.Void -> a bar x = x () }}} {{{ {-# LANGUAGE RankNTypes #-} module Data.Void where type Void = forall a b. a -> b }}} https://gist.github.com/phadej/8b628d579ddf6958d937 motivated by: http://stackoverflow.com/questions/28159068/packagename- with-ghc-generics I'd propose to change `Datatype` class to be: {{{ class Datatype d where -- | The name of the datatype (unqualified) datatypeName :: t d (f :: * -> *) a -> [Char] -- | The fully-qualified name of the module where the type is declared moduleName :: t d (f :: * -> *) a -> [Char] -- | The package name of the module where the type is declared packageName :: t d (f :: * -> *) a -> [Char] -- | Marks if the datatype is actually a newtype isNewtype :: t d (f :: * -> *) a -> Bool isNewtype _ = False }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10030> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8594: sysctl name "hw.ncpu" (HW_NCPU) is deprecated in Mac OS X
by GHC 06 Apr '16

06 Apr '16

#8594: sysctl name "hw.ncpu" (HW_NCPU) is deprecated in Mac OS X ------------------------------------+--------------------------------- Reporter: kseo | Owner: simonmar Type: task | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.6.3 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+--------------------------------- According to the OS X man page for sysctl(https://developer.apple.com/library/mac/documentation/Darwin/Referen…, HW_NCPU used by the current implementation of getNumberOfProcessors() is deprecated. Instead, Mac OS X provides the following 4 options: * hw.physicalcpu: The number of physical processors available in the current power management mode. * hw.physicalcpu_max: The maximum number of physical processors that could be available this boot. * hw.logicalcpu: The number of logical processors available in the current power management mode. * hw.logicalcpu_max: The maximum number of logical processors that could be available this boot. I am not sure which one fits best to GHC runtime. Any idea? sysconf implementation of getNumberOfProcessors() seems to prefer _SC_NPROCESSORS_ONLN to _SC_NPROCESSORS_CONF when both are defined. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8594> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8731: long compilation time for module with large data type and partial record selectors
by GHC 30 Mar '16

30 Mar '16

#8731: long compilation time for module with large data type and partial record selectors -------------------------+------------------------------------------------- Reporter: | Owner: carter | Status: new Type: bug | Milestone: Priority: | Version: 7.8.1-rc1 normal | Operating System: Unknown/Multiple Component: | Type of failure: Compile-time performance bug Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- in both ghc 7.6 and 7.8rc, the Constants module in LLVM-General-Pure (and a few other similar modules) have surprisingly long (and noticable!) compilation times. This seems to related to how GHC handles a many constructor data type with overlapping field names. the time is nearly the same for building a static module with O1 and O2 {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O2 1 ↵ [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O2 7.52s user 0.23s system 99% cpu 7.755 total }}} {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O1 [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O1 6.62s user 0.20s system 100% cpu 6.768 total }}} heck even with -O0 its slow (though not terrible) {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O0 [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O0 2.76s user 0.14s system 101% cpu 2.873 total }}} Seems like there might something wrong in how we handle data types like this, the complexity need not -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8731> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9405: Ticky results should be displayed even during interrupts (Ctrl-c)
by GHC 24 Mar '16

24 Mar '16

#9405: Ticky results should be displayed even during interrupts (Ctrl-c) -------------------------------------+------------------------------------- Reporter: thoughtpolice | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- After talking with Simon & Simon today, we discussed ticky profiling, and it dawned on us that ticky probably isn't reported when the program is interrupted via the user. But it should be! The motivating case is when you're dealing with an infinite loop and you want to find the binding that has a high entry count (i.e. it's the looping body). But the only way to move forward is to interrupt it, which doesn't spit out the reports. Fixing this would make ticky much more useful in such cases. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9405> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9803: Poor error message for unbound variable in pattern synonym
by GHC 17 Mar '16

17 Mar '16

#9803: Poor error message for unbound variable in pattern synonym -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- When I say {{{ pattern OneElt = [x] }}} I get {{{ Right-hand side of bidirectional pattern synonym cannot be used as an expression [x] }}} I have two complaints with this error message: 1. It's very unclear what's actually wrong with the pattern -- `[x]` looks like a perfectly fine expression, until I realize that `x` is unbound. 2. The herald of the error is more than 80 characters (if you count the indentation) and wraps on my 80-character terminal. GHC tends to avoid this elsewhere, and so the wrapping is suboptimal. I would easily say that issue (1) is more important than issue (2). Perhaps this would be better: {{{ Variable `x' is unbound in the bidirectional pattern synonym `OneElt': [x] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9803> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8132: Warning for Typeable instances misplaced
by GHC 16 Mar '16

16 Mar '16

#8132: Warning for Typeable instances misplaced -------------------------+------------------------------------------------- Reporter: | Owner: scottgw | Status: new Type: bug | Milestone: Priority: | Version: 7.7 normal | Operating System: Unknown/Multiple Component: | Type of failure: Incorrect warning at Compiler | compile-time Keywords: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- There is currently a warning for hand-rolled instances of Typeable. However, this leads to some pretty surprising error messages: because the instance is ignored any code that relies on that instance in the same module just fails, which appears pretty weird to the user. {{{ #!haskell import Data.Typeable data K = K instance Typeable K where typeRep _ = undefined ex :: TypeRep ex = typeRep (undefined :: Proxy K) }}} Gives as an error: {{{ No instance for (Typeable * K) arising from a use of ‛typeRep’ In the expression: typeRep (undefined :: Proxy K) In an equation for ‛ex’: ex = typeRep (undefined :: Proxy K) }}} Which is of course surprising because the user just defined the instance. After commenting out the code that uses the instance, one gets: {{{ TypEx.hs:1:1: Warning: Typeable instances can only be derived; ignoring the following instance: instance Typeable * K -- Defined at TypEx.hs:5:10 }}} This information should clearly be somehow presented before or with the previous error if the user is to have any way to figure out what is going on. I suppose this could be fixed by: 1. Turning the Typeable instance warning into an error 2. Checking the missing instance in the existing error for Typeable and suggest that the user should look for hand written instances as a source of the problem. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8132> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9887: No message when GCHI reusing compiled code
by GHC 12 Mar '16

12 Mar '16

#9887: No message when GCHI reusing compiled code -------------------------------------+------------------------------------- Reporter: jsrice | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: Other hour) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Running ":l Main.hs" at the GHCI prompt would load the compiled module. I am new to Haskell and this was a stumbling block that made it so that I could not interactively debug my code with GHCI. Deleting the object files was suggested to me on IRC and that allowed me to get the "*Main" prompt I was looking for. A message warning users "reusing compiled code" would likely save some future users some time. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9887> 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 06 Mar '16

06 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] #9043: Add missing type class instances for data types in GHC.Generics
by GHC 27 Feb '16

27 Feb '16

#9043: Add missing type class instances for data types in GHC.Generics ------------------------------------+------------------------------------- Reporter: ocharles | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- GHC.Generics offers a bunch of data types which have valid instances of various type classes in base, such as Functor. There's no good reason not to have these instances, so they should be added. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9043> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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