June 2015 - ghc-tickets

[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 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] #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] #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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[GHC] #10316: Move Typeable type-rep generation from use site to definition site
by GHC 27 Feb '16

27 Feb '16

#10316: Move Typeable type-rep generation from use site to definition site -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 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: | -------------------------------------+------------------------------------- This ticket is a continuation of #9858. The interim solution for 7.10 was to generate `Typeable` data structures on the fly, as needed in client modules. This ticket is about moving the generation of the runtime representation of type constructors to their definition sites. (#9858 already has too much going on in it, so I started a fresh ticket for this refactoring.) The branch is `wip/T9858-typeable-spj`. In favour of (A) code at use site (as in 7.10): * Pay as you go. No code at all is generated unless you use `Typeable` In favour of (B) code at definition site: * More sharing. We make a `TyCon` (see `Data.Typeable.Internal`) for `T` (say) just once, in the module that defines `T`. * We may ultimately want the `TyCon` for `T` to include its source location, and perhaps more besides. If it is defined in `T` it becomes easier to do that. General observation: (B) is like `Typeable` was before, when it was an ordinary class. The difference now is that all types are `Typeable`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10316> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8710: Overlapping patterns warning misplaced
by GHC 27 Feb '16

27 Feb '16

#8710: Overlapping patterns warning misplaced -------------------------+------------------------------------------------- Reporter: | Owner: goldfire | Status: new Type: bug | Milestone: Priority: low | Version: 7.7 Component: | Operating System: Unknown/Multiple Compiler | Type of failure: Incorrect warning at Keywords: | compile-time Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- Consider {{{ {-# OPTIONS_GHC -fwarn-overlapping-patterns #-} len [] = 0 len (_:t) = 1 + len t len _ = error "urk" }}} GHC reports the problem with this definition at the first line of it. I think it would be more helpful to have it at the last line, which is the pattern that will never match. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8710> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9917: ddump-llvm runs opt/llc even when -fllvm isnt set
by GHC 27 Feb '16

27 Feb '16

#9917: ddump-llvm runs opt/llc even when -fllvm isnt set -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: -------------------------------------+------------------------------------- to reproduce put {{{ main= putStrLn "hello world" }}} in hello.hs and then invoke `ghc hello.hs -O2 -v3 -fforce-recomp -ddump-llvm` then at some point you'll see something like {{{ *** LLVM Optimiser: opt-3.4 /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_2.ll -o /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_4.bc -O2 '--enable-tbaa=true' *** LLVM Compiler: llc-3.4 -O2 '-relocation-model=pic' /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_4.bc -o /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_5.lm_s '--enable-tbaa=true' '-mattr=+sse2' *** LLVM Mangler: }}} in the output -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9917> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10217: Provide link to GPG signature on download page.
by GHC 25 Feb '16

25 Feb '16

#10217: Provide link to GPG signature on download page. -------------------------------------+------------------------------------- Reporter: f-a | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.10.1 Component: | Operating System: Unknown/Multiple Documentation | Type of failure: Documentation Keywords: GPG, | bug signature | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- As now, in the section "Binary packages" of GHC download page, you can read: > SHA-256 hashes for all the binary distributions are available here. with a link to the hashes' file. It would be great to provide a link to the signature of this file too, i.e.: > SHA-256 hashes for all the binary distributions are available here[link] (GPG signature available here[link], signed with key <keyID>). Hashes and Signatures are advertised in the mailing list release post, but I guess it would be nice for clarity's sake having them on the download page too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10217> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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