June 2014 - ghc-tickets

[GHC] #9061: Warnings for redundant imports doesn't take name shadowing into account (Regression)
by GHC 23 Jun '14

23 Jun '14

#9061: Warnings for redundant imports doesn't take name shadowing into account (Regression) -------------------------+------------------------------------------------- Reporter: | Owner: bergmark | Status: new Type: bug | Milestone: Priority: | Version: 7.8.2 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: | -------------------------+------------------------------------------------- Reproduction: {{{ module Log where import Prelude hiding (log) f :: () f = log where log = () }}} Compiling this with -Wall On GHC 7.8.2: {{{ > ghc Log.hs -Wall [1 of 1] Compiling Log ( Log.hs, Log.o ) Log.hs:3:1: Warning: The import of ‘Prelude’ is redundant except perhaps to import instances from ‘Prelude’ To import instances alone, use: import Prelude() }}} The suggestion is incorrect since removing the import statement gives the following warning: {{{ Log.hs:4:15: Warning: This binding for ‘log’ shadows the existing binding imported from ‘Prelude’ at Log.hs:1:8-10 (and originally defined in ‘GHC.Float’) }}} On GHC 7.6.3 the Reproduction does not give any warnings (which is correct). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9061> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9128: Possible bug in strictness analyzer when where clause declared NOINLINE
by GHC 23 Jun '14

23 Jun '14

#9128: Possible bug in strictness analyzer when where clause declared NOINLINE -----------------------------------------+--------------------------------- Reporter: aalevy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: strictness bytestring | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | crash Related Tickets: | Test Case: | Blocking: -----------------------------------------+--------------------------------- I've encountered the following error message using a relatively straight forward library that wraps postgresql-simple in certain edge cases: {{{ *** Exception: Oops! Entered absent arg a_sYDl{v} [lid] bytestring-0.10.4.0:Data.ByteString.Internal.ByteString{tc r5T} }}} This happens on an invocation of a function, `dbSelect` under certain compilation conditions: {{{ dbSelect :: (Model a) => Connection -> DBSelect a -> IO [a] {-# INLINE #-} dbSelect conn dbs = map lookupRow <$> query_ conn q where {-# NOINLINE #-} q = renderDBSelect dbs }}} A DBSelect is just a data-structure with different `Query` (wrapper around strict bytestring) fields for clauses in a SQL select query. `renderDBSelect` generates a single `Query` value from the DBSelect (by way of contructing a Blaze.Builder as an intermediate step). When compiled with no optimizations, this works fine, no issues. With -O1, I get the error above. The errors goes away, if I compile with -fno- strictness or remove the NOINLINE *or* INLINE pragmas. We've worked around this for now in the library by removgin the NOINLINE pragmas, but tracking this down it seems like the strictness analyzer might be falsly assuming `q` is never actually evaluated. For reference, this is a commit that still exhibits the bug: https://github.com/alevy/postgresql- orm/tree/93075d56ae5ffeb8f80ecc8c01436713c2656a6b I've also attached a small test application that excercises the bug. Because of how the library sets up a scratch database, the test application requires postgres and pg_ctl to be available in the path. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9128> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9096: GADT definition not accepted in prefix notation
by GHC 23 Jun '14

23 Jun '14

#9096: GADT definition not accepted in prefix notation ------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- Brian Nguyen writes on haskell-cafe: The following does not work: {{{ data Foo a where {Foo :: (->) a (Foo a)} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9096> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9115: The kind of (=>)
by GHC 23 Jun '14

23 Jun '14

#9115: The kind of (=>) ------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- This is mainly a request for clarification, and not very important. Is there any good (theoretical, implementation, practical, ...) reason why (with `ConstraintKinds`) enabled, the `=>` symbol on the type-level is still treated as a built-in syntactic construct rather than a type-level operator with {{{ GHCi> :kind (=>) (=>) :: Constraint -> * -> * }}} Note that I'm not actually proposing to make it re-definable, but to treat it similarly to the `(->)` type operator. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9115> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6018: Injective type families
by GHC 22 Jun '14

22 Jun '14

#6018: Injective type families -------------------------------+------------------------------------------- Reporter: lunaris | Owner: simonpj Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.4.1 Component: Compiler | Keywords: TypeFamilies, Injective Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #4259 None/Unknown | Test Case: | Blocking: | -------------------------------+------------------------------------------- Changes (by ekmett): * cc: ekmett@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6018#comment:31> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8146: Library package cannot be found
by GHC 20 Jun '14

20 Jun '14

#8146: Library package cannot be found --------------------------------+------------------------------------------ Reporter: conradwt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Installing GHC failed Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | --------------------------------+------------------------------------------ {{{ ./sync-all get warning: libffi-tarballs already present; omitting == libffi-tarballs: running git config --local core.ignorecase true warning: utils/hsc2hs already present; omitting == utils/hsc2hs: running git config --local core.ignorecase true warning: utils/haddock already present; omitting == utils/haddock: running git config --local core.ignorecase true == running git clone https://github.com/ghc/packages/array.git libraries/array Cloning into 'libraries/array'... fatal: repository 'https://github.com/ghc/packages/array.git/' not found git failed: 32768 at ./sync-all line 119. == Checking for old haddock repo == Checking for old binary repo == Checking for old mtl repo == Checking for old Cabal repo == Checking for old time from tar ball }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8146> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8667: sync-all doesn't work properly if you run from a fork on github
by GHC 20 Jun '14

20 Jun '14

#8667: sync-all doesn't work properly if you run from a fork on github ------------------------------------+------------------------------------- Reporter: schyler | Owner: hvr Type: bug | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The intuitive behaviour when working with projects on github is to make your own fork so that you can use the online interface (or GitHub for {windows,osx} apps). One would assume that this behaviour was endorsed because of the ~130 forks to the ghc repo, however forking the repo actually causes ./sync-all to stop working (it asks for a username and password to whomever@ github.com) It seems the only way for a person to work with the project from github is to clone directly from the original repo. This sounds like a bug. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8667> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9216: hiding imports doesn't seem to check if an import exists
by GHC 20 Jun '14

20 Jun '14

#9216: hiding imports doesn't seem to check if an import exists --------------------------+------------------------------------------------ Reporter: flazz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.6.3 Compiler | Operating System: Unknown/Multiple Keywords: import | Type of failure: GHC accepts invalid program hiding | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | --------------------------+------------------------------------------------ {{{ module Main where import Prelude hiding (thisDoesNotExist0x1234) -- should it fail here? main = putStrLn "hiya" }}} This seems to interpret just fine in ghci and compile fine in ghc – it seems that it shouldn't. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9216> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9206: OverloadedString breaks show?
by GHC 20 Jun '14

20 Jun '14

#9206: OverloadedString breaks show? ------------------------------------+------------------------------------- Reporter: j80JjBjVNRMajmA | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- The file `test.hs` contains {{{ import GHC.Exts main = putStrLn $ show (fromString "01") }}} and results in: `ghc -XNoOverloadedStrings test.hs` {{{ overloadedString.hs:4:20: No instance for (Show a0) arising from a use of ‘show’ The type variable ‘a0’ is ambiguous Note: there are several potential instances: instance Show Double -- Defined in ‘GHC.Float’ instance Show Float -- Defined in ‘GHC.Float’ instance (Integral a, Show a) => Show (GHC.Real.Ratio a) -- Defined in ‘GHC.Real’ ...plus 44 others In the second argument of ‘($)’, namely ‘show (fromString "01")’ In the expression: putStrLn $ show (fromString "01") In an equation for ‘main’: main = putStrLn $ show (fromString "01") overloadedString.hs:4:26: No instance for (IsString a0) arising from a use of ‘fromString’ The type variable ‘a0’ is ambiguous Note: there is a potential instance available: instance IsString [Char] -- Defined in ‘Data.String’ In the first argument of ‘show’, namely ‘(fromString "01")’ In the second argument of ‘($)’, namely ‘show (fromString "01")’ In the expression: putStrLn $ show (fromString "01") }}} OverloadedStrings breaks things (by making them magically work, which is probably why nobody complained?) `ghc -XOverloadedStrings -e main test.hs` {{{ "01" }}} and another `test2.hs`: {{{ import GHC.Exts instance IsString Double where fromString = read main = putStrLn $ show (fromString "01") }}} `ghc -XOverloadedStrings -e main test2.hs` {{{ "1.0" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9206> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1475: Adding imports and exports with Template Haskell
by GHC 19 Jun '14

19 Jun '14

#1475: Adding imports and exports with Template Haskell -------------------------------------+------------------------------------ Reporter: igloo | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Template Haskell | Version: 6.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by goldfire): I still want it. `singletons` generates gobs of boilerplate, some of which it is important to export. It's not terribly hard for users to write the export lists manually, but it's just more boilerplate that would be nice to automate. However, for my use case, I care only about TH writing to ''export'' lists, not ''import'' lists. TH-controlled export lists wouldn't hit the problem SPJ points out in comment:18. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1475#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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