July 2015 - ghc-tickets

[GHC] #9385: Additions to Control.Monad
by GHC 31 Jul '15

31 Jul '15

#9385: Additions to Control.Monad -------------------------------------+------------------------------------- Reporter: olf | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: libraries/base | 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: -------------------------------------+------------------------------------- I'd like to propose the following additions/changes to Control.Monad: `mfilter` can be generalised: {{{#!hs gen_mfilter :: Monad m => (a -> m ()) -> m a -> m a gen_mfilter f ma = (\a -> liftM (const a) (f a)) =<< ma }}} Now we obtain the old `mfilter` as {{{#!hs gen_mfilter.(guard.) }}} Further, `m ()` is a monoid for every monad, which would cause conflicts for `[()]`, to name one example. (The usual monoid instance of `[()]` is addition of natural numbers, while the monadic monoid instance is multiplication.) More generally, the monoid `m ()` acts on every type `m a` in the following way: {{{#!hs mtimes :: Monad m => m () -> m a -> m a mtimes = gen_mfilter.const = liftM2 (flip const) when = mtimes.guard }}} For example, each element of a list can be duplicated like this: {{{#!hs mtimes [(),()] }}} To see why these functions are useful, consider the `DDist` monad of the ProbabilityMonads package: Since `DDist ()` is essentially the monoid of real numbers with multiplication, `gen_mfilter f` updates a distribution by multiplying the weight of `x` by `f x`. Another example is the state monad `ST s`, where type `(a -> ST s ())` is essentially `a -> s -> s`, so these functions encode changes that, when used with `gen_mfilter` alter state, not the value. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9385> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2530: deriving Show adds extra parens for constructor with record syntax
by GHC 31 Jul '15

31 Jul '15

#2530: deriving Show adds extra parens for constructor with record syntax -------------------------------------+------------------------------------- Reporter: spl | Owner: Type: bug | Status: closed Priority: lowest | Milestone: 7.12.1 Component: Compiler | Version: 6.8.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D669 -------------------------------------+------------------------------------- Comment (by nomeata): JFTR if you come across this bug and are worried: A quick test shows that `read . show` still works fine, even if `read` and `show` come from different versions of GHC, in all combinations. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2530#comment:27> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10489: Panic in TcEvidence due to wrong role
by GHC 31 Jul '15

31 Jul '15

#10489: Panic in TcEvidence due to wrong role -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- This single line tickles it: {{{ convert d = let d' = case d of '0' -> '!' in d' }}} produces {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.11.20150604 for x86_64-apple-darwin): ASSERT failed! file compiler/typecheck/TcEvidence.hs line 600 Sym cobox_af8M Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} The failing assertion is about roles. Will look into this tomorrow. Labeling this "highest" because it's a very silly regression. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10489> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2514: Add/Expose Binary API that allows dumping of any GHC Binary instance
by GHC 31 Jul '15

31 Jul '15

#2514: Add/Expose Binary API that allows dumping of any GHC Binary instance -------------------------------------+------------------------------------- Reporter: nominolo | Owner: nominolo Type: feature request | Status: closed Priority: lowest | Milestone: Component: GHC API | Version: 6.9 Resolution: wontfix | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * status: infoneeded => closed * resolution: => wontfix * milestone: 7.12.1 => Comment: No response from submitter, closing this (7 year old) feature request. If you still want this, please follow [wiki:WorkingConventions/AddingFeatures] and reopen. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2514#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4938: Core2 CPU not detected correctly
by GHC 31 Jul '15

31 Jul '15

#4938: Core2 CPU not detected correctly -------------------------------------+------------------------------------- Reporter: altaic | Owner: Type: bug | Status: closed Priority: low | Milestone: Component: Compiler | Version: 7.1 Resolution: worksforme | Keywords: Operating System: MacOS X | Architecture: Type of failure: Building GHC | Unknown/Multiple failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * status: infoneeded => closed * resolution: => worksforme * milestone: 7.12.1 => Comment: Cross-compilation support should be better than it was 4 years ago. Please reopen if you're still having problems. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4938#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10701: -fth-dec-file uses qualified names from hidden modules
by GHC 30 Jul '15

30 Jul '15

#10701: -fth-dec-file uses qualified names from hidden modules -------------------------------------+------------------------------------- Reporter: Fabian | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: TH | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- In cross compilation builds, the current TH situation is a bit of a showstopper. However, much TH code is 'safe' to cross-compile. Before the TH situation is solved, it would be great if GHC could automate as much of the work-around process as possible. -dth-dec-file is a big step on the way to create a non-TH version of the source. However, there are some problems with the generated code. One is that qualified names from hidden modules are used. A instance declaration for Aeson.ToJSON is outputted as follows: {{{#!hs instance Data.Aeson.Types.Class.ToJSON InputDropboxFiles where }}} Ideally, GHC would be able to combine the splice output with the original file, replacing all $() with the corresponding splice, and even generate correct imports. I personally think this would be a great solution to the TH problem. Most cross-compilation projects could just generate the non-TH version with the host GHC, and the few that depends on architecture specific variables can be edited before cross-compiled -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10701> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10702: -fth-dec-file uses qualified names in binding positions
by GHC 30 Jul '15

30 Jul '15

#10702: -fth-dec-file uses qualified names in binding positions -------------------------------------+------------------------------------- Reporter: Fabian | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #10701 Differential Revisions: | -------------------------------------+------------------------------------- {{{#!hs instance Data.Aeson.ToJSON InputDropboxFiles where Data.Aeson.toJSON x@(InputDropboxFiles {}) = Data.Aeson.object (Data.Maybe.catMaybes [Just ((Data.Aeson..=) "root" (inputDropboxFilesRoot x)), Just ((Data.Aeson..=) "path" (inputDropboxFilesPath x)), fmap ((Data.Aeson..=) "rev") (inputDropboxFilesRev x), Just ((Data.Aeson..=) "access_token" (inputDropboxFilesAccess_token x))]) }}} Data.Aeson.toJSON should be toJSON at line 2 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10702> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5333: Arrow command combinators and infixr cause the desugarer to fail
by GHC 30 Jul '15

30 Jul '15

#5333: Arrow command combinators and infixr cause the desugarer to fail -------------------------------------+------------------------------------- Reporter: peteg | Owner: ross Type: bug | Status: closed Priority: low | Milestone: 7.12.1 Component: Compiler | Version: 7.0.3 (Parser) | Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | arrows/should_compile/T5333 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * status: new => closed * testcase: => arrows/should_compile/T5333 * resolution: => fixed Comment: I added the test from the description, and it is currently passing. Please reopen if there is still work to be done here; I didn't quite read the whole discussion. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5333#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9260: Unnecessary error using GHC.TypeLits
by GHC 30 Jul '15

30 Jul '15

#9260: Unnecessary error using GHC.TypeLits -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.2 Keywords: type lits, data | Operating System: Linux kinds, error message | Type of failure: Incorrect Architecture: Unknown/Multiple | warning at compile-time Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- Compiling: {{{ {-# LANGUAGE DataKinds, TypeOperators, GADTs #-} module Error where import GHC.TypeLits data Fin n where Fzero :: Fin (n + 1) Fsucc :: Fin n -> Fin (n + 1) }}} gives a strange (unnecessary) error message claiming that `Fin 1` doesn't match the expected type `Fin (0 + 1)`: {{{ % ghc --version The Glorious Glasgow Haskell Compilation System, version 7.8.2 % ghc -ignore-dot-ghci /tmp/Error.hs [1 of 1] Compiling Error ( /tmp/Error.hs, /tmp/Error.o ) /tmp/Error.hs:12:8: Couldn't match type ‘0’ with ‘1’ Expected type: Fin 1 Actual type: Fin (0 + 1) In the expression: Fsucc Fzero In an equation for ‘test’: test = Fsucc Fzero /tmp/Error.hs:12:14: Couldn't match type ‘1’ with ‘0’ Expected type: Fin 0 Actual type: Fin (0 + 1) In the first argument of ‘Fsucc’, namely ‘Fzero’ In the expression: Fsucc Fzero % }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9260> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8034: Missing ambiguity test for class methods
by GHC 30 Jul '15

30 Jul '15

#8034: Missing ambiguity test for class methods -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.12.1 Component: Compiler (Type | Version: 7.7 checker) | Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | typecheck/should_fail/T8034 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * testcase: => typecheck/should_fail/T8034 * status: new => closed * resolution: => fixed -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8034#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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