January 2015 - ghc-tickets

[GHC] #9508: Rename package key
by GHC 04 Jan '15

04 Jan '15

#9508: Rename package key -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: backpack | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- We were planning on renaming package key to something different. The two proposals on the table are "package instance" (which I don't like) and "library ID". -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9508> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9954: Required constraints are not inferred for pattern synonyms involving GADTs
by GHC 03 Jan '15

03 Jan '15

#9954: Required constraints are not inferred for pattern synonyms involving GADTs -------------------------------------+------------------------------------- Reporter: cactus | Owner: cactus Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: (Type checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects PatternSynonyms | valid program Architecture: | Blocked By: Unknown/Multiple | Related Tickets: #9953 Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Let's say we have the following setup: {{{#!hs {-# LANGUAGE GADTs, PatternSynonyms, ViewPatterns #-} data T a where MkT1 :: a -> T a MkT2 :: a -> T (Maybe a) f :: (Eq a) => a -> a f = id }}} Then the following definition works as expected: {{{#!hs pattern P1 x <- MkT1 (f -> x) }}} with the following inferred type: {{{ λ» :i P1 pattern P1 :: () => Eq t => t -> T t }}} However, trying to do the same with {{MkT2}} doesn't work: {{{#!hs pattern P2 x <- MkT2 (f -> x) }}} this results in {{{ Could not deduce (Eq a1) arising from a use of ‘f’ from the context (t ~ Maybe a1) bound by a pattern with constructor MkT2 :: forall a. a -> T (Maybe a), in a pattern synonym declaration }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9954> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #481: Recompilation check fails for TH
by GHC 03 Jan '15

03 Jan '15

#481: Recompilation check fails for TH ------------------------------------------------+-------------------------- Reporter: simonpj | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: 7.2.1 Component: Template Haskell | Version: 6.4.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result at runtime | Unknown/Multiple Blocked By: | Test Case: | TH_recompile | Blocking: ------------------------------------------------+-------------------------- Comment (by Edward Z. Yang <ezyang@…>): In [changeset:"af4d99803ea7676f88f250ad56a8c31c1c8cd5bc/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="af4d99803ea7676f88f250ad56a8c31c1c8cd5bc" Don't do a half-hearted recompilation check in compileOne Summary: The isNothing maybe_old_linkable check predates 48bc81ad466edfc80237015dbe5d78ba70eb5095, which fixed #481 by requiring recompilation information to be passed in as an argument to compileOne. As a result, the check here is redundant: the client has already taken a look at the object file to see if it is available or not. Signed-off-by: Edward Z. Yang <ezyang(a)cs.stanford.edu> Test Plan: validate Reviewers: simonmar, austin Subscribers: carter, thomie Differential Revision: https://phabricator.haskell.org/D594 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/481#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9891: Fixity declarations for pattern synonyms not persisted
by GHC 03 Jan '15

03 Jan '15

#9891: Fixity declarations for pattern synonyms not persisted -------------------------------------+------------------------------------- Reporter: klkblake | 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: Incorrect Blocked By: | result at runtime Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- It appears fixity declarations for pattern synonyms only affect modules being compiled in the same run as the module the definition is in. For example, take the following files: Foo.hs: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Foo where data Type = Type Int RawType data RawType = Product Type Type | Num pattern a :*: b <- Type _ (Product a b) infixr 7 :*: }}} Bar.hs: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Main where import Foo value = Type 0 $ Product (Type 1 Num) $ Type 2 $ Product (Type 3 Num) $ Type 4 Num somethingElse = 23 main = case value of _ :*: _ :*: _ -> putStrLn "Success" _ -> putStrLn "Fail" }}} On the first compile, the executable will print "Success". Modifying Bar and recompiling will result in it printing "Fail". Modifying both and recompiling results in "Success" again. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9891> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9495: Do What I Mean RULES for foldr2 look shady
by GHC 02 Jan '15

02 Jan '15

#9495: Do What I Mean RULES for foldr2 look shady -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | crash Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- There's a comment in the source: {{{ The foldr2/right rule isn't exactly right, because it changes the strictness of foldr2 (and thereby zip) E.g. main = print (null (zip nonobviousNil (build undefined))) where nonobviousNil = f 3 f n = if n == 0 then [] else f (n-1) I'm going to leave it though. }}} This rule is intended to allow `foldr2` to fuse with ''either'' argument list. There are thus two problems, one already documented and the other not: 1. The rule can turn working code into non-working code, although this seems to be ''relatively'' unlikely. (The problem the above example is showing is that if the left list ends at the same time the right list bottoms out, the world goes boom. So `foldr2 f [1,2,3,4] (1:2:3:4:undefined)` appears to be a problem. You could argue this is not a big deal, I suppose. 2. The `foldr2/left` and `foldr2/right` rules are not confluent. They are both active in all phases, but if both list arguments are good producers, they will each want to rewrite the expression differently. So if you actually care about which one fuses, you need to explicitly block fusion with one argument using `NOINLINE`, which of course could easily muck up some other optimization. My uninformed opinion: nix the `foldr2/right` rule, and change the documentation to indicate that `foldr2` fuses with its ''left'' argument. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9495> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1480: Template Haskell should allow reification of modules
by GHC 01 Jan '15

01 Jan '15

#1480: Template Haskell should allow reification of modules -------------------------------------+------------------------------------- Reporter: igloo | Owner: Type: feature request | Status: closed Priority: highest | Milestone: 7.8.1 Component: Template Haskell | Version: 7.7 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: 1444 | Blocking: 8398 | Differential Revisions: -------------------------------------+------------------------------------- Changes (by SamB): * related: => 1444 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1480#comment:32> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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