June 2017 - ghc-tickets

[GHC] #13867: Silly definitions remain after SpecConstr
by GHC 24 Jun '17

24 Jun '17

#13867: Silly definitions remain after SpecConstr -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider this {{{ f x xs = let g y = case y of [] -> 0 (a:as) -> g as in g (x:xs) }}} Compile with -O2 and we get this {{{ f = \ (@ t_axv) (@ a_axw) ($dNum_axx :: Num a_axw) (x_amR :: t_axv) (xs_amS :: [t_axv]) -> let { lvl_sxV [Dmd=<S,U>] :: a_axw [LclId, Str=DmdType] lvl_sxV = fromInteger @ a_axw $dNum_axx Foo.f1 } in letrec { $sg_syr [Occ=LoopBreaker] :: t_axv -> [t_axv] -> a_axw [LclId, Arity=2, Str=DmdType <L,U><L,U>] $sg_syr = \ _ [Occ=Dead] (sc1_syq :: [t_axv]) -> g_sxS sc1_syq; g_sxS [Occ=LoopBreaker] :: [t_axv] -> a_axw [LclId, Arity=1, Str=DmdType <S,1*U>] g_sxS = \ (y_amU :: [t_axv]) -> case y_amU of _ [Occ=Dead] { [] -> lvl_sxV; : a1_amV as_amW -> g_sxS as_amW }; } in $sg_syr x_amR xs_amS }}} Look at that stupid `$sg_syr` function. It should jolly well be inlined at its only call site. But it isn't because it's a loop breaker? Why is it a loop breaker? Because earlier there was a RULE for `g` that mentioned `$sg`. This is stupid. It's not killing us but it is obviously wrong. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13867> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13009: Hierarchical Module Structure for GHC
by GHC 23 Jun '17

23 Jun '17

#13009: Hierarchical Module Structure for GHC -------------------------------------+------------------------------------- Reporter: hsyl20 | Owner: Type: task | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: | ModuleDependencies/Hierarchical -------------------------------------+------------------------------------- Currently GHC's modules are not hierarchical and have very short cryptic names. I would like to revive this 8-year old proposal: https://ghc.haskell.org/trac/ghc/wiki/ModuleDependencies/Hierarchical Pros: * cleaner code base and overall code structure easier to grasp * better integration with other packages when using GHC API * better documentation (cf https://www.stackage.org/lts-7.14/package/ghc-8.0.1) Cons: * break the GHC (plugin) API * may make "rebase" harder during the transition period -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13009> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12379: WARN pragma gives warning `warning: [-Wdeprecations]'
by GHC 23 Jun '17

23 Jun '17

#12379: WARN pragma gives warning `warning: [-Wdeprecations]' -------------------------------------+------------------------------------- Reporter: zilinc | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Incorrect (amd64) | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Example: {{{#!hs -- Warn.hs module Warn where __todo :: String -> a {-# WARNING __todo "TODO" #-} __todo msg = error $ "TODO: " ++ msg }}} {{{#!hs -- Main.hs {- OPTIONS_GHC -Wall #-} import Warn inc :: Int -> Int inc n | n >= 0 = n + 1 inc _ = __todo "what about negatives?" }}} When compile the files (or ghci), I get {{{ UseWarn.hs:9:9: warning: [-Wdeprecations] In the use of ‘__todo’ (imported from Warn): "TODO" }}} Should the flag be `-Wwarnings-deprecations`? And `-Wdeprecations` is not in the user guide, if it is a genuine flag. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12379> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13295: Failure to resolve type parameter determined by type family
by GHC 22 Jun '17

22 Jun '17

#13295: Failure to resolve type parameter determined by type family -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ScopedTypeVariables #-} import Data.Proxy -- Defined to get the type forall x . 'D x data D where D :: a -> D type family F t :: D -- Will try to create values of this type through the type family -- F, i.e. G (F t) data G (d :: D) where G :: G ('D x) -- This is rejected because the type variable x in 'D x is ambiguous. -- But is it really? If there's an instance of F t then x is determined. introG :: Proxy t -> G (F t) introG _ = G -- introG is well-typed if we add an equality constraint. -- Can GHC not figure this out without our help? introG' :: forall t x . ( F t ~ 'D x ) => Proxy t -> G (F t) introG' _ = G }}} Here's the type error: {{{ • Couldn't match type ‘F t’ with ‘'D x0’ Expected type: G (F t) Actual type: G ('D x0) The type variable ‘x0’ is ambiguous • In the expression: G In an equation for ‘introG’: introG _ = G }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13295> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 22 Jun '17

22 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: nakaji_dayo Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by nakaji_dayo): * owner: (none) => nakaji_dayo Comment: I try to implement this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 22 Jun '17

22 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nakaji_dayo): Replying to [comment:19 RyanGlScott]: > We could include this warning under the scope of -Wincomplete-patterns, but I think it's best to keep these two things separate, since one might conceivably wish to disable partial record warnings while still having -Wincomplete-patterns on. I agree. I thought it is safety to separate it. > Yes. The underscore prefix is already an established convention for silencing other warnings. Thanks a lot. I learned.\\ I agree. This rule seems even good in `partial record selector` case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 22 Jun '17

22 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): > `-Wpartial-records` may be unnecessary, Because I think It is same meaning to `-Wincomplete-patterns`. We could include this warning under the scope of `-Wincomplete-patterns`, but I think it's best to keep these two things separate, since one might conceivably wish to disable partial record warnings while still having `-Wincomplete-patterns` on. > It seems useful. But, I do not know if it should affect coding style. > Is there any existing design that control warnings by function (or variable) name? Yes. The underscore prefix is already an established convention for silencing other warnings. For instance, in the code below, GHC will warn about an unused variable `x` in a pattern match: {{{#!hs f x = 42 }}} But GHC will not warn if you prefix `x` with an underscore: {{{#!hs f _x = 42 }}} Similarly, if you have an unused top-level function, GHC will normally warn about it: {{{#!hs module M (a) where a, b :: Int a = 1 b = 2 }}} But not if it's prefixed with an underscore: {{{#!hs module M (a) where a, _b :: Int a = 1 _b = 2 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 22 Jun '17

22 Jun '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nakaji_dayo): RyanGlScott: Thanks for reply and design.\\ I have additional questions. > Introduce a flag for this purpose (proposal: -Wpartial-records) `-Wpartial-records` may be unnecessary, Because I think It is same meaning to `-Wincomplete-patterns`. > One can disable this warning by prefixing the partial record selector with an underscore (e.g., data A = B1 { b :: Int } | B2 { b :: Int, _wat :: Char }). It seems useful. But, I do not know if it should affect coding style.\\ Is there any existing design that control warnings by function (or variable) name? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13859: Bad error message when compacting a Compact#
by GHC 22 Jun '17

22 Jun '17

#13859: Bad error message when compacting a Compact# -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When I run this: {{{ main :: IO () main = do cpt@(Compact cpt# _ _) <- compact (55 :: Int) _ <- compactAdd cpt (MyCompact cpt#) return () data MyCompact = MyCompact Compact# }}} I get this error message: {{{ compaction failed: cannot compact mutable objects }}} This error message is misleading. I don't really know if it makes sense to allow a `Compact#` to be stored in a compact region, but if someone tries to do it, I would rather the error say: {{{ cannot compact Compact# values }}} Or something like that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13859> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13858: Compiling with LaTeX docs on Mint requires additional packages
by GHC 22 Jun '17

22 Jun '17

#13858: Compiling with LaTeX docs on Mint requires additional packages -------------------------------------+------------------------------------- Reporter: HairyDude | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.0.2 Keywords: | Operating System: Linux Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- [[Building/Preparation/Linux]] gives a list of optional packages required for building documentation. Having installed these (following the instructions for Debian on Mint 17.1), I tried to build GHC 8.0.2 from source, and compilation stopped with a LaTeX prompt. I hit enter a few times until `make` exited with an error, resulting in the following being the end of `make`'s output. {{{ cd docs/users_guide/build-pdf/users_guide ; xelatex -halt-on-error users_guide.tex This is XeTeX, Version 3.1415926-2.5-0.9999.3 (TeX Live 2013/Debian) restricted \write18 enabled. entering extended mode (./users_guide.tex LaTeX2e <2011/06/27> Babel <3.9h> and hyphenation patterns for 2 languages loaded. (./sphinxmanual.cls Document Class: sphinxmanual 2009/06/02 Document class (Sphinx manual) (/usr/share/texlive/texmf-dist/tex/latex/base/report.cls Document Class: report 2007/10/19 v1.4h Standard LaTeX document class (/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))) ! LaTeX Error: File `cmap.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: (/usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty (/usr/share/texlive/texmf-dist/tex/latex/base/t1enc.def)) (/usr/share/texlive/texmf-dist/tex/generic/babel/babel.sty (/usr/share/texlive/texmf-dist/tex/generic/babel-english/english.ldf (/usr/share/texlive/texmf-dist/tex/generic/babel/babel.def (/usr/share/texlive/texmf-dist/tex/generic/babel/xebabel.def)))) (/usr/share/texlive/texmf-dist/tex/latex/psnfss/times.sty) (./fncychap.sty) (/usr/share/texlive/texmf-dist/tex/latex/tools/longtable.sty) (./sphinx.sty (/usr/share/texlive/texmf-dist/tex/latex/fancyhdr/fancyhdr.sty) (/usr/share/texlive/texmf-dist/tex/latex/base/textcomp.sty (/usr/share/texlive/texmf-dist/tex/latex/base/ts1enc.def)) ! LaTeX Error: File `fancybox.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: ! LaTeX Error: File `titlesec.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: (./tabulary.sty (/usr/share/texlive/texmf-dist/tex/latex/tools/array.sty)) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsmath.sty For additional information on amsmath, use the `?' option. (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty)) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsbsy.sty) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsopn.sty)) (/usr/share/texlive/texmf-dist/tex/latex/base/makeidx.sty) ! LaTeX Error: File `framed.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: (/usr/share/texlive/texmf-dist/tex/latex/base/ifthen.sty) (/usr/share/texlive/texmf-dist/tex/latex/graphics/color.sty (/usr/share/texlive/texmf-dist/tex/latex/latexconfig/color.cfg) (/usr/share/texlive/texmf-dist/tex/xelatex/xetex-def/xetex.def)) ! LaTeX Error: File `fancyvrb.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: ! LaTeX Error: File `threeparttable.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: ! LaTeX Error: File `footnote.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) Enter file name: ! Undefined control sequence. <recently read> \makesavenoteenv l.28 \makesavenoteenv {tabulary} No pages of output. Transcript written on users_guide.log. make[1]: *** [docs/users_guide/users_guide.pdf] Error 1 make: *** [all] Error 2 }}} The missing files are in the packages {{{texlive-latex-recommended}}} and {{{texlive-latex-extra}}}. I've corrected the wiki page but perhaps {{{configure}}} should test for their presence. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13858> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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