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[GHC] #15014: Exhaustivity check should suggest when COMPLETE could be helpful
by GHC 08 Apr '18

08 Apr '18

#15014: Exhaustivity check should suggest when COMPLETE could be helpful -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.3 Component: Compiler | Version: 8.5 (Type checker) | Keywords: | Operating System: Unknown/Multiple PatternSynonyms, | PatternMatchWarnings | Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ MacBook-Pro-97:ghc ezyang$ cat A.hs {-# LANGUAGE PatternSynonyms #-} module A where pattern F :: a -> b -> (a, b) pattern F x y = (x, y) g :: (a, b) -> (a, b) g (F x y) = (x, y) MacBook-Pro-97:ghc ezyang$ inplace/bin/ghc-stage2 -c A.hs -Wall -fforce- recomp A.hs:8:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘g’: Patterns not matched: _ | 8 | g (F x y) = (x, y) | ^^^^^^^^^^^^^^^^^^ MacBook-Pro-97:ghc ezyang$ inplace/bin/ghc-stage2 --version The Glorious Glasgow Haskell Compilation System, version 8.5.20180304 }}} Any time the exhaustiveness checker throws up its hands and says that `_` is not matched, we ought to give a hint that this may have occurred due to pattern synonyms, and that the author of the pattern synonyms can help out by specifying a COMPLETE pragma. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15014> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15013: Building nofib using llvm and HEAD fails
by GHC 08 Apr '18

08 Apr '18

#15013: Building nofib using llvm and HEAD fails -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.2 Component: Compiler | Version: (LLVM) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ == make all ; in /home/Andi/ghc_head/nofib/shootout/pidigits ------------------------------------------------------------------------ HC = /home/Andi/ghc_head/inplace/bin/ghc-stage2 HC_OPTS = -O2 -Rghc-timing -H32m -hisuf hi -fllvm -rtsopts -O2 RUNTEST_OPTS = -ghc-timing ==nofib== pidigits: time to compile Main follows... /home/Andi/ghc_head/inplace/bin/ghc-stage2 -O2 -Rghc-timing -H32m -hisuf hi -fllvm -rtsopts -O2 -c Main.hs -o Main.o ghc-stage2.exe: panic! (the 'impossible' happened) (GHC version 8.5.20180401 for x86_64-unknown-mingw32): Each block should be reachable from only one ProcPoint Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug <<ghc: 506688344 bytes, 156 GCs, 7738569/16639872 avg/max bytes residency (5 samples), 37M in use, 0.000 INIT (0.000 elapsed), 0.344 MUT (0.333 elapsed), 0.062 GC (0.112 elapsed) :ghc>> make[1]: *** [../../mk/suffix.mk:23: Main.o] Error 1 Failed making all in pidigits: 1 make: *** [../mk/ghc-recurse.mk:69: all] Error 1 $ opt --version LLVM (http://llvm.org/) LLVM version 5.0.1 Optimized build. Default target: x86_64-w64-windows-gnu Host CPU: skylake }}} This is on commit 8b823f270e53627ddca1a993c05f1ab556742d96 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15013> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15011: Automate update of VersionHistory table
by GHC 07 Apr '18

07 Apr '18

#15011: Automate update of VersionHistory table -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Continuous | Version: 8.2.2 Integration | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- wiki:Commentary/Libraries/VersionHistory should really be updated automatically from CI builds. This is currently generated manually with https://github.com/bgamari/ghc-utils/tree/master/library-versions. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15011> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1965: Allow unconstrained existential contexts in newtypes
by GHC 07 Apr '18

07 Apr '18

#1965: Allow unconstrained existential contexts in newtypes -------------------------------------+------------------------------------- Reporter: guest | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 6.8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by glaebhoerl): * cc: glaebhoerl (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1965#comment:36> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12891: Automate symbols inclusion in RtsSymbols.c from Rts.h
by GHC 07 Apr '18

07 Apr '18

#12891: Automate symbols inclusion in RtsSymbols.c from Rts.h -------------------------------------+------------------------------------- Reporter: Phyx- | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.0.1 Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #12846 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Public symbols that we export in the public headers (rooted from Rts.h) need to be added to the symbols table of the RTS. We currently do this by hand but the list can quickly grow out of sync. Investigate a way to automate either the inclusion or a check during build time. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12891> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14238: `:kind` suppresses visible dependent quantifiers by default in GHCi 8.2.1
by GHC 07 Apr '18

07 Apr '18

#14238: `:kind` suppresses visible dependent quantifiers by default in GHCi 8.2.1 -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Load this program into GHCi on 8.2.1 or later: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} import Data.Kind data Foo (k :: Type) :: k -> Type where MkFoo :: Foo (k1 -> k2) f -> Foo k1 a -> Foo k2 (f a) }}} And ask it what the kind of `Foo` is: {{{ GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Main ( Bug.hs, interpreted ) Ok, 1 module loaded. λ> :k Foo Foo :: k -> * }}} This is just plain wrong: the actual kind of `Foo` should be `forall k -> k -> *`. Normally, one can omit `forall`s from a kind signature, but this is a special case where we're using a //visible// forall. In other words, `forall k -> k -> *` is not the same as `k -> *`, as the former takes two arguments, whereas the latter takes one. A workaround is to force GHCi to come to its senses by explicitly enabling `-fprint-explicit-foralls`: {{{ λ> :set -fprint-explicit-foralls λ> :k Foo Foo :: forall k -> k -> * }}} This is actually a regression since GHC 8.0.2, since GHCi did the right thing by default then: {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Main ( Bug.hs, interpreted ) Ok, modules loaded: Main. λ> :k Foo Foo :: forall k -> k -> Type }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14238> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14089: Segmentation fault/access violation using Yesod and Postgresql
by GHC 07 Apr '18

07 Apr '18

#14089: Segmentation fault/access violation using Yesod and Postgresql --------------------------------------+--------------------------------- Reporter: Burtannia | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- When trying to build a Yesod site with Postgresql I got the following: I tried to use PostgreSQL and got the following: website-0.0.0: configure (lib) Configuring website-0.0.0... website-0.0.0: build (lib) Preprocessing library website-0.0.0... [ 1 of 11] Compiling Settings ( src\Settings.hs, .stack- work\dist\ca59d0ab\build\Settings.o ) [ 2 of 11] Compiling Settings.StaticFiles ( src\Settings\StaticFiles.hs, .stack-work\dist\ca59d0ab\build\Settings\StaticFiles.o ) Segmentation fault/access violation in generated code -- While building package website-0.0.0 using: C:\sr\setup-exe-cache\x86_64-windows\Cabal- simple_Z6RU0evB_1.24.2.0_ghc-8.0.2.exe --builddir=.stack- work\dist\ca59d0ab build lib:website --ghc-options " -ddump-hi -ddump-to- file" Process exited with code: ExitFailure 1 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14089> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15004: Building HEAD fails with -j3 because of unrecorded dependencies.
by GHC 06 Apr '18

06 Apr '18

#15004: Building HEAD fails with -j3 because of unrecorded dependencies. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- There seem to be some missing dependencies. {{{ "inplace/bin/ghc-stage1" -hisuf hi -osuf o -hcsuf hc -static -O -H64m -Wall -this-unit-id ghc-prim-0.5.2.0 -hide-all-packages -i -ilibraries/ghc-prim/. -ilibraries/ghc-prim/dist-install/build -Ilibraries /ghc-prim/dist-install/build -ilibraries/ghc-prim/dist- install/build/./autogen -Ilibraries/ghc-prim/dist-install/build/./autogen -Ilibraries/ghc-prim/. -optP-include -optPlibraries/ghc-prim/dist- install/build/./autogen/cabal_macros.h -package-id rts -this-unit-id ghc- prim -XHaskell2010 -O2 -no-user-package-db -rtsopts -Wno-trustworthy- safe -Wno-deprecated-flags -Wnoncanonical-monad-instances -odir libraries/ghc-prim/dist-install/build -hidir libraries/ghc-prim/dist- install/build -stubdir libraries/ghc-prim/dist-install/build -dynamic- too -c libraries/ghc-prim/./GHC/Magic.hs -o libraries/ghc-prim/dist- install/build/GHC/Magic.o -dyno libraries/ghc-prim/dist- install/build/GHC/Magic.dyn_o libraries/base/GHC/IO.hs-boot:9:12: error: • Failed to load interface for ‘GHC.Integer.Type’ There are files missing in the ‘integer-gmp-1.0.1.0’ package, try running 'ghc-pkg check'. Use -v to see a list of the files searched for. • In the type signature: mplusIO :: IO a -> IO a -> IO a | 9 | mplusIO :: IO a -> IO a -> IO a | ^^^^^^^^^^^^^^^^^^^^ }}} It seems Magic.hs depends in integer-gmp. Which happened to be not yet built so it fails. I'm not sure which import it is that is missing but recording it here. Commit for head is 72b5f649ede82ab3bb429aa72ee1c572f415b0eb Building single threaded for a while and then continuing the build with -j3 seems to be a valid workaround. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15004> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11815: Data.List: Add a function to get consecutive elements (mapConsecutives)
by GHC 06 Apr '18

06 Apr '18

#11815: Data.List: Add a function to get consecutive elements (mapConsecutives) -------------------------------------+------------------------------------- Reporter: holmisen | Owner: Type: feature | Status: new request | Priority: low | Milestone: Component: | Version: libraries/base | 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: -------------------------------------+------------------------------------- A recurring pattern is to get a list of all consecutive elements of a list, for further processing. I propose adding the following function to `Data.List` for this: {{{ mapConsecutives :: (a -> a -> b) -> [a] -> [b] mapConsecutives _ [] = [] mapConsecutives f xs = zipWith f xs (tail xs) }}} Since it requires pattern matching, to separate the empty case, it is not practical to inline at each use site. Sidenote: A similar function `mapAdjacent` is available in the `utility- ht` library (with a partial implementation(!)) [1]. I realise that `Data.List` is often imported unqualified and hence additions may cause trouble. I would have raised this on the libraries mailing list first, but the guidelines for proposals pointed me here. [1] http://hackage.haskell.org/package/utility-ht-0.0.11/docs/Data-List- HT.html#v:mapAdjacent -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11815> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14951: SpecContsr needs two runs when one should suffice
by GHC 06 Apr '18

06 Apr '18

#14951: SpecContsr needs two runs when one should suffice -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: SpecConstr | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #14844 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is a spin-off of #14844, which is a spin-off of #14068, but applies on its own. Consider this code: {{{ module T14844Example (topLvl) where topLvl large = (bar1, bar2, foo) where foo :: Integer -> (a -> b -> Bool) -> (a,b) -> Bool foo 0 _ _ = False foo s f t = l s' t where l 0 t = False l 1 t = case t of (x,y) -> f x y l n (x,y) = l (n-1) (x,y) s' = large s bar1 :: Integer -> (a -> b -> Bool) -> a -> b -> Bool bar1 s f x y = foo s f (x,y) bar2 :: Integer -> (a -> b -> Bool) -> a -> b -> Bool bar2 s f x y = foo (s + 1) f (x,y) }}} Status quo: `l` gets specialized, because of the two call patterns `s' t0` and `(s-1) (x,y)`, the second one is interesting *and* its second argument gets scrutinized (the `scu_occs` field reports `ScrutOcc` for `t`). But `foo` does not get specialized: It does have an interesting call pattern, but `scu_occs` reports `UnkOcc`, because `foo`’s parameters are just passed to `t`. But: When we decide to !SpecConstr `l`, we know that one of the calls to `l` is of the shape `s' t0`. This is a boring call, and we do not create a specialization for it. But we create a specialization for `l` using the the other call pattern. This means we know that it would be beneficial if `t0` were a constructor. So can we, at this point, decide to include `t0 ↦ ScrutOcc` in `scu_occs`? First experiments look good, so I am working on this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14951> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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