November 2018 - ghc-tickets

Re: [GHC] #4505: Segmentation fault on long input (list of pairs)
by GHC 14 Nov '18

14 Nov '18

#4505: Segmentation fault on long input (list of pairs) -------------------------------------+------------------------------------- Reporter: cathper | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.0.1 Resolution: | Keywords: Segmentation | fault, segfault, long input Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: GHC rejects | (amd64) valid program | Test Case: Blocked By: 4258 | Blocking: Related Tickets: | Differential Rev(s): Phab:D1180 Wiki Page: | -------------------------------------+------------------------------------- Comment (by michaelpj): I ran into this recently when attempting to embed some static data into a program from a Core plugin. Having found http://hackage.haskell.org/package/ghc-8.4.3/docs/MkCore.html#v:mkWordExpr I thought I could sneak a bytestring in as a list of word expressions - which triggered this issue when the list got long enough. Again, this does only trigger when compiling without -O, but people do occasionally do that. I worked around it by essentially mimicing what `fileEmbed` does to make a bytestring literal in TH (http://hackage.haskell.org/package/file- embed-0.0.11/docs/src/Data.FileEmbed.html#bsToExp), but this is somewhat clumsy as you have to rely on having the `ByteString` names around. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4505#comment:53> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15893: View Patterns affect typechecking in an unpredictable manner
by GHC 14 Nov '18

14 Nov '18

#15893: View Patterns affect typechecking in an unpredictable manner -------------------------------------+------------------------------------- Reporter: theindigamer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 8.4.3 Keywords: ViewPatterns | 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: -------------------------------------+------------------------------------- Copying the text from my [https://stackoverflow.com/questions/53294823 /viewpatterns-affects-typechecking-in-an-unpredictable-manner StackOverflow question]. {{{ {-# LANGUAGE ViewPatterns #-} import Data.Text (Text) import qualified Data.Text as T import qualified Data.Vector.Unboxed as UV import qualified Data.Vector.Generic as V bar :: Int -> UV.Vector Char -> (Text, Text) bar i v = (t_pre, t_post) where f = T.pack . V.toList (f -> t_pre, f -> t_post) = V.splitAt i v }}} This gives an unexpected type error (tested with GHC 8.4.3), concerning ambiguous type variables and `f` being out of scope. {{{ • Ambiguous type variable ‘v0’ arising from a use of ‘V.toList’ prevents the constraint ‘(V.Vector v0 Char)’ from being solved. Relevant bindings include f :: v0 Char -> Text (bound at Weird.hs:11:5) Probable fix: use a type annotation to specify what ‘v0’ should be. These potential instances exist: instance V.Vector UV.Vector Char -- Defined in ‘Data.Vector.Unboxed.Base’ ...plus one instance involving out-of-scope types instance primitive-0.6.3.0:Data.Primitive.Types.Prim a => V.Vector Data.Vector.Primitive.Vector a -- Defined in ‘Data.Vector.Primitive’ • In the second argument of ‘(.)’, namely ‘V.toList’ In the expression: T.pack . V.toList In an equation for ‘f’: f = T.pack . V.toList | 11 | f = T.pack . V.toList | ^^^^^^^^ Weird.hs:13:6: error: Variable not in scope: f :: UV.Vector Char -> t | 13 | (f -> t_pre, f -> t_post) = V.splitAt i v | ^ Weird.hs:13:18: error: Variable not in scope: f :: UV.Vector Char -> t1 | 13 | (f -> t_pre, f -> t_post) = V.splitAt i v | ^ }}} Some of the other answers on SO have done some digging (e.g. enabling FlexibleContexts / NoMonomorphismRestriction doesn't solve the issue). I haven't yet figured out how to minimize the example further to remove the dependency on Vector... Is this a compiler bug or a documentation bug? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15893> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14293: View patterns with locally defined functions in restructuring don't compile
by GHC 14 Nov '18

14 Nov '18

#14293: View patterns with locally defined functions in restructuring don't compile -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE ViewPatterns #-} foo x = x Just (id -> res) = pure 'a' -- WORKS Just (foo -> res') = pure 'a' -- FAILS bar (foo -> res) = res -- WORKS {- [1 of 1] Compiling Main ( T14293.hs, interpreted ) T14293.hs:6:7-9: error: Variable not in scope: foo :: Char -> t | 6 | Just (foo -> res') = pure 'a' | ^^^ Failed, 0 modules loaded. -} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14293> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13114: UniqSet definition seems shady
by GHC 13 Nov '18

13 Nov '18

#13114: UniqSet definition seems shady -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: task | Status: new Priority: low | Milestone: 8.4.1 Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- Currently, {{{#!hs type UniqSet a = UniqFM a }}} The key invariant of `UniqSet` is expressed in the somewhat-poorly-named `Note [Unsound mapUniqSet]`, and not enforced by the types. It seems likely that the clean thing is {{{#!hs newtype UniqSet a = US (UniqFM a) }}} Unfortunately there's an awful lot of code using `UniqSet` and assuming it's the same as `UniqFM`. To make this work, we'd need to expand the `UniqSet` API somewhat and figure out what to do at use sites using it interchangeably with `UniqFM`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13114> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15832: returnIO/bindIO destroys runtime explicit stack information in some cases
by GHC 12 Nov '18

12 Nov '18

#15832: returnIO/bindIO destroys runtime explicit stack information in some cases -------------------------------------+------------------------------------- Reporter: infinity0 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- Tested in GHC 8.2.2, 8.4.3 and 8.6.1: Test-good.hs {{{#!hs import GHC.Base data X = X Int deriving (Eq, Show) main :: IO () main = (returnIO undefined) `bindIO` (const (print $ X (error "XXX"))) }}} Test-bad.hs {{{#!hs import GHC.Base data X = X Int deriving (Eq, Show) main :: IO () main = (returnIO undefined) `bindIO` (\_ -> (print $ X (error "XXX"))) }}} build.sh {{{#!shell #!/bin/sh set -e p="${1:-stg}" for i in good bad; do rm -rf ghc*_* Test-$i Test-$i.dump-* Test-$i.hi Test-$i.o ghc "-ddump-$p" -dsuppress-module-prefixes -dsuppress-uniques \ -keep-tmp-files -dumpdir . -ddump-to-file \ -fno-cse -prof -fprof-auto -fprof-auto-calls -fprof-cafs \ -dinitial-unique=0 -dunique-increment=1 \ Test-$i.hs ./Test-$i +RTS -xc || true done colordiff -ruw Test-*.dump-"$p" | less -R }}} Running `sh build.sh` gives the following output: {{{ [1 of 1] Compiling Main ( Test-good.hs, Test-good.o ) Linking Test-good ... *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Main.main, called from Main.main, called from Main.main, called from Main.main, called from Main.main, called from Main.CAF:main --> evaluated by: Main.main, called from Main.main, called from Main.main, called from Main.CAF:main --> evaluated by: Main.main, called from Main.main, called from Main.main Test-good: XXX CallStack (from HasCallStack): error, called at Test-good.hs:6:57 in main:Main CallStack (from -prof): Main.main (Test-good.hs:6:57-67) Main.main (Test-good.hs:6:54-68) Main.main (Test-good.hs:6:46-68) Main.main (Test-good.hs:6:39-69) Main.main (Test-good.hs:6:8-70) Main.CAF:main (Test-good.hs:6:1-4) [1 of 1] Compiling Main ( Test-bad.hs, Test-bad.o ) Linking Test-bad ... *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Main.main, called from Main.main, called from Main.main, called from Main.main Test-bad: XXX CallStack (from HasCallStack): error, called at Test-bad.hs:6:57 in main:Main CallStack (from -prof): Main.main (Test-bad.hs:6:57-67) Main.main (Test-bad.hs:6:54-68) Main.main (Test-bad.hs:6:46-68) Main.main (Test-bad.hs:6:8-70) }}} As you can see, in Test-bad.hs all the entries below "evaluated by" are missing. I am not familiar with STG output, but running the script also shows you a diff of the STG dump. It seems innocent enough. Running `sh build.sh cmm` shows many more differences. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15832> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15054: ghc internal error appeared in GHCI
by GHC 12 Nov '18

12 Nov '18

#15054: ghc internal error appeared in GHCI -------------------------------------+------------------------------------- Reporter: radrow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: GHCi | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- After playing with vectors in ghci I got following error: {{{ ghc: internal error: Unable to commit 1048576 bytes of memory }}} It happened randomly, on empty prompt while no query was being evaluated I am using latest version of GHC on Arch Linux Here is my whole session: {{{ >λ= import Criterion Criterion Criterion.IO.Printf Criterion.Main.Options Criterion.Report Criterion.Analysis Criterion.Internal Criterion.Measurement Criterion.Types Criterion.IO Criterion.Main Criterion.Monad >λ= import Criterion.Main >λ= import Data.Vector >λ= import Data.Vector as V >λ= main = default defaultConfig defaultMain defaultMainWith >λ= defaultMain [bench "TESTXD" $ whnf ([1..100000]!!) 9999] benchmarking TESTXD time 19.81 μs (19.66 μs .. 19.99 μs) 0.999 R² (0.999 R² .. 1.000 R²) mean 13.47 μs (12.93 μs .. 14.11 μs) std dev 853.8 ns (542.7 ns .. 1.249 μs) variance introduced by outliers: 65% (severely inflated) >λ= defaultMain [bench "TESTXD" $ whnf ([1..100000]!!) 9999] benchmarking TESTXD time 19.62 μs (19.39 μs .. 19.99 μs) 0.999 R² (0.998 R² .. 1.000 R²) mean 13.49 μs (12.85 μs .. 14.51 μs) std dev 1.154 μs (524.9 ns .. 1.704 μs) variance introduced by outliers: 77% (severely inflated) >λ= v = V.fromList [1..100000] Display all 192 possibilities? (y or n) V.! V.fold1M' V.indexed V.prescanl V.unsafeDrop V.!? V.fold1M'_ V.init V.prescanl' V.unsafeFreeze V.++ V.fold1M_ V.iscanl V.prescanr V.unsafeHead V.// V.foldM V.iscanl' V.prescanr' V.unsafeHeadM V.MVector V.foldM' V.iscanr V.product V.unsafeIndex V.Vector V.foldM'_ V.iscanr' V.replicate V.unsafeIndexM V.accum V.foldM_ V.iterateN V.replicateM V.unsafeInit V.accumulate V.foldl V.iterateNM V.reverse V.unsafeLast V.accumulate_ V.foldl' V.izipWith V.scanl V.unsafeLastM V.all V.foldl1 V.izipWith3 V.scanl' V.unsafeSlice V.and V.foldl1' V.izipWith4 V.scanl1 V.unsafeTail V.any V.foldr V.izipWith5 V.scanl1' V.unsafeTake V.backpermute V.foldr' V.izipWith6 V.scanr V.unsafeThaw V.break V.foldr1 V.izipWithM V.scanr' V.unsafeUpd V.concat V.foldr1' V.izipWithM_ V.scanr1 V.unsafeUpdate V.concatMap V.forM V.last V.scanr1' V.unsafeUpdate_ V.cons V.forM_ V.lastM V.sequence V.unstablePartition V.constructN V.force V.length V.sequence_ V.unzip V.constructrN V.freeze V.map V.singleton V.unzip3 V.convert V.fromList V.mapM V.slice V.unzip4 V.copy V.fromListN V.mapM_ V.snoc V.unzip5 V.create V.generate V.mapMaybe V.span V.unzip6 V.createT V.generateM V.maxIndex V.splitAt V.update V.drop V.head V.maxIndexBy V.sum V.update_ V.dropWhile V.headM V.maximum V.tail V.zip V.elem V.ifilter V.maximumBy V.take V.zip3 V.elemIndex V.ifoldM V.minIndex V.takeWhile V.zip4 V.elemIndices V.ifoldM' V.minIndexBy V.thaw V.zip5 V.empty V.ifoldM'_ V.minimum V.toList V.zip6 V.enumFromN V.ifoldM_ V.minimumBy V.unfoldr V.zipWith V.enumFromStepN V.ifoldl V.modify V.unfoldrM V.zipWith3 V.enumFromThenTo V.ifoldl' V.notElem V.unfoldrN V.zipWith4 V.enumFromTo V.ifoldr V.null V.unfoldrNM V.zipWith5 V.filter V.ifoldr' V.or V.uniq V.zipWith6 V.filterM V.imap V.partition V.unsafeAccum V.zipWithM V.find V.imapM V.postscanl V.unsafeAccumulate V.zipWithM_ V.findIndex V.imapM_ V.postscanl' V.unsafeAccumulate_ V.findIndices V.imapMaybe V.postscanr V.unsafeBackpermute V.fold1M V.indexM V.postscanr' V.unsafeCopy >λ= defaultMain [bench "TESTXD" $ whnf ([1..100000]!!) 9999, bench "TESTV" $ whnf (\x -> (V.!) v x)] <interactive>:8:93: error: parse error (possibly incorrect indentation or mismatched brackets) ] λ= defaultMain [bench "TESTXD" $ whnf ([1..100000]!!) 9999, bench "TESTV" $ whnf (\x -> (V.!) v x) <interactive>:9:74: error: • Couldn't match expected type ‘Benchmarkable’ with actual type ‘Int -> Benchmarkable’ • Probable cause: ‘whnf’ is applied to too few arguments In the second argument of ‘($)’, namely ‘whnf (\ x -> (!) v x)’ In the expression: bench "TESTV" $ whnf (\ x -> (!) v x) In the first argument of ‘defaultMain’, namely ‘[bench "TESTXD" $ whnf ([1 .. 100000] !!) 9999, >λ= defaultMain [bench "TESTXD" $ whnf ([1..100000]!!) 9999, bench "TESTV" $ whnf (\x -> (V.!) v x) 9999] benchmarking TESTXD time 20.61 μs (20.47 μs .. 20.80 μs) 0.999 R² (0.999 R² .. 1.000 R²) mean 14.41 μs (13.85 μs .. 14.88 μs) std dev 805.2 ns (588.3 ns .. 1.036 μs) variance introduced by outliers: 59% (severely inflated) benchmarking TESTV time 1.796 ms (1.768 ms .. 1.831 ms) 0.997 R² (0.995 R² .. 0.999 R²) mean 1.426 ms (1.367 ms .. 1.481 ms) std dev 153.6 μs (123.2 μs .. 190.1 μs) variance introduced by outliers: 69% (severely inflated) (V.!) >λ= >λ= (V.!) v 999 1000 >λ= (V.!) v 9999 10000 >λ= l = [1..100000]) <interactive>:13:16: error: parse error on input ‘)’ >λ= l = [1..100000] >λ= l !! 9999 10000 >λ= l !! 99999 100000 >λ= l !! 999999 *** Exception: Prelude.!!: index too large >λ= l = [1..10000000] >λ= l !! 999999 1000000 >λ= l !! 9999999 10000000 >λ= l !! 99999999 *** Exception: Prelude.!!: index too large >λ= sum l <interactive>:22:1: error: Ambiguous occurrence ‘sum’ It could refer to either ‘Data.Vector.sum’, imported from ‘Data.Vector’ or ‘Prelude.sum’, imported from ‘Prelude’ (and originally defined in ‘Data.Foldable’) >λ= Prelude.sum l 50000005000000 >λ= Prelude.sum l 50000005000000 >λ= v = V.fr V.freeze V.fromList V.fromListN >λ= v = V.fromList l >λ= V.last v 10000000 >λ= :sprint v v = _ Display all 1088 possibilities? (y or n) >λ= V.sum v 50000005000000 >λ= V.sum v 50000005000000 >λ= V.last v 10000000 >λ= relast l read readIO readLn reads realToFrac rem replicate return readFile readList readParen readsPrec recip repeat replicateM reverse >λ= Prelude.last l 10000000 >λ= Prelude.last l 10000000 >λ= V.last v 10000000 >λ= :t (//) (//) :: Vector a -> [(Int, a)] -> Vector a >λ= :t v v :: (Enum a, Num a) => Vector a >λ= l = [1..10000000] :: [Int] >λ= last l <interactive>:37:1: error: Ambiguous occurrence ‘last’ It could refer to either ‘Data.Vector.last’, imported from ‘Data.Vector’ or ‘Prelude.last’, imported from ‘Prelude’ (and originally defined in ‘GHC.List’) >λ= import Prelude as P >λ= P.last l 10000000 >λ= v = from fromEnum fromInteger fromIntegral fromList fromListN fromRational >λ= v = fromList l >λ= :t v v :: Vector Int >λ= V.last v 10000000 >λ= V.last v 10000000 >λ= V.last v 10000000 >λ= v = fromList l >λ= P.last l 10000000 >λ= P.last l 10000000 >λ= V.last v 10000000 >λ= V.last v 10000000 >λ= V.last v 10000000 >λ= P.last l 10000000 >λ= P.last l 10000000 >λ= l = [1..100000000] :: [Int] >λ= v = fromList l >λ= P.last l 100000000 >λ= V.last v 100000000 >λ= V.last v 100000000 >λ= :t v v :: Vector Int >λ= :t v v :: Vector Int >λ= :sprint v v = Data.Vector.Vector 0 100000000 _ >λ= ghc: internal error: Unable to commit 1048576 bytes of memory (GHC version 8.2.2 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug [1] 12349 killed stack ghci }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15054> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15880: GHC.Stats: Add info on amount of pinned memory
by GHC 12 Nov '18

12 Nov '18

#15880: GHC.Stats: Add info on amount of pinned memory -------------------------------------+------------------------------------- Reporter: nh2 | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.3 Component: Runtime | Version: 8.6.2 System | 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: -------------------------------------+------------------------------------- https://hackage.haskell.org/package/base-4.12.0.0/docs/GHC-Stats.html `GHC.Stats`'s `GCDetails` tells us, separately, the amount of * total heap data (including large objects and compact data) * large ojects * compact data * "Total amount of memory in use by the RTS" (`gcdetails_mem_in_use_bytes`) There currently doesn't seem to be a way to get the amount of pinned memory in use. So some questions: * Is pinned memory accounted for in `gcdetails_mem_in_use_bytes`? * If yes, is it pretty much that value minus `gcdetails_live_bytes`, or are there other memory uses that count to the latter? * If I wanted to add the amount of pinned memory directly to `GHC.Stats`, where would I take that value from? In general, my goal is to collect _all_ easily (cheaply) collectable memory info so that I can add it to `ekg`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15880> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15888: Quantified constraints can be loopy
by GHC 12 Nov '18

12 Nov '18

#15888: Quantified constraints can be loopy -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 Keywords: | Operating System: Unknown/Multiple QuantifiedConstraints | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider this abuse: {{{#!hs {-# LANGUAGE QuantifiedConstraints, UndecidableInstances #-} module Bug where data T1 a data T2 a class C a where meth :: a instance (forall a. C (T2 a)) => C (T1 b) where meth = error "instance T1" instance (forall a. C (T1 a)) => C (T2 b) where meth = error "instance T2" example :: T1 Int example = meth }}} GHC says {{{ • Reduction stack overflow; size = 201 When simplifying the following type: C (T1 a) Use -freduction-depth=0 to disable this check (any upper bound you could choose might fail unpredictably with minor updates to GHC, so disabling the check is recommended if you're sure that type checking should terminate) • In the expression: meth In an equation for ‘example’: example = meth }}} Of course, I've taken on some responsibility for my actions here by saying `UndecidableInstances`, but GHC really should be able to figure this out. Here's what's happening: 1. We get a Wanted `C (T1 Int)`. 2. GHC chooses the appropriate instance, emitting a Wanted `forall a. C (T2 a)`. 3. GHC skolemizes the `a` to `a1` and tries solve a Wanted `C (T2 a1)`. 4. GHC chooses the appropriate instance, emitting a Wanted `forall a. C (T1 a)`. 5. GHC skolemizes the `a` to `a2` and tries to solve a Wanted `C (T1 a2)`. And around and around we go. (This loop is guessed at from knowing GHC's algorithms in general. I did not look at a trace.) We ''could'' get this one, though. Before skolemizing, we could stash the Wanted in the `inert_solved_dicts`, which is where we record uses of top- level instances. (See `Note [Solved dictionaries]` in TcSMonad.) Then, later, when we see the same Wanted arise again, we would just use the cached value, making a well-formed recursive dictionary. This deficiency was discovered in `singletons` (https://github.com/goldfirere/singletons/issues/371) Perhaps that's not "the wild", but it's not quite contrived either. Note that we don't need two datatypes to trigger this, but having one recursive instance like this seems awfully silly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15888> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15886: Spurious warning about incomplete pattern with PatternSynonyms
by GHC 12 Nov '18

12 Nov '18

#15886: Spurious warning about incomplete pattern with PatternSynonyms -------------------------------------+------------------------------------- Reporter: selinger | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Incorrect (amd64) | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE ViewPatterns #-} {-# LANGUAGE PatternSynonyms #-} module Test where f :: Int -> Bool f (id -> a) = True pattern X a <- (id -> a) g :: Int -> Bool g (X a) = True }}} When compiling with -Wincomplete-patterns, this code produces an (incorrect) warning for `g`, but not for `f`. The only difference is that `g` uses a pattern synonym. {{{ K.hs:12:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘g’: Patterns not matched: _ | 12 | g (X a) = True | ^^^^^^^^^^^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15886> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15594: --abi-hash with Backpack incorrectly loads modules from dependent packages
by GHC 12 Nov '18

12 Nov '18

#15594: --abi-hash with Backpack incorrectly loads modules from dependent packages -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Repro at: https://github.com/alexbiehl/cabal-backpack-register- repro/blob/master/src/Lib.hs -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15594> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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