January 2017 - ghc-tickets

[GHC] #12957: In a record-update construct:ghc-stage2: panic! (the 'impossible' happened)
by GHC 08 Feb '17

08 Feb '17

#12957: In a record-update construct:ghc-stage2: panic! (the 'impossible' happened) -------------------------------------+------------------------------------- Reporter: niteria | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 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: -------------------------------------+------------------------------------- While compiling `Repro.hs` with `HEAD` I get this: {{{ $ ~/local/ghc-inaccessible-right-side/inplace/bin/ghc-stage2 Repro.hs [1 of 1] Compiling Repro ( Repro.hs, Repro.o ) Repro.hs:22:35: warning: [-Woverlapping-patterns] Pattern match has inaccessible right hand side In a record-update construct:ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20161209 for x86_64-unknown-linux): unused Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} It doesn't reproduce on 7.10.2. I'm 90% sure it reproduces on 8.0.2 (I have a branch with some unrelated patches). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12957> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13144: FoatOut is not floating bottoming expressions properly
by GHC 08 Feb '17

08 Feb '17

#13144: FoatOut is not floating bottoming expressions properly -------------------------------------+------------------------------------- Reporter: simonpj | Owner: 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 part of Eric's program in #13143, and pretty much exactly what is in `GHC.Arr`. {{{ {-# INLINE index #-} index :: (Int, Int) -> Int -> Int index b@(l,h) i | l <= i && i < h = 0 | otherwise = indexError b i 0 {-# NOINLINE indexError #-} indexError :: (Int, Int) -> Int -> Int -> b indexError rng i tp = error (show rng) }}} Before float-out we have {{{ index = \ (b_ay8 :: (Int, Int)) (i_ayb :: Int) -> case b_ay8 of wild_Xe { (l_ay9, h_aya) -> case && (leInt l_ay9 i_ayb) (ltInt i_ayb h_aya) of { False -> indexError @ Int wild_Xe i_ayb (I# 0#); True -> GHC.Types.I# 0# } } }}} and after float-out we see {{{ index = \ (b_ay8 :: (Int, Int)) (i_ayb :: Int) -> case b_ay8 of wild_Xe { (l_ay9, h_aya) -> case && (leInt l_ay9 i_ayb) (ltInt i_ayb h_aya) of { False -> indexError @ Int b_ay8 i_ayb lvl_s2cd; True -> GHC.Types.I# 0# } } }}} We've floated the `(I# 0#)`. ''But we should have floated the entire call to `indexError` thus'': {{{ False -> lvl_xxx b_ay8 i_ayb }}} with {{{ lvl_xxx b i = indexError @Int b i (I# 0#) }}} Why? Because it makes the expression smaller and moves the error handling code out of the way. Float-out makes some attempt to to this, but it's not right yet. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13144> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10635: -fwarn-redundant-constraints should not be part of -Wall
by GHC 07 Feb '17

07 Feb '17

#10635: -fwarn-redundant-constraints should not be part of -Wall -------------------------------------+------------------------------------- Reporter: Lemming | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple (Type checker) | Type of failure: Incorrect Keywords: | warning at compile-time Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When I compile existing code with GHC-7.11.20150707 I get lot of "redundant constraints" warnings. Generally I think that this warning can be very useful for minimizing constraints, nonetheless there are good reasons not choose minimal constraints for a type signature. E.g. if I have to implement `Data.Map.singleton` I do not need the `Ord k` constraint for the key type. However, I might add it anyway in order to be able to change the implementation in future such that it uses `Ord k` dictionary. Thus I suggest to exclude `-fwarn-redundant-constraints` from `-Wall`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10635> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13143: NOINLINE and worker/wrapper
by GHC 07 Feb '17

07 Feb '17

#13143: NOINLINE and worker/wrapper -------------------------------------+------------------------------------- Reporter: simonpj | Owner: 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: -------------------------------------+------------------------------------- Currently we do no worker/wrapper on a NOINLINE thing. In `WorkWrap`: {{{ tryWW dflags fam_envs is_rec fn_id rhs | isNeverActive inline_act -- No point in worker/wrappering if the thing is never inlined! -- Because the no-inline prag will prevent the wrapper ever -- being inlined at a call site. }}} But if we have, say, {{{ {-# NOINLINE f #-} f (x,y) = error (show x) g True p = f p g False p = snd p + 1 }}} then strictness analysis will discover `f` is strict, and `g`, but ''because `f` has no wrapper'', the worker for `g` will rebox the thing. So we get {{{ f (x,y) = error (show x) $wg b x y = let p = (x,y) -- Yikes! Reboxing! in case b of True -> f p False -> y + 1 g b p = case p of (x,y) -> $wg b x y }}} Now, in this case the reboxing will float into the `True` branch, an so the allocation will only happen on the error path. But it won't float inwards if there are multiple branches that call `(f p)`, so the reboxing will happen on every call of `g`. Disaster. Solution: do worker/wrapper even on NOINLINE things; but move the NOINLINE pragma to the worker. --------------------------- This actually happens! In `GHC.Arr` we have {{{ {-# NOINLINE indexError #-} indexError :: Show a => (a,a) -> a -> String -> b indexError rng i tp = error (...) index b i | inRange b i = unsafeIndex b i | otherwise = indexError b i "Char" }}} The `inRange` generates multiple alternatives, which the `indexError` is duplicated into, and exactly this phenomenon takes place. Eric (gridaphobe) offered this standalone example {{{ module Err where tabulate :: (Int -> a) -> (Int, Int) -> [Int] tabulate f (l,u) = array (l,u) [l..u] {-# INLINE array #-} array :: (Int, Int) -> [Int] -> [Int] array (l,u) is = [index (l,u) i | i <- is] {-# INLINE index #-} index :: (Int, Int) -> Int -> Int index b@(l,h) i | l <= i && i < h = 0 | otherwise = indexError b i 0 {-# NOINLINE indexError #-} indexError :: (Int, Int) -> Int -> Int -> b indexError rng i tp = error (show rng) }}} Compile this with GHC 8, and shudder at the terrible code we get for `$wtabulate`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13143> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13166: Warning: Can't find file "C:\...\lib/include\ghcversion.h" in directories
by GHC 06 Feb '17

06 Feb '17

#13166: Warning: Can't find file "C:\...\lib/include\ghcversion.h" in directories -------------------------------------+------------------------------------- Reporter: domenkozar | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm not exactly sure yet where this is coming from, but I'd like to report an warning on Windows during preprocessing phase: {{{ [00:03:39] Preprocessing library cardano-sl-0.1.0.0... [00:03:39] Warning: Can't find file "C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib/include\ghcversion.h" in directories [00:03:39] src/Pos [00:03:39] . [00:03:39] .stack-work\dist\b7fec021\build [00:03:39] .stack-work\dist\b7fec021\build [00:03:39] .stack-work\dist\b7fec021\build\autogen [00:03:39] .stack-work\dist\b7fec021\build [00:03:39] C:\OpenSSL-Win64\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\msys2-20150512\mingw64\include [00:03:39] C:\projects\pos-haskell-prototype\rocksdb\include [00:03:39] C:\OpenSSL-Win64\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\msys2-20150512\mingw64\include [00:03:39] C:\projects\pos-haskell-prototype\rocksdb\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows-ghc-8.0.1 \vector-algorithms-0.7.0.1-8R8UpWgvBC926XMxBjYPpx\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows- ghc-8.0.1\zlib-0.6.1.2-4CWLN1T27kOJhNvXgy46ZV\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\process-1.4.2.0\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows- ghc-8.0.1\vector-0.11.0.0-BEDZb5o2QOhGbIm6ky7rl6\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows-ghc-8.0.1\old- time-1.1.0.3-IcvdkJUsE9M8t3io8peAEp\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\directory-1.2.6.2\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows- ghc-8.0.1\primitive-0.6.1.0-Ip44DqhfCp21tTUYbecwa\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\time-1.6.0.1\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\Win32-2.3.1.1\include [00:03:39] C:\sr\snapshots\a78c6a89\lib\x86_64-windows- ghc-8.0.1\network-2.6.3.1-nK9qnsiJR03CWuPIGMmX\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\bytestring-0.10.8.1\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib\base-4.9.0.0\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib \integer-gmp-1.0.0.1\include [00:03:39] C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib/include [00:03:39] Asked for by: src/Pos/CLI.hs at line 2 col 1 }}} It appears to trigger for each module using cpphs. The file is present, so I suspect the problem is in unix path character in `C:\Users\appveyor\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.1\lib/include\ghcversion.h`. Using verbose mode we can observe that's the case: {{{ "cpphs" "-DWITH_WEB" "-DWITH_WALLET" "-include" ".stack- work\dist\ca59d0ab\build\autogen\cabal_macros.h" "--cpp" "-I" ".stack- work\dist\ca59d0ab\build" "-I" ".stack-work\dist\ca59d0ab\build" "-I" ".stack-work\dist\ca59d0ab\build\autogen" "-I" ".stack- work\dist\ca59d0ab\build" "-I" "C:\OpenSSL-Win64\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\msys2-20150512\mingw64\include" "-I" "C:\rocksdb\include" "-I" "C:\OpenSSL-Win64\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\msys2-20150512\mingw64\include" "-I" "C:\rocksdb\includ e" "-I" "C:\sr\snapshots\b3566c00\lib\x86_64-windows-ghc-8.0.2\vector- algorithms-0.7.0.1-C2u1KYklHg84I6SQQVEAin\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\zlib-0.6.1.2-7negTfm2ujt1gW4wr40MUp\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\process-1.4.2.0-KoK49SuYVPk1TQ4YVt6ZK5\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\vector-0.11.0.0-LMwQhhnXj8U3T5Bm1JFxG\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows-ghc-8.0.2\old- time-1.1.0.3-KWRsMSdY26c2L27Y9n9cyq\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\directory-1.2.6.2-qiZgXsB5o98ZsOYUWltfF\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\primitive-0.6.1.0-6AbSTw9JXz141LE5p6LGH\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib\time-1.6.0.1\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib\Win32-2.3.1.1\include" "-I" "C:\sr\snapshots\bb34f894\lib\x86_64-windows- ghc-8.0.2\network-2.6.3.1-AwRxOQvT8JM9e8zDFK7aCI\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib\bytestring-0.10.8. 1\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib\base-4.9.1.0\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib \integer-gmp-1.0.0.1\include" "-I" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib/include" "-D__GLASGOW_HASKELL__=800" "-include" "C:\Users\Administrator\AppData\Local\Programs\stack\x86_64-windows\ghc-8.0.2\lib/include\ghcversion.h" "-Dmingw32_BUILD_OS=1" "-Dx86_64_BUILD_ARCH=1" "-Dmingw32_HOST_OS=1" "-Dx86_64_HOST_ARCH=1" "-D__GLASGOW_HASKELL_TH__=1" "-D_ _SSE__=1" "-D__SSE2__=1" "-includeC:\Users\ADMINI~1\AppData\Local\Temp\2\ghc2384_0\ghc_18.h" "-x" "assembler-with-cpp" "src\Pos\Binary\Crypto.hs" "-o" "C:\Users\ADMINI~1\AppData\Local\Temp\2\ghc2384_0\ghc_17.hscpp" }}} I highly suspect https://github.com/ghc/ghc/blob/master/utils/ghc- pkg/Main.hs#L1956 since it does some unclear path mungling, probably leaving undosified suffix. Note that those functions were copied from `compiler/main/SysTools.hs` which changed significantly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13166> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11760: runST with lazy blackholing breaks referential transparency
by GHC 05 Feb '17

05 Feb '17

#11760: runST with lazy blackholing breaks referential transparency -------------------------------------+------------------------------------- Reporter: Yuras | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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 thunk created with `runST` can be evaluated twice by different threads producing different results. An example (taken from https://twitter.com/obadzz/status/714081240475951105) {{{#!hs {-# LANGUAGE RecordWildCards #-} import qualified Data.STRef.Lazy as S import Control.Monad import Control.Monad.ST.Lazy import Control.Concurrent data ListRef s a = ListRef { element :: a , readCounter :: Int , rest :: Maybe (S.STRef s (ListRef s a)) } toList :: S.STRef s (ListRef s a) -> ST s [(a, Int)] toList r = do ListRef{..} <- S.readSTRef r S.modifySTRef r $ \e -> e { readCounter = readCounter + 1 } xs <- maybe (return []) toList rest return $ (element, readCounter) : xs circularList :: ST s (S.STRef s (ListRef s Char)) circularList = do x3 <- S.newSTRef (ListRef 'c' 0 Nothing) x2 <- S.newSTRef (ListRef 'b' 0 (Just x3)) x1 <- S.newSTRef (ListRef 'b' 0 (Just x2)) S.modifySTRef x3 $ \e -> e { rest = Just x1 } return x1 l :: [(Char, Int)] l = take 15 $ runST $ circularList >>= toList main :: IO () main = do void $ forkIO $ print l void $ forkIO $ print l void getLine print l }}} The output (run multiple times to reproduce): {{{ $ ghc --make -O -threaded -outputdir=.build test.hs [1 of 1] Compiling Main ( test.hs, .build/Main.o ) Linking test ... $ ./test +RTS -N2 [('b',0),('b',0),('c',0),('b',1),('b',1),('c',1),('b',2),('b',2),('c',2),('b',3),('b',3),('c',3),('b',5),('b',4),('c',4)] [('b',0),('b',0),('c',0),('b',1),('b',1),('c',1),('b',2),('b',2),('c',2),('b',3),('b',3),('c',3),('b',4),('b',4),('c',4)] [('b',0),('b',0),('c',0),('b',1),('b',1),('c',1),('b',2),('b',2),('c',2),('b',3),('b',3),('c',3),('b',4),('b',4),('c',4)] $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.1 $ }}} Note that the last 3 elements are `('b',5),('b',4),('c',4)` or `('b',4),('b',4),('c',4)`. I was able to reproduce it with few weeks old HEAD. With `-feager- blackholing` it works as expected. `unsafePerformIO` uses `noDuplicate` to prevent such kind of issue. Should `runST` do something similar? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11760> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10823: Expose keepAlive to Template Haskell
by GHC 03 Feb '17

03 Feb '17

#10823: Expose keepAlive to Template Haskell -------------------------------------+------------------------------------- Reporter: spinda | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- {{{keepAlive}}} is a [https://github.com/ghc/ghc/blob/efa7b3a474bc373201ab145c129262a73c86f959/co… function in TcRnMonad] that adds a {{{Name}}} to the set of {{{Name}}}s to keep when pruning out dead code. A concrete use case for exposing this to Template Haskell is in LiquidHaskell, which will soon function as a Core plugin. In LiquidHaskell, a subset of Haskell functions can be "lifted" to the logic level and used in types. For example: {{{ module Test (ok) where [lq| inline gt |] gt x y = x > y [lq| ok :: x:Int -> { v:Int | gt x v } |] ok x = x + 1 }}} LiquidHaskell runs a transformation from the {{{CoreBind}}} for {{{gt}}} to its internal representation of decidable logic. Since Core plugins are run after "dead" code is removed at the end of desugaring, and since {{{gt}}} is not exported, the {{{CoreBind}}} for {{{gt}}} would not reach the {{{CoreBinds}}} LH receives as a Core plugin. The solution for this is to be able to mark names with {{{keepAlive}}} from Template Haskell. Proposed specification: {{{ keepAlive :: Name -> Q () }}} where {{{Name}}} is a Template Haskell {{{Name}}}. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10823> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13181: Introduce GHC.TypeNats module with natVal
by GHC 03 Feb '17

03 Feb '17

#13181: Introduce GHC.TypeNats module with natVal -------------------------------------+------------------------------------- Reporter: phadej | Owner: phadej Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 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: -------------------------------------+------------------------------------- See [https://mail.haskell.org/pipermail/libraries/2017-January/027615.html libraries thread] Currently we have in the GHC.TypeLits module {{{ natVal :: forall n proxy. KnowNat n => proxy n -> Integer }}} However, the result integer is never negative. Numeric.Natural module is in base since base-4.8.0.0. --- I propose that we introduce new module GHC.TypeNats with natVal and natVal' {{{ natVal :: forall n proxy. KnownNat n => proxy n -> Natural }}} and {{{ natVal' :: forall n. KnownNat n => Proxy# n -> Natural }}} and other KnownNat related terms and type families. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13181> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13186: Change EvNum to EvNum :: Natural -> EvLit
by GHC 03 Feb '17

03 Feb '17

#13186: Change EvNum to EvNum :: Natural -> EvLit -------------------------------------+------------------------------------- Reporter: phadej | Owner: Type: feature | Status: new request | 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: #8306 #8412 | #13181 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Currently we carry `Nat` kind as an Integer internally. Just changing the type of EvNum (and related isomorphic types like `HsTyLit` etc) does pretty far. The core problem is that we should be able to output Natural literals into Core. Also this would need change to parser, to accept only Naturals in types. Currently negative literals are caught in the renamer (due the fact that template-haskell might inject negative integers as well). This will propagate to template-haskell, changing TyLit there as well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13186> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13098: Template Haskell support for Pattern Synonym's Complete Pragma
by GHC 02 Feb '17

02 Feb '17

#13098: Template Haskell support for Pattern Synonym's Complete Pragma -------------------------------------+------------------------------------- Reporter: magesh.b | Owner: mpickering Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- #8779 provides exhaustive checking support for Pattern Synonym via Complete pragma. https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms/CompleteSigs It would be nice, if we are able to generate those pragma via TH. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13098> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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