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[GHC] #12950: unnecessarily complicated left-hand side causing RULE left-hand side too complicated to desugar
by GHC 21 Dec '16

21 Dec '16

#12950: unnecessarily complicated left-hand side causing RULE left-hand side too complicated to desugar -------------------------------------+------------------------------------- Reporter: nfrisby | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: #10555,#12074 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 7.10.2 rejects the `SPECIALIZE` pragma in the following snippet with "RULE left-hand side too complicated to desugar". {{{#!hs class C a where type TF a; m :: a -> TF a instance C Int where type TF Int = String; m = show overloaded :: C a => a -> (a,TF a) {-# INLINABLE overloaded #-} overloaded a = (a,m a) {-# SPECIALIZE overloaded :: Int -> (Int,TF Int) #-} }}} This use case is so simple/basic/prevalent that it seems inappropriate to reject it. The actual message is {{{ RULE left-hand side too complicated to desugar Optimised lhs: case cobox_awc of _ [Occ=Dead] { GHC.Types.Eq# cobox -> overloaded @ Int $dC_awb } Orig lhs: case cobox_awc of cobox_awc { GHC.Types.Eq# cobox -> overloaded @ Int $dC_awb } }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12950> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12968: GHC crash with TypeInType and pattern synonym
by GHC 21 Dec '16

21 Dec '16

#12968: GHC crash with TypeInType and pattern synonym -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- I decided to try playing with the proposed new `Typeable` interface, faking up types and functions in GHC 8.0.1. Unfortunately, it seems I did something impossible: {{{#!hs {-# LANGUAGE TypeInType, GADTs, ScopedTypeVariables, PatternSynonyms, ViewPatterns #-} module TypeReflection where data TypeRep (a :: k) data TRAppG (fun :: k2) where TRAppG :: forall k1 (a :: k1 -> k2) (b :: k1) . TypeRep a -> TypeRep b -> TRAppG (a b) pattern TRApp :: forall k2 (fun :: k2). () => forall k1 (a :: k1 -> k2) (b :: k1). (fun ~ a b) => TypeRep a -> TypeRep b -> TypeRep fun pattern TRApp a b <- ((undefined :: TypeRep fun -> TRAppG fun) -> TRAppG a b) }}} The error: {{{ [1 of 1] Compiling TypeReflection ( TypeReflectionTemplate.hs, TypeReflectionTemplate.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): StgCmmEnv: variable not found $dIP_a1Aj local binds for: typeRep $tcTypeable $tc'C:Typeable $tcTypeRep $tc'TRAppG $WTRAppG $tcTRAppG $trModule $tcTRAppG1_r1KE $tc'TRAppG1_r1KS $tcTypeRep1_r1KT $tcTypeable1_r1KU $tc'C:Typeable1_r1KV $trModule1_r1KW $trModule2_r1KX scrut_s1Lg cont_s1Lh fail_s1Li sat_s1Lj sat_s1Lk sat_s1Ll sat_s1Lm sat_s1Ln sat_s1Lo sat_s1Lp sat_s1Lq sat_s1Lr sat_s1Ls sat_s1Lt }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12968> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9509: No automatic specialization of inlinable imports in 7.8
by GHC 21 Dec '16

21 Dec '16

#9509: No automatic specialization of inlinable imports in 7.8 -------------------------------------+------------------------------------- Reporter: dolio | 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: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- According to the GHC manual, any uses of an imported definition that is overloaded and INLINABLE will automatically cause a SPECIALIZE to be generated for those uses, if appropriate. However, this no longer appears to be the case in 7.8(.3). Here is a simple test case: {{{#!hs module A (foo) where import Data.IORef foo :: Ord a => a -> IO a foo x = newIORef x >>= readIORef >>= \y -> case compare x y of LT -> return x ; _ -> return y {-# INLINABLE foo #-} }}} {{{#!hs module Main (main) where import A main = foo (5 :: Int) >>= print }}} `foo` is constructed to be long enough that GHC 7.8.3 will elect to not inline it. When compiling with 7.6.3, the core contains the following: {{{ Main.$sfoo1 :: GHC.Types.Int -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Types.Int #) [GblId, Arity=2, Caf=NoCafRefs, Str=DmdType LL, Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=2, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [20 0] 55 30}] Main.$sfoo1 = \ (x_XkE :: GHC.Types.Int) (eta_B1 :: GHC.Prim.State# GHC.Prim.RealWorld) -> case GHC.Prim.newMutVar# @ GHC.Types.Int @ GHC.Prim.RealWorld x_XkE eta_B1 of _ { (# ipv_amT, ipv1_amU #) -> case GHC.Prim.readMutVar# @ GHC.Prim.RealWorld @ GHC.Types.Int ipv1_amU ipv_amT of ds1_amJ { (# ipv2_Xn8, ipv3_Xna #) -> case x_XkE of wild_axu { GHC.Types.I# x#_axw -> case ipv3_Xna of _ { GHC.Types.I# y#_axA -> case GHC.Prim.<# x#_axw y#_axA of _ { GHC.Types.False -> ds1_amJ; GHC.Types.True -> (# ipv2_Xn8, wild_axu #) } } } } } Main.$sfoo :: GHC.Types.Int -> GHC.Types.IO GHC.Types.Int [GblId, Arity=2, Caf=NoCafRefs, Str=DmdType LL, Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=0, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=ALWAYS_IF(unsat_ok=True,boring_ok=True)}] Main.$sfoo = Main.$sfoo1 `cast` (<GHC.Types.Int> -> Sym <(GHC.Types.NTCo:IO <GHC.Types.Int>)> :: (GHC.Types.Int -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Types.Int #)) ~# (GHC.Types.Int -> GHC.Types.IO GHC.Types.Int)) ... ------ Local rules for imported ids -------- "SPEC A.foo [GHC.Types.Int]" [ALWAYS] forall ($dOrd_sxj :: GHC.Classes.Ord GHC.Types.Int) A.foo @ GHC.Types.Int $dOrd_sxj = Main.$sfoo }}} However, in 7.8.3 and newer (I'm actually using 7.9.20140725 for this particular output, but 7.8.3 is similar), we see the following: {{{ Main.main1 :: GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, () #) [GblId, Arity=1, Str=DmdType <L,U>, Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=1, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [0] 100 0}] Main.main1 = \ (s_aIb :: GHC.Prim.State# GHC.Prim.RealWorld) -> case ((A.foo @ GHC.Types.Int GHC.Classes.$fOrdInt Main.main2) `cast` (GHC.Types.NTCo:IO[0] <GHC.Types.Int>_R :: GHC.Types.IO GHC.Types.Int ~R# (GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Types.Int #)))) s_aIb of _ [Occ=Dead] { (# ipv_aIe, ipv1_aIf #) -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout (GHC.Show.$fShowInt_$cshow ipv1_aIf) GHC.Types.True ipv_aIe } }}} There is no local rules section in 7.8.3. Putting a manual SPECIALIZE pragma in the main module generates comparable code to 7.6.3, so it does not appear to be a failure at that level. Rather, GHC seems to just not be generating the SPECIALIZE equivalent. Presumably this is a regression, but even if not, the manual should be revised. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9509> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11598: Cache coercion kinds and roles
by GHC 21 Dec '16

21 Dec '16

#11598: Cache coercion kinds and roles -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire 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: -------------------------------------+------------------------------------- Because we never inspect the structure of a coercion, it is easy to cache coercions' kinds and role at the top level, using something like this: {{{ data Coercion = MkCoercion { coercionKind :: Pair Type , coercionRole :: Role , coercionRep :: CoercionRep } data CoercionRep = -- the long, recursive datatype we have now }}} In the process, various role and type information currently stored in the recursive structure could be dropped. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11598> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13022: Pattern Synonyms using other synonyms causes ghc panic
by GHC 21 Dec '16

21 Dec '16

#13022: Pattern Synonyms using other synonyms causes ghc panic -------------------------------------+------------------------------------- Reporter: AveryGlitch | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Here's a (somewhat) minimal example: {{{#!hs {-# LANGUAGE PatternSynonyms #-} data Some = Thing Int Int pattern A x = Thing x 0 pattern B x = Thing x 1 pattern C x = Thing x 2 pattern D = C 3 }}} And here's what happened when I tried to load this into ghci: {{{ *Main> :l ghc_bug.hs [1 of 1] Compiling Main ( ghc_bug.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): kindPrimRep.go rep_a3fP Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13022> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12444: Regression: panic! on inaccessible code with constraint
by GHC 21 Dec '16

21 Dec '16

#12444: Regression: panic! on inaccessible code with constraint -------------------------------------+------------------------------------- Reporter: zilinc | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Running the following program with ghci-8.0.1: {{{#!hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} module Prove where data Nat = Zero | Succ Nat data SNat (n :: Nat) where SZero :: SNat Zero SSucc :: SNat n -> SNat (Succ n) type family (:+:) (a :: Nat) (b :: Nat) :: Nat where m :+: Zero = m m :+: (Succ n) = Succ (m :+: n) sadd :: ((Succ n1 :+: n) ~ Succ (n1 :+: n), (Succ n1) ~ m) => SNat m -> SNat n -> SNat (m :+: n) sadd SZero n = n }}} -ddump-tc-trace shows: {{{ ... dischargeFmv s_a9qV[fuv:4] = t_a9qW[tau:5] (1 kicked out) doTopReactFunEq (occurs) old_ev: [D] _ :: ((n1_a9qu[sk] :+: 'Succ s_a9qV[fuv:4]) :: Nat) GHC.Prim.~# (s_a9qV[fuv:4] :: Nat)ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): ctEvCoercion [D] _ :: (t_a9qW[tau:5] :: Nat) ~# ('Succ (n1_a9qu[sk] :+: s_a9qV[fuv:4]) :: Nat) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} It is rightly rejected by ghci-7.10.2: {{{ Prove.hs:42:6: Couldn't match type ‘'Succ n1’ with ‘'Zero’ Inaccessible code in a pattern with constructor SZero :: SNat 'Zero, in an equation for ‘sadd’ In the pattern: SZero In an equation for ‘sadd’: sadd SZero n = n Failed, modules loaded: none. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12444> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13020: Use a fixed SDK for Mac OS X builds
by GHC 21 Dec '16

21 Dec '16

#13020: Use a fixed SDK for Mac OS X builds -------------------------------------+------------------------------------- Reporter: gracjan | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Apple releases new systems with new SDK versions. Official documentation says that it is enough to use newest SDK with MACOSX_TARGET set to lowest supported version of Mac OS X. This is not always true, as they try to keep all new features conditionally included, but they sometimes fail. For example `/usr/include/sys/mman.h` file has been changed between SDK10.10 and SDK10.11 without any compatibility flags and resulted in #13005 (Mac OSX uses `MAP_ANON` in place of `MAP_ANONYMOUS`). The solution is: - download the lowest supported SDK from https://github.com/phracker /MacOSX-SDKs - set the path using -isysroot param to gcc Overall would be best to compile using all supported SDKs, but given lack of CI machines I think it is better to build with minimum version. Apple is pretty good at keeping backward compatibility on source level. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13020> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13019: 'stack upgrade' failed with the message "ghc: panic! (the 'impossible' happened)"
by GHC 21 Dec '16

21 Dec '16

#13019: 'stack upgrade' failed with the message "ghc: panic! (the 'impossible' happened)" -------------------------------------+------------------------------------- Reporter: welf | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: stack upgrade | Operating System: MacOS X Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- MacBook Pro, MacOS Sierra 10.12.2 $ stack upgrade Fetched package index. http-client-0.5.3.3: configure http-client-0.5.3.3: build pid1-0.1.0.0: configure pid1-0.1.0.0: build optparse-applicative-0.13.0.0: configure optparse-applicative-0.13.0.0: build text-metrics-0.1.0: configure pid1-0.1.0.0: copy/register text-metrics-0.1.0: build aeson-1.0.2.1: configure aeson-1.0.2.1: build th-orphans-0.13.1: configure text-metrics-0.1.0: copy/register th-orphans-0.13.1: build store-core-0.3: configure store-core-0.3: build store-core-0.3: copy/register th-orphans-0.13.1: copy/register th-utilities-0.2.0.1: configure th-utilities-0.2.0.1: build optparse-applicative-0.13.0.0: copy/register optparse-simple-0.0.3: configure optparse-simple-0.0.3: build optparse-simple-0.0.3: copy/register http-client-0.5.3.3: copy/register http-client-tls-0.3.3: configure http-client-tls-0.3.3: build th-utilities-0.2.0.1: copy/register store-0.3: configure store-0.3: build http-client-tls-0.3.3: copy/register store-0.3: copy/register aeson-1.0.2.1: copy/register binary-tagged-0.1.4.1: configure binary-tagged-0.1.4.1: build yaml-0.8.20: configure yaml-0.8.20: build path-0.5.9: configure path-0.5.9: build aeson-compat-0.3.6: configure aeson-compat-0.3.6: build http-conduit-2.2.3: configure http-conduit-2.2.3: build persistent-2.6: configure path-0.5.9: copy/register persistent-2.6: build path-io-1.1.0: configure aeson-compat-0.3.6: copy/register path-io-1.1.0: build binary-tagged-0.1.4.1: copy/register http-conduit-2.2.3: copy/register path-io-1.1.0: copy/register yaml-0.8.20: copy/register hpack-0.15.0: configure hpack-0.15.0: build persistent-2.6: copy/register persistent-template-2.5.1.6: configure persistent-template-2.5.1.6: build persistent-sqlite-2.6: configure hpack-0.15.0: copy/register persistent-sqlite-2.6: build persistent-template-2.5.1.6: copy/register persistent-sqlite-2.6: copy/register stack-1.3.0: configure [1 of 1] Compiling Main ( /private/var/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/stack- upgrade83426/stack-1.3.0/Setup.hs, /private/v ar/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/stack- upgrade83426/stack-1.3.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/Main.o ) Linking /private/var/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/stack- upgrade83426/stack-1.3.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/s etup ... Configuring stack-1.3.0... stack-1.3.0: build Preprocessing library stack-1.3.0... [ 1 of 121] Compiling Text.PrettyPrint.Leijen.Extended ( src/Text/PrettyPrint/Leijen/Extended.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/buil d/Text/PrettyPrint/Leijen/Extended.o ) [ 2 of 121] Compiling Stack.Ghci.Script ( src/Stack/Ghci/Script.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Stack/Ghci/Script.o ) [ 3 of 121] Compiling Stack.FileWatch ( src/Stack/FileWatch.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Stack/FileWatch.o ) [ 4 of 121] Compiling System.Process.PagerEditor ( src/System/Process/PagerEditor.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Pro cess/PagerEditor.o ) [ 5 of 121] Compiling System.Process.Log ( src/System/Process/Log.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Process/Log.o ) [ 6 of 121] Compiling Paths_stack ( .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/autogen/Paths_stack.hs, .stack- work/dist/x86_64-osx/Cab al-1.22.5.0/build/Paths_stack.o ) [ 7 of 121] Compiling Path.Find ( src/Path/Find.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Path/Find.o ) [ 8 of 121] Compiling Path.Extra ( src/Path/Extra.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Path/Extra.o ) [ 9 of 121] Compiling System.Process.Read ( src/System/Process/Read.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/System/Process/Read.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-apple-darwin): Loading temp shared object failed: dlopen(/var/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/ghc85411_0/libghc_57.dylib, 5): no suitable image found. Did find: /var/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/ghc85411_0/libghc_57.dylib: malformed mach-o: load commands size (47464) > 32768 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Completed 22 action(s). -- While building package stack-1.3.0 using: /private/var/folders/b2/q9qtc29x3m542jp596km0lgw0000gn/T/stack- upgrade83426/stack-1.3.0/.stack- work/dist/x86_64-osx/Cabal-1.22.5.0/setup/setup --builddir=.stack- work/dist/x86_64-osx/Cabal-1.22.5.0 build lib:stack exe:stack --ghc- options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13019> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13015: Remove as much Haskell code as we can from Lexer.x
by GHC 21 Dec '16

21 Dec '16

#13015: Remove as much Haskell code as we can from Lexer.x -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Parser) | 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: -------------------------------------+------------------------------------- I want to reduce the code in Lexer.x so (1) when I use hasktags I jump to some real source, not the postprocess output, and (2) so that I can avoid suppressing warnings on our Haskell source code, and not just the lexer code. If we are willing to introduce an hs-boot file with the following signatures: {{{ bol :: Int layout :: Int layout_do :: Int layout_if :: Int layout_left :: Int option_prags :: Int }}} We can do quite well; the only functions we can't extract are: begin, pop, multiline_doc_comment, lineCommentToken, nested_doc_comment, withLexedDocType, do_bol, setLine, setFile, warnTab, addTabWarning, lexer, lexTokenAlr, lexToken, lexTokenStream, linePrags, fileHeaderPrags, ignoredPrags, oneWordPrags, twoWordPrags, dispatch_pragmas and known_pragma. Some of these, like lexToken, we can't expect to be able to move to a separate file, as they depend on Alex generated data types and functions (AlexRoutine, alexScanUser). But if we boot-ify lexToken, we can move even more code out. One question, however, is the performance cost of going through an hs-boot file, as these don't inline. I think the constants are fairly safe (inlining opportunities should only occur when we compile Lexer.x, at which point we will have unfoldings for them), but I am less certain about lexToken. Any advice? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13015> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13012: ApiAnnotations comments are not machine checked
by GHC 21 Dec '16

21 Dec '16

#13012: ApiAnnotations comments are not machine checked -------------------------------------+------------------------------------- Reporter: ezyang | Owner: alanz Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Parser) | 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: -------------------------------------+------------------------------------- Sprinkled throughout the codebase are comments like this: {{{ -- | let(rec) -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnLet', -- 'ApiAnnotation.AnnOpen' @'{'@, -- 'ApiAnnotation.AnnClose' @'}'@,'ApiAnnotation.AnnIn' }}} The comments are intended to describe the set of annotations that might be possibly associated with an AST node of this constructor. However, the source of truth about these comments is the Parser itself. It's not difficult to imagine that these comments might get out of date if changes are made to the Parser. Nor does the comment in `ApiAnnotations` nor the wiki page (https://ghc.haskell.org/trac/ghc/wiki/ApiAnnotations) explain what the comments are for, and I only recently figured out what they actually mean. (I'm working on a doc patch to improve this.) Ideally, the set of permissible annotations would be encoded in *machine- readable* form, as a contract that we can use to check that the parser upholds the contract. Here is my suggestion: we create a function to recursively traverse a parsed module, and verify that the only annotations associated with any given SrcSpan are the "valid" ones for that AST element. We can enable this extra pass as an "annotation lint" and turn it on for all tests in the test suite. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13012> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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