July 2017 - ghc-tickets

[GHC] #13608: Expose the type of quasiquotes
by GHC 22 Sep '17

22 Sep '17

#13608: Expose the type of quasiquotes -------------------------------------+------------------------------------- Reporter: | Owner: (none) facundo.dominguez | Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.0.1 Haskell | Keywords: QuasiQuotes | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: 12778 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It happens with inline-java that {{{ [java| 0.0 |] }}} produces a static method in java {{{ Object fresh_name() { return 0.0; } }}} where {{{ double fresh_name() { return 0.0; } }}} would be preferred. This is better because the user would get an error if the expression does not match the expected result type. Examining the context in which the quasiquote is used would allow to build the later variant. However, GHC provides no way to grab the type that it expects of the quasiquote. The quasiquote desugars as follows: {{{ [java| 0.0 |] ====> $(parseExp java " 0.0 ") }}} We have experimented with a patch that desugars instead like {{{ [java| 0.0 |] ====> let __ghc_qq_<loc_hash> = $(parseExp java " 0.0 ") in __ghc_qq_<loc_hash> }}} The quasiquoter can learn then of the expected type by doing: {{{ do qqName <- getCurrentQuasiQuoteName addModFinalizer $ reify qqName >>= ... where getCurrentQuasiQuoteName :: Q Name getCurrentQuasiQuoteName = do loc <- TH.location return $ mkName $ "__ghc_qq_" ++ hash loc }}} Where `getCurrentQuasiQuoteName` can be provided in `Language.Haskell.TH.Quote`. This addresses the same concern that I initially intended to solve with the more complex proposal in #12778. I hope to submit a patch this week, but it would be useful if people want to provide some feedback about the proposal meanwhile. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13608> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13847: record construction accepts local unqualified name instead of qualified imported name
by GHC 21 Sep '17

21 Sep '17

#13847: record construction accepts local unqualified name instead of qualified imported name -------------------------------------+------------------------------------- Reporter: j.waldmann | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given {{{ module A where data A = A { foo :: () } deriving Show }}} the following code is accepted {{{ module Main where import qualified A foo = "foo" main = print $ A.A { foo = () } }}} albeit with a warning {{{ B.hs:4:16: warning: [-Wmissing-fields] • Fields of ‘A.A’ not initialised: foo }}} Indeed the `foo = ()` is type-checked as if it were `A.foo = ()` but the `foo` field is actually not assigned. Evaluation gives {{{ *Main> main A {foo = *** Exception: B.hs:4:16-31: Missing field in record construction foo }}} The code should be rejected outright? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13847> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13644: overloaded name used in record pattern matching leads to panic! (the 'impossible' happened) in ghc
by GHC 21 Sep '17

21 Sep '17

#13644: overloaded name used in record pattern matching leads to panic! (the 'impossible' happened) in ghc -------------------------------------+------------------------------------- Reporter: pjljvdlaar | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In Haskell, 1. The scope of definitions can be controled. 2. The same name can be used to define both a function and a field of record. 3. The user can use that name in record pattern matching when only the function is within scope. For example {{{ FuncId{ name = nm } }}} resulting in the following bug {{{ [38 of 39] Compiling TxsUtils ( src\TxsUtils.hs, .stack- work\dist\1f7101f2\build\Txs Utils.o ) ghc.EXE: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): translateConPatVec: lookup Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13644> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13964: Pattern-match warnings for datatypes with COMPLETE sets break abstraction
by GHC 21 Sep '17

21 Sep '17

#13964: Pattern-match warnings for datatypes with COMPLETE sets break abstraction -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Here's a file: {{{#!hs {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE ViewPatterns #-} module Bug (Boolean(F, TooGoodToBeTrue), catchAll) where data Boolean = F | T deriving Eq pattern TooGoodToBeTrue :: Boolean pattern TooGoodToBeTrue <- ((== T) -> True) where TooGoodToBeTrue = T {-# COMPLETE F, TooGoodToBeTrue #-} catchAll :: Boolean -> Int catchAll F = 0 -- catchAll TooGoodToBeTrue = 1 }}} If you compile this with `-Wall`, the warning will warn about `T`, not `TooGoodToBeTrue` (the other conlike in the `COMPLETE` set): {{{ $ /opt/ghc/8.2.1/bin/ghc -fforce-recomp -Wall Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:15:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘catchAll’: Patterns not matched: T | 15 | catchAll F = 0 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} Perhaps this isn't so bad, since it's intra-module. But the problem persists even across modules: {{{#!hs module Foo where import Bug catchAll2 :: Boolean -> Int catchAll2 F = 0 -- catchAll2 TooGoodToBeTrue = 1 }}} {{{ $ /opt/ghc/8.2.1/bin/ghc -fforce-recomp -c Bug.hs $ /opt/ghc/8.2.1/bin/ghc -fforce-recomp -c -Wall Foo.hs Foo.hs:6:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘catchAll2’: Patterns not matched: Bug.T | 6 | catchAll2 F = 0 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} This one is really bad, since it's warning about `Bug.T`, which should be hidden! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13964> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13959: substTyVar's definition is highly dubious
by GHC 21 Sep '17

21 Sep '17

#13959: substTyVar's definition is highly dubious -------------------------------------+------------------------------------- Reporter: RyanGlScott | 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: -------------------------------------+------------------------------------- Currently, we have: {{{#!hs substTyVar :: TCvSubst -> TyVar -> Type substTyVar (TCvSubst _ tenv _) tv = ASSERT( isTyVar tv ) case lookupVarEnv tenv tv of Just ty -> ty Nothing -> TyVarTy tv }}} But as Richard pointed out to me, the `Nothing` case is flat-out wrong. If `tv` isn't in the substitution, we need to check if any of the variables in `tv`'s kind are in the substitution, and if so, apply the substitution to them. Fixing this might seem straightforward enough: {{{#!diff diff --git a/compiler/types/TyCoRep.hs b/compiler/types/TyCoRep.hs index 5ac63e5..4f7d650 100644 --- a/compiler/types/TyCoRep.hs +++ b/compiler/types/TyCoRep.hs @@ -2191,11 +2191,11 @@ subst_ty subst ty go (CoercionTy co) = CoercionTy $! (subst_co subst co) substTyVar :: TCvSubst -> TyVar -> Type -substTyVar (TCvSubst _ tenv _) tv +substTyVar subst@(TCvSubst _ tenv _) tv = ASSERT( isTyVar tv ) case lookupVarEnv tenv tv of Just ty -> ty - Nothing -> TyVarTy tv + Nothing -> TyVarTy (updateTyVarKind (substTyUnchecked subst) tv) substTyVars :: TCvSubst -> [TyVar] -> [Type] substTyVars subst = map $ substTyVar subst }}} But note that I'm using `substTyUnchecked`, not `substTy`, since if you try using the latter, GHC will pretty quickly fall over on a `./validate --slow` build, as `substTy`'s assertions are violated all over the place. I'm fairly certain I know why the assertions would be tripping up, however. To build most of the in-scope sets used for `substTyVar`'s substitutions, the `mkVarSet :: [Var] -> VarSet` function is used. But `mkVarSet` only grabs the `Unique`s of the type variables themselves, not the variables in the kind of each type variable. This means the in-scope sets will frequently be too narrow to encompass the kind variables, which absolutely must be in the set if we want to change `substTyVar` as described above. I'm not sure what the solution is here. Perhaps we should be using a variant of `mkVarSet` called `mkTyVarSet` that grabs the `Unique`s of the kind variables as well? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13959> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8919: Why is xhtml library installed but not exported to users?
by GHC 20 Sep '17

20 Sep '17

#8919: Why is xhtml library installed but not exported to users? ------------------------------------+------------------------------------- Reporter: simons | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Build System | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- GHC 7.8.1-rc2 installs the xhtml library, but doesn't export it, i.e. it's completely invisible to users. Is there a particular reason why this setup is necessary? If GHC needs that library internally anywhere, would it be possible to link it statically and *not* install it? Or, if that's not possible, if the library needs to be installed, please make it visible to users. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8919> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9281: Rewrite `integer-gmp` to use only non-allocating GMP functions
by GHC 19 Sep '17

19 Sep '17

#9281: Rewrite `integer-gmp` to use only non-allocating GMP functions -------------------------------------+------------------------------------- Reporter: hvr | Owner: hvr Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries (other) | Version: Keywords: integer-gmp | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- After some promising results with a proof-of-concept implementation, I'm optimistic we can rewrite `integer-gmp` to use only non-allocating GMP lib functions without suffering from serious regressions. If successful, this would - allow to avoid the custom GMP allocator hack, and thus - avoid issues when linking against other C libraries using GMP, - simplify code, as we would perform all heap allocations in Haskell code (and never inside Cmm/C code as its done now), - and finally maybe even remove a few more superfluous temporary heap allocations. This rewrite can be done incrementally. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9281> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13481: T12622 fails in ghci way
by GHC 19 Sep '17

19 Sep '17

#13481: T12622 fails in ghci way -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- `T12622`, which is intended to test StaticPointers, fails in the GHCi way with a core lint warning, {{{ *** Core Lint errors : in result of Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}) *** <no location info>: warning: In the expression: >>= @ IO $fMonadIO @ (Bool -> Bool) @ () (break<10>(s_a1DF) lvl_s3bD) lvl_s3bE s_a1DF :: StaticPtr (Bool -> Bool) [LclId, Unf=Unf{Src=<vanilla>, TopLvl=False, Value=False, ConLike=False, WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 70 0}] is out of scope *** Offending Program *** g :: Bool [LclIdX] g = break<15>() True $trModule_s3b7 :: Addr# [LclId] $trModule_s3b7 = "main"# $trModule_s3b6 :: TrName [LclId] $trModule_s3b6 = TrNameS $trModule_s3b7 $trModule_s3b9 :: Addr# [LclId] $trModule_s3b9 = "Main"# $trModule_s3b8 :: TrName [LclId] $trModule_s3b8 = TrNameS $trModule_s3b9 $trModule :: Module [LclIdX] $trModule = Module $trModule_s3b6 $trModule_s3b8 lvl_s3bj :: Addr# [LclId] lvl_s3bj = "error"# lvl_s3bk :: [Char] [LclId] lvl_s3bk = unpackCString# lvl_s3bj lvl_s3bl :: Addr# [LclId] lvl_s3bl = "main"# lvl_s3bm :: [Char] [LclId] lvl_s3bm = unpackCString# lvl_s3bl lvl_s3bn :: Addr# [LclId] lvl_s3bn = "Main"# lvl_s3bo :: [Char] [LclId] lvl_s3bo = unpackCString# lvl_s3bn lvl_s3bp :: Addr# [LclId] lvl_s3bp = "T12622.hs"# lvl_s3bq :: [Char] [LclId] lvl_s3bq = unpackCString# lvl_s3bp lvl_s3br :: Int [LclId] lvl_s3br = I# 21# lvl_s3bs :: Int [LclId] lvl_s3bs = I# 14# lvl_s3bt :: Int [LclId] lvl_s3bt = I# 21# lvl_s3bu :: Int [LclId] lvl_s3bu = I# 64# lvl_s3bv :: SrcLoc [LclId] lvl_s3bv = SrcLoc lvl_s3bm lvl_s3bo lvl_s3bq lvl_s3br lvl_s3bs lvl_s3bt lvl_s3bu lvl_s3bw :: ([Char], SrcLoc) [LclId] lvl_s3bw = (lvl_s3bk, lvl_s3bv) $dIP_s3bc :: CallStack [LclId] $dIP_s3bc = pushCallStack lvl_s3bw emptyCallStack lvl_s3bx :: Addr# [LclId] lvl_s3bx = "couldn't find "# lvl_s3by :: [Char] [LclId] lvl_s3by = unpackCString# lvl_s3bx lookupKey :: forall a. StaticPtr a -> IO a [LclIdX, Arity=1] lookupKey = \ (@ a_a23X) (p_X1DX :: StaticPtr a_a23X) -> break<8>(p_X1DX) >>= @ IO $fMonadIO @ (Maybe (StaticPtr a_a23X)) @ a_a23X (break<1>(p_X1DX) unsafeLookupStaticPtr @ a_a23X (break<0>(p_X1DX) staticKey @ a_a23X p_X1DX)) (\ (ds_d3as :: Maybe (StaticPtr a_a23X)) -> case ds_d3as of { Nothing -> break<7>(p_X1DX) error @ 'LiftedRep @ (IO a_a23X) ($dIP_s3bc `cast` (Sym (N:IP[0] <"callStack">_N <CallStack>_N) :: (CallStack :: *) ~R# ((?callStack::CallStack) :: Constraint))) (break<6>(p_X1DX) ++ @ Char lvl_s3by (break<5>(p_X1DX) show @ StaticPtrInfo $fShowStaticPtrInfo (break<4>(p_X1DX) staticPtrInfo @ a_a23X p_X1DX))); Just p_a1DI -> break<3>(p_a1DI) return @ IO $fMonadIO @ a_a23X (break<2>(p_a1DI) deRefStaticPtr @ a_a23X p_a1DI) }) $dTypeable_s3bA :: TypeRep Bool [LclId] $dTypeable_s3bA = mkTrCon @ * @ Bool $tcBool ([] @ SomeTypeRep) s_s3bC :: StaticPtr (Bool -> Bool) [LclId] s_s3bC = case break<9>() sg @ Bool ($dTypeable_s3bA `cast` (Sym N:Typeable[0] <*>_N <Bool>_N :: (TypeRep Bool :: *) ~R# (Typeable Bool :: Constraint))) of { T s_a38b -> s_a38b } lvl_s3bD :: IO (Bool -> Bool) [LclId] lvl_s3bD = lookupKey @ (Bool -> Bool) s_s3bC lvl_s3bE :: (Bool -> Bool) -> IO () [LclId] lvl_s3bE = \ (f_a1DG :: Bool -> Bool) -> break<12>(f_a1DG) print @ Bool $fShowBool (break<11>(f_a1DG) f_a1DG True) main :: IO () [LclIdX] main = break<14>() break<13>(s_s3bC) >>= @ IO $fMonadIO @ (Bool -> Bool) @ () (break<10>(s_a1DF) lvl_s3bD) lvl_s3bE main :: IO () [LclIdX] main = runMainIO @ () main *** End of Offense *** <no location info>: error: Compilation had errors *** Exception: ExitFailure 1 ===== program output begins here ===== program output begins here T12622:6:30: error: Not in scope: ‘Main.main’ No module named ‘Main’ is imported. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13481> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13525: hWaitForInput with timeout causes program to abort
by GHC 19 Sep '17

19 Sep '17

#13525: hWaitForInput with timeout causes program to abort --------------------------------------+---------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- This program, {{{#!hs import System.IO import System.Timeout main = hWaitForInput stdin (5 * 1000) }}} causes the program to abort (tested on Linux), {{{ $ ghc hi.hs [1 of 1] Compiling Main ( hi.hs, hi.o ) Linking hi ... $ ./hi fdReady: msecs != 0, this shouldn't happenAborted }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13525> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9157: cmm common block not eliminated
by GHC 19 Sep '17

19 Sep '17

#9157: cmm common block not eliminated ------------------------------------+------------------------------------- Reporter: wojteknar | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- For the toTuple# function (in the attached file) GHC generates a cmm switch statement, with all the alternatives, unsurprisingly, the same. Yet, cmm common block elimination does not kick in. In this particular example, the whole case statement could be annihilated, because all alternatives lead to the same code. BTW, this is how they match in France. {{{ #!ocaml type alt = A of int | B of int | C of int | D of int let g x = match x with A v | B v | C v | D v -> v }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9157> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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