November 2018 - ghc-tickets

[GHC] #15471: Polymorphism, typed splices and type inference don't mix
by GHC 04 Mar '19

04 Mar '19

#15471: Polymorphism, typed splices and type inference don't mix -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- Trying to quote and splice a polymorphic function doesn't work unless you have a type signature. {{{ {-# LANGUAGE TemplateHaskell #-} module A where foo1 x = x test_foo = [|| foo1 ||] }}} {{{ {-# LANGUAGE TemplateHaskell #-} module B where import A qux = $$(test_foo) }}} The type of `qux` is `Any -> Any`! Which is clearly wrong. Adding a type signature to `qux` fixes the problem. {{{ qux :: a -> a qux = $$(test_foo) }}} Either there should be a better error or this should just work. It seems that this has always been broken. Ryan tested on GHC 7.8.4 for me. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15471> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 19

[GHC] #12919: Equality not used for substitution
by GHC 04 Mar '19

04 Mar '19

#12919: Equality not used for substitution -------------------------------------+------------------------------------- Reporter: int-index | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | 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: -------------------------------------+------------------------------------- This code {{{ {-# LANGUAGE TypeInType, TypeFamilies, GADTs, ConstraintKinds #-} import Data.Kind data N = Z data V :: N -> Type where VZ :: V Z type family VC (n :: N) :: Type where VC Z = Type type family VF (xs :: V n) (f :: VC n) :: Type where VF VZ f = f data Dict c where Dict :: c => Dict c prop :: xs ~ VZ => Dict (VF xs f ~ f) prop = Dict }}} fails with this error: {{{ Op.hs:20:8: error: • Couldn't match type ‘f’ with ‘VF 'VZ f’ arising from a use of ‘Dict’ ‘f’ is a rigid type variable bound by the type signature for: prop :: forall (xs :: V 'Z) f. xs ~ 'VZ => Dict VF xs f ~ f at Op.hs:19:9 • In the expression: Dict In an equation for ‘prop’: prop = Dict • Relevant bindings include prop :: Dict VF xs f ~ f (bound at Op.hs:20:1) }}} However, if I substitute `xs` with `VZ` (by hand) in the type of `prop`, it compiles. Can be reproduced with GHC 8.0.1 but not HEAD. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12919> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15549: Core Lint error with empty closed type family
by GHC 04 Mar '19

04 Mar '19

#15549: Core Lint error with empty closed type family -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 (Type checker) | Keywords: TypeFamilies, | Operating System: Unknown/Multiple TypeInType | Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following program gives a Core Lint error on GHC 8.2.2 and later: {{{#!hs {-# LANGUAGE EmptyCase #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE UndecidableInstances #-} module Bug where import Data.Kind import Data.Void data family Sing (a :: k) data V1 :: Type -> Type data instance Sing (z :: V1 p) class Generic a where type Rep a :: Type -> Type to :: Rep a x -> a class PGeneric a where type To (z :: Rep a x) :: a class SGeneric a where sTo :: forall x (r :: Rep a x). Sing r -> Sing (To r :: a) ----- instance Generic Void where type Rep Void = V1 to x = case x of {} type family EmptyCase (a :: j) :: k where instance PGeneric Void where type To x = EmptyCase x instance SGeneric Void where sTo x = case x of }}} {{{ $ /opt/ghc/8.4.3/bin/ghc Bug.hs -dcore-lint -fforce-recomp [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) *** Core Lint errors : in result of Simplifier *** Bug.hs:38:7: warning: [in body of lambda with binder x_aZ8 :: Sing r_a12q] Kind application error in coercion ‘(Sing (D:R:RepVoid[0] <x_a12p>_N) <r_a12q>_N)_R’ Function kind = forall k. k -> * Arg kinds = [(V1 x_a12p, *), (r_a12q, Rep Void x_a12p)] Fun: V1 x_a12p (r_a12q, Rep Void x_a12p) Bug.hs:38:7: warning: [in body of lambda with binder x_aZ8 :: Sing r_a12q] Kind application error in coercion ‘D:R:SingV1z0[0] <x_a12p>_N <r_a12q>_N’ Function kind = V1 x_a12p -> * Arg kinds = [(r_a12q, Rep Void x_a12p)] Fun: V1 x_a12p (r_a12q, Rep Void x_a12p) Bug.hs:38:7: warning: [in body of lambda with binder x_aZ8 :: Sing r_a12q] Kind application error in coercion ‘D:R:SingV1z0[0] <x_a12p>_N <r_a12q>_N’ Function kind = V1 x_a12p -> * Arg kinds = [(r_a12q, Rep Void x_a12p)] Fun: V1 x_a12p (r_a12q, Rep Void x_a12p) <no location info>: warning: In the type ‘R:SingV1z x_a12p r_a12q’ Kind application error in type ‘R:SingV1z x_a12p r_a12q’ Function kind = forall p -> V1 p -> * Arg kinds = [(x_a12p, *), (r_a12q, Rep Void x_a12p)] Fun: V1 x_a12p (r_a12q, Rep Void x_a12p) <no location info>: warning: In the type ‘R:SingV1z x_a12p r_a12q’ Kind application error in type ‘R:SingV1z x_a12p r_a12q’ Function kind = forall p -> V1 p -> * Arg kinds = [(x_a12p, *), (r_a12q, Rep Void x_a12p)] Fun: V1 x_a12p (r_a12q, Rep Void x_a12p) *** Offending Program *** <elided> $csTo_a12n :: forall x (r :: Rep Void x). Sing r -> Sing (To r) [LclId, Arity=1, Str=<L,U>x, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=True)}] $csTo_a12n = \ (@ x_a12p) (@ (r_a12q :: Rep Void x_a12p)) (x_aZ8 :: Sing r_a12q) -> case x_aZ8 `cast` ((Sing (D:R:RepVoid[0] <x_a12p>_N) <r_a12q>_N)_R ; D:R:SingV1z0[0] <x_a12p>_N <r_a12q>_N :: (Sing r_a12q :: *) ~R# (R:SingV1z x_a12p r_a12q :: *)) of nt_s13T { } }}} GHC 8.0.2 does not appear to suffer from this Core Lint error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15549> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14729: normaliseType is not well-kinded
by GHC 04 Mar '19

04 Mar '19

#14729: normaliseType is not well-kinded -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- Suppose we have {{{ Proxy :: forall k. k -> Type type family F a type instance F Int = Bool }}} and we're trying to normalise the target {{{ Proxy (F Int) x }}} Clearly, for this target to be well kinded, we need `x :: F Int`. Currently, the output of `normaliseType` is `Proxy Bool x`, which is just plain wrong. I need to implement logic like in `flatten_args` on [https://github.com/goldfirere/ghc my branch] in `normaliseType` to fix this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14729> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14759: ListSetOps WARNING causes tests to fail
by GHC 04 Mar '19

04 Mar '19

#14759: ListSetOps WARNING causes tests to fail -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- Example log: ``` +WARNING: file compiler/utils/ListSetOps.hs, line 58 + [Distribution.Backpack, Distribution.Backpack.FullUnitId, + Distribution.Backpack.ModuleShape, + Distribution.Backpack.PreModuleShape, + Distribution.Backpack.ReadyComponent, + Distribution.CabalSpecVersion, Distribution.Compat.Graph, + Distribution.Compat.Semigroup, Distribution.Compiler, + Distribution.License, Distribution.ModuleName, + Distribution.SPDX.License, Distribution.SPDX.LicenseExceptionId, + Distribution.SPDX.LicenseExpression, Distribution.SPDX.LicenseId, + Distribution.SPDX.LicenseReference, + Distribution.Simple.BuildTarget, Distribution.Simple.Compiler, + Distribution.Simple.Doctest, Distribution.Simple.Haddock, + Distribution.Simple.InstallDirs, Distribution.Simple.PackageIndex, + Distribution.Simple.Program.Find, Distribution.Simple.Program.GHC, + Distribution.Simple.Program.Types, Distribution.Simple.Setup, + Distribution.System, Distribution.Types.AbiDependency, + Distribution.Types.AbiHash, Distribution.Types.Benchmark, + Distribution.Types.BenchmarkInterface, + Distribution.Types.BenchmarkType, Distribution.Types.BuildInfo, + Distribution.Types.BuildType, Distribution.Types.ComponentId, + Distribution.Types.ComponentLocalBuildInfo, + Distribution.Types.ComponentName, + Distribution.Types.ComponentRequestedSpec, + Distribution.Types.CondTree, Distribution.Types.Condition, + Distribution.Types.Dependency, Distribution.Types.ExeDependency, + Distribution.Types.Executable, Distribution.Types.ExecutableScope, + Distribution.Types.ExposedModule, Distribution.Types.ForeignLib, + Distribution.Types.ForeignLibOption, + Distribution.Types.ForeignLibType, + Distribution.Types.GenericPackageDescription, + Distribution.Types.IncludeRenaming, + Distribution.Types.InstalledPackageInfo, + Distribution.Types.LegacyExeDependency, Distribution.Types.Library, + Distribution.Types.LocalBuildInfo, Distribution.Types.Mixin, + Distribution.Types.Module, Distribution.Types.ModuleReexport, + Distribution.Types.ModuleRenaming, + Distribution.Types.MungedPackageId, + Distribution.Types.MungedPackageName, + Distribution.Types.PackageDescription, + Distribution.Types.PackageId, Distribution.Types.PackageName, + Distribution.Types.PkgconfigDependency, + Distribution.Types.PkgconfigName, + Distribution.Types.SetupBuildInfo, Distribution.Types.SourceRepo, + Distribution.Types.TargetInfo, Distribution.Types.TestSuite, + Distribution.Types.TestSuiteInterface, Distribution.Types.TestType, + Distribution.Types.UnitId, Distribution.Types.UnqualComponentName, + Distribution.Types.Version, Distribution.Types.VersionRange, + Distribution.Utils.ShortText, Distribution.Verbosity, + Language.Haskell.Extension, Control.Applicative, Data.Complex, + Data.Functor.Compose, Data.Functor.Const, Data.Functor.Identity, + Data.Functor.Product, Data.Functor.Sum, Data.Monoid, + Data.Semigroup, Data.Semigroup.Internal, Data.Version, Data.Void, + GHC.Exts, GHC.Generics, GHC.IO.Exception, Data.Graph, + Data.IntMap.Internal, Data.IntSet.Internal, Data.Map.Internal, + Data.Sequence.Internal, Data.Set.Internal, Data.Tree, + Text.PrettyPrint.Annotated.HughesPJ, Text.PrettyPrint.HughesPJ, + Data.Text, Data.Text.Lazy] + [] +WARNING: file compiler/utils/ListSetOps.hs, line 58 + [Control.Applicative, Data.Functor.Const, Data.Functor.Identity, + Data.Monoid, Data.Semigroup.Internal, GHC.Generics, + GHC.IO.Exception] + [Distribution.Backpack, Distribution.Backpack.FullUnitId, + Distribution.Backpack.ModuleShape, + Distribution.Backpack.PreModuleShape, + Distribution.Backpack.ReadyComponent, + Distribution.CabalSpecVersion, Distribution.Compat.Graph, + Distribution.Compat.Semigroup, Distribution.Compiler, + Distribution.License, Distribution.ModuleName, + Distribution.SPDX.License, Distribution.SPDX.LicenseExceptionId, + Distribution.SPDX.LicenseExpression, Distribution.SPDX.LicenseId, + Distribution.SPDX.LicenseReference, + Distribution.Simple.BuildTarget, Distribution.Simple.Compiler, + Distribution.Simple.Doctest, Distribution.Simple.Haddock, + Distribution.Simple.InstallDirs, Distribution.Simple.PackageIndex, + Distribution.Simple.Program.Find, Distribution.Simple.Program.GHC, + Distribution.Simple.Program.Types, Distribution.Simple.Setup, + Distribution.System, Distribution.Types.AbiDependency, + Distribution.Types.AbiHash, Distribution.Types.Benchmark, + Distribution.Types.BenchmarkInterface, + Distribution.Types.BenchmarkType, Distribution.Types.BuildInfo, + Distribution.Types.BuildType, Distribution.Types.ComponentId, + Distribution.Types.ComponentLocalBuildInfo, + Distribution.Types.ComponentName, + Distribution.Types.ComponentRequestedSpec, + Distribution.Types.CondTree, Distribution.Types.Condition, + Distribution.Types.Dependency, Distribution.Types.ExeDependency, + Distribution.Types.Executable, Distribution.Types.ExecutableScope, + Distribution.Types.ExposedModule, Distribution.Types.ForeignLib, + Distribution.Types.ForeignLibOption, + Distribution.Types.ForeignLibType, + Distribution.Types.GenericPackageDescription, + Distribution.Types.IncludeRenaming, + Distribution.Types.InstalledPackageInfo, + Distribution.Types.LegacyExeDependency, Distribution.Types.Library, + Distribution.Types.LocalBuildInfo, Distribution.Types.Mixin, + Distribution.Types.Module, Distribution.Types.ModuleReexport, + Distribution.Types.ModuleRenaming, + Distribution.Types.MungedPackageId, + Distribution.Types.MungedPackageName, + Distribution.Types.PackageDescription, + Distribution.Types.PackageId, Distribution.Types.PackageName, + Distribution.Types.PkgconfigDependency, + Distribution.Types.PkgconfigName, + Distribution.Types.SetupBuildInfo, Distribution.Types.SourceRepo, + Distribution.Types.TargetInfo, Distribution.Types.TestSuite, + Distribution.Types.TestSuiteInterface, Distribution.Types.TestType, + Distribution.Types.UnitId, Distribution.Types.UnqualComponentName, + Distribution.Types.Version, Distribution.Types.VersionRange, + Distribution.Utils.ShortText, Distribution.Verbosity, + Language.Haskell.Extension, Control.Applicative, Data.Complex, + Data.Functor.Compose, Data.Functor.Const, Data.Functor.Identity, + Data.Functor.Product, Data.Functor.Sum, Data.Monoid, + Data.Semigroup, Data.Semigroup.Internal, Data.Version, Data.Void, + GHC.Exts, GHC.Generics, GHC.IO.Exception, Data.Graph, + Data.IntMap.Internal, Data.IntSet.Internal, Data.Map.Internal, + Data.Sequence.Internal, Data.Set.Internal, Data.Tree, + Text.PrettyPrint.Annotated.HughesPJ, Text.PrettyPrint.HughesPJ, + Data.Text, Data.Text.Lazy] +WARNING: file compiler/utils/ListSetOps.hs, line 58 + [] + [Distribution.Backpack, Distribution.Backpack.FullUnitId, + Distribution.Backpack.ModuleShape, + Distribution.Backpack.PreModuleShape, + Distribution.Backpack.ReadyComponent, + Distribution.CabalSpecVersion, Distribution.Compat.Graph, + Distribution.Compat.Semigroup, Distribution.Compiler, + Distribution.License, Distribution.ModuleName, + Distribution.SPDX.License, Distribution.SPDX.LicenseExceptionId, + Distribution.SPDX.LicenseExpression, Distribution.SPDX.LicenseId, + Distribution.SPDX.LicenseReference, + Distribution.Simple.BuildTarget, Distribution.Simple.Compiler, + Distribution.Simple.Doctest, Distribution.Simple.Haddock, + Distribution.Simple.InstallDirs, Distribution.Simple.PackageIndex, + Distribution.Simple.Program.Find, Distribution.Simple.Program.GHC, + Distribution.Simple.Program.Types, Distribution.Simple.Setup, + Distribution.System, Distribution.Types.AbiDependency, + Distribution.Types.AbiHash, Distribution.Types.Benchmark, + Distribution.Types.BenchmarkInterface, + Distribution.Types.BenchmarkType, Distribution.Types.BuildInfo, + Distribution.Types.BuildType, Distribution.Types.ComponentId, + Distribution.Types.ComponentLocalBuildInfo, + Distribution.Types.ComponentName, + Distribution.Types.ComponentRequestedSpec, + Distribution.Types.CondTree, Distribution.Types.Condition, + Distribution.Types.Dependency, Distribution.Types.ExeDependency, + Distribution.Types.Executable, Distribution.Types.ExecutableScope, + Distribution.Types.ExposedModule, Distribution.Types.ForeignLib, + Distribution.Types.ForeignLibOption, + Distribution.Types.ForeignLibType, + Distribution.Types.GenericPackageDescription, + Distribution.Types.IncludeRenaming, + Distribution.Types.InstalledPackageInfo, + Distribution.Types.LegacyExeDependency, Distribution.Types.Library, + Distribution.Types.LocalBuildInfo, Distribution.Types.Mixin, + Distribution.Types.Module, Distribution.Types.ModuleReexport, + Distribution.Types.ModuleRenaming, + Distribution.Types.MungedPackageId, + Distribution.Types.MungedPackageName, + Distribution.Types.PackageDescription, + Distribution.Types.PackageId, Distribution.Types.PackageName, + Distribution.Types.PkgconfigDependency, + Distribution.Types.PkgconfigName, + Distribution.Types.SetupBuildInfo, Distribution.Types.SourceRepo, + Distribution.Types.TargetInfo, Distribution.Types.TestSuite, + Distribution.Types.TestSuiteInterface, Distribution.Types.TestType, + Distribution.Types.UnitId, Distribution.Types.UnqualComponentName, + Distribution.Types.Version, Distribution.Types.VersionRange, + Distribution.Utils.ShortText, Distribution.Verbosity, + Language.Haskell.Extension, Control.Applicative, Data.Complex, + Data.Functor.Compose, Data.Functor.Const, Data.Functor.Identity, + Data.Functor.Product, Data.Functor.Sum, Data.Monoid, + Data.Semigroup, Data.Semigroup.Internal, Data.Version, Data.Void, + GHC.Exts, GHC.Generics, GHC.IO.Exception, Data.Graph, + Data.IntMap.Internal, Data.IntSet.Internal, Data.Map.Internal, + Data.Sequence.Internal, Data.Set.Internal, Data.Tree, + Text.PrettyPrint.Annotated.HughesPJ, Text.PrettyPrint.HughesPJ, + Data.Text, Data.Text.Lazy] +WARNING: file compiler/utils/ListSetOps.hs, line 58 + [Distribution.Backpack, Distribution.Backpack.FullUnitId, + Distribution.Backpack.ModuleShape, + Distribution.Backpack.PreModuleShape, + Distribution.Backpack.ReadyComponent, + Distribution.CabalSpecVersion, Distribution.Compat.Graph, + Distribution.Compat.Semigroup, Distribution.Compiler, + Distribution.License, Distribution.ModuleName, + Distribution.SPDX.License, Distribution.SPDX.LicenseExceptionId, + Distribution.SPDX.LicenseExpression, Distribution.SPDX.LicenseId, + Distribution.SPDX.LicenseReference, + Distribution.Simple.BuildTarget, Distribution.Simple.Compiler, + Distribution.Simple.Doctest, Distribution.Simple.Haddock, + Distribution.Simple.InstallDirs, Distribution.Simple.PackageIndex, + Distribution.Simple.Program.Find, Distribution.Simple.Program.GHC, + Distribution.Simple.Program.Types, Distribution.Simple.Setup, + Distribution.System, Distribution.Types.AbiDependency, + Distribution.Types.AbiHash, Distribution.Types.Benchmark, + Distribution.Types.BenchmarkInterface, + Distribution.Types.BenchmarkType, Distribution.Types.BuildInfo, + Distribution.Types.BuildType, Distribution.Types.ComponentId, + Distribution.Types.ComponentLocalBuildInfo, + Distribution.Types.ComponentName, + Distribution.Types.ComponentRequestedSpec, + Distribution.Types.CondTree, Distribution.Types.Condition, + Distribution.Types.Dependency, Distribution.Types.ExeDependency, + Distribution.Types.Executable, Distribution.Types.ExecutableScope, + Distribution.Types.ExposedModule, Distribution.Types.ForeignLib, + Distribution.Types.ForeignLibOption, + Distribution.Types.ForeignLibType, + Distribution.Types.GenericPackageDescription, + Distribution.Types.IncludeRenaming, + Distribution.Types.InstalledPackageInfo, + Distribution.Types.LegacyExeDependency, Distribution.Types.Library, + Distribution.Types.LocalBuildInfo, Distribution.Types.Mixin, + Distribution.Types.Module, Distribution.Types.ModuleReexport, + Distribution.Types.ModuleRenaming, + Distribution.Types.MungedPackageId, + Distribution.Types.MungedPackageName, + Distribution.Types.PackageDescription, + Distribution.Types.PackageId, Distribution.Types.PackageName, + Distribution.Types.PkgconfigDependency, + Distribution.Types.PkgconfigName, + Distribution.Types.SetupBuildInfo, Distribution.Types.SourceRepo, + Distribution.Types.TargetInfo, Distribution.Types.TestSuite, + Distribution.Types.TestSuiteInterface, Distribution.Types.TestType, + Distribution.Types.UnitId, Distribution.Types.UnqualComponentName, + Distribution.Types.Version, Distribution.Types.VersionRange, + Distribution.Utils.ShortText, Distribution.Verbosity, + Language.Haskell.Extension, Control.Applicative, Data.Complex, + Data.Functor.Compose, Data.Functor.Const, Data.Functor.Identity, + Data.Functor.Product, Data.Functor.Sum, Data.Monoid, + Data.Semigroup, Data.Semigroup.Internal, Data.Version, Data.Void, + GHC.Exts, GHC.Generics, GHC.IO.Exception, Data.Graph, + Data.IntMap.Internal, Data.IntSet.Internal, Data.Map.Internal, + Data.Sequence.Internal, Data.Set.Internal, Data.Tree, + Text.PrettyPrint.Annotated.HughesPJ, Text.PrettyPrint.HughesPJ, + Data.Text, Data.Text.Lazy] + [] *** unexpected failure for cabal09(normal) ``` This is probably orph calculation. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14759> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15865: Typed template haskell and implicit parameters lead to incorrect results
by GHC 04 Mar '19

04 Mar '19

#15865: Typed template haskell and implicit parameters lead to incorrect results -------------------------------------+------------------------------------- Reporter: mpickering | 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: -------------------------------------+------------------------------------- In a similar vein to #15863 but this time with implicit parameters. https://gist.github.com/b6919b13abe0954fdad844e16e0edb48 {{{ {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE TemplateHaskell #-} module A where import Language.Haskell.TH import Data.List (sortBy) sort :: (?cmp :: a -> a -> Ordering) => [a] -> [a] sort = sortBy ?cmp me :: Q (TExp ([Int] -> [Int])) me = let ?cmp = compare in [|| sort ||] }}} In module `A` we quote a value which has an implicit argument but in its context we bind the implicit so the type of the quote is the monomorphic type. {{{ {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE TemplateHaskell #-} module B where import A foo :: [Int] -> [Int] foo = --let ?cmp = compare in $$(me) }}} When we splice in `me`, we get an error about an unbound implicit parameter which is totally bogus as we already bound it in `A`. There is also dynamic binding if another implicit parameter with the same name is in scope but the type of `me` mentions nothing about implicit parameters so this shouldn't be allowed. {{{ B.hs:8:10: error: • Unbound implicit parameter (?cmp::Int -> Int -> Ordering) arising from a use of ‘sort’ • In the expression: sort In the result of the splice: $me To see what the splice expanded to, use -ddump-splices In the Template Haskell splice $$(me) | 8 | foo = $$(me) | ^^ Failed, one module loaded. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15865> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #15863: Splcing a type class method selects the wrong instance
by GHC 04 Mar '19

04 Mar '19

#15863: Splcing a type class method selects the wrong instance -------------------------------------+------------------------------------- Reporter: mpickering | 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: -------------------------------------+------------------------------------- Consider these 4 modules as concocted by Csongor. The wrong instance is selected when you splice in `B.me` into `D`. https://gist.github.com/mpickering/959a95525647802414ab50e8e6ed490c {{{ module A where class C a where foo :: a -> String instance C Int where foo _ = "int" }}} {{{ {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE NoMonomorphismRestriction #-} module B where import A import Language.Haskell.TH instance C a => C [a] where foo _ = "list" me :: Q (TExp ([Int] -> String)) me = [|| foo ||] }}} {{{ {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE NoMonomorphismRestriction #-} module C where import A import Language.Haskell.TH instance {-# OVERLAPPING #-} C [Int] where foo _ = "list2" }}} {{{ {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE NoMonomorphismRestriction #-} module D where import A import B import C main2 = $$(me) [1 :: Int] }}} {{{ >>> main2 "list2" }}} In `B`, `B.me` is created by quoting `foo`. `B.me :: Q (TExp ([Int] -> String))` so in order to type check this quote we need to solve the instance `C [Int]` which we should do by using the instance defined in `B` (and `A`). In module `C` we define a different overlapping instance (note that this could be in a completely different library not under our control). When we then splice `B.me` into `D`, the instance from `C` is used and can be witnessed by printing `main2` which shows `"list2"` rather than `"list"` as expected. This is a symptom of the fact that the renamed rather than the typechecked AST is serialised I think. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15863> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #15849: Error message: "Perhaps you need a let in a do block", when there is no do block.
by GHC 04 Mar '19

04 Mar '19

#15849: Error message: "Perhaps you need a let in a do block", when there is no do block. -------------------------------------+------------------------------------- Reporter: cdsmith | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- This code: {{{#!haskell main = return () foo = return () }}} Gives the error message: {{{ parse error on input ‘=’ Perhaps you need a 'let' in a 'do' block? e.g. 'let x = 5' instead of 'x = 5' }}} But this isn't in a do block. It would be awesome if GHC checked whether there's a do block before giving a suggestion that depends on there being a do block. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15849> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 5

[GHC] #15467: unregisterised validation failures
by GHC 04 Mar '19

04 Mar '19

#15467: unregisterised validation failures --------------------------------------+--------------------------------- Reporter: alpmestan | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: T7040_ghci | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- The most recent completed run of `validate-x86_64-linux-unreg` on Circle CI (https://circleci.com/gh/ghc/ghc/7733) shows 13 unexpected failures and 1 unexpected pass. **Summary** {{{ Unexpected passes: concurrent/T13615/T13615.run T13615 [unexpected] (ghci) Unexpected failures: codeGen/should_compile/T9329.run T9329 [exit code non-0] (normal) codeGen/should_run/cgrun018.run cgrun018 [exit code non-0] (normal) codeGen/should_run/cgrun018.run cgrun018 [exit code non-0] (g1) codeGen/should_run/cgrun069.run cgrun069 [exit code non-0] (normal) codeGen/should_run/cgrun069.run cgrun069 [exit code non-0] (g1) codeGen/should_run/T9577.run T9577 [bad stdout] (normal) concurrent/should_run/T3429.run T3429 [bad exit code] (debug_numa) driver/T14075/T14075.run T14075 [bad stderr] (normal) rts/T7040_ghci.run T7040_ghci [bad stderr] (ghci) rts/T14702.run T14702 [bad exit code] (threaded1) rts/nursery-chunks1.run nursery-chunks1 [bad stderr] (threaded1) rts/numa001.run numa001 [bad exit code] (debug_numa) ../../libraries/base/tests/T11760.run T11760 [bad exit code] (normal) }}} All failures but `T7040_ghci` happen in the debug validation job too (see #15466). `recomp007` doesn't fail here and `T7040_ghci` "replaces" it. I'm therefore only including the details for `T7040_ghci` here, as you can find out everything about the other faiilures in #15466. --- **T7040_ghci** {{{ Actual stderr output differs from expected: --- /dev/null 2018-08-01 14:20:42.758797000 +0000 +++ ./rts/T7040_ghci.run/T7040_ghci.run.stderr.normalised 2018-08-02 04:15:35.594990695 +0000 @@ -0,0 +1,4 @@ + +T7040_ghci:6:30: + Not in scope: ‘Main.main’ + No module named ‘Main’ is imported. *** unexpected failure for T7040_ghci(ghci) }}} I suspect this is one of those cases where ghci can't load the module because of unboxed sums and what not, I havent' checked yet, but we were seeing that type of error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15467> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11982: Typechecking fails for parallel monad comprehensions with polymorphic let
by GHC 04 Mar '19

04 Mar '19

#11982: Typechecking fails for parallel monad comprehensions with polymorphic let -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- {{{ {-# LANGUAGE MonadComprehensions, ParallelListComp #-} module Foo where foo xs ys = [ (f y True, f x 'c') | let f _ z = z, x <- xs | y <- ys ] }}} This fails with {{{ Foo.hs:5:52: error: * Cannot instantiate unification variable `t0' with a type involving foralls: forall t2 t3. t3 -> t2 -> t2 GHC doesn't yet support impredicative polymorphism * In a stmt of a monad comprehension: let f _ z = z, x <- xs | y <- ys In the expression: [(f y True, f x 'c') | let f _ z = z, x <- xs | y <- ys] In an equation for `foo': foo xs ys = [(f y True, f x 'c') | let f _ z = z, x <- xs | y <- ys] }}} NB: `ApplicativeDo` has a related problem: the implementation is quite different and has the effect of monomorphising the let-bound variable. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11982> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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