December 2018 - ghc-tickets

[GHC] #15840: Inline data constructor wrappers very late
by GHC 04 Mar '19

04 Mar '19

#15840: Inline data constructor wrappers very late -------------------------------------+------------------------------------- Reporter: aspiwack | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.7 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 came up in the context of the implementation of linear types, where more data constructors have wrapper. But this should be of more general use. I want to share this in case someone can find an objection to this approach. Currently, writing a RULE involving a data constructor with a wrapper is perilous: the wrapper will be inlined in phase 2, probably before the RULE is even triggered (necessarily if the RULE only runs in phase 1). I want to remedy this situation. This proposal is mainly from Simon Peyton Jones, any misrepresentation is, of course, my own. The proposal is to inline all data constructor wrappers in phase 0. After all the RULE business has been dealt with. If we do that, we need to be quite careful about case-of-know-constructor: In {{{#!hs case $WK u of { K x -> e; … } }}} `$WK` wouldn't unfold until very late. But we don't want the `case` expression to be blocked! Otherwise we may, for instance, prevent the function's size to be small enough to be inlined. Hence a maybe some rules will not trigger. That would not be acceptable. Fortunately, in order to decide whether case-of-known-constructor can perform, the simplifier calls `exprIsConApp_maybe`. Also fortunate is that in the situation above, we really don't care about any RULE stuff (at least not in relation with `K`). So what we can do is make `exprIsConApp_maybe` a bit smarter and teach it to see through data constructor wrappers. Let's take an unpacking wrapper as an example: {{{#!hs data T = MkT {-# UNPACK #-} !(Int, Bool) $WMkT p = case p of (i,b) -> MkT i b }}} We have to see that `$WMkT u` is a constructor application. Hence we need to be able to peek through cases. We also need to be able to witness that we have done so. So the type of `exprIsConApp_maybe` would change from {{{#!hs exprIsConApp_maybe :: InScopeEnv -> CoreExpr -> Maybe (DataCon, [Type], [CoreExpr]) }}} to {{{#!hs exprIsConApp_maybe :: InScopeEnv -> CoreExpr -> Maybe ([Float],DataCon, [Type], [CoreExpr]) }}} Where `Float`-s are lets or cases with a single alternative (much like in the FloatOut pass). We then need to change case-of-known-constructor to also perform case-of- lets and case-of-cases when such floats are found. In summary: data constructor wrappers would be inlined in phase 0, except when they can trigger a case-of-known constructor, in which case they would be inlined immediately. Does anyone sees something which could go wrong with this plan? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15840> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15952: Reduce zonking-related invariants in the type checker
by GHC 04 Mar '19

04 Mar '19

#15952: Reduce zonking-related invariants in the type checker -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 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: -------------------------------------+------------------------------------- The type checker currently maintains two invariants, documented in `Note [The well-kinded type invariant]` in TcType and `Note [The tcType invariant]` in TcHsType. These are a pain to maintain, and Simon and I cooked up a plan not to. Step 1. The tcType invariant is all about `tcInferApps`, at least according to the Note. Previously, we couldn't zonk in `tcInferApps`, because types were knot-tied. But now we can! So, `tcInferApps` could take the type only (not its kind), zonk it, then get the type's (zonked) kind. This might also mean that `tc_infer_hs_type` no longer needs to return a type/kind pair, but could just return a type. After this is done, we can likely remove all the zonks that are in service to the tcType invariant, findable by a search. Step 2. The well-kinded type invariant is also about the need to zonk sometimes. But, instead, we could just always zonk on-the-fly. That is, we introduce new functions like `tcTypeKind` and `tcSubstTy` that zonk as they go. To make sure we're calling the right function at the right time, we introduce `newtype TcType = TcType { unTcType :: Type }`. Then, we're forced to call monadic functions on `TcType`s. This will likely lead to code duplication between `Type` and `TcType`, but we might be able to banish `zonkTcType` (and its many friends) entirely. Also gone would be the `naked` functions, which are all about maintaining the well-kinded type invariant. This step would, as a side effect, fix #15799 and #15918, which is about treating `TcType`s differently from `Type`s. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15952> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 10

[GHC] #16077: AvailTC Invariant being violated
by GHC 04 Mar '19

04 Mar '19

#16077: AvailTC Invariant being violated -------------------------------------+------------------------------------- Reporter: harpocrates | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- The `AvailTC Invariant` (from `basicTypes/Avail.hs`) states that: {{{ If the type or class is itself to be in scope, it must be *first* in this list. Thus, typically: @AvailTC Eq [Eq, ==, \/=]@ }}} Here is a case where this invariant is not upheld: * `pkgA/pkgA.cabal`: {{{ name: pkgA version: 1.0.0 build-type: Simple cabal-version: >= 1.2 library exposed-modules: A build-depends: base }}} * `pkgA/A.hs` {{{ {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeFamilies #-} module A ( C(..) , T(TI) , error ) where class C a where data T a instance C Int where data T Int = TI { ti :: Int } }}} * `pkgB/pkgB.cabal` {{{ name: pkgB version: 1.0.0 build-type: Simple cabal-version: >= 1.2 library exposed-modules: B build-depends: base, pkgA }}} * `pkgB/B.hs` {{{ module B ( module A ) where import A hiding (error) }}} Now, check out the exports for `A` vs. `B`: {{{ $ cabal new-build pkgA pkgB --ghc-options -ddump-rn-trace | grep rnExports Warning: The package list for 'hackage.haskell.org' is 38 days old. Run 'cabal update' to get the latest list of available packages. rnExports: Exports: [error, C{C, T;}, T{T, TI;}] rnExports: Exports: [C{C, T;}, T{TI;}] }}} Why is `T{TI;}` in the second line not `T{T, TI;}`? Shouldn't the exports for `B` be identical to those for `A` (except for `error`)? This is causing a crash in Haddock: https://github.com/haskell/haddock/issues/979. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16077> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #8657: -fregs-graph still has a limit on spill slots
by GHC 04 Mar '19

04 Mar '19

#8657: -fregs-graph still has a limit on spill slots -----------------------------------+--------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler (NCG) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time crash Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -----------------------------------+--------------------------------------- The limit on spill slots was removed for the linear register allocator in 7.8, but not for `-fregs-graph`. SHA-1 fails to compile with `-fregs-graph` in 7.8. Related: #7679 (`-fregs-graph` generates poor code with the new codegen). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8657> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 18

[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

1 25

[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

1 10

[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

1 15

[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

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