July 2016 - ghc-tickets

[GHC] #12381: Type family not reduced
by GHC 22 Aug '16

22 Aug '16

#12381: Type family not reduced -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 (Type checker) | 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: -------------------------------------+------------------------------------- Andres pointed out that the following fails to compile with GHC 8.0.1 but succeeds with `master` (f53d761df9762232b54ec57a950d301011cd21f8), {{{#!hs {-# LANGUAGE TypeInType, TypeFamilies #-} module Kinds where import GHC.Types type family G (a :: Type) :: Type type instance G Int = Bool type family F (a :: Type) :: G a type instance F Int = True }}} Error: {{{ Hi.hs:10:23: error: • Expected kind ‘G Int’, but ‘'True’ has kind ‘Bool’ • In the type ‘True’ In the type instance declaration for ‘F’ }}} We should figure out what fixed this so it can hopefully be merged for 8.0.2. I initially suspected the patch cited in #12175 but sadly this doesn't seem to be the case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12381> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12408: "ghc: panic! (the 'impossible' happened)" only when compiled with "-O"
by GHC 22 Aug '16

22 Aug '16

#12408: "ghc: panic! (the 'impossible' happened)" only when compiled with "-O" -------------------------------------+------------------------------------- Reporter: clinton | 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: -------------------------------------+------------------------------------- On Debian GNU/Linux x86, GHC 8.0.1 crashes compiling the attached code, but only when "-O1" is given. Without optimization, it compiles fine. {{{#!hs {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} module Main where import Prelude hiding ( (.) , (+) , (*) ) import qualified Prelude main :: IO () main = return () x :: Int x = 42 f a b c = (c * (a + b)) == ((c * a) + (c * b)) g = f x x x newtype Sum a = Sum { getSum :: a } newtype Product a = Product { getProduct :: a } type family CatParam t :: * class Semigroupoid p where type CatSrc p t :: * type CatDest p t :: * type CatT p a b :: * (.) :: ( p ~ CatParam catAB, p ~ CatParam catBC, p ~ CatParam catAC, a ~ CatSrc p catAB, b ~ CatSrc p catBC, a ~ CatSrc p catAC, b ~ CatDest p catAB, c ~ CatDest p catBC, c ~ CatDest p catAC, catAB ~ CatT p a b, catBC ~ CatT p b c, catAC ~ CatT p a c ) => catBC -> catAB -> catAC data BasicSumSemigroup (t :: *) :: * type instance CatParam (Sum Int) = BasicSumSemigroup Int instance (Num t) => Semigroupoid (BasicSumSemigroup t) where type CatSrc (BasicSumSemigroup _) _ = () type CatDest (BasicSumSemigroup _) _ = () type CatT (BasicSumSemigroup t) _ _ = Sum t (Sum x) . (Sum y) = Sum ((Prelude.+) x y) data BasicProductSemigroup (t :: *) :: * type instance CatParam (Product Int) = BasicProductSemigroup Int instance (Num t) => Semigroupoid (BasicProductSemigroup t) where type CatSrc (BasicProductSemigroup _) _ = () type CatDest (BasicProductSemigroup _) _ = () type CatT (BasicProductSemigroup t) _ _ = Product t (Product x) . (Product y) = Product ((Prelude.*) x y) type family RingParamFromSum p :: * type family RingParamFromProduct p :: * class NearRingWithoutId t where type SumP t type ProdP t type LeftDistrib t origLeftCat rightArg type RightDistrib t origLeftCat leftArg (+) :: ( t ~ RingParamFromSum sumP, Semigroupoid sumP, p ~ sumP, p ~ CatParam catAB, p ~ CatParam catBC, p ~ CatParam catAC, a ~ CatSrc p catAB, b ~ CatSrc p catBC, a ~ CatSrc p catAC, b ~ CatDest p catAB, c ~ CatDest p catBC, c ~ CatDest p catAC, catAB ~ CatT p a b, catBC ~ CatT p b c, catAC ~ CatT p a c, catAB ~ Sum noSumCatAB, catBC ~ Sum noSumCatBC, catAC ~ Sum noSumCatAC ) => noSumCatBC -> noSumCatAB -> noSumCatAC (+) x y = getSum ((Sum x) . (Sum y)) (*) :: ( t ~ RingParamFromProduct prodP, Semigroupoid prodP, p ~ prodP, p ~ CatParam catAB, p ~ CatParam catBC, p ~ CatParam catAC, a ~ CatSrc p catAB, b ~ CatSrc p catBC, a ~ CatSrc p catAC, b ~ CatDest p catAB, c ~ CatDest p catBC, c ~ CatDest p catAC, catAB ~ CatT p a b, catBC ~ CatT p b c, catAC ~ CatT p a c, catAB ~ Product noProdCatAB, catBC ~ Product noProdCatBC, catAC ~ Product noProdCatAC, sumCatAB ~ Sum noProdCatAB, sumCatBC ~ Sum noProdCatBC, sumCatAC ~ Sum noProdCatAC, ps ~ sumP, ps ~ CatParam sumCatAB, ps ~ CatParam sumCatBC, ps ~ CatParam sumCatAC, sumABSrc ~ CatSrc p sumCatAB, sumBCSrc ~ CatSrc p sumCatBC, sumACSrc ~ CatSrc p sumCatAC, sumABDest ~ CatDest p sumCatAB, sumBCDest ~ CatDest p sumCatBC, sumACDest ~ CatDest p sumCatAC, sumACSrc ~ LeftDistrib t sumBCSrc noProdCatAB, sumACSrc ~ RightDistrib t sumACSrc noProdCatBC, sumACDest ~ LeftDistrib t sumBCDest noProdCatAB, sumACDest ~ RightDistrib t sumACDest noProdCatBC ) => noProdCatBC -> noProdCatAB -> noProdCatAC (*) x y = getProduct ((Product x) . (Product y)) data TestInt type instance RingParamFromSum (BasicSumSemigroup Int) = TestInt type instance RingParamFromProduct (BasicProductSemigroup Int) = TestInt instance NearRingWithoutId TestInt where type SumP TestInt = BasicSumSemigroup Int type ProdP TestInt = BasicProductSemigroup Int type LeftDistrib TestInt _ _ = () type RightDistrib TestInt _ _ = () }}} The following error results: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): Template variable unbound in rewrite rule Variable: cobox_s3PM Rule "SPEC f @ Int @ Int @ Int @ Int @ Int @ Int @ Int" Rule bndrs: [cobox_s3PM, cobox_s3PN, cobox_s3PO, cobox_s3PP, cobox_s3PQ, cobox_s3PR, cobox_s3PS, cobox_s3PT, cobox_s3PU, cobox_s3PV, cobox_s3PW, cobox_s3PX, cobox_s3PY, cobox_s3PZ, cobox_s3Q0, cobox_s3Q1, cobox_s3Q2, cobox_s3Q3, cobox_s3Q4, cobox_s3Q5, cobox_s3Q6, cobox_s3Q7, cobox_s3Q8, cobox_s3Q9, cobox_s3Qa, cobox_s3Qb, cobox_s3Qc, cobox_s3Qd, cobox_s3Qe, cobox_s3Qf, cobox_s3Qg, cobox_s3Qh, cobox_s3Qi, cobox_s3Qj, cobox_s3Qk, cobox_s3Ql, cobox_s3Qm, cobox_s3Qn, cobox_s3Qo, cobox_s3Qp, cobox_s3Qq, cobox_s3Qr, cobox_s3Qs, cobox_s3Qt, cobox_s3Qu, cobox_s3Qv, cobox_s3Qw, cobox_s3Qx, cobox_s3Qy, cobox_s3Qz, cobox_s3QA, cobox_s3QB, $dSemigroupoid_X3SC, $dSemigroupoid_X3SE, $dNearRingWithoutId_s3QE, $dNearRingWithoutId_s3QF, $dEq_s3QG] LHS args: [TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatDest (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: cobox_s3PP, CO: cobox_s3PQ, CO: cobox_s3PR, CO: cobox_s3PS, CO: cobox_s3PT, CO: cobox_s3PU, CO: cobox_s3PV, CO: cobox_s3PW, CO: cobox_s3PX, CO: cobox_s3PY, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: cobox_s3Q0, CO: <CatParam (Product Int)>_N, CO: cobox_s3Q2, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: cobox_s3Q6, CO: cobox_s3Q7, CO: cobox_s3Q8, CO: cobox_s3Q9, CO: cobox_s3Qa, CO: cobox_s3Qb, CO: cobox_s3Qc, CO: cobox_s3Qd, CO: cobox_s3Qe, CO: <CatParam (Product Int)>_N, CO: cobox_s3Qg, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: <CatParam (Sum Int)>_N, CO: cobox_s3Qk, CO: cobox_s3Ql, CO: cobox_s3Qm, CO: <CatDest (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatSrc (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: cobox_s3Qs, CO: <CatParam (Sum Int)>_N, CO: cobox_s3Qu, CO: <CatSrc (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: cobox_s3Qz, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, $dSemigroupoid_X3SC, $dSemigroupoid_X3SE, $dNearRingWithoutId_s3QE, $dNearRingWithoutId_s3QF, $dEq_s3QG] Actual args: [TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, TYPE: Int, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatDest (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatT D:R:CatParamSum[0] ((CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatT D:R:CatParamSum[0] ((CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamSum[0]) <Sum Int>_N)_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: (CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N ; Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Product Int>_N)_N, CO: <CatParam (Product Int)>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatDest D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: (RightDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((LeftDistrib ((RingParamFromProduct D:R:CatParamProduct[0])_N ; D:R:RingParamFromProductBasicProductSemigroup[0]) ((CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) <Int>_N)_N ; D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) <Int>_N)_N ; D:R:RightDistribTestInt__1[0] <()>_N <Int>_N ; Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N, CO: (CatSrc D:R:CatParamProduct[0] <Sum Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:RightDistribTestInt__1[0] <()>_N <Int>_N) ; (RightDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:LeftDistribTestInt__1[0] <()>_N <Int>_N) ; (LeftDistrib (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N) (Sym (D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatSrc (Sym D:R:CatParamProduct[0]) <Sum Int>_N)_N) <Int>_N)_N) <Int>_N)_N, CO: (CatT D:R:CatParamProduct[0] ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatParam (Product Int)>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: <CatParam (Sum Int)>_N, CO: (CatT D:R:CatParamSum[0] ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: (CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N ; Sym (D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ; (CatDest (Sym D:R:CatParamSum[0]) <Sum Int>_N)_N, CO: (CatT D:R:CatParamSum[0] ((CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatDest (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatSrc (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: (CatT D:R:CatParamSum[0] ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatParam (Sum Int)>_N, CO: (CatT D:R:CatParamSum[0] ((CatSrc D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatSrcBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N) ((CatDest D:R:CatParamSum[0] <Sum Int>_N)_N ; D:R:CatDestBasicSumSemigroup_1[0] <Int>_N <Sum Int>_N))_N ; D:R:CatTBasicSumSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatSrc (CatParam (Sum Int)) (Sum Int)>_N, CO: <CatParam (Sum Int)>_N, CO: <CatDest (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, CO: (CatT D:R:CatParamProduct[0] ((CatSrc D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatSrcBasicProductSemigroup_1[0] <Int>_N <Product Int>_N) ((CatDest D:R:CatParamProduct[0] <Product Int>_N)_N ; D:R:CatDestBasicProductSemigroup_1[0] <Int>_N <Product Int>_N))_N ; D:R:CatTBasicProductSemigroup__1[0] <Int>_N <()>_N <()>_N, CO: <CatSrc (CatParam (Product Int)) (Product Int)>_N, CO: <CatParam (Product Int)>_N, ($c._a32V @ Int $fNumInt) `cast` (Sym (N:Semigroupoid[0] <BasicSumSemigroup Int>_N) ; (Semigroupoid (Sym D:R:CatParamSum[0]))_R :: ((forall catAB_awI[sk] catBC_awJ[sk] catAC_awK[sk] a_awL[sk] b_awM[sk] c_awN[sk]. ((BasicSumSemigroup Int :: *) ~ (CatParam catAB_awI[sk] :: *), (BasicSumSemigroup Int :: *) ~ (CatParam catBC_awJ[sk] :: *), (BasicSumSemigroup Int :: *) ~ (CatParam catAC_awK[sk] :: *), (a_awL[sk] :: *) ~ (CatSrc (BasicSumSemigroup Int) catAB_awI[sk] :: *), (b_awM[sk] :: *) ~ (CatSrc (BasicSumSemigroup Int) catBC_awJ[sk] :: *), (a_awL[sk] :: *) ~ (CatSrc (BasicSumSemigroup Int) catAC_awK[sk] :: *), (b_awM[sk] :: *) ~ (CatDest (BasicSumSemigroup Int) catAB_awI[sk] :: *), (c_awN[sk] :: *) ~ (CatDest (BasicSumSemigroup Int) catBC_awJ[sk] :: *), (c_awN[sk] :: *) ~ (CatDest (BasicSumSemigroup Int) catAC_awK[sk] :: *), (catAB_awI[sk] :: *) ~ (CatT (BasicSumSemigroup Int) a_awL[sk] b_awM[sk] :: *), (catBC_awJ[sk] :: *) ~ (CatT (BasicSumSemigroup Int) b_awM[sk] c_awN[sk] :: *), (catAC_awK[sk] :: *) ~ (CatT (BasicSumSemigroup Int) a_awL[sk] c_awN[sk] :: *)) => catBC_awJ[sk] -> catAB_awI[sk] -> catAC_awK[sk]) :: *) ~R# (Semigroupoid (CatParam (Sum Int)) :: Constraint)), ($c._a32m @ Int $fNumInt) `cast` (Sym (N:Semigroupoid[0] <BasicProductSemigroup Int>_N) ; (Semigroupoid (Sym D:R:CatParamProduct[0]))_R :: ((forall catAB_awI[sk] catBC_awJ[sk] catAC_awK[sk] a_awL[sk] b_awM[sk] c_awN[sk]. ((BasicProductSemigroup Int :: *) ~ (CatParam catAB_awI[sk] :: *), (BasicProductSemigroup Int :: *) ~ (CatParam catBC_awJ[sk] :: *), (BasicProductSemigroup Int :: *) ~ (CatParam catAC_awK[sk] :: *), (a_awL[sk] :: *) ~ (CatSrc (BasicProductSemigroup Int) catAB_awI[sk] :: *), (b_awM[sk] :: *) ~ (CatSrc (BasicProductSemigroup Int) catBC_awJ[sk] :: *), (a_awL[sk] :: *) ~ (CatSrc (BasicProductSemigroup Int) catAC_awK[sk] :: *), (b_awM[sk] :: *) ~ (CatDest (BasicProductSemigroup Int) catAB_awI[sk] :: *), (c_awN[sk] :: *) ~ (CatDest (BasicProductSemigroup Int) catBC_awJ[sk] :: *), (c_awN[sk] :: *) ~ (CatDest (BasicProductSemigroup Int) catAC_awK[sk] :: *), (catAB_awI[sk] :: *) ~ (CatT (BasicProductSemigroup Int) a_awL[sk] b_awM[sk] :: *), (catBC_awJ[sk] :: *) ~ (CatT (BasicProductSemigroup Int) b_awM[sk] c_awN[sk] :: *), (catAC_awK[sk] :: *) ~ (CatT (BasicProductSemigroup Int) a_awL[sk] c_awN[sk] :: *)) => catBC_awJ[sk] -> catAB_awI[sk] -> catAC_awK[sk]) :: *) ~R# (Semigroupoid (CatParam (Product Int)) :: Constraint)), $fNearRingWithoutIdTestInt `cast` ((NearRingWithoutId (Sym D:R:RingParamFromSumBasicSumSemigroup[0] ; (RingParamFromSum (Sym D:R:CatParamSum[0]))_N))_R :: (NearRingWithoutId TestInt :: Constraint) ~R# (NearRingWithoutId (RingParamFromSum (CatParam (Sum Int))) :: Constraint)), $fNearRingWithoutIdTestInt `cast` ((NearRingWithoutId (Sym D:R:RingParamFromProductBasicProductSemigroup[0] ; (RingParamFromProduct (Sym D:R:CatParamProduct[0]))_N))_R :: (NearRingWithoutId TestInt :: Constraint) ~R# (NearRingWithoutId (RingParamFromProduct (CatParam (Product Int))) :: Constraint)), $fEqInt, x, x, x] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12408> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12239: Dependent type family does not reduce
by GHC 20 Aug '16

20 Aug '16

#12239: Dependent type family does not reduce -------------------------------------+------------------------------------- Reporter: int-index | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: TypeInType, | Operating System: Unknown/Multiple TypeFamilies | Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When a type family is used in a kind of an argument for another type family, it does not reduce. Here's example code: {{{ {-# LANGUAGE TypeInType, GADTs, TypeFamilies #-} import Data.Kind (Type) data N = Z | S N data Fin :: N -> Type where FZ :: Fin (S n) FS :: Fin n -> Fin (S n) type family FieldCount (t :: Type) :: N type family FieldType (t :: Type) (i :: Fin (FieldCount t)) :: Type data T type instance FieldCount T = S (S (S Z)) type instance FieldType T FZ = Int type instance FieldType T (FS FZ) = Bool type instance FieldType T (FS (FS FZ)) = String }}} Unfortunately, I get these errors during typechecking: {{{ [1 of 1] Compiling Main ( fieldtype.hs, fieldtype.o ) fieldtype.hs:19:27: error: • Expected kind ‘Fin (FieldCount T)’, but ‘'FZ’ has kind ‘Fin ('S n0)’ • In the second argument of ‘FieldType’, namely ‘FZ’ In the type instance declaration for ‘FieldType’ fieldtype.hs:20:28: error: • Expected kind ‘Fin (FieldCount T)’, but ‘'FS 'FZ’ has kind ‘Fin ('S ('S n0))’ • In the second argument of ‘FieldType’, namely ‘FS FZ’ In the type instance declaration for ‘FieldType’ fieldtype.hs:21:28: error: • Expected kind ‘Fin (FieldCount T)’, but ‘'FS ('FS 'FZ)’ has kind ‘Fin ('S ('S ('S n0)))’ • In the second argument of ‘FieldType’, namely ‘FS (FS FZ)’ In the type instance declaration for ‘FieldType’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12239> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8955: Syscall intrinsic
by GHC 18 Aug '16

18 Aug '16

#8955: Syscall intrinsic ----------------------------------------------+---------------------------- Reporter: schyler | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less than a day) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- Reddit thread: http://www.reddit.com/r/haskell/comments/220ae4/libc_considered_harmful/ Mentions there are some nice things that can be done with a syscall intrinsic. Also, marginally increased speed for calling syscalls since it doesn't need to go through libffi into C-land. Should be easy to implement. llvm backend has `llvm.syscall` already. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8955> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12432: TypeInType: open type family application as type family return kind fails to compile
by GHC 18 Aug '16

18 Aug '16

#12432: TypeInType: open type family application as type family return kind fails to compile -------------------------------------+------------------------------------- Reporter: j6carey | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Linux Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- With TypeInType enabled, I can use a closed type family to compute the return kind of a type family from its arguments. But an equivalent open type family used in the same way triggers a compilation failure, as if the relevant instance of that open type family were not considered. (Of course, there may be some subtle prohibition of which I am not aware at the present time.) I will attach a test case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12432> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11385: Unify named wildcards in different type applications
by GHC 16 Aug '16

16 Aug '16

#11385: Unify named wildcards in different type applications -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple NamedWildCards TypeApplications | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- ([https://www.reddit.com/r/haskell/comments/4030lv/unifying_distinct_type_var… motivating post]) I would like to use type application to specialize {{{#!hs Sub :: forall (a :: Constraint) (b :: Constraint). (a => Dict b) -> a :- b Sub @(Ord _a) @(Eq _a) :: forall {a}. (Ord a => Dict (Eq a)) -> Ord a :- Eq a }}} and {{{#!hs map :: forall a b. (a -> b) -> [a] -> [b] map @_a @_a :: forall {a}. (a -> a) -> [a] -> [a] }}} Is there a fundamental reason why named wildcards are not allowed to unify between type applications within the same expression? [https://downloads.haskell.org/~ghc/master/users-guide/glasgow_exts.html #named-wildcards Documentation]: > These are called named wildcards. All occurrences of the same named wildcard within one type signature will unify to the same type. I don't know if this is intended. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11385> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9498: GHC links against unversioned .so files
by GHC 16 Aug '16

16 Aug '16

#9498: GHC links against unversioned .so files ------------------------------------+-------------------------------- Reporter: Kritzefitz | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (FFI) | Version: 7.6.3 Keywords: Debian | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: ------------------------------------+-------------------------------- Greetings, GHC tries to load unversioned dynamic libraries instead of versioned (i.e. libfoo.so instead of libfoo.so.1.2.3). This is a problem, since Distributions like Debian (I don't know about other distributions) don't include unversioned .SOs in their runtime packages and the unversioned are only available in the -dev packages as a symlink to the verioned ones. This means FFI libraries depend on the -dev packages, even though they don't really need them. It would be nice if GHC would try to load the versioned libraries as well. Regards Sven -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9498> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12384: Type family not reduced, again
by GHC 16 Aug '16

16 Aug '16

#12384: Type family not reduced, again -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This one looks similar to #12381, but unfortunately, it does not seem to be fixed in HEAD: {{{#!hs {-# LANGUAGE TypeInType, TypeFamilies, FlexibleInstances #-} import GHC.Types type family F (a :: Type) :: Type class C a where type D (a :: Type) :: F a instance (F a ~ Bool) => C a where type D a = True }}} This yields (in 8.0.1 and 8.1.20160709): {{{ Constraint.hs:11:14: error: • Expected kind ‘F a’, but ‘'True’ has kind ‘Bool’ • In the type ‘True’ In the type instance declaration for ‘D’ In the instance declaration for ‘C a’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12384> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11794: Switch to LLVM 3.8
by GHC 15 Aug '16

15 Aug '16

#11794: Switch to LLVM 3.8 -------------------------------------+------------------------------------- Reporter: erikd | Owner: erikd Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (LLVM) | 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: -------------------------------------+------------------------------------- LLVM 8.0 has been released and I (@erikd) already have patches for make GHC compile with LLVM 3.8. This ticket is just a placeholder so that when GHCHQ want to move to the new version, they just have to let me know in this ticket and I'll prepare the patch. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11794> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12418: Make `MonadCont (ContT r m)` polykinded (r::k), (m::k -> Type)
by GHC 11 Aug '16

11 Aug '16

#12418: Make `MonadCont (ContT r m)` polykinded (r::k), (m::k -> Type) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Core | Version: 8.0.1 Libraries | 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: -------------------------------------+------------------------------------- == Issue == The current `MonadCont (ContT r m)` instance seems to have `r::Type` and `m::Type -> Type`. While this is accepted {{{ >>> :t callCC :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a callCC :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a }}} this gets rejected {{{ >>> :set -XPolyKinds >>> :t callCC :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a <interactive>:1:1: error: • No instance for (MonadCont (ContT r1 m1)) arising from a use of ‘callCC’ • In the expression: callCC :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a }}} and this doesn't reduce {{{ >>> :t callCC @(ContT _ _) callCC @(ContT _ _) :: MonadCont (ContT t t1) => ((a -> ContT t t1 b) -> ContT t t1 a) -> ContT t t1 a }}} the kinds must be specified {{{ >>> :t callCC @(ContT (_::Type) _) callCC @(ContT (_::Type) _) :: ((a -> ContT t t1 b) -> ContT t t1 a) -> ContT t t1 a }}} == Solution == This is unfortunate since since `callCC` can be kind polymorphic: {{{#!hs newtype ContT' r m a = ContT' { runContT' :: (a -> m r) -> m r } callCC' :: forall k a (r :: k) (m :: k -> Type) b. ((a -> ContT' r m b) -> ContT' r m a) -> ContT' r m a callCC' f = ContT' $ \ c -> runContT' (f (\ x -> ContT' $ \ _ -> c x)) c instance forall k (r::k) (m::k -> Type). MonadCont (ContT' r m) where callCC = callCC' }}} this works now {{{ >>> :t callCC @(ContT' _ _) callCC @(ContT' _ _) :: forall k (t :: k) (t1 :: k -> *) a b. ((a -> ContT' t t1 b) -> ContT' t t1 a) -> ContT' t t1 a }}} {{{ >>> :t callCC :: ((a -> ContT' r m b) -> ContT' r m a) -> ContT' r m a callCC :: ((a -> ContT' r m b) -> ContT' r m a) -> ContT' r m a :: forall k a (r :: k) (m :: k -> *) b. ((a -> ContT' r m b) -> ContT' r m a) -> ContT' r m a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12418> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 9