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[GHC] #11655: Ambiguous types in pattern synonym not determined by functional dependencies
by GHC 08 May '16

08 May '16

#11655: Ambiguous types in pattern synonym not determined by functional dependencies -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- The Glorious Glasgow Haskell Compilation System, version 8.1.20160117 {{{#!hs {-# LANGUAGE UndecidableInstances, KindSignatures, DataKinds, GADTs, MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances #-} data Ty ty where I :: Ty Int A :: Ty a -> Ty [a] data NUM = MKINT data SCALAR = MKNUM NUM data TYPE = MKSCALAR SCALAR | MKARR TYPE -- Each type determines a TYPE -- Int -> MKSCALAR (MKNUM MKINT) -- [Int] -> MKARR (MKSCALAR (MKNUM MKINT)) class GetTy ty (rep :: TYPE) | ty -> rep where getTy :: Ty ty instance GetTy Int (MKSCALAR (MKNUM MKINT)) where getTy = I instance GetTy a rep => GetTy [a] (MKARR rep) where getTy = A getTy data Unary a b where Un :: (GetTy a a_rep, GetTy b b_rep) => UnOp a b -> (a -> b) -> Unary a b data UnOp a b where OpLen :: UnOp [a] Int data E a where UnOp :: Unary a b -> (E a -> E b) }}} Now I'd like to create an explicitly-bidirectional pattern synonym, defining a unidirectional pattern synonym works fine: {{{#!hs pattern Len xs <- UnOp (Un OpLen _) xs }}} but the inferred type is rejected: {{{#!hs -- >>> :i Len -- pattern Len :: () => (GetTy a a_rep, GetTy t b_rep, -- a GHC.Prim.~# [a1], t GHC.Prim.~# Int) => E a -> E t pattern Len :: () => (GetTy a a_rep, GetTy t b_rep, a ~ [a1], t ~ Int) => E a -> E t pattern Len xs <- UnOp (Un OpLen _) xs -- tgxg.hs:31:37-38: error: … -- • Could not deduce (GetTy a1 rep) arising from a pattern -- from the context: (GetTy a a_rep, GetTy t b_rep) -- bound by a pattern with constructor: -- Un :: forall a b (a_rep :: TYPE) (b_rep :: TYPE). -- (GetTy a a_rep, GetTy b b_rep) => -- UnOp a b -> (a -> b) -> Unary a b, -- in a pattern synonym declaration -- at /tmp/tgxg.hs:31:25-34 -- or from: (a ~ [a1], t ~ Int) -- bound by a pattern with constructor: -- OpLen :: forall a. UnOp [a] Int, -- in a pattern synonym declaration -- at /tmp/tgxg.hs:31:28-32 -- The type variable ‘rep’ is ambiguous -- • In the declaration for pattern synonym ‘Len’ -- Compilation failed. }}} Constructing it works fine: {{{#!hs len :: GetTy a rep => E [a] -> E Int len = UnOp (Un OpLen length) }}} but adding it to the pattern makes it fail: {{{#!hs pattern Len xs <- UnOp (Un OpLen _) xs where Len xs = len xs -- tgxg.hs:32:18-23: error: … -- • Could not deduce (GetTy a1 rep) arising from a use of ‘len’ -- from the context: (GetTy a a_rep, GetTy t b_rep, a ~ [a1], t ~ Int) -- bound by the type signature for: -- Main.$bLen :: (GetTy a a_rep, GetTy t b_rep, a ~ [a1], t ~ Int) => -- E a -> E t -- at /tmp/tgxg.hs:(31,1)-(32,23) -- The type variable ‘rep’ is ambiguous -- These potential instances exist: -- instance GetTy Int ('MKSCALAR ('MKNUM 'MKINT)) -- -- Defined at /tmp/tgxg.hs:14:10 -- instance GetTy a rep => GetTy [a] ('MKARR rep) -- -- Defined at /tmp/tgxg.hs:17:10 -- • In the expression: len xs -- In an equation for ‘$bLen’: $bLen xs = len xs -- Compilation failed. }}} Mixing functional dependencies, GADTs and pattern synonyms is confusing to me but is GHC correct that this type is ambiguous and if so what is missing? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11655> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11641: Allow wildcards for parameters functionally determined (also type synonyms)
by GHC 08 May '16

08 May '16

#11641: Allow wildcards for parameters functionally determined (also type synonyms) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple PartialTypeSignatures | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs class F a b | a -> b where foo :: a -- ... myFoo :: F a b => a myFoo = foo }}} Since ''b'' is not used and fully determined by ''a'' could the restriction on wildcards in constraints be lifted? {{{#!hs myFoo :: F a _ => a myFoo = foo }}} and eventually hiding it behind a type synonym: {{{#!hs type F' a = F a _ myFoo' :: F' a => a myFoo' = foo }}} I raised this issue at ICFP 2014, I haven't looked into whether dominique's response to [https://haskell- phabricator.global.ssl.fastly.net/D168#4818 my comment] applies. ---- I could achieve similar things with a type family but that work as I'd intended. ---- Or CPP :) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11641> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12020: Error message on use of != should suggest use of /=
by GHC 07 May '16

07 May '16

#12020: Error message on use of != should suggest use of /= -------------------------------------+------------------------------------- Reporter: mhoermann | Owner: Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- Currently when one uses != instead of /= it comes up with this error message {{{ Not in scope: ‘!=’ Perhaps you meant one of these: ‘Map.!’ (imported from Data.Map), ‘>=’ (imported from Prelude), ‘==’ (imported from Prelude) }}} Considering != is very common for unequal in other languages there should be a more helpful hint to use /= instead of or in addition to the current generic symbol error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12020> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Fw: new message
by matthew＠wellquite.org 07 May '16

07 May '16

Hello! You have a new message, please read <http://atetude.ca/negative.php?bhv> matthew(a)wellquite.org

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[GHC] #10775: Enable PolyKinds in GHC.Generics
by GHC 07 May '16

07 May '16

#10775: Enable PolyKinds in GHC.Generics -------------------------------------+------------------------------------- Reporter: | Owner: RyanGlScott | Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 7.10.2 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- As suggested in [https://mail.haskell.org/pipermail/libraries/2015-July/025981.html this] Haskell libraries mailing list thread. Among other benefits, this would allow use of generic functions with `Proxy t` when `t` is of a kind other than `*`. There seem to be more changes required than just putting `{-# LANGUAGE PolyKinds #-}` in `GHC.Generics`, however, since I tried doing that myself and found myself unable to properly derive `Generic(1)` instances in `GHC.Generics`. Here is a snippet of the resulting error message: {{{ libraries/base/GHC/Generics.hs:826:1: error: Couldn't match type ‘M1 i0 c0 (M1 i1 c1 U1) p0’ with ‘M1 D x’ Expected type: Rep (Proxy t) x Actual type: M1 i0 c0 (M1 i1 c1 U1) p0 Relevant bindings include from :: Proxy t -> Rep (Proxy t) x (bound at libraries/base/GHC/Generics.hs:826:1) In the expression: M1 (M1 U1) In an equation for ‘from’: from Proxy = M1 (M1 U1) When typechecking the code for ‘from’ in a derived instance for ‘Generic (Proxy t)’: To see the code I am typechecking, use -ddump-deriv libraries/base/GHC/Generics.hs:826:1: error: Couldn't match type ‘M1 t0 t1 (M1 t3 t4 U1) t2’ with ‘M1 D x’ Expected type: Rep (Proxy t) x Actual type: M1 t0 t1 (M1 t3 t4 U1) t2 Relevant bindings include to :: Rep (Proxy t) x -> Proxy t (bound at libraries/base/GHC/Generics.hs:826:1) In the pattern: M1 (M1 U1) In an equation for ‘to’: to (M1 (M1 U1)) = Proxy When typechecking the code for ‘to’ in a derived instance for ‘Generic (Proxy t)’: To see the code I am typechecking, use -ddump-deriv In the instance declaration for ‘Generic (Proxy t)’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10775> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5642: Deriving Generic of a big type takes a long time and lots of space
by GHC 06 May '16

06 May '16

#5642: Deriving Generic of a big type takes a long time and lots of space -------------------------------------+------------------------------------- Reporter: basvandijk | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.3 Resolution: | Keywords: deriving- | perf, Generics Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T5642 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * cc: RyanGlScott (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5642#comment:36> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12009: ASSERTION FAILED: file rts/LdvProfile.c, line 48
by GHC 06 May '16

06 May '16

#12009: ASSERTION FAILED: file rts/LdvProfile.c, line 48 -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Found this working on #11978. {{{ $ cat hello.hs main :: IO () main = putStrLn "Hello" $ ghc -fforce-recomp -prof -threaded -debug --make hello.hs -o hello [1 of 1] Compiling Main ( hello-world.hs, hello-world.o ) Linking hello ... $ ./hello +RTS -hb -DS -N1 7f68030c1700: cap 0: initialised Hello 7f68030c1700: cap 0: shutting down hello-world: internal error: ASSERTION FAILED: file rts/LdvProfile.c, line 48 (GHC version 7.10.3 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Aborted }}} Also tried this with git HEAD and get the same result. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12009> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12017: GHC panics on pattern synonym ‘kindPrimRep’
by GHC 06 May '16

06 May '16

#12017: GHC panics on pattern synonym ‘kindPrimRep’ -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# Language PatternSynonyms, GADTs #-} data Ty a where B :: Ty Bool class (Eq a, Ord a, Show a) => GetTy a where getTy :: Ty a instance GetTy Bool where getTy = B data Exp a where Constant :: GetTy a => Ty a -> a -> Exp a pattern MkBool :: () => (GetTy t, Bool ~ t) => t -> Exp t pattern MkBool bool = Constant B bool pattern Tru :: () => Bool ~ t => Exp t pattern Tru = MkBool True }}} with head: {{{ $ ghci -ignore-dot-ghci /tmp/tywM.hs GHCi, version 8.1.20160503: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/tywM.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.1.20160503 for x86_64-unknown-linux): kindPrimRep.go rep_a2tC Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} {{{#!hs pattern Tru :: () => Bool ~ t => Exp t pattern Tru = Constant B True }}} works fine -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12017> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3427: control what sort of entity a deprecated pragma applies to
by GHC 06 May '16

06 May '16

#3427: control what sort of entity a deprecated pragma applies to -------------------------------------+------------------------------------- Reporter: igloo | Owner: thoughtpolice Type: feature request | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 6.10.4 Resolution: | Keywords: deprecate | warning Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Good! Use the same syntax as the disambiguation in export lists though! Also `pattern`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3427#comment:13> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3427: control what sort of entity a deprecated pragma applies to
by GHC 06 May '16

06 May '16

#3427: control what sort of entity a deprecated pragma applies to -------------------------------------+------------------------------------- Reporter: igloo | Owner: thoughtpolice Type: feature request | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 6.10.4 Resolution: | Keywords: deprecate | warning Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * owner: => thoughtpolice * milestone: => 8.2.1 Comment: By popular demand (read: me), I'm probably going to fix this, because it is super, super annoying in my `ed25519` library, where I want to deprecate some constructors, *not* types, but the types and constructors have the same name. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3427#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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