July 2018 - ghc-tickets

Re: [GHC] #3984: Handle multiline input in GHCi history
by GHC 30 Jul '18

30 Jul '18

#3984: Handle multiline input in GHCi history -------------------------------------+------------------------------------- Reporter: aavogt | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 6.12.1 Resolution: | Keywords: 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 bgamari): I would guess so. Perhaps you would like to pick it up? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3984#comment:24> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15441: Data type with phantoms using TypeInType isn't coercible
by GHC 30 Jul '18

30 Jul '18

#15441: Data type with phantoms using TypeInType isn't coercible -------------------------------------+------------------------------------- Reporter: glittershark | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.2 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: -------------------------------------+------------------------------------- I'm *pretty* sure this is a problem with TypeInType in particular. I'd expect the following to compile: {{{#!hs {-# LANGUAGE GADTs, TypeInType, TypeApplications #-} module Bug where import Prelude import Data.Coerce import Data.Kind data Foo a = Foo data Bar (a :: Type) (b :: Foo a) where Bar :: Bar a 'Foo x = coerce @(Bar Int 'Foo) @(Bar Bool 'Foo) }}} But it doesn't -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15441> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10056: Inconsistent precedence of ~
by GHC 30 Jul '18

30 Jul '18

#10056: Inconsistent precedence of ~ -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 (Parser) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects Architecture: | valid program Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The following compiles as expected: {{{#!hs {-# LANGUAGE TypeFamilies #-} type family Foo a b f :: (Foo a b ~ Int) => a -> b -> b f = error "" }}} but this fails: {{{#!hs {-# LANGUAGE TypeFamilies #-} type family a \\ b f :: (a \\ b ~ Int) => a -> b -> b f = error "" }}} with the error > "The second argument of `(\\)` should have kind `*`, but `b ~ Int` has kind `Constraint`." Thus the first example is being parsed as `(Foo a b) ~ Int`, while the second is parsed as `a \\ (b ~ Int)`. I believe the second example should compile, i.e. `(\\)` and `Foo` should have the same precedence, both of which are higher than `(~)`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10056> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14873: GHC HEAD regression (piResultTy)
by GHC 30 Jul '18

30 Jul '18

#14873: GHC HEAD regression (piResultTy) -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 8.5 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (Originally noticed [https://travis- ci.org/goldfirere/singletons/jobs/347945148#L1179 here].) The following program typechecks on GHC 8.2.2 on GHC 8.4.1, but panics on GHC HEAD: {{{#!hs {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} module Bug where import Data.Kind (Type) data family Sing (a :: k) newtype instance Sing (f :: k1 ~> k2) = SLambda { applySing :: forall t. Sing t -> Sing (Apply f t) } data TyFun :: Type -> Type -> Type type a ~> b = TyFun a b -> Type infixr 0 ~> type family Apply (f :: k1 ~> k2) (x :: k1) :: k2 class SingI (a :: k) where sing :: Sing a data ColSym1 :: f a -> a ~> Bool type instance Apply (ColSym1 x) y = Col x y class PColumn (f :: Type -> Type) where type Col (x :: f a) (y :: a) :: Bool class SColumn (f :: Type -> Type) where sCol :: forall (x :: f a) (y :: a). Sing x -> Sing y -> Sing (Col x y :: Bool) instance (SColumn f, SingI x) => SingI (ColSym1 (x :: f a) :: a ~> Bool) where sing = SLambda (sCol (sing @_ @x)) }}} {{{ $ /opt/ghc/head/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.5.20180201 for x86_64-unknown-linux): piResultTy k_aZU[tau:1] (a_aW8[sk:1] |> <*>_N) Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:947:35 in ghc:Type }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14873> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15456: (ImplicitParams) Allow ? in binding patterns
by GHC 30 Jul '18

30 Jul '18

#15456: (ImplicitParams) Allow ? in binding patterns -------------------------------------+------------------------------------- Reporter: Welperooni | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple ImplicitParams | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is mostly useful when dealing with ImplicitParams. Suppose "foo" takes an implicit parameter "?msg" {{{#!hs -- Invalid, parse error in pattern ?msg bar ?msg = foo \?msg -> foo -- With -XViewPatterns, same issue bar ( ... -> ?msg) = foo }}} Instead, you are forced to create a local let binding {{{#!hs bar msg = let ?msg = msg in foo \msg -> let ?msg = msg in foo bar ( ... -> msg) = let ?msg = msg in foo }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15456> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13451: Bind implicit parameter in patterns
by GHC 30 Jul '18

30 Jul '18

#13451: Bind implicit parameter in patterns -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple ImplicitParams | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Is there any reason why variables for `ImplicitParams` can't be bound in patterns, so you can write {{{#!hs data Exp = Val Int | Op Op Exp Exp data Op = Add | Mul data Protect where Protect :: (?op :: Op) => Protect protectOp :: Exp -> Maybe Protect protectOp (Op ?op _ _) = Just Protect protectOp _ = Nothing }}} instead of {{{#!hs protectOp :: Exp -> Maybe Protect protectOp (Op op _ _) = Just Protect where ?op = op protectOp _ = Nothing }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13451> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3984: Handle multiline input in GHCi history
by GHC 29 Jul '18

29 Jul '18

#3984: Handle multiline input in GHCi history -------------------------------------+------------------------------------- Reporter: aavogt | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 6.12.1 Resolution: | Keywords: 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 fredefox): Has this been dropped? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3984#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11549: Add -fshow-runtime-rep
by GHC 29 Jul '18

29 Jul '18

#11549: Add -fshow-runtime-rep -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: highest | Milestone: 8.0.1 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: -------------------------------------+------------------------------------- As discussed in several interwoven threads ([https://mail.haskell.org/pipermail/ghc-devs/2016-February/011268.html original], [https://mail.haskell.org/pipermail/haskell- cafe/2016-February/122914.html café]), it has been suggested to add a flag `-fshow-runtime-rep`. Without this flag enabled, the pretty printer will instantiate any `RuntimeRep` type parameters to `PtrRep Lifted`. This has the effect of changing {{{ ($) :: forall (r :: RuntimeRep) (a :: *) (b :: TYPE r). (a -> b) -> a -> b }}} to {{{ ($) :: (a -> b) -> a -> b }}} under the default GHCi settings. Note that `Levity` becomes `RuntimeRep` after #11471 is complete. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11549> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15273: Datatypes with CUSKs should quantify over unknown kinds
by GHC 29 Jul '18

29 Jul '18

#15273: Datatypes with CUSKs should quantify over unknown kinds -------------------------------------+------------------------------------- Reporter: goldfire | 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): Phab:D4845 | Wiki Page: -------------------------------------+------------------------------------- In [https://github.com/ghc-proposals/ghc-proposals/pull/54 the future], we will be able to give full kind signatures to datatype declarations. But in the present, we use CUSKs to write kind signatures. However, consider {{{#!hs data T (a :: Proxy k) }}} That has a CUSK, according to the CUSK rules. Yet we don't know the kind of `k`. Currently, this definition is rejected, accusing the user of lying about having a complete kind. However, let's instead pretend the user had written {{{#!hs type T :: Proxy k -> Type data T a }}} After all, that's what the CUSK is shorthand for. In this case, it's clear that we should infer `T :: forall k1 (k :: k1). Proxy k -> Type`, just the way we would do with a term-level type signature. This turns out to be quite easy. See Phab:D4845. This change allows strictly more programs to be accepted, and I think it falls under the threshold for requiring a proposal. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15273> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10184: Coercible solver incomplete with recursive newtypes
by GHC 29 Jul '18

29 Jul '18

#10184: Coercible solver incomplete with recursive newtypes -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: low | Milestone: ⊥ Component: Compiler | Version: 7.10.1-rc3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The following module fails to compile due to infinite recursion: {{{ import Data.Coerce newtype Bar a = Bar (Either a (Bar a)) newtype Age = MkAge Int x :: Bar Age x = coerce (Bar (Left (5 :: Int))) }}} It tries to coerce `Bar Int` to `Bar Age`. This is clearly doable, via tyconapp decomposition. But we don't find it. Before worrying too much about it, though, we'll wait for a real example. Do speak up if this problem is ruining your day! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10184> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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