October 2018 - ghc-tickets

Re: [GHC] #4861: Documentation for base does not include special items
by GHC 04 Oct '18

04 Oct '18

#4861: Documentation for base does not include special items -------------------------------------+------------------------------------- Reporter: NeilMitchell | Owner: (none) Type: bug | Status: patch Priority: low | Milestone: ⊥ Component: Core Libraries | Version: 7.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Documentation | Unknown/Multiple bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5167 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ryan Scott <ryan.gl.scott@…>): In [changeset:"feb8a671a4e92922ddac108686f0eace97dd331f/ghc" feb8a67/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="feb8a671a4e92922ddac108686f0eace97dd331f" Improve generated `GHC.Prim` docs Summary: * Extended `genprimcode` to generate Haddock-compatible deprecations, as well as displaying information about which functions are LLVM-only and which functions can fail with an unchecked exception. * Ported existing deprecations to the new format, and also added a deprecation on `par#` (see Trac #15227). * Emit an error on fixity/deprecation of builtins, unless we are processing the module in which that name is defined (see Trac #15233). That means the following is no longer accepted (outside of `GHC.Types`): ``` infixr 7 : {-# DEPRECATED (:) "cons is deprecated" #-} ``` * Generate `data (->) a b` with docs and fixity in `GHC.Prim`. This means: GHC can now parse `data (->) a b` and `infixr 0 ->` (only in `GHC.Prim`) and `genprimcode` can digest `primtype (->) a b` (See Trac #4861) as well as some misc fixes along the way. Reviewers: bgamari, RyanGlScott Reviewed By: RyanGlScott Subscribers: RyanGlScott, rwbarton, mpickering, carter GHC Trac Issues: #15227, #15233, #4861 Differential Revision: https://phabricator.haskell.org/D5167 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4861#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13365: Kind-inference for poly-kinded GADTs
by GHC 04 Oct '18

04 Oct '18

#13365: Kind-inference for poly-kinded GADTs -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- With `-XPolyKinds`, GADTs require kind signatures where they should be inferred. Moreover, the error when these kind sigs are omitted is baffling. {{{ {-# LANGUAGE PolyKinds, GADTs #-} import GHC.TypeLits data C (x :: k) a where C1 :: (KnownNat x) => a -> Foo x a C2 :: a -> Foo Int a }}} {{{ error: • Expected kind ‘k’, but ‘x1’ has kind ‘Nat’ • In the first argument of ‘Foo’, namely ‘x’ In the type ‘Foo x a’ In the definition of data constructor ‘C1’ }}} From this error, I would never expect that putting a kind signature on `a` would help here. But a signature shouldn't be required at all: it's clear from the GADT constructors that `a :: *`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13365> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15675: Type operators in existential context cannot be parsed
by GHC 04 Oct '18

04 Oct '18

#15675: Type operators in existential context cannot be parsed -------------------------------------+------------------------------------- Reporter: int-index | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.4.3 (Parser) | 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: -------------------------------------+------------------------------------- {{{#!haskell {-# LANGUAGE TypeOperators, MultiParamTypeClasses, ExistentialQuantification #-} class a + b data D1 = forall a b. (a + b) => D1 a b data D2 = forall a b. a + b => D2 a b }}} The declaration `D1` is accepted, while `D2` is rejected. There is no reason to reject `D2` except for shortcomings of the current grammar. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15675> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15457: (~) and (!) are parsed inconsistently in types (plus documentation warts)
by GHC 04 Oct '18

04 Oct '18

#15457: (~) and (!) are parsed inconsistently in types (plus documentation warts) -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.4.3 (Parser) | 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: -------------------------------------+------------------------------------- (Spawned from https://ghc.haskell.org/trac/ghc/ticket/10056?replyto=41#comment:41) `~` and `!` are slightly special in the parser to allow strict annotations and lazy annotations (with `-XStrict`) in data types. As a result, we initially parse all uses of `~`/`!` as bangs, and we use a post-parsing pass (`mergeOps`/`splitTilde`) to figure out which uses of `~` are actually meant to refer to the equality type constructor. There's a couple of unsatisfying things here: 1. `splitTilde` handles `~`, but not `!`. This means that any use of `!` as a type operator will not work, as evidenced by this GHCi session: {{{ λ> type a ! b = Either a b <interactive>:1:6: error: Malformed head of type or class declaration: a !b }}} We should update `splitTilde` to handle `!` as well. (And perhaps give that function a new name to reflect its more ambitious goals.) 2. `Note [Parsing ~]` is supposed to explain all of this hullabaloo, but it does a rather poor job of it. Let's add some more prose to it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15457> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15483: ghc -M requires -dep-suffix for no good reason
by GHC 03 Oct '18

03 Oct '18

#15483: ghc -M requires -dep-suffix for no good reason -------------------------------------+------------------------------------- Reporter: ulysses4ever | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: 8.6.1 Component: Driver | 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: -------------------------------------+------------------------------------- Doing {{{ ghc -M Foo.hs }}} gives {{{ You must specify at least one -dep-suffix }}} I went to the documentation and noticed ([https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/separate_co… #makefile-dependencies 7.8.12]) an example: {{{ depend : ghc -dep-suffix '' -M $(HC_OPTS) $(SRCS) }}} So, empty suffix is fine. Why not default to empty string then? I found a commit which introduced the requirement ([https://github.com/ghc/ghc/commit/af072fc35d8dbe7962e62700da052593e999c0ef af072fc]): it says, it fixed #7381, and this doesn't seem to do anything with `dep-suffix` in particular. So, maybe there is no good reason to require that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15483> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5518: Some unicode symbols are not allow in literal characters or strings
by GHC 03 Oct '18

03 Oct '18

#5518: Some unicode symbols are not allow in literal characters or strings ---------------------------------+-------------------------------------- Reporter: ertai | Owner: ulysses4ever Type: bug | Status: merge Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #15525 | Differential Rev(s): Phab:D5066 Wiki Page: | ---------------------------------+-------------------------------------- Changes (by ulysses4ever): * status: patch => merge * related: => #15525 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5518#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1087: bang patterns with infix ops
by GHC 03 Oct '18

03 Oct '18

#1087: bang patterns with infix ops -------------------------------------+------------------------------------- Reporter: dons | Owner: int-index Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.6 (Parser) | Resolution: | Keywords: bang patterns 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 int-index): * owner: (none) => int-index -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1087#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] Batch modify: #15499, #15667, #8763, #12005, #13704, #14907, ...
by GHC 03 Oct '18

03 Oct '18

Batch modification to #15499, #15667, #8763, #12005, #13704, #14907, #15053, #15196, #15481, #15552, #15578, #13477 by RyanGlScott: milestone to 8.6.2 Comment: Moving to the 8.6.2 milestone, since these tickets were all recently marked as merge. -- Tickets URL: <http://ghc.haskell.org/trac/ghc/query?id=15499%2C15667%2C8763%2C12005%2C137…> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12556: `stimes` adds extra power to Semigroup
by GHC 03 Oct '18

03 Oct '18

#12556: `stimes` adds extra power to Semigroup -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: task | Status: new Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ ghci> stimes 0 (undefined :: [_]) [] }}} ghci> stimes 0 undefined () }}} makes it seem like `stimes 0` has some knowledge about `mempty` from `Monoid` but it has the following type {{{#!hs stimes 0 :: Semigroup a => a -> a }}} Desired behaviour? Given that type (assuming it only has the power of `<>`) I would have assumed this behaviour {{{ ghci> data L a = N | C a (L a) deriving Show ghci> instance Semigroup (L a) where (<>) = undefined ghci| ghci> stimes 0 (undefined :: L _) *** Exception: stimes: positive multiplier expected }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12556> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15693: Abstracting out pattern into a pattern synonym fails with scary error
by GHC 03 Oct '18

03 Oct '18

#15693: Abstracting out pattern into a pattern synonym fails with scary error -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- This '''works''' {{{#!hs {-# Language DataKinds, TypeOperators, PolyKinds, PatternSynonyms, GADTs #-} import Data.Kind data Ctx :: Type -> Type where E :: Ctx(Type) (:&:) :: a -> Ctx(as) -> Ctx(a -> as) data ApplyT(kind::Type) :: kind -> Ctx(kind) -> Type where AO :: a -> ApplyT(Type) a E AS :: ApplyT(ks) (f a) ctx -> ApplyT(k -> ks) f (a:&:ctx) foo :: ApplyT(Type -> Type -> Type) Either a -> () foo (ASSO (Left a)) = () pattern ASSO a = AS (AS (AO a)) }}} but then you might think, let's give a name (pattern synonym) to `ASSO (Left a)` This '''fails''' {{{#!hs {-# Language DataKinds, TypeOperators, PolyKinds, PatternSynonyms, GADTs #-} import Data.Kind data Ctx :: Type -> Type where E :: Ctx(Type) (:&:) :: a -> Ctx(as) -> Ctx(a -> as) data ApplyT(kind::Type) :: kind -> Ctx(kind) -> Type where AO :: a -> ApplyT(Type) a E AS :: ApplyT(ks) (f a) ctx -> ApplyT(k -> ks) f (a:&:ctx) pattern ASSO a = AS (AS (AO a)) pattern ASSOLeft a = ASSO (Left a) }}} {{{ $ ghci -ignore-dot-ghci 464.hs GHCi, version 8.7.20180828: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( hs/464.hs, interpreted ) hs/464.hs:16:22: error: • Couldn't match type ‘k1’ with ‘*’ ‘k1’ is a rigid type variable bound by the signature for pattern synonym ‘ASSOLeft’ at hs/464.hs:16:1-34 Expected type: ApplyT kind a b Actual type: ApplyT (* -> * -> *) Either (a1 ':&: (a20 ':&: 'E)) • In the expression: ASSO (Left a) In an equation for ‘ASSOLeft’: ASSOLeft a = ASSO (Left a) | 16 | pattern ASSOLeft a = ASSO (Left a) | ^^^^^^^^^^^^^ hs/464.hs:16:28: error: • Could not deduce: k1 ~ * from the context: (kind ~ (k -> ks), a ~~ f, b ~~ (a2 ':&: ctx), ks ~ (k1 -> ks1), f a2 ~~ f1, ctx ~~ (a3 ':&: ctx1), ks1 ~ *, f1 a3 ~~ a4, ctx1 ~~ 'E) bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) (ctx :: Ctx ks) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) (ctx1 :: Ctx ks1) a3. (kind ~ (k -> ks), a ~~ f, b ~~ (a1 ':&: ctx), ks ~ (k1 -> ks1), f a1 ~~ f1, ctx ~~ (a2 ':&: ctx1), ks1 ~ *, f1 a2 ~~ a3, ctx1 ~~ 'E) => a3 -> ApplyT kind a b, in a pattern synonym declaration at hs/464.hs:16:22-34 ‘k1’ is a rigid type variable bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) (ctx :: Ctx ks) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) (ctx1 :: Ctx ks1) a3. (kind ~ (k -> ks), a ~~ f, b ~~ (a1 ':&: ctx), ks ~ (k1 -> ks1), f a1 ~~ f1, ctx ~~ (a2 ':&: ctx1), ks1 ~ *, f1 a2 ~~ a3, ctx1 ~~ 'E) => a3 -> ApplyT kind a b, in a pattern synonym declaration at hs/464.hs:16:22-34 When matching types a3 :: k1 b0 :: * Expected type: a4 Actual type: Either a1 b0 • In the pattern: Left a In the pattern: ASSO (Left a) In the declaration for pattern synonym ‘ASSOLeft’ | 16 | pattern ASSOLeft a = ASSO (Left a) | ^^^^^^ Failed, no modules loaded. Prelude> }}} ---- Can I, as a user, assume that any valid pattern `foo (ASSO (Left a)) = ...` can be abstracted into a pattern synonym? There error message is too scary for me to sensibly know what to expect -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15693> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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