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[GHC] #12072: GHC panic on type wildcard in left-hand side of data family
by GHC 25 Aug '16

25 Aug '16

#12072: GHC panic on type wildcard in left-hand side of data family -------------------------------------+------------------------------------- Reporter: andreash | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While playing around with data families I received the following output by ghc/ghci: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): rnHsTyKi HsWildcardTy Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} I had accidentally left a wildcard `_` on the left-hand side of a data instance definition. To reproduce enter the following code into a file and try to load that file into ghci, or try to compile it with ghc: {{{#!hs data family Bug x data instance Bug _ = Bug }}} The expected behavior would be a (non-panic) error message of some sort. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12072> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12165: Multiple pattern type signatures accepted
by GHC 25 Aug '16

25 Aug '16

#12165: Multiple pattern type signatures accepted -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This hogwash is accepted: {{{ pattern P :: a -> b -> Maybe (a,b) pattern P :: foo => bar => blah -> urgh pattern P x y = Just (x, y) }}} A little experimentation shows that only the first pattern signature is examined. Others are accepted and ignored. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12165> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12535: Bad error message when unidirectional pattern synonym used in bidirectional pattern synonym
by GHC 25 Aug '16

25 Aug '16

#12535: Bad error message when unidirectional pattern synonym used in bidirectional pattern synonym -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: 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: -------------------------------------+------------------------------------- If I write: {{{ {-# LANGUAGE PatternSynonyms #-} module I where pattern P2 x y <- (x, y) pattern P1 x y = P2 x y }}} I get the error: {{{ ezyang@sabre:~$ ghc-8.0 -c I.hs I.hs:5:18: error: • non-bidirectional pattern synonym ‘P2’ used in an expression • In the expression: P2 x y In an equation for ‘$bP1’: $bP1 x y = P2 x y }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12535> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #393: functions without implementations
by GHC 25 Aug '16

25 Aug '16

#393: functions without implementations -------------------------------------+------------------------------------- Reporter: c_maeder | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler (Type | Version: None checker) | Resolution: | Keywords: newcomer 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 Iceland_jack): Probably not worth it, but fake definitions are generated for Commentary/PrimOps {{{#!hs newArray# :: Int# -> a -> State# s -> (# State# s,MutableArray# s a #) newArray# = let x = x in x sameMutableArray# :: MutableArray# s a -> MutableArray# s a -> Int# sameMutableArray# = let x = x in x nullAddr# :: Addr# nullAddr# = let x = x in x }}} If this feature is enabled the bodies could be omitted and if we make holes representation-polymorphic (#12531) it's not such a reach to allow top-level unlifted bindings as well when body is omitted: {{{#!hs newArray# :: Int# -> a -> State# s -> (# State# s,MutableArray# s a #) sameMutableArray# :: MutableArray# s a -> MutableArray# s a -> Int# nullAddr# :: NullAddr# }}} This might avoid hacky tests mentioned in `[Compiling GHC.Prim]`. ---- === Note `[Placeholder declarations]` === > We are generating fake declarations for things in [https://hackage.haskell.org/package/ghc-prim-0.4.0.0/candidate/docs/src /GHC-Prim.html GHC.Prim], just to keep GHC's renamer and typechecker happy enough for what Haddock needs. Our main plan is to say > {{{#!hs > foo :: <type> > foo = foo > }}} > We have to silence GHC's complaints about unboxed-top-level declarations with an ad-hoc fix in `TcBinds`: see Note `[Compiling GHC.Prim]` in `TcBinds`. > > > That works for all the primitive functions except `tagToEnum#`. If we generate the binding > {{{#!hs > tagToEnum# = tagToEnum# > }}} > GHC will complain about "`tagToEnum#` must appear applied to one argument". We could hack GHC to silence this complaint when compiling `GHC.Prim`, but it seems easier to generate > {{{#!hs > tagToEnum# = let x = x in x > }}} > We don't do this for *all* bindings because for ones with an unboxed RHS we would get other complaints (e.g.can't unify "`*`" with "`#`"). === Note `[Compiling GHC.Prim]` === > Module `GHC.Prim` has no source code: it is the host module for primitive, built-in functions and types. However, for Haddock-ing purposes we generate (via `utils/genprimopcode`) a fake source file `GHC/Prim.hs`, and give it to Haddock, so that it can generate documentation. It contains definitions like > {{{#!hs > nullAddr# :: NullAddr# > }}} > which would normally be rejected as a top-level unlifted binding. But we don't want to complain, because we are only "compiling" this fake mdule [sic] for documentation purposes. Hence this hacky test for `gHC_PRIM` in `checkStrictBinds`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/393#comment:35> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5927: A type-level "implies" constraint on Constraints
by GHC 24 Aug '16

24 Aug '16

#5927: A type-level "implies" constraint on Constraints -------------------------------------+------------------------------------- Reporter: illissius | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.4.1 checker) | 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 Iceland_jack): Would there be a difference between {{{#!hs data Some :: (Type -> Constraint) -> Type where Some :: c a => a -> Some c }}} and {{{#!hs data Some' :: (Type -> Constraint) -> Type where Some' :: (ctx `Implies` c, c a) => a -> Some' ctx }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5927#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3314: Add compilation date to +RTS --info
by GHC 24 Aug '16

24 Aug '16

#3314: Add compilation date to +RTS --info -------------------------------------+------------------------------------- Reporter: Orphi | Owner: ak3n Type: feature request | Status: closed Priority: lowest | Milestone: Component: Compiler | Version: 6.10.2 Resolution: wontfix | 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 ak3n): Since there is no so much need for such feature, ticket is closed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3314#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3314: Add compilation date to +RTS --info
by GHC 24 Aug '16

24 Aug '16

#3314: Add compilation date to +RTS --info -------------------------------------+------------------------------------- Reporter: Orphi | Owner: ak3n Type: feature request | Status: closed Priority: lowest | Milestone: Component: Compiler | Version: 6.10.2 Resolution: wontfix | 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: | -------------------------------------+------------------------------------- Changes (by ak3n): * status: new => closed * differential: Phab:D2460 => * resolution: => wontfix -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3314#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11466: Constraint synonym with Implicit Parameter
by GHC 24 Aug '16

24 Aug '16

#11466: Constraint synonym with Implicit Parameter -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (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: -------------------------------------+------------------------------------- This: {{{ {-# LANGUAGE ConstraintKinds, ImplicitParams #-} module Foo where type Foo = ?foo::() }}} gives {{{ Foo.hs:3:1: error: • Illegal implicit parameter ‘?foo::()’ • In the type synonym declaration for ‘Foo’ }}} in GHC HEAD. It used to work in GHC-7.10. Did not check GHC-8.0. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11466> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12527: GHC segfault while linking llvm-general while compiling a file using Template Haskell
by GHC 24 Aug '16

24 Aug '16

#12527: GHC segfault while linking llvm-general while compiling a file using Template Haskell -------------------------------------+------------------------------------- Reporter: HMPerson1 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- If I have a file {{{#!hs -- Lib.hs module Lib where [d| foo = 1 |] }}} and I add `llvm-general` as a dependency, compiling with -v yields the attached log, followed by `segmentation fault (core dumped)`. Investigating with gdb, the back trace is {{{ ... Loading package llvm-general-3.5.1.2 ... linking ... Thread 1 "ghc" received signal SIGSEGV, Segmentation fault. 0x000000004490f604 in ?? () (gdb) bt #0 0x000000004490f604 in ?? () #1 0x0000000044a8798d in ?? () #2 0x0000000000000132 in ?? () #3 0x0000000044a98b38 in ?? () #4 0x0000000044a87b30 in ?? () #5 0x00007fffeed667b1 in ocRunInit_ELF (oc=0xf7f520) at rts/Linker.c:6198 #6 resolveObjs_ () at rts/Linker.c:3196 #7 resolveObjs () at rts/Linker.c:3218 #8 0x00007ffff5eb03a3 in ?? () from /home/michael/.stack/programs/x86_64-linux/ghc-7.10.3/lib/ghc-7.10.3/bin/../ghc_0AG9TOjDEtx4Ji3wSwHOBe/libHSghc-7.10.3 -0AG9TOjDEtx4Ji3wSwHOBe-ghc7.10.3.so #9 0x0000000000000000 in ?? () }}} Note that without the quasi-quotation in `Lib.hs` it will compile fine, and without the `llvm-general` dependency it will also compile fine. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12527> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12528: ghc: panic! while cimpiling
by GHC 24 Aug '16

24 Aug '16

#12528: ghc: panic! while cimpiling -------------------------------------+------------------------------------- Reporter: nek0 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While building one of my projects, GHC crashes with the following message: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): find_tycon Block [] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} The project I'm trying to build can be found at https://github.com/nek0/eidolon. The file it crashes at is called `Foundation.hs` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12528> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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