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[GHC] #14218: GHC.Stack.HasCallStack not compatible with ConstraintKinds
by GHC 01 Nov '17

01 Nov '17

#14218: GHC.Stack.HasCallStack not compatible with ConstraintKinds -------------------------------------+------------------------------------- Reporter: ntc2 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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 programs `Good` and `Bad` are the same, except that `Bad` uses a constraint synonym including `GHC.Stack.HasCallStack` whereas `Good` inlines the constraints. I expect them to produce the same output, but they don't: {{{ $ ./Good ["callStack","f"] $ ./Bad ["f"] }}} Here is the source for `Good.hs`: {{{#!hs {-# LANGUAGE MultiParamTypeClasses #-} -- For nullary 'Trivial' class module Main where import qualified GHC.Stack as Ghc class Trivial where instance Trivial where -- | Print the functions on the call stack. callStack :: (Ghc.HasCallStack, Trivial) => IO () callStack = print $ map fst (Ghc.getCallStack Ghc.callStack) f :: (Ghc.HasCallStack, Trivial) => IO () f = callStack main :: IO () main = f -- Should print @["callStack", "f"]@. }}} Here is the source for `Bad.hs`: {{{#!hs {-# LANGUAGE ConstraintKinds #-} -- For 'C' {-# LANGUAGE MultiParamTypeClasses #-} -- For nullary 'Trivial' class module Main where import qualified GHC.Stack as Ghc class Trivial where instance Trivial where type C = (Ghc.HasCallStack, Trivial) -- | Print the functions on the call stack. callStack :: C => IO () callStack = print $ map fst (Ghc.getCallStack Ghc.callStack) f :: C => IO () f = callStack main :: IO () main = f -- Should print @["callStack", "f"]@. }}} Tested compiled and interpreted with GHC 8.2.1 and 8.0.2. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14218> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13372: Attach CallStack to IOError, add CallStack constraints to relevant functions in base
by GHC 01 Nov '17

01 Nov '17

#13372: Attach CallStack to IOError, add CallStack constraints to relevant functions in base -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.1 libraries/base | 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: -------------------------------------+------------------------------------- In #12096 it is requested that we add CallStack to SomeException. This is a more conservative request for adding CallStack to IOError only. IOError is already an abstract data type, so it is a simple matter to augment it with space for a CallStack. The main design flex point is whether or not a `CallStack` should be associated with an IOError when it is constructed, or when it is thrown. There are pros and cons to both: 1. If it is associated at construction time, the call stack will reflect when the IOError was constructed, not when it was thrown. This could be arbitrarily far away from the actual throw site. I've been mostly using CallStack for monadic code, and so my primary concern is with where in the monadic code the exception was thrown, so this info isn't really what I want. 2. If it is associated at throw time, there are a few other problems. First, if someone uses throwIO rather than ioError, we won't actually associate a CallStack with the value. Second, if a user is rethrowing an exception, they may accidentally overwrite the old stack trace; but it was the original one that I wanted. For now, I suggest going with (1). Here is the proposal: * Add `ioeGetCallStack` and `ioeSetCallStack`, for setting and getting the `CallStack` recorded in `IOError` * `userError` and `mkIOError` gain a `HasCallStack` constraint. We have a choice for `annotateIOError`, but my suggestion is to NOT annotate it. * Let's annotate all functions that (transitively) may raise an IOError in base with `HasCallStack`. The primary benefit is now if I have a "file not found" exception or similar, I automatically get a stack trace saying exactly what code was run where the file was not found. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13372> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5889: -fno-prof-count-entries leads to linking errors
by GHC 31 Oct '17

31 Oct '17

#5889: -fno-prof-count-entries leads to linking errors -------------------------------------+------------------------------------- Reporter: akio | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.4.1 Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: GHC rejects | (amd64) valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * priority: normal => highest * milestone: => 8.4.1 Comment: I'll try to reproduce this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5889#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14406: Core Lint error when compiling ghc with -g3
by GHC 31 Oct '17

31 Oct '17

#14406: Core Lint error when compiling ghc with -g3 -------------------------------------+------------------------------------- Reporter: duog | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Building ghc with the following build.mk: {{{ BuildFlavour = validate ifneq "$(BuildFlavour)" "" include mk/flavours/$(BuildFlavour).mk endif GhcLibHcOpts += -g3 GhcRtsHcOpts += -g3 GhcStage2Opts += -g3 }}} gives {{{ *** Core Lint errors : in result of Simplifier *** <no location info>: warning: [RHS of str_sjjS :: Addr#] The type of this binder is unlifted: str_sjjS Binder's type: Addr# *** Offending Program *** ... str_sjjS :: Addr# [LclId, Unf=Unf{Src=<vanilla>, TopLvl=False, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 20 0}] str_sjjS = src<libraries/base/Data/Data.hs:1099:38-41> ":%"# ... libraries/base/ghc.mk:4: recipe for target 'libraries/base/dist- install/build/Data/Data.o' failed }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14406> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14386: GHC doesn't allow Coercion between partly-saturated type constructors
by GHC 31 Oct '17

31 Oct '17

#14386: GHC doesn't allow Coercion between partly-saturated type constructors -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Keywords: roles | 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 define an "opposite category" `newtype Op cat a b = Op (cat b a)` then representationally it forms an involution: applying `Op` twice gives the same representation as not applying it at all {{{ $ ... -ignore-dot-ghci GHCi, version 8.3.20170920: http://www.haskell.org/ghc/ :? for help Prelude> import Data.Coerce Prelude Data.Coerce> import Data.Type.Coercion Prelude Data.Coerce Data.Type.Coercion> newtype Op cat a b = Op (cat b a) Prelude Data.Coerce Data.Type.Coercion> :t coerce :: Op (Op cat) a b -> cat a b coerce :: Op (Op cat) a b -> cat a b :: Op (Op cat) a b -> cat a b Prelude Data.Coerce Data.Type.Coercion> :t Coercion :: Coercion (Op (Op cat) a b) (cat a b) Coercion :: Coercion (Op (Op cat) a b) (cat a b) :: Coercion (Op (Op cat) a b) (cat a b) }}} But these don't work: {{{ Prelude Data.Coerce Data.Type.Coercion> :t Coercion :: Coercion (Op (Op cat) a) (cat a) <interactive>:1:1: error: • Couldn't match representation of type ‘Op (Op cat1) a1’ with that of ‘cat1 a1’ arising from a use of ‘Coercion’ • In the expression: Coercion :: Coercion (Op (Op cat) a) (cat a) Prelude Data.Coerce Data.Type.Coercion> :t Coercion :: Coercion (Op (Op cat) cat <interactive>:1:38: error: parse error (possibly incorrect indentation or mismatched brackets) Prelude Data.Coerce Data.Type.Coercion> :t Coercion :: Coercion (Op (Op cat)) cat <interactive>:1:1: error: • Couldn't match representation of type ‘cat1’ with that of ‘Op (Op cat1)’ arising from a use of ‘Coercion’ ‘cat1’ is a rigid type variable bound by an expression type signature: forall (cat1 :: * -> * -> *). Coercion (Op (Op cat1)) cat1 at <interactive>:1:13-38 • In the expression: Coercion :: Coercion (Op (Op cat)) cat }}} I'm wondering if this is intentional -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14386> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12143: ApplicativeDo Fails to Desugar 'return True'
by GHC 31 Oct '17

31 Oct '17

#12143: ApplicativeDo Fails to Desugar 'return True' -------------------------------------+------------------------------------- Reporter: MichaelBurge | Owner: 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: -------------------------------------+------------------------------------- If I bring in a spurious parameter, ApplicativeDo correctly infers Functor. {{{ Prelude> :t \m -> do { x <- m; return True; } \m -> do { x <- m; return True; } :: Functor f => f t -> f Bool Prelude> :t \m -> do { m; return True; } \m -> do { m; return True; } :: Monad m => m a -> m Bool }}} However, without the spurious parameter, ApplicativeDo assumes monad. {{{ Prelude> :t do { return True; } do { return True; } :: Monad m => m Bool }}} The first block in particular shows two examples that seem inconsistent when placed next to each other. It seems like if 'x' is unused, then 'x <- m' and 'm' should be equivalent. I would expect all of these to desugar to Functor or Applicative. And maybe 'return True' should be Monad, but 'do { return True; }' should be Applicative? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12143> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14390: Panic when defining an instance for (~~) [ppr_equality: homogeneity]
by GHC 31 Oct '17

31 Oct '17

#14390: Panic when defining an instance for (~~) [ppr_equality: homogeneity] -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- In GHC 8.2.1 and HEAD, compiling this file panics: {{{#!hs import Data.Type.Equality instance (~~) Int Int }}} {{{ $ /opt/ghc/8.2.1/bin/ghc Bug.hs [1 of 1] Compiling Main ( Bug.hs, Bug.o ) Bug.hs:2:10: error:ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-unknown-linux): ppr_equality: homogeneity ~~ Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/iface/IfaceType.hs:1008:31 in ghc:IfaceType }}} We should probably give a similar error as for when one attempts to define an instance for `(~)`: {{{#!hs instance (~) Int Int }}} {{{ $ /opt/ghc/8.2.1/bin/ghc Bug.hs [1 of 1] Compiling Main ( Bug.hs, Bug.o ) Bug.hs:1:10: error: • Illegal instance declaration for ‘Int ~ Int’ Manual instances of this class are not permitted. • In the instance declaration for ‘(~) Int Int’ | 1 | instance (~) Int Int | ^^^^^^^^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14390> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14080: GHC panic while forcing the thunk for TyThing IsFile (regression)
by GHC 30 Oct '17

30 Oct '17

#14080: GHC panic while forcing the thunk for TyThing IsFile (regression) -------------------------------------+------------------------------------- Reporter: inaki | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: hs-boot | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: #13803, #13981 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider the following set of files: {{{#!hs -- A.hs {-# LANGUAGE KindSignatures #-} {-# LANGUAGE TypeFamilies #-} module A (AI(..)) where import GHC.Exts (Constraint) class AI (info :: *) where type S info :: * -> Constraint }}} {{{#!hs -- C.hs module C () where import {-# SOURCE #-} qualified OC as OC import {-# SOURCE #-} qualified OV as OV }}} {{{#!hs -- IF.hs module IF where import qualified C as C import {-# SOURCE #-} qualified OF as OF class IsF o }}} {{{#!hs -- IF.hs-boot module IF where class IsF o }}} {{{#!hs -- OC.hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE EmptyDataDecls #-} module OC () where import A (AI(..)) data I instance AI I where type S I = (~) () }}} {{{#!hs -- OC.hs-boot module OC where }}} {{{#!hs -- OF.hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE EmptyDataDecls #-} module OF () where import A (AI(..)) import {-# SOURCE #-} qualified IF as IF data P instance AI P where type S P = IF.IsF }}} {{{#!hs -- OF.hs-boot module OF where }}} {{{#!hs -- OV.hs module OV () where }}} {{{#!hs -- OV.hs-boot module OV where }}} This works with `ghc-8.0.2` and earlier versions, but fails with `ghc-8.2.1`. When I run `ghc IF` for `8.2.1` I get {{{ [ 1 of 10] Compiling A ( A.hs, A.o ) [ 2 of 10] Compiling IF[boot] ( IF.hs-boot, IF.o-boot ) [ 3 of 10] Compiling OC[boot] ( OC.hs-boot, OC.o-boot ) [ 4 of 10] Compiling OC ( OC.hs, OC.o ) [ 5 of 10] Compiling OF[boot] ( OF.hs-boot, OF.o-boot ) [ 6 of 10] Compiling OF ( OF.hs, OF.o ) [ 7 of 10] Compiling OV[boot] ( OV.hs-boot, OV.o-boot ) [ 8 of 10] Compiling C ( C.hs, C.o ) [ 9 of 10] Compiling IF ( IF.hs, IF.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-unknown-linux): tcIfaceGlobal (local): not found You are in a maze of twisty little passages, all alike. While forcing the thunk for TyThing IsF which was lazily initialized by initIfaceCheck typecheckLoop, I tried to tie the knot, but I couldn't find IsF in the current type environment. If you are developing GHC, please read Note [Tying the knot] and Note [Type-checking inside the knot]. Consider rebuilding GHC with profiling for a better stack trace. Contents of current type environment: [] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/iface/TcIface.hs:1696:23 in ghc:TcIface Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} For context, this is a minimal testcase of the panic reported in #13803 for `gi-gio`, which persists after fixing the panic in the minimal testcase in ticket:13803#comment:9. (It seems like the original code was hitting more than one issue.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14080> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13222: Update formalism for join points
by GHC 30 Oct '17

30 Oct '17

#13222: Update formalism for join points -------------------------------------+------------------------------------- Reporter: lukemaurer | Owner: lukemaurer Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: JoinPoints | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I rather flagrantly violated the entreaties in `CoreLint` about updating the formalism (namely by adding join points). Need to fix that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13222> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14405: Remove core-spec.pdf from repository
by GHC 30 Oct '17

30 Oct '17

#14405: Remove core-spec.pdf from repository -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- Currently we track `core-spec.pdf` in the repository, which is generated from ott sources. This is a rather flagrant violation of a central tenant of version control: don't track derived files. However, simonpj would like to ensure that there is an easily accessible copy of this artifact somewhere, so we can't remove it yet. Let's ensure that it is produced by documentation artifact produced by CircleCI. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14405> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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