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[GHC] #13673: Core lint error with defer-typed-holes
by GHC 09 May '17

09 May '17

#13673: Core lint error with defer-typed-holes -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- Another Core Lint error {{{#!hs {-# Options_GHC -dcore-lint -fdefer-typed-holes #-} {-# Language ViewPatterns, PatternSynonyms, GeneralizedNewtypeDeriving, DeriveTraversable #-} import Data.Bifunctor.Fix import Data.Bifunctor.Tannen import Test.QuickCheck import Test.QuickCheck.Function import Control.Applicative newtype ZL a = ZL { getZL :: Fix (Tannen Maybe (,)) a } deriving (Eq, Ord, Read, Show, Functor, Applicative, Foldable, Traversable) fromList :: [a] -> ZL a fromList [] = Nil fromList (x:xs) = x:::fromList xs pattern Nil :: ZL a pattern Nil = ZL (In (Tannen Nothing)) foo :: ZL a -> Maybe (a, ZL a) foo (ZL (In (Tannen (Just (as, a))))) = Just (a, ZL as) infixr 5 ::: pattern (:::) :: a -> ZL a -> ZL a pattern a:::as <- ZL (In (Tannen (Just (ZL -> as, a)))) where a:::ZL as = ZL (In (Tannen (Just (as, a)))) u (Fn f) as bs = let (xs, ys) = (ZipList as, ZipList bs) in getZipList (liftA2 f xs ys) == toList (liftA2 f (fromList as) (fromList bs)) }}} unfortunately I don't have time to reduce it -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13673> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13672: Pattern match on LHS of pattern synonym declaration
by GHC 09 May '17

09 May '17

#13672: Pattern match on LHS of pattern synonym declaration -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Changing `ZipList` to a newtype {{{#!hs import Data.Bifunctor.Fix import Data.Bifunctor.Tannen type ZipList = Fix (Tannen Maybe (,)) pattern Nil :: ZipList a pattern Nil = In (Tannen Nothing) infixr 5 ::: pattern (:::) :: a -> ZipList a -> ZipList a pattern a:::as = In (Tannen (Just (as, a))) }}} works fine for the `Nil` pattern synonym (it remains implicitly bidirectional) {{{#!hs newtype ZipList a = ZL (Fix (Tannen Maybe (,)) a) pattern Nil :: ZipList a pattern Nil = ZL (In (Tannen Nothing)) }}} but `(:::)` needs to be explicitly bidirectional {{{#!hs infixr 5 ::: pattern (:::) :: a -> ZipList a -> ZipList a pattern a:::as <- ZL (In (Tannen (Just (ZL -> as, a)))) where a:::ZL as = ZL (In (Tannen (Just (as, a)))) }}} ---- I would like to write it as {{{#!hs pattern (:::) :: a -> ZipList a -> ZipList a pattern a:::ZL as = ZL (In (Tannen (Just (as, a)))) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13672> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13671: Core lint error with PatternSynonyms and undefined
by GHC 09 May '17

09 May '17

#13671: Core lint error with PatternSynonyms and undefined -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- I've submitted quite a few Core Lint errors lately, I don't have access to GHC HEAD so ignore this ticket if this has already been resolved {{{#!hs {-# Options_GHC -dcore-lint #-} {-# Language ViewPatterns, PatternSynonyms #-} import Data.Bifunctor.Fix import Data.Bifunctor.Tannen newtype ZipList a = ZL { getZipList :: Fix (Tannen Maybe (,)) a } pattern Nil :: ZipList a pattern Nil = ZL (In (Tannen Nothing)) infixr 5 ::: pattern (:::) :: a -> ZipList a -> ZipList a pattern a:::as <- ZL (In (Tannen (undefined -> (a, as)))) where a:::as = undefined }}} `↑` works fine without `-dcore-lint` but fails with it. Works fine if `undefined -> (a, as)` is replaced with `let x = x in x -> (a, as)`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13671> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13668: Space leak re-introduced
by GHC 09 May '17

09 May '17

#13668: Space leak re-introduced -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- Test `perf/compiler/T9675` is failing for me on a clean HEAD {{{ =====> T9675(optasm) 1 of 1 [0, 0, 0] cd "./T9675.run" && "/5playpen/simonpj/HEAD-5/inplace/test spaces/ghc- stage2" -c T9675.hs -no-user-package-db -rtsopts -fno-warn-missed- specialisations -fshow-warning-groups -fdiagnostics-color=never -fno- diagnostics-show-caret -dno-debug-output +RTS -G1 -RTS -O -fasm +RTS -V0 -tT9675.comp.stats --machine-readable -RTS"/5playpen/simonpj/HEAD-5/inplace/test spaces/ghc-stage2" -c T9675.hs -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show- caret -dno-debug-output +RTS -G1 -RTS -O -fasm +RTS -V0 -tT9675.comp.stats --machine-readable -RTS max_bytes_used value is too high: Expected T9675(optasm) max_bytes_used: 17675240 +/-15% Lower bound T9675(optasm) max_bytes_used: 15023954 Upper bound T9675(optasm) max_bytes_used: 20326526 Actual T9675(optasm) max_bytes_used: 25571248 Deviation T9675(optasm) max_bytes_used: 44.7 % peak_megabytes_allocated value is too high: Expected T9675(optasm) peak_megabytes_allocated: 63 +/-15% Lower bound T9675(optasm) peak_megabytes_allocated: 53 Upper bound T9675(optasm) peak_megabytes_allocated: 73 Actual T9675(optasm) peak_megabytes_allocated: 93 Deviation T9675(optasm) peak_megabytes_allocated: 47.6 % *** unexpected stat test failure for T9675(optasm) }}} Compiling with `-RTS -S` gives {{{ Alloc Copied Live GC GC TOT TOT Page Flts bytes bytes bytes user elap user elap 1139048 56288 158880 0.028 0.028 0.032 0.032 0 0 (Gen: 0) 1036832 99080 193448 0.018 0.018 0.052 0.052 0 0 (Gen: 0) 1036784 137552 223696 0.018 0.018 0.073 0.073 0 0 (Gen: 0) 1015208 145088 231232 0.018 0.018 0.094 0.094 0 0 (Gen: 0) 1084448 505864 636944 0.019 0.019 0.116 0.116 0 0 (Gen: 0) 1039312 660432 783288 0.020 0.020 0.137 0.137 0 0 (Gen: 0) 1377128 845976 1001624 0.020 0.020 0.159 0.159 0 0 (Gen: 0) 1707720 1168392 1352664 0.024 0.024 0.186 0.186 0 0 (Gen: 0) 2411008 1554360 1764288 0.023 0.023 0.214 0.214 0 0 (Gen: 0) 3128632 1885104 2164224 0.021 0.021 0.239 0.240 0 0 (Gen: 0) 3891928 3029560 3501264 0.025 0.025 0.271 0.272 0 0 (Gen: 0) 6618768 4554248 5412752 0.031 0.031 0.312 0.313 0 0 (Gen: 0) 8966136 5509176 6359368 0.033 0.033 0.358 0.359 0 0 (Gen: 0) 10948736 6299736 7158072 0.034 0.034 0.409 0.410 0 0 (Gen: 0) 12489360 8415312 9277728 0.043 0.044 0.466 0.468 0 0 (Gen: 0) 16486944 7800096 8662512 0.043 0.043 0.528 0.529 0 0 (Gen: 0) 15450408 9812088 10674504 0.044 0.044 0.590 0.591 0 0 (Gen: 0) 19459168 11429320 12291736 0.054 0.054 0.671 0.673 0 0 (Gen: 0) 22684384 8611624 9474040 0.046 0.046 0.745 0.747 0 0 (Gen: 0) 17026576 10661064 11523480 0.045 0.045 0.810 0.812 0 0 (Gen: 0) 21146552 9790592 10653008 0.044 0.044 0.882 0.884 0 0 (Gen: 0) 19421144 9891256 10753672 0.045 0.045 0.955 0.957 0 0 (Gen: 0) 19622512 8678360 9540776 0.042 0.042 1.026 1.028 0 0 (Gen: 0) 17212344 9845688 10708104 0.042 0.042 1.088 1.091 0 0 (Gen: 0) 19568256 9928304 10790720 0.045 0.045 1.159 1.162 0 0 (Gen: 0) 19673096 8159672 9022088 0.040 0.040 1.223 1.226 0 0 (Gen: 0) 16172824 9362616 10225032 0.039 0.039 1.277 1.280 0 0 (Gen: 0) 18536544 10809776 11672192 0.051 0.051 1.347 1.350 0 0 (Gen: 0) 21412128 15177144 16039560 0.065 0.065 1.434 1.437 0 0 (Gen: 0) 30181520 16438872 17301288 0.071 0.071 1.541 1.544 0 0 (Gen: 0) 32568088 11742016 12604432 0.053 0.053 1.633 1.636 0 0 (Gen: 0) 23285000 13139928 14002344 0.054 0.054 1.714 1.718 0 0 (Gen: 0) 26054072 15188040 16050456 0.060 0.060 1.803 1.807 0 0 (Gen: 0) 30184528 10990656 11853072 0.050 0.050 1.890 1.894 0 0 (Gen: 0) 21814064 12636584 13499000 0.050 0.050 1.961 1.965 0 0 (Gen: 0) 25295544 13754616 14812696 0.059 0.059 2.048 2.052 0 0 (Gen: 0) 27448728 16160496 17210352 0.066 0.066 2.147 2.151 0 0 (Gen: 0) 30295624 22372880 24471344 0.090 0.090 2.279 2.283 0 0 (Gen: 0) 44477824 24497712 25572240 0.092 0.092 2.431 2.436 0 0 (Gen: 0) 48692880 2937512 3436608 0.017 0.017 2.548 2.571 0 0 (Gen: 0) 1840 0.000 0.000 662,063,640 bytes allocated in the heap 334,683,080 bytes copied during GC 25,572,240 bytes maximum residency (40 sample(s)) 1,194,192 bytes maximum slop 93 MB total memory in use (0 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 40 colls, 0 par 1.684s 1.685s 0.0421s 0.0924s TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1) SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled) INIT time 0.001s ( 0.001s elapsed) MUT time 0.862s ( 0.885s elapsed) GC time 1.684s ( 1.685s elapsed) EXIT time 0.001s ( 0.009s elapsed) Total time 2.549s ( 2.581s elapsed) Alloc rate 767,692,191 bytes per MUT second Productivity 33.9% of total user, 34.6% of total elapsed }}} It looks as if a space leak has come back; space usage on this benchmark dropped by half when Reid fixed the `CoreTidy` leak. I don't know which commit re-introduced it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13668> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13655: Spurious untouchable type variable in connection with rank-2 type and constraint family
by GHC 09 May '17

09 May '17

#13655: Spurious untouchable type variable in connection with rank-2 type and constraint family -------------------------------------+------------------------------------- Reporter: jeltsch | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 (Type checker) | 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: -------------------------------------+------------------------------------- The following code cannot be compiled: {{{#!hs {-# LANGUAGE ConstraintKinds, Rank2Types, TypeFamilies #-} import GHC.Exts (Constraint) type family F a b :: Constraint data T b c = T f :: (forall b . F a b => T b c) -> a f _ = undefined }}} GHC outputs the following error message: {{{ Untouchable.hs:9:6: error: • Couldn't match type ‘c0’ with ‘c’ ‘c0’ is untouchable inside the constraints: F a b bound by the type signature for: f :: F a b => T b c0 at Untouchable.hs:9:6-37 ‘c’ is a rigid type variable bound by the type signature for: f :: forall a c. (forall b. F a b => T b c) -> a at Untouchable.hs:9:6 Expected type: T b c0 Actual type: T b c • In the ambiguity check for ‘f’ To defer the ambiguity check to use sites, enable AllowAmbiguousTypes In the type signature: f :: (forall b. F a b => T b c) -> a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13655> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13659: Bug report: "AThing evaluated unexpectedly tcTyVar a_alF"
by GHC 09 May '17

09 May '17

#13659: Bug report: "AThing evaluated unexpectedly tcTyVar a_alF" -------------------------------------+------------------------------------- Reporter: costaparas | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following code: {{{#!hs {-# LANGUAGE GADTs, EmptyDataDecls, TypeFamilies, TypeOperators, DataKinds, FlexibleInstances #-} {- Defines a C-like printf function using DataKinds extensions. -} module Printf where -- format string parameterized by a list of types data Format (fmt :: [*]) where X :: Format '[] -- empty string, i.e. "" L :: a -> String -> Format '[] -- string literal, e.g. "hello" S :: a -> Format '[String] -- "%s" I :: Format a -> Format '[Int, a] -- "%d" }}} produces the following error: GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Printf ( Printf.hs, interpreted ) a.hs:12:27:ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): AThing evaluated unexpectedly tcTyVar a_alF Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug when run using **ghci Printf.hs** on Liunx Ubuntu 16.04 LTS 64-bit with Intel® Core™ i7-7500U CPU @ 2.70GHz -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13659> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13646: strict patterns with no bindings (e.g. `let !() = ...`) trigger -Wunused-pattern-binds
by GHC 09 May '17

09 May '17

#13646: strict patterns with no bindings (e.g. `let !() = ...`) trigger -Wunused- pattern-binds -------------------------------------+------------------------------------- Reporter: exphp | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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 each of the following programs, a bang pattern is used to force evaluation of a bottom, the intent being to perform fail-fast error checking. Unfortunately, however, they also generate `-Wunused-pattern- binds`. {{{#!hs {-# OPTIONS_GHC -Wall #-} {-# LANGUAGE BangPatterns #-} main :: IO () main = do let !Nothing = Just () pure () }}} {{{#!hs {-# OPTIONS_GHC -Wall #-} {-# LANGUAGE BangPatterns #-} import Control.Exception main :: IO () main = do let !() = assert False () pure () }}} {{{ src/Lib.hs:6:9: warning: [-Wunused-pattern-binds] This pattern-binding binds no variables: !Nothing = Just () Linking src/Lib ... Lib: src/Lib.hs:6:9-26: Irrefutable pattern failed for pattern Nothing -------------------- src/Lib.hs:8:9: warning: [-Wunused-pattern-binds] This pattern-binding binds no variables: !() = assert False () Linking src/Lib ... Lib: Assertion failed CallStack (from HasCallStack): assert, called at src/Lib.hs:8:15 in main:Main }}} For clarity, non-monadic `let ... in` patterns are also affected; I only gloss over them because there tends to be other equally ergonomic alternatives in such cases. I found this #9127 (ticket), where a patch was accepted to allow wildcards of the form `!_`. However, `!_` is unsatisfactory and perhaps even dangerous for such usage, as it does not constrain the type in any manner. In particular, there is nothing to prevent somebody from writing {{{#!hs main = do let !_ = assert someCondition -- (missing an argument) pure () }}} which //is// in fact useless. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13646> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8332: hp2ps does not escape parentheses
by GHC 09 May '17

09 May '17

#8332: hp2ps does not escape parentheses ------------------------------------+------------------------------------- Reporter: luite | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Profiling | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- If some symbol name in the key includes a (, but is cut off before the ), hp2ps generates an invalid postscript file. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8332> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4820: "Invalid object in isRetainer" when doing retainer profiling in GHC 7 branch
by GHC 09 May '17

09 May '17

#4820: "Invalid object in isRetainer" when doing retainer profiling in GHC 7 branch ----------------------------------+-------------------------------------- Reporter: dleuschner | Owner: (none) Type: bug | Status: infoneeded Priority: highest | Milestone: 8.4.1 Component: Profiling | Version: 8.0.1 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 (amd64) Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11978 | Differential Rev(s): Wiki Page: | ----------------------------------+-------------------------------------- Changes (by bgamari): * milestone: 8.2.1 => 8.4.1 Comment: Bumping off to 8.4. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4820#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13211: NegativeLiterals -0.0 :: Double
by GHC 09 May '17

09 May '17

#13211: NegativeLiterals -0.0 :: Double -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Compare {{{ rwbarton@morphism:~$ ghc-8.0.1 -e '-0.0' -0.0 rwbarton@morphism:~$ ghc-8.0.1 -XNegativeLiterals -e '-0.0' 0.0 }}} This behavior is logical, but unexpected. The logic is that with `NegativeLiterals` the literal `-0.0` means `fromRational ((-0)%0)`, which equals `fromRational 0`, which for `Double` is positive zero, not negative zero. But this seems unfortunate. Perhaps it would be best if `-0.0` (or `-` applied to any other literal mathematically equal to zero) was desugared as `negate 0.0` even under `NegativeLiterals`, since there doesn't seem to be any other reason to write `-0.0`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13211> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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