January 2017 - ghc-tickets

[GHC] #9287: changed dependency generation
by GHC 23 May '17

23 May '17

#9287: changed dependency generation ------------------------------------+-------------------------------------- Reporter: maeder | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Documentation | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Documentation bug Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+-------------------------------------- "ghc -M" for ghc-7.8.x changed in that an error occurs: {{{ You must specify at least one -dep-suffix }}} By chance (#8746) I found that {{{ ghc -M -dep-suffix "" B.hs }}} works, but only for the new ghc-7.8.x. For module B importing module A the following dependencies are generated: {{{ # DO NOT DELETE: Beginning of Haskell dependencies A.o : A.hs B.o : B.hs B.o : A.hi # DO NOT DELETE: End of Haskell dependencies }}} The same command used with ghc-7.6.x produces wrong dependencies: {{{ # DO NOT DELETE: Beginning of Haskell dependencies A.o A._o : A.hs B.o B._o : B.hs B.o : A.hi B._o : A._hi # DO NOT DELETE: End of Haskell dependencies }}} Obviously, only for dynamic linking a dep-suffix should be needed. However for ghc-7.6. this must be "dyn" and for ghc-7.8.x this must "dyn_" plus the empty suffix! {{{ ghc-7.6.3 -M -dep-suffix dyn B.hs ghc-7.8.2 -M -dep-suffix dyn_ -dep-suffix "" B.hs }}} Both calls produce: {{{ # DO NOT DELETE: Beginning of Haskell dependencies A.o A.dyn_o : A.hs B.o B.dyn_o : B.hs B.o : A.hi B.dyn_o : A.dyn_hi # DO NOT DELETE: End of Haskell dependencies }}} The changed behavior is not documented in http://www.haskell.org/ghc/docs/7.8.2/html/users_guide/separate- compilation.html#makefile-dependencies The (accidental?) change should also be documented in the release notes! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9287> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13092: family instance consistency checks are too pessimistic
by GHC 22 May '17

22 May '17

#13092: family instance consistency checks are too pessimistic -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: rwbarton Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- FamInst has this logic for checking type family instance consistency among imports: {{{ Note [Checking family instance consistency] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For any two family instance modules that we import directly or indirectly, we check whether the instances in the two modules are consistent, *unless* we can be certain that the instances of the two modules have already been checked for consistency during the compilation of modules that we import. [...] How do we know which pairs of modules have already been checked? Any pair of modules where both modules occur in the `HscTypes.dep_finsts' set (of the `HscTypes.Dependencies') of one of our directly imported modules must have already been checked. Everything else, we check now. (So that we can be certain that the modules in our `HscTypes.dep_finsts' are consistent.) }}} However, suppose one of the modules `A` we import directly is itself a type family instance module. Then it too has been checked for consistency with its dependencies `B`, `C`, etc., so we should skip checking the pairs `A` & `B`, `A` & `C`, etc. The current behavior means that whenever we directly import a type family instance module, we still have to load the interface files for all its type family module dependencies, which largely defeats the purpose of the optimization in this case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13092> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9445: GHC Panic: Tick Exhausted with high factor
by GHC 22 May '17

22 May '17

#9445: GHC Panic: Tick Exhausted with high factor -------------------------------------+------------------------------------- Reporter: adinapoli | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: panic | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: Difficulty: Unknown | None/Unknown Blocked By: | Test Case: Related Tickets: 5539 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Hello guys, this is an old bug which has been reported so many times that I'm not sure this will be noise or something useful. In a nutshell I have been hit by this bug installing the library "SFML", which relies heavily on FFI. The only interesting thing of this report is that it was necessary an very high simpl-factor to make the installation go through! Pre-bump: {{{ Resolving dependencies... In order, the following will be installed: SFML-0.2.0.0 (reinstall) Warning: Note that reinstalls are always dangerous. Continuing anyway... Configuring SFML-0.2.0.0... Building SFML-0.2.0.0... Preprocessing library SFML-0.2.0.0... [...] [34 of 71] Compiling SFML.Graphics.Transform ( dist/build/SFML/Graphics/Transform.hs, dist/build/SFML/Graphics/Transform.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.8.3 for x86_64-apple-darwin): Simplifier ticks exhausted When trying UnfoldingDone $j_sZQW{v} [lid] To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 2655928 }}} And this was the magic line: {{{ cabal install SFML --ghc-option=-fsimpl-tick-factor=1630 }}} HTH, it turns out it's quite an annoying one! And yes, "1630" was the smaller factor which made the installation possible. Alfredo -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9445> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9700: Support C structures in Haskell FFI
by GHC 22 May '17

22 May '17

#9700: Support C structures in Haskell FFI -------------------------------------+------------------------------------- Reporter: Yuras | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: Phab:D252 -------------------------------------+------------------------------------- This ticket is for tracking progress on [[CStructures]] language extension proposal. The idea is to support C structures in Haskell FFI. See wiki for details. If it will be accepted, I'm going to implement it in few steps. The first one is to support structures as return value. Platform specific part for that is already implemented, see Phab:D252 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9700> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11593: Template Haskell: Add a way to get names that are neither capturable nor capturing.
by GHC 21 May '17

21 May '17

#11593: Template Haskell: Add a way to get names that are neither capturable nor capturing. -------------------------------------+------------------------------------- Reporter: cgibbard | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Template | Version: 7.10.3 Haskell | Keywords: | Operating System: Unknown/Multiple yhjulwwiefzojcbxybbruweejw | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- From the documentation on newName: "Although names generated by newName cannot ''be captured'', they can ''capture'' other names." We recently ran into a case where we'd really have liked a way to create a name which can't interact at all with other names in the code, apart from where it is used in the construction of the TH expression. In this code: https://github.com/reflex-frp/reflex/blob/develop/src/Reflex/Dynamic/TH.hs The `newName "dynamicQuotedExpressionVariable"` used to be simply `newName "dyn"`, and we ended up having occurrences of `dyn` in the quasiquoted expressions (which would be constructed by NameG) get captured by that newName rather than referring to reflex-dom's definition of `dyn`. There ought to be some Q Name action which can be executed to give fresh names which can be used internally by a TH macro without fear that they can be referred to in any way other than using the Name value obtained from the action. The documentation for `Name` seems to suggest that newName is presently the closest thing, so perhaps we need a new primitive for creating totally-non-interacting Names. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11593> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8048: Register spilling produces ineffecient/highly contending code
by GHC 21 May '17

21 May '17

#8048: Register spilling produces ineffecient/highly contending code -------------------------------------+------------------------------------- Reporter: schyler | Owner: Type: bug | Status: new Priority: normal | Milestone: _|_ Component: Compiler | Version: 7.6.3 Keywords: register | Operating System: Unknown/Multiple allocator spill | Type of failure: Runtime Architecture: Unknown/Multiple | performance bug Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- The native codegen and llvm both produce ineffecient code for functions using structures with many strict fields or unboxed values. Consider the following program: {{{ {-# LANGUAGE BangPatterns #-} module Spill where import GHC.Exts data S = S !Int !Int !Int !Int !Int !Int !Int !Int !Int spill :: S -> S -> S -> S spill (S !a !b !c !d !e !f !g !h !i) (S !j !k !l !m !n !o !p !q !r) (S !s !t !u !v !w !x !y !z _) = S (a + j + s) (b + c) (k + r) (a + b + c + d + e + f + g + h + i) (j + k + l + m + n + o + p + q + r) (s + t + u + v + w + x + y + z) (a + b + c) (j + k + l) (s + t + u) }}} Parts of the code produced for this (which is identical regardless of -funbox-strict-fields) looks like: {{{ _cnc: addq $80,%r12 cmpq 144(%r13),%r12 ja _cni movq $Spill.S_con_info,-72(%r12) movq 32(%rbp),%rax movq %rax,-64(%r12) movq 24(%rbp),%rax movq %rax,-56(%r12) movq 16(%rbp),%rax movq %rax,-48(%r12) movq 8(%rbp),%rax movq %rax,-40(%r12) movq 40(%rbp),%rax movq %rax,-32(%r12) movq 48(%rbp),%rax movq %rax,-24(%r12) movq 56(%rbp),%rax movq %rax,-16(%r12) movq 64(%rbp),%rax movq %rax,-8(%r12) movq 7(%rbx),%rax movq %rax,0(%r12) leaq -71(%r12),%rbx addq $72,%rbp jmp *0(%rbp) }}} {{{ _csv: movq 63(%rbx),%rax movq %rax,-56(%rbp) movq 55(%rbx),%rax movq %rax,-48(%rbp) movq 47(%rbx),%rax movq %rax,-40(%rbp) movq 39(%rbx),%rax movq %rax,-32(%rbp) movq 31(%rbx),%rax movq %rax,-24(%rbp) movq 23(%rbx),%rax movq %rax,-16(%rbp) movq 71(%rbx),%rax movq %rax,-8(%rbp) movq 15(%rbx),%rax movq %rax,0(%rbp) }}} And likewise for LLVM: {{{ .LBB10_1: # %coZ movq 7(%rbx), %rcx movq $Spill_S_con_info, 8(%rax) movq 8(%rbp), %rdx movq %rdx, 16(%rax) movq 16(%rbp), %rdx movq %rdx, 24(%rax) movq 24(%rbp), %rdx movq %rdx, 32(%rax) movq 32(%rbp), %rdx movq %rdx, 40(%rax) movq 40(%rbp), %rdx movq %rdx, 48(%rax) movq 48(%rbp), %rdx movq %rdx, 56(%rax) movq 56(%rbp), %rdx movq %rdx, 64(%rax) movq 64(%rbp), %rdx movq %rdx, 72(%rax) movq %rcx, (%r12) movq 72(%rbp), %rax leaq 72(%rbp), %rbp leaq -71(%r12), %rbx jmpq *%rax # TAILCALL }}} Quoting from #ghc "the [register allocator] core algo is '96 vintage". Improvements are needed; * Take into consideration pipelining and handle spills less dramatically, attempting to reduce register contention * Sink memory reads in order to reduce register pressure -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8048> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12136: SIGABRT on right-shift operation against long negative integer
by GHC 20 May '17

20 May '17

#12136: SIGABRT on right-shift operation against long negative integer --------------------------------------+---------------------------------- Reporter: khibino | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 7.10.3 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- When the code like bellow is executed, the '''shiftR''' call causes SIGABRT. c128.hs {{{#!hs import Data.Bits x:: Integer x = 1 - (1 `shiftL` (128 + 64)) main :: IO () main = print $ x `shiftR` 128 }}} I make this report using examples in GHC 7.10.3, and I found the same problem in GHC 8.0.1 too. backtrace using GDB {{{ % ghc -O0 c128.hs [1 of 1] Compiling Main ( c128.hs, c128.o ) Linking c128 ... % gdb ./c128 GNU gdb (Debian 7.10-1+b1) 7.10 ... Reading symbols from ./c128...(no debugging symbols found)...done. (gdb) run Starting program: /home/hibi/src/haskell/crash/Haskell/c128 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Program received signal SIGABRT, Aborted. 0x00007ffff6ed4478 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:55 55 ../sysdeps/unix/sysv/linux/raise.c: そのようなファイルやディレクトリはありません. (gdb) bt #0 0x00007ffff6ed4478 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:55 #1 0x00007ffff6ed58fa in __GI_abort () at abort.c:89 #2 0x00000000004716df in integer_gmp_mpn_rshift_2c () #3 0x000000000046e004 in salz_info () #4 0x0000000000000000 in ?? () (gdb) frame 2 #2 0x00000000004716df in integer_gmp_mpn_rshift_2c () (gdb) disas Dump of assembler code for function integer_gmp_mpn_rshift_2c: 0x0000000000471630 <+0>: push %r13 ... 0x00000000004716d8 <+168>: jne 0x4716c0 <integer_gmp_mpn_rshift_2c+144> 0x00000000004716da <+170>: callq 0x402c80 <abort@plt> => 0x00000000004716df <+175>: nop 0x00000000004716e0 <+176>: lea 0x0(,%rdx,8),%rdx ... End of assembler dump. (gdb) }}} I found '''abort''' call in '''integer_gmp_mpn_rshift_2c'''. ghc-7.10.3/libraries/integer-gmp2/cbits/wrappers.c {{{#!c mp_limb_t integer_gmp_mpn_rshift_2c (mp_limb_t rp[], const mp_limb_t sp[], const mp_size_t sn, const mp_bitcnt_t count) { ... // round if non-zero bits were shifted out if (nz_shift_out) if (mpn_add_1(rp, rp, rn, 1)) abort(); /* should never happen */ return rp[rn-1]; } }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12136> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12897: yesod-auth-1.4.13.2 failed during the building phase.
by GHC 19 May '17

19 May '17

#12897: yesod-auth-1.4.13.2 failed during the building phase. -------------------------------------+------------------------------------- Reporter: onomatopoeia | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: MacOS X Architecture: x86 | Type of failure: Compile-time | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Resolving dependencies... Configuring yesod-auth-1.4.13.2... Building yesod-auth-1.4.13.2... Failed to install yesod-auth-1.4.13.2 Build log ( /Users/simonrobins/.cabal/logs/yesod-auth-1.4.13.2.log ): Configuring yesod-auth-1.4.13.2... Building yesod-auth-1.4.13.2... Preprocessing library yesod-auth-1.4.13.2... [ 1 of 12] Compiling Yesod.PasswordStore ( Yesod/PasswordStore.hs, dist/build/Yesod/PasswordStore.dyn_o ) Yesod/PasswordStore.hs:166:31: Warning: Defaulting the following constraint(s) to type ‘Integer’ (Integral b0) arising from a use of ‘^’ at Yesod/PasswordStore.hs:166:31 (Num b0) arising from the literal ‘32’ at Yesod/PasswordStore.hs:166:32-33 In the first argument of ‘(-)’, namely ‘2 ^ 32’ In the first argument of ‘(*)’, namely ‘(2 ^ 32 - 1)’ In the second argument of ‘(>)’, namely ‘(2 ^ 32 - 1) * hLen’ Yesod/PasswordStore.hs:419:1: Warning: Defined but not used: ‘toStrict’ Yesod/PasswordStore.hs:422:1: Warning: Defined but not used: ‘fromStrict’ [ 2 of 12] Compiling Yesod.Auth.Message ( Yesod/Auth/Message.hs, dist/build/Yesod/Auth/Message.dyn_o ) Yesod/Auth/Message.hs:23:1: Warning: The import of ‘mappend’ from module ‘Data.Monoid’ is redundant Yesod/Auth/Message.hs:698:1: Warning: Defined but not used: ‘croatianMessage’ Yesod/Auth/Message.hs:459:1: Warning: Pattern match(es) are overlapped In an equation for ‘finnishMessage’: finnishMessage Password = ... Yesod/Auth/Message.hs:459:1: Warning: Pattern match(es) are non-exhaustive In an equation for ‘finnishMessage’: Patterns not matched: CurrentPassword [ 3 of 12] Compiling Yesod.Auth.Routes ( Yesod/Auth/Routes.hs, dist/build/Yesod/Auth/Routes.dyn_o ) [ 4 of 12] Compiling Yesod.Auth ( Yesod/Auth.hs, dist/build/Yesod/Auth.dyn_o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-apple-darwin): Loading temp shared object failed: dlopen(/var/folders/jf/bqzbd3l92vvbl4wb9vdkv8f80000gn/T/ghc55090_0/libghc_15.dylib, 5): no suitable image found. Did find: /var/folders/jf/bqzbd3l92vvbl4wb9vdkv8f80000gn/T/ghc55090_0/libghc_15.dylib: malformed mach-o: load commands size (36560) > 32768 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug cabal: Error: some packages failed to install: yesod-1.4.3 depends on yesod-auth-1.4.13.2 which failed to install. yesod-auth-1.4.13.2 failed during the building phase. The exception was: ExitFailure 1 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12897> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13119: yesod-auth-1.4.15: ghc: panic! (the 'impossible' happened) Linker error
by GHC 19 May '17

19 May '17

#13119: yesod-auth-1.4.15: ghc: panic! (the 'impossible' happened) Linker error ---------------------------------+--------------------------------- Reporter: mcmayer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: ghc panic | Operating System: MacOS X Architecture: x86 | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ---------------------------------+--------------------------------- On Mac OS X 10.12.2 the [http://brew.sh] installation of Haskell `stack` is used (`brew install haskell-stack`). Next, the `yesod-simple` template is instantiated and built, e.g. {{{ stack new my-web yesod-simple cd my-web stack build }}} The error looks like this: {{{ ➜ my-web stack build yesod-auth-1.4.15: configure yesod-auth-1.4.15: build Progress: 1/4 -- While building package yesod-auth-1.4.15 using: /Users/mmayer/.stack/setup-exe-cache/x86_64-osx/Cabal- simple_mPHDZzAJ_1.22.5.0_ghc-7.10.3 --builddir=.stack- work/dist/x86_64-osx/Cabal-1.22.5.0 build --ghc-options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 Logs have been written to: /private/tmp/my-web/.stack-work/logs/yesod- auth-1.4.15.log Configuring yesod-auth-1.4.15... Building yesod-auth-1.4.15... Preprocessing library yesod-auth-1.4.15... [ 1 of 12] Compiling Yesod.PasswordStore ( Yesod/PasswordStore.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Yesod/PasswordStore.o ) /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/PasswordStore.hs:166:31: Warning: Defaulting the following constraint(s) to type ‘Integer’ (Integral b0) arising from a use of ‘^’ at Yesod/PasswordStore.hs:166:31 (Num b0) arising from the literal ‘32’ at Yesod/PasswordStore.hs:166:32-33 In the first argument of ‘(-)’, namely ‘2 ^ 32’ In the first argument of ‘(*)’, namely ‘(2 ^ 32 - 1)’ In the second argument of ‘(>)’, namely ‘(2 ^ 32 - 1) * hLen’ /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/PasswordStore.hs:419:1: Warning: Defined but not used: ‘toStrict’ /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/PasswordStore.hs:422:1: Warning: Defined but not used: ‘fromStrict’ [ 2 of 12] Compiling Yesod.Auth.Message ( Yesod/Auth/Message.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Yesod/Auth/Message.o ) /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/Auth/Message.hs:24:1: Warning: The import of ‘mappend’ from module ‘Data.Monoid’ is redundant /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/Auth/Message.hs:460:1: Warning: Pattern match(es) are overlapped In an equation for ‘finnishMessage’: finnishMessage Password = ... /private/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/stack44665 /yesod-auth-1.4.15/Yesod/Auth/Message.hs:460:1: Warning: Pattern match(es) are non-exhaustive In an equation for ‘finnishMessage’: Patterns not matched: CurrentPassword [ 3 of 12] Compiling Yesod.Auth.Routes ( Yesod/Auth/Routes.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Yesod/Auth/Routes.o ) [ 4 of 12] Compiling Yesod.Auth ( Yesod/Auth.hs, .stack- work/dist/x86_64-osx/Cabal-1.22.5.0/build/Yesod/Auth.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-apple-darwin): Loading temp shared object failed: dlopen(/var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/ghc44706_0/libghc_21.dylib, 5): no suitable image found. Did find: /var/folders/mj/9fhlhndj3jl8mrd9czmhvz_00000gn/T/ghc44706_0/libghc_21.dylib: malformed mach-o: load commands size (35848) > 32768 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} The same happens on `ghc-8.0.1` (`stack build yesod-auth`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13119> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11325: Type of hole does not get refined after pattern matching on [GADT] constructors
by GHC 19 May '17

19 May '17

#11325: Type of hole does not get refined after pattern matching on [GADT] constructors -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 (Type checker) | Keywords: GADTs | Operating System: Linux Architecture: x86 | Type of failure: Incorrect | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- From [https://www.youtube.com/watch?v=6snteFntvjM A Practical Introduction to Haskell GADTs] from LambdaConf 2015, example from attachment Hole.hs: {{{#!hs {-# LANGUAGE GADTs #-} data STy ty where SInt :: STy Int SBool :: STy Bool SMaybe :: STy a -> STy (Maybe a) zero :: STy ty -> ty zero ty = case ty of SInt -> 5 SBool -> False SMaybe a -> _ }}} When running with "GHCi, version 7.11.20151226": {{{ % ghci -ignore-dot-ghci /tmp/Hole.hs GHCi, version 7.11.20151226: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/Hole.hs, interpreted ) /tmp/Hole.hs:12:15: error: • Found hole: _ :: ty Where: ‘ty’ is a rigid type variable bound by the type signature for: zero :: forall ty. STy ty -> ty at /tmp/Hole.hs:8:9 • In the expression: _ In a case alternative: SMaybe a -> _ In the expression: case ty of { SInt -> 5 SBool -> False SMaybe a -> _ } • Relevant bindings include a :: STy a (bound at /tmp/Hole.hs:12:10) ty :: STy ty (bound at /tmp/Hole.hs:9:6) zero :: STy ty -> ty (bound at /tmp/Hole.hs:9:1) Failed, modules loaded: none. Prelude> }}} when older versions (GHCi version 7.10.2) refine the type of `_` to `Maybe a`: {{{ % ghci-7.10.2 -ignore-dot-ghci /tmp/Hole.hs GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/Hole.hs, interpreted ) /tmp/Hole.hs:12:15: Found hole ‘_’ with type: Maybe a Where: ‘a’ is a rigid type variable bound by a pattern with constructor SMaybe :: forall a. STy a -> STy (Maybe a), in a case alternative at /tmp/Hole.hs:12:3 Relevant bindings include a :: STy a (bound at /tmp/Hole.hs:12:10) ty :: STy ty (bound at /tmp/Hole.hs:9:6) zero :: STy ty -> ty (bound at /tmp/Hole.hs:9:1) In the expression: _ In a case alternative: SMaybe a -> _ In the expression: case ty of { SInt -> 5 SBool -> False SMaybe a -> _ } Failed, modules loaded: none. Prelude> }}} Regression? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11325> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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