#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by inaki): * keywords: => hs-boot Comment: A possibly related issue is [ticket:13710], although in the current code there are no record wildcards involved. I haven't tried the fix in issue:13710#comment:12. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by inaki): Sure, here it is: https://www.mpp.mpg.de/~inaki/gi-gio-2.0.12.tar.gz -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Hrm, it looks like you could also use this instead for `GIGioInterfacesFile.hs`: {{{#!hs module GIGioInterfacesFile where import Data.Text import {-# SOURCE #-} qualified GIGioObjectsFileEnumerator as Gio.FileEnumerator import {-# SOURCE #-} qualified GIGioObjectsMountOperation as Gio.MountOperation class IsFile o }}} That still requires an external dependency (`text`), but it's a far easier dependency to install than `haskell-gi-base`, at least. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): OK, here's a version of `GIGioInterfacesFile` with no external dependencies: {{{#!hs module GIGioInterfacesFile where import Control.DeepSeq () import {-# SOURCE #-} qualified GIGioObjectsFileEnumerator as Gio.FileEnumerator import {-# SOURCE #-} qualified GIGioObjectsMountOperation as Gio.MountOperation class IsFile o }}} I have yet to figure out why the import of `Control.DeepSeq` is needed here. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): OK, here is as small as I can possibly make this: a "meager" five files: {{{#!hs -- D.hs {-# LANGUAGE TypeFamilies #-} module D (D) where type family D a type instance D Int = Int }}} {{{#!hs -- E.hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TypeFamilies #-} module E where import GHC.Exts (Constraint) import {-# SOURCE #-} Y class C i where type CF i :: * -> Constraint data E instance C E where type CF E = Y }}} {{{#!hs -- E.hs-boot module E where }}} {{{#!hs -- Y.hs module Y where import D () import {-# SOURCE #-} E class Y o }}} {{{#!hs -- Y.hs-boot module Y where class Y o }}} {{{ $ /opt/ghc/8.2.1/bin/ghci Y.hs GHCi, version 8.2.0.20170522: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 5] Compiling D ( D.hs, interpreted ) [2 of 5] Compiling E[boot] ( E.hs-boot, interpreted ) [3 of 5] Compiling Y[boot] ( Y.hs-boot, interpreted ) [4 of 5] Compiling E ( E.hs, interpreted ) [5 of 5] Compiling Y ( Y.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.0.20170522 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 Y which was lazily initialized by initIfaceCheck typecheckLoop, I tried to tie the knot, but I couldn't find Y 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:1689:23 in ghc:TcIface }}} Note that the name of `D.hs` actually matters here. For instance, if you rename `D.hs` to `Z.hs`, it'll actually compile! {{{ $ /opt/ghc/8.2.1/bin/ghci Y.hs GHCi, version 8.2.0.20170522: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 5] Compiling E[boot] ( E.hs-boot, interpreted ) [2 of 5] Compiling Y[boot] ( Y.hs-boot, interpreted ) [3 of 5] Compiling E ( E.hs, interpreted ) [4 of 5] Compiling Z ( Z.hs, interpreted ) [5 of 5] Compiling Y ( Y.hs, interpreted ) Ok, modules loaded: E, E, Y, Y, Z. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by ezyang): This is a family instance consistency check problem, as can be seen when you turn on tracing: {{{ checkForConflictsghc-stage2: panic! (the 'impossible' happened) (GHC version 8.3.20170517 for x86_64-unknown-linux): tcIfaceGlobal (local): not found }}} We begin checking for conflicts immediately before the panic. The problem is reminiscent of #11062 (fixed in 25b70a29f6236b591252bf5a361a1547f0ffee51). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): It also means that less work is done (and perhaps even fewer interface files read, which is big) if the axiom is never actually needed. So it might be ''more'' efficient. Not reading interface files too eagerly is one of the original reasons for the whole `forkM` story in `TcIface`. Would you like to try? Please comment the change, with a reference to this ticket. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: 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-rc2 Resolution: | 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by ezyang): So, here is a test case which is not solved by the test above: {{{ -- F.hs {-# LANGUAGE TypeFamilies #-} module F where type family F a :: * -- A.hs-boot module A where data T -- B.hs {-# LANGUAGE TypeFamilies #-} module B where import {-# SOURCE #-} A import F type instance F T = Int -- C.hs {-# LANGUAGE TypeFamilies #-} module C where import {-# SOURCE #-} A import F type instance F T = Bool -- A.hs module A where import B import C }}} Right now, we decide to defer a type family consistency check if the family was recursively defined. If the RHS refers to a recursively defined type, there's no problem: we don't need to look at it for consistency checking. But if the LHS is recursively defined, as is in this example, we DO need to defer the check. But it's a bit irritating to figure out whether or not there's actually a reference to a recursively defined type in the LHS, since this involves traversing the LHS types, and if we're not careful we'll end up pulling in the TyThing anyway. There are two other possibilities: (1) always defer checking instances which are defined inside the recursive look (by looking at the Name of the axiom), or (2) annotating IfaceAxiom with the set of boot types its LHS refers to, for easy checking. Not entirely sure what the best action is. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: Panic while forcing the thunk for TyThing IsFile (regression) -------------------------------------+------------------------------------- Reporter: inaki | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Resolution: | 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: | Differential Rev(s): Phab:D3742 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"fdb6a5bfd545094782fb539951b561ac2467443d/ghc" fdb6a5b/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="fdb6a5bfd545094782fb539951b561ac2467443d" Make IfaceAxiom typechecking lazier. Fixes #13803, but adds a note about a yet to be fixed #13981. Signed-off-by: Edward Z. Yang Test Plan: validate Reviewers: bgamari, austin Reviewed By: bgamari Subscribers: simonpj, rwbarton, thomie GHC Trac Issues: #13803 Differential Revision: https://phabricator.haskell.org/D3742 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13803: Panic while forcing the thunk for TyThing IsFile (regression) -------------------------------------+------------------------------------- Reporter: inaki | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.2.1-rc2 Resolution: fixed | 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: | Differential Rev(s): Phab:D3742 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: merge => closed * resolution: => fixed Comment: Merged to `ghc-8.2` with 31c5c7c5ba8587d6e06782c260db1b3313a05df6. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler