[GHC] #13803: Panic while forcing the thunk for TyThing IsFile (regression)
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Thu Jun 8 20:12:09 UTC 2017
#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: |
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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>
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