panic with boot and -jX

% cat A.hs
module A where

% cat A.hs-boot
module A ( A ) where

type A = Maybe ()

yay :: A -> IO ()

% cat B.hs
module B where

import {-# SOURCE #-} A

This panics:

% rm -rf o ; ghc -j2 -outputdir o B
[1 of 3] Compiling A[boot]          ( A.hs-boot, o/A.o-boot )
[2 of 3] Compiling A                ( A.hs, o/A.o )

<no location info>: error:
    ghc: panic! (the 'impossible' happened)
  (GHC version 8.2.0.20170503 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 A
  which was lazily initialized by initIfaceCheck typecheckLoop,
  I tried to tie the knot, but I couldn't find A
  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:
    [r15J :-> Identifier ‘$trModule’]
  Call stack:
      CallStack (from HasCallStack):
        prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1134:58 in ghc:Outputable
        callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in ghc:Outputable
        pprPanic, called at compiler/iface/TcIface.hs:1689:23 in ghc:TcIface

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

This works:

% rm -rf o ; ghc -j1 -outputdir o B
[1 of 3] Compiling A[boot]          ( A.hs-boot, o/A.o-boot )
[2 of 3] Compiling A                ( A.hs, o/A.o )

A.hs-boot:3:1: error:
    ‘A.A’ is exported by the hs-boot file, but not exported by the module
  |
3 | type A = Maybe ()
  | ^^^^^^^^^^^^^^^^^

Trac metadata

Trac field	Value
Version	8.2.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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