InteractiveEval error handling gets a boot ModSummary instead of normal ModSummary

Given:

A.hs

module A where

data A = A

f :: A -> Bool
f C = False

A.hs-boot

module A where

data A

f :: A -> Bool

B.hs

module B where

import {-# SOURCE #-} A

data B = B A

g :: B -> Bool
g (B a) = f a

ghci reports:

$ ghci B.hs
GHCi, version 8.0.0.20160411: http://www.haskell.org/ghc/  :? for help
[1 of 3] Compiling A[boot]          ( A.hs-boot, interpreted )
[2 of 3] Compiling A                ( A.hs, interpreted )

A.hs:6:3: error: Not in scope: data constructor ‘C’
*** Exception: expectJust showModule
CallStack (from HasCallStack):
  error, called at compiler/utils/Maybes.hs:48:27 in ghc:Maybes
> 

So instead of a normal error telling me that the C constructor does not exist, I get an additional exception from expectJust because something went wrong in GHCs internal error reporting routine.

Looking at https://github.com/ghc/ghc/blob/master/compiler/main/InteractiveEval.hs#L956, the expectJust exception is due to the fact that while reporting an error about A.hs, GHCi somehow got a hold of the ModSummary of A.hs-boot instead of A.hs

Trac metadata

Trac field	Value
Version	8.0.1-rc3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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