Dependency tracking (--make) broken for re-exported modules

Say, I re-export a module, from which I hide some bindings:

module B (module A) where
import A hiding (a1)

where A is defined thus:

module A where
a1 = 5
a2 = 42
a3 = 113

I use B from C:

module C where
import B
a2 = 142

Build C, with ghc --make C.hs, observing redefinition error (of a2).

Now hide also a2 in B like this (by editing B.hs):

module B (module A) where
import A hiding (a1, a2)

Build C again, and observe that the error persists, because B has not been rebuilt, and its interface file not regenerated.

Deleting B.hi and recompiling resolves the situation.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture