Bogus "unused import" warning

In DsMeta (in the source code for GHC itself), there's an import

  import qualified OccName

With -fwarn-unused-imports we get the warning

deSugar/DsMeta.hs:45:0:
    Warning: Module `OccName' is imported, but nothing from it is used,
               except perhaps instances visible in `OccName'
             To suppress this warning, use: import OccName()

But that's wrong: there are several uses of things imported from OccName.

I tried to reproduce this in a much smaller program, and failed, so something not entirely trivial is happening. Hence this ticket, to make sure we don't forget.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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Operating system	Unknown
Architecture	Unknown