#1148: Bad warnings about unused imports that are in fact needed
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Reporter: brianh | Owner:
Type: bug | Status: new
Priority: lowest | Milestone: 6.8
Component: Compiler | Version: 6.6
Severity: trivial | Resolution:
Keywords: warning unused import | Difficulty: Unknown
Testcase: | Architecture: x86
Os: Windows |
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Comment (by simonpj):
I took a look. The whole way that unused-imports are reported is wrong,
really. We collect a set of "free variables", which are used '''Names''',
but that loses the info about whether the program text mentioned the thing
qualified or unqualified. And that makes a difference to whether an
import is unnecessary:
{{{
import qualifed Foo( x, y )
import Foo( x )
p = x
q = Foo.x
}}}
If (but only if) the binding for `p` is omitted, the second import is
unnecessary. So we should really collect the set of used '''RdrNames'''.
This would not be too big a deal. In lookupOccRn, record the RdrName for
non-local lookups in a mutable variable. Look at that set in
`reportUnusedNames`.
But it'd take a couple of hours.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1148>
GHC <http://www.haskell.org/ghc/>
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