proposal #2254: have Control.Arrow re-export (>>>) and (<<<)

Ian Lynagh igloo at
Fri May 2 08:43:39 EDT 2008

On Fri, May 02, 2008 at 09:13:52AM +0100, Simon Peyton-Jones wrote:
> Aha.  So now it's unclear what the desired behaviour is.  Do we want a warning for import statements that can be deleted altogether?  If not, I can easily remove it!  Or is it just the wording of the warning that is bad?

I would like what the warning says, rather than what it does. Something

For each use of a variable foo, mark imports
    import M (..., foo, ...)
as "used" if any exist; otherwise mark any imports
    import M
which export foo as "used".

Then warn about any imports not marked as "used" (except imports of the
    import M ()
of course).

> |     Warning: Module `A' is imported, but nothing from it is used,
> |                except perhaps instances visible in `A'
> |              To suppress this warning, use: import A()


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