ghc warnings messed up in 6.01

[Sven Panne]

John Meacham wrote:
> [...] ;ghc -W -fglasgow-exts  Foo.hs

The current HEAD version (no idea about the release branch) of ghc correctly
says:

Foo.hs:1:
     Warning: Module `List' is imported, but nothing from it is used
	     (except perhaps instances visible in `List')

Foo.hs:7: Warning: Defined but not used: ds

> [...] problem 1 is particularly bad, since a single unused toplevel could
> cascade to generating a ton of warnings, all of which must be sorted
> through to find the actual cause. [...]

This is your personal opinion and actually a matter of taste: I prefer the
new "transitive" way of issuing the warnings, otherwise you only get a
single warning about "ds" being unused, remove it, recompile, get the next
warning, etc. etc. With the new way you can simply remove everything which
appears in the "unused foo" warnings and you're done.

Cheers,
    S.