Warnings about unused variables or imports
duncan.coutts at worc.ox.ac.uk
Tue May 6 05:31:15 EDT 2008
On Tue, 2008-05-06 at 10:09 +0100, Simon Peyton-Jones wrote:
> There is something more substantial here. Suppose we have
> module Foo( g ) where
> import Bar( f4 )
> f1 = f2
> f2 = f3
> f3 = f4
> g = 7
> At the moment GHC takes the view that f1,f2,f3,f4, and the import are
> *all* unused. If we said that just f1 was unused, then you'd delete
> it and get a new warning about f2; you delete that and get a new
> warning about f3; and so on.
> Yet the current behaviour is clearly confusing, even to a clued-up
> user, let alone a beginner.
Perhaps to eliminate the confusion we just need to distinguish directly
unused and indirectly unused in the warning message:
Foo.hs:3:8: Warning: Defined but not used: `f1'
Foo.hs:4:8: Warning: Defined but used only by other things that are
themselves unused: `f2'
Foo.hs:5:8: Warning: Defined but used only by other things that are
themselves unused: `f3'
(suggestions for better messages text welcome)
and similarly for the unused import.
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