"error in method definition" when using A: f used after import A: f

[rfourquet]

Sorry for the unexpressive title
MWE:

julia> module A
       function f end
       end

       module O
       import ..A: f
       using ..A: f

       f(x) = 0
       end
ERROR: error in method definition: function A.f must be explicitly imported to be extended
Stacktrace:
[...]

The error is fixed by deleting the using ..A: f line.
The problem is that if the using and import statements are in different files, it's not trivial to make sense of the error message when the thing you are looking at is the above import statement.

[JeffBezanson]

I guess the best thing to do here is give an error if a using follows an import (or vice-versa) of the same identifier.