Export functions included from different modules with the same name

Here is my example:

module AB

using Reexport


@reexport using .A
@reexport using .B


And, both A, B has functions close!. Then, using close! causes warning like this:
WARNING: both A and B export "close!"; uses of it in module AB must be qualified
(Of course, both A.close! and B.close! accept different types of arguments).

Is there something I missed?

Yes, this is impossible. It has been requested elsewhere (under the limitation you mention that the two functions take strictly different arguments) but I don’t know if it’s on anyone’s roadmap to do this (maybe by 2.0).

What you should do is have AB define close!, and then A and B add methods to it

# in AB

# no methods, just defining the name
function close! end

export close!
# in A
import AB: close!

close!(x) = #...
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Thank you very much!
I’m a little bit new to Julia, so I’m little bit confused.
Is it a kind of extension of existing functions?

They will be methods under the close! function. The multiple dispatch design of Julia means that you can have methods acting on different tuples of argument types under the same function name. In this case the recommended way is to declare the function in module AB, and add methods to it from module A and module B.

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Yes, exactly. It is the same idea as when you implement an object that should have length(obj), you do

Base.length(x::MyType) = # ...

to extend the function length from Base to your own type. In your case, the AB package creates an interface that A and B extend for their own specific cases, which is a common design pattern.

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