Ignore non public names of main package in extension

[gdalle]

I have started using ExplicitImports in JuliaDiff/DifferentiationInterface.jl#573 and I'm wondering whether we could cut extensions some slack when they use private names from the main package. Since they are necessarily developed in lockstep and versioned together, would that be a reasonable default?

[ericphanson]

this seems reasonable to me; probably we should treat them like submodules?

[gdalle]

I guess, I don't know exactly how submodules are handled here but conceptually they're the same to me

[ericphanson]

I think submodules get handled here:

https://github.com/ericphanson/ExplicitImports.jl/blob/f4d64b0853f9f59befa219d2b52745ee65a76053/src/improper_explicit_imports.jl#L186-L189

if they have an ancestor module who defines the name that we are importing, then we filter that out. So I guess we need to add a check there (ancestor OR extension base)