Fix extension function imports

[sebek64]

This pull request aims to fix some scenarios where extension function is not properly imported. As described for example here, the import is always needed. This change forces the import to be created, even if it means creating an alias.

I don't know this library so well, so I hope I didn't break some other scenarios. I'm willing to update the pull request by your suggestions.

[Egorand]

This pull request aims to fix some scenarios where extension function is not properly imported.

Can you please include unit tests that demonstrate the problem you're trying to solve, and that fail without your fix and pass with your fix?

[sebek64]

Unit test added - fails if applied without the fixing commits, succeeds now.

[Egorand]

Thanks for the test! I'm actually seeing similar behaviour with types - if there's a type with the same name as another type in the same package, we'll use the fully-qualified name for the former. It's not a big deal for types and non-extension members, but definitely breaks compilation for extensions.

I wonder if it's worth special-casing extension members, or should we just generate aliases for all names that clash with names of elements in the same package?.. I'm planning to take a closer look at your PR over the weekend, or next week at the latest.

[sebek64]

Honestly, I don't care about the particular solution, as long as the generated code would be compilable. I'm leaving the decision up to you, I can adjust the PR if you request in some way, or feel free to implement it your way and reject this one as unnecessary.
It's not time pressing for me, so if the fixed release is available in a month or two, it's fine. As a workaround, I'm moving things around packages to force the imports to be aliased (not to have the extension functions used from the current package).

[Egorand]

Note that there are APIs to add alias imports manually, you can use them as well as a workaround.

[Egorand]

The change looks good, thanks! Left a couple comments, once they're addressed we can merge the PR.

[Egorand]

Merged, thank you!