Import modules' extension methods only with unqualified import statements

[hubertp]

Previously, a qualified import would always bring extension methods into the scope. This is because extensions methods weren't taking into account the qualifiers at all and imported scope was blindly added to the existing module scope.

For example, given a module with an extension method in one module (A.enso)

type A
    X
    Y
...
Integer.foo self a = ....

we weren't consistent with how extension method foo could be brought into the scope.
All of

• import project.A
• import project.A.A
• from project.A import all
• from project.A.A import X, Y

would bring it into the scope.

Now, only

• import project.A
• from project.A import all

would.

The change limits that by taking into account import qualifiers of the types that are being brought and creating a copy of the original ModuleScope.

This meant that in pretty much every test file of our testsuite we had to import Test.Extensions module.
This fixes problem 2) in https://www.pivotaltracker.com/n/projects/2539304/stories/183833055

Important Notes

Note that one cannot

import Standard.Table as Table_Module

because of the 2-component name restriction that gets desugared to Standard.Table.Main and we have to write

import Standard.Table.Main as Table_Module

in a few places. Once we move Json.to_table extension this can be improved.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• [ x All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.

[farmaazon]

Can someone explain me what exactly is limited? If someone pick an extension method foo for type Type defined in module Module in component browser, what import shall be added?

[hubertp]

Can someone explain me what exactly is limited? If someone pick an extension method foo for type Type defined in module Module in component browser, what import shall be added.

I updated the description. Let me know if this is still confusing.

[farmaazon]

Thank you. Now I see it. Seemingly, no additional update in Component Browser is required (it uses import Module).

[hubertp]

Discovered some more corner cases. I will ping again once I'm done with them.

[hubertp]

OK, added a bunch of tests that cover exporting as well. Now it really looks like it works as expected.

@JaroslavTulach @4e6 mind having a look?

[hubertp]

@jdunkerley something to keep in mind in further refactorings (this is because of up_to)

[JaroslavTulach]

If the tests are working, then the change is likely good. Few (not that important) comments inline.