Also expose 'parent' when it's abstract

[thaven]

When generating methods to implement e.g. an interface, it is also very useful to have an alias to the (abstract) function being overridden. E.g. to have access to UDAs.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✗	19715	minor	AutoImplement `self` and `parent` aliases are incorrect for overloaded functions

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#6876"

[thewilsonator]

Tests please

[thaven]

I added a separate test now (and removed the static assert that I originally added in the existing test). The test is a stripped-down version of the actual code I need this change for.

It seems it actually works for non-overloaded functions, but fails for overloaded ones. I think I'll need to loop through the overload set to find the correct overload to alias.

[thaven]

It turns out the problem with overloading is an existing bug and also applies to the self alias...

[thaven]

Created Issue 19715 about the self and parent aliases.

Could this PR move on without that fix (by temporarily commenting out an overload in the test + adding a TODO referencing the issue)?

[thewilsonator]

Yes, fixing senate issues separately is usually a good idea.

[thaven]

Rebased this old PR on current master. Let's see how the tests turn out now. (previous run, long ago, just got stuck somewhere)