Fix/issue 20756 implicitconversiontargets interfaces

[FeepingCreature]

Repro:

interface A { }
interface B : A { }

static assert(is(ImplicitConversionTargets!B == AliasSeq!(A)));

Expected: AliasSeq!(A)

Got: AliasSeq!()

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20756	enhancement	ImplicitConversionTargets ignores interface inheritance

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#7453"

[FeepingCreature]

I'm a bit worried that the docs explicitly call out "a class derived from Object". Does supporting interfaces break anything?

[thewilsonator]

If you're changing the docs, you should clarify if it works with extern(C++)/extern(Objective-C) classes or not.

[FeepingCreature]

I cannot think of any reason why it wouldn't, but I don't know anything about C++ classes/interfaces and their D binding. Who could I ping about that?

[thewilsonator]

Sorry I missed this. Probably @jacob-carlborg and/or @Geod24

[jacob-carlborg]

I guess the above example should work for for C++ and Objective-C interfaces. But keep in mind they don't inherit from Object.

There are also COM interfaces, which I don't know how they behave.

Ideally there should be tests for all kinds. Although Objective-C interfaces are deprecated.

[RazvanN7]

ping @FeepingCreature . What is the status of this?

[FeepingCreature]

Rebased, but note that I don't remember what I needed this for.

[FeepingCreature]

Actually, can't this definitely be closed? Looking at the changelog, we have AllImplicitConversionTargets now, and that handles interfaces just fine.

edit: Ah shit, it doesn't. I'll make a separate PR before that's released, so we don't make a new template with the exact same issue...