fix issue 23140

[RubyTheRoobster]

Fix issue 23140: https://issues.dlang.org/show_bug.cgi?id=23140

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	23140	regression	Array!T where T is a shared class no longer works

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 "stable + phobos#8526"

[schveiguy]

This needs a test to show that it works.

[RubyTheRoobster]

I added the tests. And they do fail under the current dmd.

[Tynukua]

Not sure but Unshared could be added to std.traits?

[RubyTheRoobster]

Not sure but Unshared could be added to std.traits?

It could, but it really doesn't make sense: the Unshared template is used to take a type, whether shared or not, and convert it to the unshared version. On the other hand, I was told in this forum post (from which I got the idea) that it was a private template in std.traits.

Unrelated, but shouldn't this PR be marked as regression?

[RubyTheRoobster]

I just realized (from looking at Ali's slides for dconf) that std.traits has a template called Unqual, that removes ALL qualifiers, not just shared.

Edit: For some reason, using Unqal doesn't work, and the compiler spews a thousand errors, so I'm sticking to Unshared.

[BorisCarvajal]

This still fails:

const class C {} // or immutable
Array!C ac;

in fact this has always failed:

class C {}
Array!(const C) ac;

I don't know the internals of Array but I think a more appropriate fix is to only cast away modifiers on memory-related calls and let the type system flow at a higher level, like when using Array.opIndex. Your patch removes shared from the type system (for Array!(shared C) ac, ac[0] is not shared).

[RubyTheRoobster]

There is a regression that as of now prevents me from going any further, and could be related to the pull request that caused this one.

Edit: I have found a work around, but it involves Unshared. Hopefully this single usage doesn't result in breaking the type system.

[RubyTheRoobster]

So the assert statement on line 1416 is failing, and I honestly can't figure out why.

[RubyTheRoobster]

As for const and immutable classes, that's another issue unrelated to this one caused by std.algorithm.mutate.move not supporting them.

Still, that doesn't prevent me from looking into fixing them.