fix issue 19708 - Can't use __traits(getAttributes, ...)[...] as a type

[ghost]

The first part of the fix is simply to extract Types from TypeExprs when a TypeTrait returning a TypeTuple contained some .

The second part is more delicate. A flag used by the TypeTraits was not set correctly because the TypeTrait was not directly aliased but wrapper in a TypeNext. To fix te problem the type next is replaced by its content after aliasing it. It's fixed by refactoring a bit the feature using a new SCOPE member.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19708	normal	Can't use __traits(getAttributes, ...)[...] as a type

Testing this PR locally

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

dub fetch digger
dub run digger -- build "stable + dmd#10144"

[ghost]

Don't auto-merge for now because I may try something with Scope.flags to replace TypeTraits.inAliasDeclaration.

[ghost]

Yeah it really looks like using the scope flags fixes a flaw in the original design. There nothing really special anymore in aliasSemantic now. 🎉

[MoonlightSentinel]

@Basile-z Thank you for picking this up.

Once this fix is released the workaround should be removed from the spec
(https://dlang.org/spec/attribute.html#uda)

[thewilsonator]

So, it this good to go?

[ghost]

Once this fix is released the workaround should be removed from the spec

Yes I see that point 4 still uses a Tuple.

So, it this good to go?

Yes.