[clang] [clang] Document the type_visibility attribute (PR #79157)

[Louis Dionne via cfe-commits]

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@@ -3220,8 +3220,8 @@ def TypeVisibility : InheritableAttr {
   let Args = [EnumArgument<"Visibility", "VisibilityType",
                            ["default", "hidden", "internal", "protected"],
                            ["Default", "Hidden", "Hidden", "Protected"]>];
-//  let Subjects = [Tag, ObjCInterface, Namespace];
-  let Documentation = [Undocumented];
+  let Subjects = SubjectList<[Tag, ObjCInterface, Namespace], ErrorDiag>;
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ldionne wrote:

I'm not certain if this is correct, and whether this means I need to add some tests.

https://github.com/llvm/llvm-project/pull/79157