Attribute Macro not_a_component 

#[not_a_component]

Say of a public widget why it is not a described component, where it is declared: #[not_a_component(layout, "the language's stack")]. The toolkit’s coverage check reads it: every public widget is either described (impl Described) or says why not, so a widget that works in Tilo is either in tilolang or names the reason it never will be.

The kinds:

• layout: a layout the language’s own primitive builds (name it);
• shell: window management the system owns, never inside an app’s window;
• system: a surface only the system may draw (a prompt for a secret or a permission, the palette, system search), which an app must not be able to forge;
• part: a part of another component, reached through it (name it);
• framework: behaviour the framework applies around a view, not something a view places.

The item is left as it is.