[brenelz]

A .rx app could not use @solidjs/router. A JS component applied in markup was UNKNOWN_COMPONENT, a component passed as a value was COMPONENT_AS_VALUE, and a JS module's .d.rx could not declare a component at all (PARSE). This blocks a routed version of the solid-v2/with-reactivescript template (solidjs/templates#347).

Root cause

The language had no way to talk about a component that lives in JS. A .d.rx for a JS module accepted only fn, error and type, and the checker refused any component that was not applied in a view, because .rx has no way to apply a value. @solidjs/router 2.0 (2.0.0-next.44) needs both: createRouter({ routes }) returns the router component, and each route names its page as a component value. Its links are plain <a href>; the 0.x <Router>, <Route> and <A> components are gone.

What changed

Spec 09 gains MO-11 (taken by default, open to veto) with a design note that weighs three options: declared components, a routing form in the language, and a TSX route table. It takes the first, because it uses the router's API as it is and works for any Solid component library.

• MO-11a. A JS .d.rx may declare export component X(props: { … }), with TypeScript field types, optional catches(…) per field, and fails(…) and shape(…) after. With no children it lowers to <X /> rather than children={[]}, because next.44's router reads props.children as its root layout.
• MO-11f. A JS fn whose result is Component (or Component<P>) is a factory. Its call runs once where it is bound, and the bound name is applied as a component (<Router />). It cannot be exported, because only its own module knows what it was given.
• MO-11c. A component is a value only on a JS component's Component prop or inside a factory's argument literals. There it is checked as if applied, with no arguments, beneath that application: escaping failures (R-f-5), required contexts (RG-7b), the client-only first load (CN-3d) and HTML nesting (SV-7d) are all checked above <Router /> for every route. DV-24 records the assumption that the library renders it beneath the application it was passed to, and the precision it costs: a provide or errored inside a layout route is not credited to its pages.
• MO-11d/e. Hooks are MO-10 primitives (useParams returns a store whose fields track; useNavigate returns an io function), and a route's data is an await over its params.

Both the reference (ref/) and the crate (compiler/) implement it, with the TSX projection writing .d.ts stubs for declared components and factories. New scenarios: S-module-5 (declared components and component values) and S-module-6 (the router), both checked only, since the runners have no router. examples/router/ routes between two pages with a param and per-route data, and compiler/test/vite.mjs builds it and navigates it in Chromium. It fetches @solidjs/router@2.0.0-next.44 with npm pack into .out/, so it needs the network on a fresh run. The guide gains a "Components and routers" section.

How it was verified

• npm test in ref/: 132 scenarios pass.
• npm run crate: 386/386. npm run crate -- --lower: 215/215, with Solid's compiler built at ref/SOLID_NEXT. With a newer ../solid-next, 23 existing programs differ on both sides of this change.
• npm run crate -- --project: every program agrees; the one FAIL prelude line is already on main.
• npm run types, and again with RX_CRATE=1: 179/179.
• cargo test --release, npm test in compiler/, and npm test in tooling/rx-language-server (16 + 4) pass.
• SOLID_VITE_PLUGIN=<a 3.0.0-next.57 build> node compiler/test/vite.mjs: every app builds, including both router runs (links change pages without a reload, a param and its data reach the page, navigate() works, the page's NotFound boundary shows, back works, a deep link loads). todo (dev) fails with a refused connection, as it does on main.
• The with-reactivescript template with a router added builds with vite build, navigates the same way in Chromium (one document load), passes rx-tsc --noEmit against the router's own .d.ts, passes its Vitest tests, and works under the dev server.
• npm run compiled fails S-guess-reask-refresh, S-latest-reask, S-solid-44 and S-solid-46, identically on main.

Left open

These are listed as decision 8 in spec/09-modules.md.

• A factory's component cannot take a component value itself, so next.44's root layout as <Router>{Layout}</Router> is refused; use a parent route with children instead. Markup children on <Router> are accepted and fail at run time.
• A JS component's own failures default to none rather than Error.
• No declaration word yet credits a layout route's errored and provide to its pages (DV-24's precision).
• The hooks' router context is not checked statically.
• .rx cannot pass a type argument to useParams<{ id: string }>(), so a param is string | undefined in rx-tsc.
• Not covered: TSX importing an .rx page (overlaps Type an entry's default export; stop rx-tsc crashing on .d.rx #65), and the router under SSR.

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