Rule 8.9

Method dispatch must be static, and a generic function or class must be compiled once per set of type arguments the program uses (Rule 3.9). A derived class value may occupy a base-typed position when its base view is proved read-only and dispatch-equivalent: every base-visible method or accessor has the same body on the concrete class, no receiver writes or receiver escape are lost, and the projected fields cannot observably change through an alias after construction. The proof is conservative across the compiled source; unknown receivers and unproved alias writes do not establish safety. Arguments, initializers, assignments, returns and contextual composite elements use the same conversion. A generated function takes the concrete value once and constructs its base representation, preserving effects and source evaluation order. A view that needs runtime override selection or receiver retention remains refused with the concrete type to keep; no general dynamic-dispatch restriction is imposed by WGSL itself. A class with no instance fields remains a constructible value, including method-only, static-only, inherited, mixin and generic classes. Its authored field list remains empty; GPU lowering provides an internal carrier without adding source members or inherited fields. A body a class inherits is compiled again for that class; what fails only there (a call that takes the base, a static the class does not have) must be refused when a function that is not a class’s own reaches it through calls, and must not be when nothing does, the body being dropped with every function that calls it.