gen-platform 0.1.3

gen-platform — Rust-first canonical handle for the typed- dispatcher substrate primitive (typed-tagged-union catamorphism at a language boundary). Re-exports TypedDispatcher + #[derive(TypedDispatcher)], ships a runtime Dispatcher<T> applicator for Rust consumers (controllers, daemons, reactive routers, migration runners, RBAC engines, render passes), and surfaces typed catalog primitives so any pleme-io crate can stand up a typed dispatch surface against any closed variant universe with one cargo add.

Why a dedicated crate

The mk-typed-dispatcher.nix primitive proves the value at the Nix dispatch layer. The same shape recurs across pleme-io wherever a closed variant set drives an action (see theory/QUIRK-APPLIER.md §IV-bis.1 for the catalog). gen-platform is the canonical Rust-side handle so consumers in pangea-operator, engenho controllers, magma plan walkers, anomalia remediations, shinka migrations etc. reach for the same primitive instead of hand- rolling another match ladder.

Surface

use gen_platform::{Dispatcher, TypedDispatcher};

#[derive(serde::Serialize, serde::Deserialize, gen_platform::TypedDispatcher)]
#[serde(tag = "kind", rename_all = "kebab-case")]
enum Migration {
    AddColumn { table: String, column: String },
    DropIndex { name: String },
}

let dispatcher = Dispatcher::<Migration, MyCtx, MyOverride>::new()
    .helper("add-column", |variant, ctx| { /* ... */ Default::default() })
    .helper("drop-index", |variant, ctx| { /* ... */ Default::default() })
    .into_sealed()  // enforces variant coverage
    .expect("every variant has a helper");

let result = dispatcher.apply(&[migration_a, migration_b], &mut ctx);

Re-exports

• gen_types::TypedDispatcher — the reflection trait.
• gen_types::DispatcherVariant — variant envelope shape.
• gen_macros::TypedDispatcher — #[derive] macro.

New primitives (this crate)

• Dispatcher<V, C, O> — runtime applicator. Holds typed helpers per variant kind. into_sealed() proves coverage at construction time (every reflected kind has a registered helper) — silent unknown variants become impossible.
• SealedDispatcher<V, C, O> — the post-seal handle; apply cannot fail on coverage anymore (proven at seal time).
• DispatcherError — typed error for build-time issues (missing coverage, duplicate helpers).
• MergeStrategy — how to fold per-variant overrides.