Spike: ExtractKinds + StrictPlugin for ctor-kind consistency enforcement

ctor-enforcement-spike.ts

/**
 * Spike: enforce ctor-kind consistency at the Plugin type level.
 *
 * ExtractKinds<T> recursively walks a type tree and collects all CExpr
 * kind strings — through functions, builder chains, nested objects,
 * closure returns, and callback parameter types.
 *
 * StrictPlugin uses this to reject plugins where ctors produce CExpr
 * nodes with kinds not declared in the `kinds` map.
 *
 * Tested against all patterns in the codebase:
 * - Simple arity-N (num/add)
 * - Builder chains (error/try...catch)
 * - Closure-returning (st/let → {get, set})
 * - Nested objects (redis: {get, set})
 *
 * Known gap: side-effecting ctors (st/let creates st/let via push to
 * effects array, not via return type) — can't be seen by type system.
 */

import type { CExpr } from "@mvfm/core";
import type { KindSpec, Interpreter, TraitDef } from "@mvfm/core";

// ─── ExtractKinds ───────────────────────────────────────────────────

type ExtractKinds<T> =
  T extends CExpr<any, infer K extends string, any>
    ? K
    : T extends (...args: any[]) => infer R
      ? ExtractKinds<R>
      : T extends Record<string, unknown>
        ? { [P in keyof T]: ExtractKinds<T[P]> }[keyof T]
        : never;

// ─── StrictPlugin ───────────────────────────────────────────────────

interface StrictPlugin<
  Name extends string = string,
  Ctors = any,
  Kinds extends Record<string, KindSpec<any, any>> = any,
  Traits extends Record<string, TraitDef<any, any>> = any,
  Lifts extends Record<string, string> = any,
> {
  readonly name: Name;
  readonly ctors: [ExtractKinds<Ctors>] extends [keyof Kinds] ? Ctors : never;
  readonly kinds: Kinds;
  readonly traits: Traits;
  readonly lifts: Lifts;
  readonly defaultInterpreter?: () => Interpreter;
  readonly shapes?: Record<string, unknown>;
}

// ─── Example: passes ────────────────────────────────────────────────

// const good = {
//   name: "test",
//   ctors: {
//     add: <A, B>(a: A, b: B): CExpr<unknown, "test/add", [A, B]> =>
//       makeCExpr("test/add", [a, b]),
//   },
//   kinds: {
//     "test/add": { inputs: [0, 0], output: 0 } as KindSpec<[number, number], number>,
//   },
//   traits: {},
//   lifts: {},
// } satisfies StrictPlugin;

// ─── Example: fails (unregistered kind) ─────────────────────────────

// const bad = {
//   name: "test",
//   ctors: {
//     add: <A, B>(a: A, b: B): CExpr<unknown, "test/add", [A, B]> =>
//       makeCExpr("test/add", [a, b]),
//     sub: <A, B>(a: A, b: B): CExpr<unknown, "test/sub", [A, B]> =>
//       makeCExpr("test/sub", [a, b]),
//   },
//   kinds: {
//     "test/add": { inputs: [0, 0], output: 0 } as KindSpec<[number, number], number>,
//     // "test/sub" NOT registered — `satisfies StrictPlugin` fails!
//   },
//   traits: {},
//   lifts: {},
// } satisfies StrictPlugin;