chore: Magic phantom types

compat/migrations.ts

@@ -25,7 +25,7 @@ export function updateConfig<
   noRepeat?: NoRepeat<version, type>,
   noFail = false,
 ): M.MigrationFn<version, type> {
-  return async (effects: T.Effects) => {
+  return M.migrationFn(async (effects: T.Effects) => {
     await noRepeatGuard(effects, noRepeat, async () => {
       let config = util.unwrapResultType(await getConfig({})(effects)).config;
       if (config) {
@@ -42,7 +42,7 @@ export function updateConfig<
       }
     });
     return { configured };
-  };
+  });
 }
 
 export async function noRepeatGuard<

migrations.ts

@@ -4,7 +4,15 @@ import { matches } from "./dependencies.ts";
 
 export type MigrationFn<version extends string, type extends "up" | "down"> = (
   effects: T.Effects,
-) => Promise<T.MigrationRes>;
+) => Promise<T.MigrationRes> & { _type: type; _version: version };
+
+export function migrationFn<version extends string, type extends "up" | "down">(
+  fn: (
+    effects: T.Effects,
+  ) => Promise<T.MigrationRes>,
+): MigrationFn<version, type> {
+  return fn as MigrationFn<version, type>;
+}
 
 export interface Migration<version extends string> {
   up: MigrationFn<version, "up">;
@@ -34,8 +42,7 @@ export function fromMapping<versions extends string>(
     const current = EmVer.parse(currentVersion);
     const other = EmVer.parse(version);
 
-    const filteredMigrations =
-      (Object.entries(migrations) as [
+    const filteredMigrations = (Object.entries(migrations) as [
       keyof MigrationMapping<string>,
       Migration<string>,
     ][])