wrdn-effect-value-inferred-types

You fix one pattern: a TypeScript object type manually mirrors a runtime object that already owns the shape. Prefer value-first APIs. Build the object in a named factory, then export `type X = ReturnType<typeof makeX>`. Consumers keep importing the stable type name, but the type cannot drift from the implementation. ## Trace before changing 1. **Find the source value.** Look for an object returned from a named factory, `extension: (...) => ({ ... })`, a client object, route map, or handler table. 2. **Find the duplicate type.** A nearby `interface X` or `type X = { ... }` repeats the object methods/properties. 3. **Check whether the value is the source of truth.** If the interface is a contract with multiple implementations, keep the interface. 4. **Preserve the exported type name.** Replace its definition with `ReturnType<typeof makeX>` and update callers only if needed. 5. **Use `satisfies` only at boundaries.** Do not make the implementation satisfy a duplicate shape that could drift. ## Fix shape ```ts const makePluginExtension = (ctx: PluginCtx<Store>) => { const addSource = ... const removeSource = ... return { addSource, removeSource, }; }; export type PluginExtension = ReturnType<typeof makePluginExtension>; ``` For factories that need options: ```ts const makePluginExtension = (options: PluginOptions) => (ctx: PluginCtx<Store>) => ({ addSource: ..., }); export type PluginExtension = ReturnType<ReturnType<typeof makePluginExtension>>; ``` ## Bad ```ts export interface McpPluginExtension { readonly addSource: (config: McpSourceConfig) => Effect.Effect<AddResult, Failure>; readonly removeSource: (namespace: string, scope: string) => Effect.Effect<void, Failure>; } extension: (ctx) => { return { addSource, removeSource, } satisfies McpPluginExtension; }; ``` ## Good ```ts const makeMcpPluginExtension = (ctx: PluginCtx<McpStore>) => { return { addSource, removeSource, }; }; export type McpPluginExtension = ReturnType<typeof makeMcpPluginExtension>; extension: makeMcpPluginExtension; ``` ## What not to report - Service/dependency interfaces with multiple implementations. - Public config input types that are intentionally a stable authored API. - Branded IDs, discriminated unions, or small aliases that do not mirror one object value. - Test fakes typed against an existing exported contract. - Schema-owned data shapes; use `wrdn-effect-schema-inferred-types` for those. ## Output requirements When reviewing, report: - **File and line** of the duplicate object type or `satisfies` usage. - **Value/factory** that owns the shape. - **Why** the manual type can drift. - **Fix**: the exact `ReturnType` alias to introduce. When editing, name the factory after the exported type, e.g. `makeMcpPluginExtension` for `McpPluginExtension`.