no-transport-types-in-generator

Intent: the generator returns a domain value; conversion to a transport type happens in the second argument of Effect.fn.

// ❌ no: an error branch inside the happy path
function* (request: Request) {
    const credential = yield* sessionCredential
    if (credential === undefined) return Response.redirect(new URL("/login", origin), 303)
    // …
}

// ✅ yes
const createEvent = Effect.fn("events.create")(
    function* (request: Request) {
        const credential = yield* sessionCredential // fails with Unauthenticated
        const submission = yield* form(request)
        return yield* apiCreateEvent(credential, submission)
    },
    (effect, request) =>
        effect.pipe(
            Effect.map((created) => Response.redirect(eventUrl(request, created), 303)),
            Effect.catchTags({ Unauthenticated: () => Effect.succeed(toLogin(request)) }),
        ),
)

Trigger: new T(…), T.method(…) and T(…) inside an Effect generator, callbacks passed to Effect.* combinators included, when T is a transport type.

Exemptions and blind spots: pipeables of Effect.fn, where the conversion must live. Functions the generator only defines, such as an HTTP handler it registers. return yield* new Unauthenticated(…) is a declared failure. An early return of a domain value that actually signals an error is indistinguishable from a success.

Why: an early return new Response(…) on the happy path is an error branch disguised as success, and escapes exhaustive translation.

Options:

• transportTypes: default ["Response", "NextResponse"], replaced by the configured list. Add your own transport DTOs.

Fix: none