// @target: esnext
// @strictNullChecks: false
// @noImplicitReturns: true
// @noImplicitAny: true

declare const iterableIterator: IterableIterator<number>;
declare const generator: Generator<number, string, boolean>;
declare const never: never;

function* g000() { // Generator<never, void, unknown>
}

// 'yield' iteration type inference
function* g001() { // Generator<any (implicit), void, unknown>
    yield;
}

function* g002() { // Generator<number, void, unknown>
    yield 1;
}

function* g003() { // Generator<any (implicit), void, unknown>
    // NOTE: In strict mode, `[]` produces the type `never[]`.
    //       In non-strict mode, `[]` produces the type `undefined[]` which is implicitly any.
    yield* [];
}

function* g004() { // Generator<number, void, undefined>
    yield* iterableIterator;
}

function* g005() { // Generator<number, void, boolean>
    const x = yield* generator;
}

function* g006() { // Generator<1 | 2, void, unknown>
    yield 1;
    yield 2;
}

function* g007() { // Generator<never, void, unknown>
    yield never;
}

// 'return' iteration type inference
function* g102() { // Generator<never, number, unknown>
    return 1;
}

function* g103() { // Generator<never, 1 | 2, unknown>
    if (Math.random()) return 1;
    return 2;
}

function* g104() { // Generator<never, never, unknown>
    return never;
}

// 'next' iteration type inference
function* g201() { // Generator<number, void, string>
    let a: string = yield 1;
}

function* g202() { // Generator<1 | 2, void, never>
    let a: string = yield 1;
    let b: number = yield 2;
}

declare function f1(x: string): void;
declare function f1(x: number): void;

function* g203() { // Generator<number, void, string>
	const x = f1(yield 1);
}

declare function f2<T>(x: T): T;

function* g204() { // Generator<number, void, any>
	const x = f2(yield 1);
}

// mixed iteration types inference

function* g301() { // Generator<any (implicit), void, unknown>
    yield;
    return;
}

function* g302() { // Generator<number, void, unknown>
    yield 1;
    return;
}

function* g303() { // Generator<any (implicit), string, unknown>
    yield;
    return "a";
}

function* g304() { // Generator<number, string, unknown>
    yield 1;
    return "a";
}

function* g305() { // Generator<1 | 2, "a" | "b", unknown>
    if (Math.random()) yield 1;
    yield 2;
    if (Math.random()) return "a";
    return "b";
}

function* g306() { // Generator<number, boolean, "hi">
    const a: "hi" = yield 1;
    return true;
}

function* g307<T>() { // Generator<number, T, T>
    const a: T = yield 0;
    return a;
}

function* g308<T>(x: T) { // Generator<T, T, T>
    const a: T = yield x;
    return a;
}

function* g309<T, U, V>(x: T, y: U) { // Generator<T, U, V>
    const a: V = yield x;
    return y;
}

function* g310() { // Generator<any (implicit), void, [(1 | undefined)?, (2 | undefined)?]>
	const [a = 1, b = 2] = yield;
}

function* g311() { // Generator<any (implicit), void, string>
	yield* (function*() {
		const y: string = yield;
	})();
}