flowTests.js

function bar(x: string, y: number): string {
  return x.length * y;
}

type PermissionOverwrite = {
  id: string;
  type: 'role' | 'member',
  allow: number;
  deny: number;
}

function total(numbers: Array<number>) {
  var result = 0;
  for (var i = 0; i < numbers.length; i++) {
	result += numbers[i];
  }
  return result;
}

function foo(a: string, b: number): { key: number,	bool: boolean } {}

function foo(a: string, b: number): [ string, number ] {
}

function foo(a: string, b: number):object {}

function foo(a: string, b: number):object {
}

function foo(x: string): string { return x; }

function foo(a: string, b: number):void {
	let durp: sayWhat = 2;
}

var x: boolean = someBool;

class Bar {
  y: string;
  someMethod(a: number): string {
  }
}

let array: number[] = [1, 2, 3.14, 42];

let theAnswer: number = array[3]; // 42

let offTheEnd: number = array[100]; // No error

let array2: Array<string> = ["an alternate", "syntax", "for arrays"];

let tuple: [string, number, boolean] = ["foo", 0, true];

// Indexing into the array will return the type at a given index.
(tuple[0]: string);
(tuple[1]: string);

// Indexing into an statically unknown index will return a general type.
declare var unknownNumber: number;

// `void` is none of `string`, `number`, or `boolean`
(tuple[unknownNumber]: void);
(tuple[unknownNumber]: string|number|boolean); // OK

// Values written must be compatible with the type at that index.
tuple[1] = -1;
tuple[0] = false;

let object: {foo: string, bar: number} = {foo: "foo", bar: 0};
(object.foo: string);

if (true) {
	let durp: number = 2;
}

let case = 1;

switch (case) {
	case 1:
		let durp: sayWhat;
		break;
	case 2:
		break;
}

function exampleMethod(someString: string, someRecord: Record): {resultString: string, resultString2: string} {
}

type State = {
  errorMessages: Array<string>;
  forceValidation: bool;
  invalidFields: Array<string>;
  submitting: bool;
};

//-----------------------------------------------------------------------------
// Blah blah
//-----------------------------------------------------------------------------

function lol() {
   // ...
}

type Props = {
  name: string;  // note: not null!
  address: string;
};

class AddressBookEntry extends React.Component<void /* DefaultProps */, Props, void /* state -- none in this component */> {
}