flow.js

// @flow

function giveMeStrings(arr: string[]): string {
  // do something with the array of strings
}

giveMeStrings('hello', 'goodbye');
/*
ERROR:
7: giveMeStrings('hello', 'goodbye');
                 ^ string. This type is incompatible with the expected param type of
3: function giveMeStrings(arr: string[]): string {
                               ^ array type
*/