Flag unused declarations with —noUnusedParameters and —noUnusedLocals

TypeScript 2.0 has two new flags to help you maintain a clean code base.—noUnusedParameters flags any unused function or method parameters errors.—noUnusedLocals flags any unused local (un-exported) declaration like variables, functions, classes, imports, etc…Also, unused private members of a class would be flagged as errors under —noUnusedLocals.

Example

import B, { readFile } from "./b";
//     ^ Error: `B` declared but never used
readFile();
export function write(message: string, args: string[]) {
    //                                 ^^^^  Error: 'arg' declared but never used.
    console.log(message);
}

Parameters declaration with names starting with _ are exempt from the unused parameter checking.e.g.:

function returnNull(_a) { // OK
    return null;
}