fix option type definition to match usage.

typings/commander-tests.ts

@@ -37,6 +37,12 @@ function collect(val: string, memo: string[]) {
     memo.push(val);
     return memo;
 }
+/*
+ * Collector without return all so work
+ */
+function collect2(val: string, memo: string[]) {
+    memo.push(val);
+}
 
 function increaseVerbosity(v: any, total: number) {
     return total + 1;
@@ -51,6 +57,7 @@ program
     .option('-l, --list <items>', 'A list', list)
     .option('-o, --optional [value]', 'An optional value')
     .option('-c, --collect [value]', 'A repeatable value', collect, [])
+    .option('--collect2 [value]', 'A repeatable value void return', collect2, [])
     .option('-v, --verbose', 'A value that can be increased', increaseVerbosity, 0)
     .parse(process.argv);
 

typings/index.d.ts

@@ -165,12 +165,14 @@ declare namespace commander {
      *
      * @param {string} flags
      * @param {string} [description]
-     * @param {((arg1: any, arg2: any) => void) | RegExp} [fn] function or default
+     * @param {((value: string, previous: any) => void) | RegExp} [fn] function or default
      * @param {*} [defaultValue]
      * @returns {Command} for chaining
      */
-    option(flags: string, description?: string, fn?: ((arg1: any, arg2: any) => void) | RegExp, defaultValue?: any): Command;
     option(flags: string, description?: string, defaultValue?: any): Command;
+    option(flags: string, description: string, regexp: RegExp, defaultValue?: any): Command;
+    option<T>(flags: string, description: string, fn: (value: string, previous: T) => (T | void), defaultValue?: T): Command;
+    option<T>(flags: string, description: string, fn: (value: string, previous: T) => void, defaultValue: T): Command;
 
     /**
      * Define a required option, which must have a value after parsing. This usually means