Parser#check(...) is a chainable function, just like all the others

optimist/optimist-tests.ts

@@ -35,7 +35,7 @@ parser = parser.options({});
 
 parser = parser.usage(str);
 
-parser.check(checkFn);
+parser = parser.check(checkFn);
 
 parser = parser.boolean(str);
 parser = parser.boolean([str]);

optimist/optimist.d.ts

@@ -60,7 +60,7 @@ declare module "optimist" {
 			/** Check that certain conditions are met in the provided arguments. If fn
 			throws or returns false, show the thrown error, usage information, and exit.
 			*/
-			check(fn: (argv: any) => any): void;
+			check(fn: (argv: any) => any): Parser;
 
 			/** Interpret key as a boolean. If a non-flag option follows key in process.argv,
 			that string won't get set as the value of key. If key never shows up as a