Type-check options.js and index.js (#490)

src/options.js

@@ -1,17 +1,21 @@
+// @flow
+
 // A second optional argument can be given to further configure
 // the parser process. These options are recognized:
 
-export const defaultOptions: {
-  sourceType: string,
-  sourceFilename: any,
-  startLine: number,
-  allowReturnOutsideFunction: boolean,
-  allowImportExportEverywhere: boolean,
-  allowSuperOutsideMethod: boolean,
-  plugins: Array<string>,
-  strictMode: any,
-  ranges: boolean,
-} = {
+export type Options = {
+  sourceType: "script" | "module";
+  sourceFilename?: string;
+  startLine: number;
+  allowReturnOutsideFunction: boolean;
+  allowImportExportEverywhere: boolean;
+  allowSuperOutsideMethod: boolean;
+  plugins: $ReadOnlyArray<string>;
+  strictMode: ?boolean;
+  ranges: boolean;
+};
+
+export const defaultOptions: Options = {
   // Source type ("script" or "module") for different semantics
   sourceType: "script",
   // Source filename.
@@ -44,8 +48,8 @@ export const defaultOptions: {
 
 // Interpret and default an options object
 
-export function getOptions(opts?: Object): Object {
-  const options = {};
+export function getOptions(opts: ?Options): Options {
+  const options: any = {};
   for (const key in defaultOptions) {
     options[key] = opts && key in opts ? opts[key] : defaultOptions[key];
   }