fixed arrow function return type

Author: Keyan Zhang

transforms/__testfixtures__/class.input.js

@@ -23,10 +23,10 @@ var MyComponent = React.createClass({
 
 // Class comment
 var MyComponent2 = React.createClass({
-  getDefaultProps: function() {
+  getDefaultProps: function(): Object {
     return {a: 1};
   },
-  foo: function() { // flow annotations dont work for now
+  foo: function(): void {
     pass(this.foo);
     this.forceUpdate();
   },
@@ -61,11 +61,12 @@ var MyComponent3 = React.createClass({
     };
   },
 
-  _renderText: function(text: string) { // TODO no return type yet
+  // comment here
+  _renderText: function(text: string): ReactElement<any> { // say something
     return <Text text={text} />;
   },
 
-  _renderImageRange: function(text: string, range) { // TODO no return type yet
+  _renderImageRange: function(text: string, range): ReactElement<any> {
     var image = range.image;
     if (image) {
       return (
@@ -82,7 +83,7 @@ var MyComponent3 = React.createClass({
   dontAutobindMe: function(): number { return 12; },
 
   // Function comment
-  _renderRange: function(text: string, range, bla: Promise<string>) {
+  _renderRange: function(text: string, range, bla: Promise<string>): ReactElement<any> {
     var self = this;
 
     self.dontAutobindMe();

transforms/__testfixtures__/class.output.js

@@ -27,7 +27,7 @@ class MyComponent extends React.Component {
 class MyComponent2 extends React.Component {
   static defaultProps = {a: 1};
 
-  foo = () => { // flow annotations dont work for now
+  foo = (): void => {
     pass(this.foo);
     this.forceUpdate();
   };
@@ -63,14 +63,15 @@ class MyComponent3 extends React.Component {
     };
   }
 
-  _renderText = (text: string) => { // TODO no return type yet
+  // comment here
+  _renderText = (text: string): ReactElement<any> => { // say something
     return <Text text={text} />;
   };
 
   autobindMe = () => {};
 
   // Function comment
-  _renderRange = (text: string, range, bla: Promise<string>) => {
+  _renderRange = (text: string, range, bla: Promise<string>): ReactElement<any> => {
     var self = this;
 
     self.dontAutobindMe();
@@ -95,7 +96,7 @@ class MyComponent3 extends React.Component {
     return text;
   };
 
-  _renderImageRange(text: string, range) { // TODO no return type yet
+  _renderImageRange(text: string, range): ReactElement<any> {
     var image = range.image;
     if (image) {
       return (

transforms/class.js

@@ -352,14 +352,19 @@ module.exports = (file, api, options) => {
     ];
   };
 
+  const copyReturnType = (to, from) => {
+    to.returnType = from.returnType;
+    return to;
+  };
+
   const createArrowFunctionExpression = fn =>
-    j.arrowFunctionExpression(
+    copyReturnType(j.arrowFunctionExpression(
       fn.params,
       fn.body,
       false
-    );
+    ), fn);
 
-  const createArrowPropertyFromMethod = method => // TODO fix flow annotations
+  const createArrowPropertyFromMethod = method =>
     withComments(j.classProperty(
       j.identifier(method.key.name),
       createArrowFunctionExpression(method.value),