[Fix] no-render-return-value: should warn when used in assignment expression

Fixes #2461.

Author: jichu4n

lib/rules/no-render-return-value.js

@@ -58,7 +58,8 @@ module.exports = {
           parent.type === 'VariableDeclarator' ||
           parent.type === 'Property' ||
           parent.type === 'ReturnStatement' ||
-          parent.type === 'ArrowFunctionExpression'
+          parent.type === 'ArrowFunctionExpression' ||
+          parent.type === 'AssignmentExpression'
         ) {
           context.report({
             node: callee,

tests/lib/rules/no-render-return-value.js

@@ -96,6 +96,16 @@ ruleTester.run('no-render-return-value', rule, {
     errors: [{
       message: 'Do not depend on the return value from ReactDOM.render'
     }]
+  }, {
+    code: 'this.o = ReactDOM.render(<div />, document.body);',
+    errors: [{
+      message: 'Do not depend on the return value from ReactDOM.render'
+    }]
+  }, {
+    code: 'var v; v = ReactDOM.render(<div />, document.body);',
+    errors: [{
+      message: 'Do not depend on the return value from ReactDOM.render'
+    }]
   }, {
     code: 'var inst = React.render(<div />, document.body);',
     settings: {