[no-unused-state] Add ability to handle arrow function class method

lib/rules/no-unused-state.js

@@ -237,6 +237,27 @@ module.exports = {
         ) {
           addStateFields(node.value);
         }
+
+        if (
+          !node.static &&
+          node.value &&
+          node.value.type === 'ArrowFunctionExpression'
+        ) {
+          // Create a new set for this.state aliases local to this method.
+          classInfo.aliases = new Set();
+        }
+      },
+
+      'ClassProperty:exit'(node) {
+        if (
+          classInfo &&
+          !node.static &&
+          node.value &&
+          node.value.type === 'ArrowFunctionExpression'
+        ) {
+          // Forget our set of local aliases.
+          classInfo.aliases = null;
+        }
       },
 
       MethodDefinition() {

tests/lib/rules/no-unused-state.js

@@ -387,6 +387,22 @@ eslintTester.run('no-unused-state', rule, {
           return <SomeComponent foo={foo} />;
         }
       }`,
+    `class NonRenderClassMethodFalseNegativeTest extends React.Component {
+        constructor() {
+          this.state = { foo: 0, bar: 0 };
+        }
+        doSomething() {
+          const { foo } = this.state;
+          return this.state.foo;
+        }
+        doSomethingElse() {
+          const { state: { bar }} = this;
+          return bar;
+        }
+        render() {
+          return <SomeComponent />;
+        }
+      }`,
     {
       code: `class TypeCastExpressionSpreadFalseNegativeTest extends React.Component {
         constructor() {
@@ -397,6 +413,72 @@ eslintTester.run('no-unused-state', rule, {
         }
       }`,
       parser: 'babel-eslint'
+    },
+    {
+      code: `class ArrowFunctionClassMethodDestructuringFalseNegativeTest extends React.Component {
+        constructor() {
+          this.state = { foo: 0 };
+        }
+
+        doSomething = () => {
+          const { state: { foo } } = this;
+
+          return foo;
+        }
+
+        render() {
+          return <SomeComponent />;
+        }
+      }`,
+      parser: 'babel-eslint'
+    },
+    {
+      code: `class ArrowFunctionClassMethodWithClassPropertyTransformFalseNegativeTest extends React.Component {
+        state = { foo: 0 };
+
+        doSomething = () => {
+          const { state:{ foo } } = this;
+
+          return foo;
+        }
+
+        render() {
+          return <SomeComponent />;
+        }
+      }`,
+      parser: 'babel-eslint'
+    },
+    {
+      code: `class ArrowFunctionClassMethodDeepDestructuringFalseNegativeTest extends React.Component {
+        state = { foo: { bar: 0 } };
+
+        doSomething = () => {
+          const { state: { foo: { bar }}} = this;
+
+          return bar;
+        }
+
+        render() {
+          return <SomeComponent />;
+        }
+      }`,
+      parser: 'babel-eslint'
+    },
+    {
+      code: `class ArrowFunctionClassMethodDestructuringAssignmentFalseNegativeTest extends React.Component {
+        state = { foo: 0 };
+
+        doSomething = () => {
+          const { state: { foo: bar }} = this;
+
+          return bar;
+        }
+
+        render() {
+          return <SomeComponent />;
+        }
+      }`,
+      parser: 'babel-eslint'
     }
   ],
 
@@ -642,6 +724,21 @@ eslintTester.run('no-unused-state', rule, {
         }`,
       errors: getErrorMessages(['foo'])
     },
+    {
+      code: `class UnusedStateArrowFunctionMethodTest extends React.Component {
+          constructor() {
+            this.state = { foo: 0 };
+          }
+          doSomething = () => {
+            return null;
+          }
+          render() {
+            return <SomeComponent />;
+          }
+        }`,
+      errors: getErrorMessages(['foo']),
+      parser: 'babel-eslint'
+    },
     {
       code: `class TypeCastExpressionTest extends React.Component {
           constructor() {