disallowUnusedParams: notice AssignmentPattern nodes

Fixes #2254

Author: markelog

lib/rules/disallow-unused-params.js

@@ -37,6 +37,10 @@
 var assert = require('assert');
 
 function getUnusedNodes(node, variableMap, groupIfPossible) {
+    if (node.type === 'AssignmentPattern') {
+        return getUnusedNodes(node.left, variableMap, groupIfPossible);
+    }
+
     if (node.type === 'Identifier') {
         var variable = variableMap[node.name];
 
@@ -94,6 +98,8 @@ function getUnusedNodes(node, variableMap, groupIfPossible) {
         }
         return unusedObjectNodes;
     }
+
+    return [];
 }
 
 function isComma(token) {

test/specs/rules/disallow-unused-params.js

@@ -17,7 +17,7 @@ describe('rules/disallow-unused-params', function() {
         expect(checker.checkString('function a(b, c) { return c; };')).to.have.no.errors();
     });
 
-    it('should report even with eval expression (gh-1943)', function() {
+    it('should not report even with eval expression (gh-1943)', function() {
         expect(checker.checkString('function foo(options) { return options; eval() };'))
             .to.have.no.errors();
     });
@@ -40,6 +40,11 @@ describe('rules/disallow-unused-params', function() {
         ).getErrorList()[0].message).to.contain('Param `test` is not used');
     });
 
+    it('should report for AssignmentPattern (gh-2254)', function() {
+        expect(checker.checkString('function foo(options = {}) {};')
+            .getErrorList()[0].message).to.contain('Param `options` is not used');
+    });
+
     it('should report unused param in function expression', function() {
         expect(checker.checkString(
             '(function(test) { })'