From fee2d1a02fe32772129973cf1054a49930934ef8 Mon Sep 17 00:00:00 2001
From: Yannick Croissant <yannick.croissant@gmail.com>
Date: Mon, 4 Jun 2018 23:20:04 +0200
Subject: [PATCH] Fix crash in no-unused-prop-types when encountering mixed
 union and intersection flow types (fixes #1806)

---
 lib/rules/no-unused-prop-types.js       |  2 +-
 tests/lib/rules/no-unused-prop-types.js | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/rules/no-unused-prop-types.js b/lib/rules/no-unused-prop-types.js
index b73c173c01..cff7eecafc 100644
--- a/lib/rules/no-unused-prop-types.js
+++ b/lib/rules/no-unused-prop-types.js
@@ -361,7 +361,7 @@ module.exports = {
         and property value. (key, value) => void
      */
     function iterateProperties(properties, fn) {
-      if (properties.length && typeof fn === 'function') {
+      if (properties && properties.length && typeof fn === 'function') {
         for (let i = 0, j = properties.length; i < j; i++) {
           const node = properties[i];
           const key = getKeyValue(node);
diff --git a/tests/lib/rules/no-unused-prop-types.js b/tests/lib/rules/no-unused-prop-types.js
index ba3500045a..b0bc92237b 100644
--- a/tests/lib/rules/no-unused-prop-types.js
+++ b/tests/lib/rules/no-unused-prop-types.js
@@ -4551,6 +4551,29 @@ ruleTester.run('no-unused-prop-types', rule, {
       errors: [{
         message: '\'defaultValue\' PropType is defined but prop is never used'
       }]
+    }, {
+      // Mixed union and intersection types
+      code: `
+        import React from 'react';
+        type OtherProps = {
+          firstname: string,
+          lastname: string,
+        } | {
+          fullname: string
+        };
+        type Props = OtherProps & {
+          age: number
+        };
+        class Test extends React.PureComponent<Props> {
+          render() {
+            return <div>Hello {this.props.firstname}</div>
+          }
+        }
+      `,
+      parser: 'babel-eslint',
+      errors: [{
+        message: '\'age\' PropType is defined but prop is never used'
+      }]
     }
 
     /* , {