From 4dde054bb3d19f58ff0de926d2e1e75831b15085 Mon Sep 17 00:00:00 2001
From: Davy Duperron <yamafaktory@gmail.com>
Date: Mon, 6 Mar 2017 12:44:48 +0100
Subject: [PATCH] Fix binary expression instanceof in arrow function expression
 (#913)

* Add fix for parens of BinaryExpression with instanceof op embedded into ArrowFunctionExpression.

* Add new test :rocket:.
---
 src/fast-path.js                              | 7 +++++++
 tests/arrows/__snapshots__/jsfmt.spec.js.snap | 2 ++
 tests/arrows/arrow_function_expression.js     | 1 +
 3 files changed, 10 insertions(+)

diff --git a/src/fast-path.js b/src/fast-path.js
index 5d473686..60d02783 100644
--- a/src/fast-path.js
+++ b/src/fast-path.js
@@ -305,6 +305,13 @@ FPp.needsParens = function(assumeExpressionContext) {
         return true;
       }
 
+      if (
+        node.operator === "instanceof" &&
+        parent.type === "ArrowFunctionExpression"
+      ) {
+        return true;
+      }
+
     case "LogicalExpression":
       switch (parent.type) {
         case "CallExpression":
diff --git a/tests/arrows/__snapshots__/jsfmt.spec.js.snap b/tests/arrows/__snapshots__/jsfmt.spec.js.snap
index 525a6078..b565b0ec 100644
--- a/tests/arrows/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/arrows/__snapshots__/jsfmt.spec.js.snap
@@ -9,6 +9,7 @@ export default (() => {})();
 new (() => {});
 if ((() => {}) ? 1 : 0) {}
 let f = () => ({}())
+let a = () => ({} instanceof a);
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 (a => {}).length;
 typeof (() => {});
@@ -19,6 +20,7 @@ new (() => {})();
 if ((() => {}) ? 1 : 0) {
 }
 let f = () => ({}());
+let a = () => ({} instanceof a);
 "
 `;
 
diff --git a/tests/arrows/arrow_function_expression.js b/tests/arrows/arrow_function_expression.js
index 0b6e3bac..71251bea 100644
--- a/tests/arrows/arrow_function_expression.js
+++ b/tests/arrows/arrow_function_expression.js
@@ -6,3 +6,4 @@ export default (() => {})();
 new (() => {});
 if ((() => {}) ? 1 : 0) {}
 let f = () => ({}())
+let a = () => ({} instanceof a);