From cce83a0cea42464a27864aefd878a5c4ec0efb4c Mon Sep 17 00:00:00 2001
From: Brian Ng <bng412@gmail.com>
Date: Fri, 9 Jun 2017 10:10:16 -0500
Subject: [PATCH] Fix parens issues with exponentiation in generator (#5830)

---
 packages/babel-generator/src/node/parentheses.js       | 10 +++++++++-
 .../test/fixtures/parentheses/exponentiation/actual.js |  9 +++++++++
 .../fixtures/parentheses/exponentiation/expected.js    |  9 +++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 packages/babel-generator/test/fixtures/parentheses/exponentiation/actual.js
 create mode 100644 packages/babel-generator/test/fixtures/parentheses/exponentiation/expected.js

diff --git a/packages/babel-generator/src/node/parentheses.js b/packages/babel-generator/src/node/parentheses.js
index 571a97873e..6879417c38 100644
--- a/packages/babel-generator/src/node/parentheses.js
+++ b/packages/babel-generator/src/node/parentheses.js
@@ -47,6 +47,13 @@ export function DoExpression(node: Object, parent: Object, printStack: Array<Obj
 }
 
 export function Binary(node: Object, parent: Object): boolean {
+  if (
+    node.operator === "**" &&
+    t.isBinaryExpression(parent, { operator: "**" })
+  ) {
+    return parent.left === node;
+  }
+
   if (
     ((t.isCallExpression(parent) || t.isNewExpression(parent)) && parent.callee === node) ||
     t.isUnaryLike(parent) ||
@@ -124,7 +131,8 @@ export function ClassExpression(node: Object, parent: Object, printStack: Array<
 export function UnaryLike(node: Object, parent: Object): boolean {
   return t.isMemberExpression(parent, { object: node }) ||
          t.isCallExpression(parent, { callee: node }) ||
-         t.isNewExpression(parent, { callee: node });
+         t.isNewExpression(parent, { callee: node }) ||
+         t.isBinaryExpression(parent, { operator: "**", left: node });
 }
 
 export function FunctionExpression(node: Object, parent: Object, printStack: Array<Object>): boolean {
diff --git a/packages/babel-generator/test/fixtures/parentheses/exponentiation/actual.js b/packages/babel-generator/test/fixtures/parentheses/exponentiation/actual.js
new file mode 100644
index 0000000000..9705c91b51
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/parentheses/exponentiation/actual.js
@@ -0,0 +1,9 @@
+Math.sqrt(3**2 + (-5)**2);
+a ** b ** c;
+(a ** b) ** c;
+a.b ** c;
+(-a) ** b;
+a ** -b;
+-(a**b);
+(a * b) ** c;
+a ** (b * c);
diff --git a/packages/babel-generator/test/fixtures/parentheses/exponentiation/expected.js b/packages/babel-generator/test/fixtures/parentheses/exponentiation/expected.js
new file mode 100644
index 0000000000..ac94b4db42
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/parentheses/exponentiation/expected.js
@@ -0,0 +1,9 @@
+Math.sqrt(3 ** 2 + (-5) ** 2);
+a ** b ** c;
+(a ** b) ** c;
+a.b ** c;
+(-a) ** b;
+a ** -b;
+-(a ** b);
+(a * b) ** c;
+a ** (b * c);