From 881fc14329f1b30f4e94c341f336c32dd287364f Mon Sep 17 00:00:00 2001
From: Brian Ng <bng412@gmail.com>
Date: Mon, 27 Nov 2017 12:08:35 -0600
Subject: [PATCH] Add handling parens for extends clause in generator (#6897)

---
 .../babel-generator/src/node/parentheses.js   | 23 ++++++++++--
 .../parentheses/class-extends/actual.js       | 22 ++++++++++++
 .../parentheses/class-extends/expected.js     | 35 +++++++++++++++++++
 3 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/parentheses/class-extends/actual.js
 create mode 100644 packages/babel-generator/test/fixtures/parentheses/class-extends/expected.js

diff --git a/packages/babel-generator/src/node/parentheses.js b/packages/babel-generator/src/node/parentheses.js
index e57efbf977..9c1322881c 100644
--- a/packages/babel-generator/src/node/parentheses.js
+++ b/packages/babel-generator/src/node/parentheses.js
@@ -27,6 +27,10 @@ const PRECEDENCE = {
   "**": 10,
 };
 
+const isClassExtendsClause = (node: Object, parent: Object): boolean =>
+  (t.isClassDeclaration(parent) || t.isClassExpression(parent)) &&
+  parent.superClass === node;
+
 export function NullableTypeAnnotation(node: Object, parent: Object): boolean {
   return t.isArrayTypeAnnotation(parent);
 }
@@ -35,7 +39,10 @@ export { NullableTypeAnnotation as FunctionTypeAnnotation };
 
 export function UpdateExpression(node: Object, parent: Object): boolean {
   // (foo++).test()
-  return t.isMemberExpression(parent) && parent.object === node;
+  return (
+    (t.isMemberExpression(parent) && parent.object === node) ||
+    isClassExtendsClause(node, parent)
+  );
 }
 
 export function ObjectExpression(
@@ -62,6 +69,10 @@ export function Binary(node: Object, parent: Object): boolean {
     return parent.left === node;
   }
 
+  if (isClassExtendsClause(node, parent)) {
+    return true;
+  }
+
   if (
     ((t.isCallExpression(parent) || t.isNewExpression(parent)) &&
       parent.callee === node) ||
@@ -151,7 +162,8 @@ export function YieldExpression(node: Object, parent: Object): boolean {
     t.isCallExpression(parent) ||
     t.isMemberExpression(parent) ||
     t.isNewExpression(parent) ||
-    (t.isConditionalExpression(parent) && node === parent.test)
+    (t.isConditionalExpression(parent) && node === parent.test) ||
+    isClassExtendsClause(node, parent)
   );
 }
 
@@ -170,7 +182,8 @@ export function UnaryLike(node: Object, parent: Object): boolean {
     t.isMemberExpression(parent, { object: node }) ||
     t.isCallExpression(parent, { callee: node }) ||
     t.isNewExpression(parent, { callee: node }) ||
-    t.isBinaryExpression(parent, { operator: "**", left: node })
+    t.isBinaryExpression(parent, { operator: "**", left: node }) ||
+    isClassExtendsClause(node, parent)
   );
 }
 
@@ -210,6 +223,10 @@ export function AssignmentExpression(node: Object): boolean {
   }
 }
 
+export function NewExpression(node: Object, parent: Object): boolean {
+  return isClassExtendsClause(node, parent);
+}
+
 // Walk up the print stack to determine if our node can come first
 // in statement.
 function isFirstInStatement(
diff --git a/packages/babel-generator/test/fixtures/parentheses/class-extends/actual.js b/packages/babel-generator/test/fixtures/parentheses/class-extends/actual.js
new file mode 100644
index 0000000000..308200e8d2
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/parentheses/class-extends/actual.js
@@ -0,0 +1,22 @@
+class A extends (() => {}) {}
+class A extends (B = C) {}
+class A extends (B || C) {}
+class A extends (B + C) {}
+class A extends B() {}
+class A extends class {} {}
+class A extends (B ? C : D) {}
+class A extends (new B()) {}
+class A extends (B, C) {}
+class A extends ({}) {}
+class A extends B.C {}
+class A extends function() {} {}
+class A extends (void B) {}
+class A extends (++B) {}
+
+async function f() {
+  class A extends (await C) {}
+}
+
+function* f() {
+  class A extends (yield 1) {}
+}
diff --git a/packages/babel-generator/test/fixtures/parentheses/class-extends/expected.js b/packages/babel-generator/test/fixtures/parentheses/class-extends/expected.js
new file mode 100644
index 0000000000..6885e6094e
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/parentheses/class-extends/expected.js
@@ -0,0 +1,35 @@
+class A extends (() => {}) {}
+
+class A extends (B = C) {}
+
+class A extends (B || C) {}
+
+class A extends (B + C) {}
+
+class A extends B() {}
+
+class A extends class {} {}
+
+class A extends (B ? C : D) {}
+
+class A extends (new B()) {}
+
+class A extends (B, C) {}
+
+class A extends {} {}
+
+class A extends B.C {}
+
+class A extends function () {} {}
+
+class A extends (void B) {}
+
+class A extends (++B) {}
+
+async function f() {
+  class A extends (await C) {}
+}
+
+function* f() {
+  class A extends (yield 1) {}
+}