Also do the class extend parenthesis for class expressions (#403)

src/fast-path.js

@@ -195,7 +195,7 @@ FPp.needsParens = function(assumeExpressionContext) {
   // Add parens around the extends clause of a class. It is needed for almost
   // all expressions.
   if (
-    parent.type === "ClassDeclaration" &&
+    (parent.type === "ClassDeclaration" || parent.type === "ClassExpression") &&
       parent.superClass === node && (
         node.type === "ArrowFunctionExpression" ||
         node.type === "AssignmentExpression" ||

tests/class_extends/__snapshots__/jsfmt.spec.js.snap

@@ -54,6 +54,8 @@ function* f() {
   // Flow has a bug parsing it.
   // class a extends (yield 1) {}
 }
+
+x = class extends (++b) {}
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // \"ArrowFunctionExpression\"
 class a extends (() => {
@@ -112,5 +114,7 @@ function* f() {
   // Flow has a bug parsing it.
   // class a extends (yield 1) {}
 }
+
+x = class extends (++b) {};
 "
 `;

tests/class_extends/extends.js

@@ -53,3 +53,5 @@ function* f() {
   // Flow has a bug parsing it.
   // class a extends (yield 1) {}
 }
+
+x = class extends (++b) {}