Make terminator paren comment check more strict (#5651)

packages/babel-generator/src/node/parentheses.js

@@ -199,7 +199,7 @@ export function AssignmentExpression(node: Object): boolean {
   }
 }
 
-// Walk up the print stack to deterimine if our node can come first
+// Walk up the print stack to determine if our node can come first
 // in statement.
 function isFirstInStatement(
   printStack: Array<Object>,

packages/babel-generator/src/printer.js

@@ -246,8 +246,10 @@ export default class Printer {
     if (i === str.length) return;
 
     const cha = str[i];
-    if (cha === "\n" || cha === "/") {
-      // we're going to break this terminator expression so we need to add a parentheses
+    const chaPost = str[i + 1];
+
+    // Check for newline or comment
+    if (cha === "\n" || (cha === "/" && (chaPost === "/" || chaPost === "*"))) {
       this.token("(");
       this.indent();
       parenPushNewlineState.printed = true;

packages/babel-generator/test/fixtures/types/ReturnStatement/actual.js

@@ -9,3 +9,7 @@ function bar() {
 function foo() {
   return 1, "foo";
 }
+
+() => { return /a/; }
+
+function foo() { return /a/; }

packages/babel-generator/test/fixtures/types/ReturnStatement/expected.js

@@ -8,4 +8,12 @@ function bar() {
 
 function foo() {
   return 1, "foo";
-}
+}
+
+() => {
+  return /a/;
+};
+
+function foo() {
+  return /a/;
+}

packages/babel-generator/test/fixtures/types/ThrowStatement/actual.js

@@ -1,3 +1,4 @@
 throw err;
 throw Error("foobar");
 throw new Error("foobar");
+throw /a/;

packages/babel-generator/test/fixtures/types/ThrowStatement/expected.js

@@ -1,3 +1,4 @@
 throw err;
 throw Error("foobar");
-throw new Error("foobar");
+throw new Error("foobar");
+throw /a/;