add parens on expressions with trailing comments - fixes #349

lib/6to5/generation/generator.js

@@ -148,6 +148,11 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
   };
 
   if (this[node.type]) {
+    // only compute if this node needs parens if our parent has been changed
+    // since acorn would've wrapped us in a ParanthesizedExpression
+    var needsParens = n.needsParens(node, parent);
+    if (needsParens) this.push("(");
+
     this.printLeadingComments(node, parent);
 
     newline(true);
@@ -155,11 +160,6 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
     if (opts.before) opts.before();
     this.map.mark(node, "start");
 
-    // only compute if this node needs parens if our parent has been changed
-    // since acorn would've wrapped us in a ParanthesizedExpression
-    var needsParens = n.needsParens(node, parent);
-    if (needsParens) this.push("(");
-
     this[node.type](node, this.buildPrint(node), parent);
 
     if (needsParens) this.push(")");

lib/6to5/generation/node/index.js

@@ -60,6 +60,10 @@ Node.prototype.needsParens = function () {
 
   if (!parent) return false;
 
+  if (t.isExpression(node) && node.leadingComments && node.leadingComments.length) {
+    return true;
+  }
+
   if (t.isNewExpression(parent) && parent.callee === node) {
     return t.isCallExpression(node) || _.some(node, function (val) {
       return t.isCallExpression(val);

lib/6to5/types/index.js

@@ -297,19 +297,26 @@ t.isVar = function (node) {
   return t.isVariableDeclaration(node, { kind: "var" }) && !node._let;
 };
 
+//
+
+t.COMMENT_KEYS = ["leadingComments", "trailingComments"];
+
 t.removeComments = function (child) {
-  delete child.leadingComments;
-  delete child.trailingComments;
+  _.each(t.COMMENT_KEYS, function (key) {
+    delete child[key];
+  });
   return child;
 };
 
 t.inheritsComments = function (child, parent) {
-  _.each(["leadingComments", "trailingComments"], function (key) {
+  _.each(t.COMMENT_KEYS, function (key) {
     child[key]  = _.uniq(_.compact([].concat(child[key], parent[key])));
   });
   return child;
 };
 
+//
+
 t.inherits = function (child, parent) {
   child.loc   = parent.loc;
   child.end   = parent.end;