fix tree traversal on AST_Do (#3047)

fixes #3046

lib/compress.js

@@ -530,12 +530,11 @@ merge(Compressor.prototype, {
             tw.safe_ids = save_ids;
             return true;
         });
-        def(AST_Do, function(tw) {
+        def(AST_DWLoop, function(tw, descend) {
             var saved_loop = tw.in_loop;
             tw.in_loop = this;
             push(tw);
-            this.body.walk(tw);
-            this.condition.walk(tw);
+            descend();
             pop(tw);
             tw.in_loop = saved_loop;
             return true;
@@ -714,16 +713,6 @@ merge(Compressor.prototype, {
                 }
             }
         });
-        def(AST_While, function(tw) {
-            var saved_loop = tw.in_loop;
-            tw.in_loop = this;
-            push(tw);
-            this.condition.walk(tw);
-            this.body.walk(tw);
-            pop(tw);
-            tw.in_loop = saved_loop;
-            return true;
-        });
     })(function(node, func){
         node.DEFMETHOD("reduce_vars", func);
     });

lib/transform.js

@@ -93,7 +93,12 @@ TreeTransformer.prototype = new TreeWalker;
         self.body = do_list(self.body, tw);
     });
 
-    _(AST_DWLoop, function(self, tw){
+    _(AST_Do, function(self, tw){
+        self.body = self.body.transform(tw);
+        self.condition = self.condition.transform(tw);
+    });
+
+    _(AST_While, function(self, tw){
         self.condition = self.condition.transform(tw);
         self.body = self.body.transform(tw);
     });