simplify traversal logic (#4063)

1 files changed, 14 insertions, 12 deletions

diff --git a/lib/scope.js b/lib/scope.js
index 3297b8e6..450c1062 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -559,21 +559,23 @@ AST_Toplevel.DEFMETHOD("compute_char_frequency", function(options) {
     options = _default_mangler_options(options);
     base54.reset();
     try {
-        AST_Node.prototype.print = function(stream, force_parens) {
-            this._print(stream, force_parens);
-            if (this instanceof AST_Symbol && !this.unmangleable(options)) {
-                base54.consider(this.name, -1);
-            } else if (options.properties) {
-                if (this instanceof AST_Dot) {
-                    base54.consider(this.property, -1);
-                } else if (this instanceof AST_Sub) {
-                    skip_string(this.property);
-                }
-            }
+        var fn = AST_Symbol.prototype.add_source_map;
+        AST_Symbol.prototype.add_source_map = function() {
+            if (!this.unmangleable(options)) base54.consider(this.name, -1);
         };
+        if (options.properties) {
+            AST_Dot.prototype.add_source_map = function() {
+                base54.consider(this.property, -1);
+            };
+            AST_Sub.prototype.add_source_map = function() {
+                skip_string(this.property);
+            };
+        }
         base54.consider(this.print_to_string(), 1);
     } finally {
-        AST_Node.prototype.print = AST_Node.prototype._print;
+        AST_Symbol.prototype.add_source_map = fn;
+        delete AST_Dot.prototype.add_source_map;
+        delete AST_Sub.prototype.add_source_map;
     }
     base54.sort();