remove the $self hack

operations are destructive anyway, so there's no point to clone the nodes in
the transformer.  speed++

lib/ast.js

@@ -57,9 +57,7 @@ function DEFNODE(type, props, methods, base) {
     var proto = base && new base;
     if (proto && proto.initialize || (methods && methods.initialize))
         code += "this.initialize();";
-    code += " } ";
-    code += "if (!this.$self) this.$self = this;";
-    code += " } ";
+    code += "}}";
     var ctor = new Function(code)();
     if (proto) {
         ctor.prototype = proto;
@@ -89,13 +87,12 @@ function DEFNODE(type, props, methods, base) {
 var AST_Token = DEFNODE("Token", "type value line col pos endpos nlb comments_before file", {
 }, null);
 
-var AST_Node = DEFNODE("Node", "$self start end", {
+var AST_Node = DEFNODE("Node", "start end", {
     clone: function() {
         return new this.CTOR(this);
     },
     $documentation: "Base class of all AST nodes",
     $propdoc: {
-        $self: "[AST_Node] Reference to $self.  Not modified by clone().  XXX: this could be removed.",
         start: "[AST_Token] The first token of this node",
         end: "[AST_Token] The last token of this node"
     },
@@ -904,7 +901,7 @@ TreeWalker.prototype = {
     },
     in_boolean_context: function() {
         var stack = this.stack;
-        var i = stack.length, self = stack[--i].$self;
+        var i = stack.length, self = stack[--i];
         while (i > 0) {
             var p = stack[--i];
             if ((p instanceof AST_If           && p.condition === self) ||
@@ -917,7 +914,7 @@ TreeWalker.prototype = {
             }
             if (!(p instanceof AST_Binary && (p.operator == "&&" || p.operator == "||")))
                 return false;
-            self = p.$self;
+            self = p;
         }
     },
     loopcontrol_target: function(label) {
@@ -926,15 +923,15 @@ TreeWalker.prototype = {
             for (var i = stack.length; --i >= 0;) {
                 var x = stack[i];
                 if (x instanceof AST_LabeledStatement && x.label.name == label.name) {
-                    return x.body.$self;
+                    return x.body;
                 }
             }
         } else {
             for (var i = stack.length; --i >= 0;) {
                 var x = stack[i];
-                if (x instanceof AST_Switch) return x.$self;
+                if (x instanceof AST_Switch) return x;
                 if (x instanceof AST_For || x instanceof AST_ForIn || x instanceof AST_DWLoop) {
-                    return (x.body instanceof AST_BlockStatement ? x.body : x).$self;
+                    return (x.body instanceof AST_BlockStatement ? x.body : x);
                 }
             }
         }

lib/compress.js

@@ -80,7 +80,6 @@ merge(Compressor.prototype, {
     },
     before: function(node, descend, in_list) {
         if (node._squeezed) return node;
-        this.stack[this.stack.length - 1] = node = node.clone();
         if (node instanceof AST_Scope) {
             node.drop_unused(this);
             node = node.hoist_declarations(this);
@@ -291,7 +290,7 @@ merge(Compressor.prototype, {
 
                     var ab = aborts(stat.body);
                     if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
-                               || (ab instanceof AST_Continue && self.$self === compressor.loopcontrol_target(ab.label)))) {
+                               || (ab instanceof AST_Continue && self === compressor.loopcontrol_target(ab.label)))) {
                         CHANGED = true;
                         var body = as_statement_array(stat.body).slice(0, -1);
                         stat = stat.clone();
@@ -308,7 +307,7 @@ merge(Compressor.prototype, {
 
                     var ab = aborts(stat.alternative);
                     if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
-                               || (ab instanceof AST_Continue && self.$self === compressor.loopcontrol_target(ab.label)))) {
+                               || (ab instanceof AST_Continue && self === compressor.loopcontrol_target(ab.label)))) {
                         CHANGED = true;
                         stat = stat.clone();
                         stat.body = make_node(AST_BlockStatement, stat.body, {
@@ -447,7 +446,6 @@ merge(Compressor.prototype, {
         stat.walk(new TreeWalker(function(node){
             if (node instanceof AST_Definitions) {
                 compressor.warn("Declarations in unreachable code! [{file}:{line},{col}]", node.start);
-                node = node.clone();
                 node.remove_initializers();
                 target.push(node);
                 return true;
@@ -1187,7 +1185,7 @@ merge(Compressor.prototype, {
         var last_branch = self.body[self.body.length - 1];
         if (last_branch) {
             var stat = last_branch.body[last_branch.body.length - 1]; // last statement
-            if (stat instanceof AST_Break && compressor.loopcontrol_target(stat.label) === self.$self)
+            if (stat instanceof AST_Break && compressor.loopcontrol_target(stat.label) === self)
                 last_branch.body.pop();
         }
         return self;
@@ -1204,11 +1202,7 @@ merge(Compressor.prototype, {
     });
 
     AST_Definitions.DEFMETHOD("remove_initializers", function(){
-        this.definitions = this.definitions.map(function(def){
-            def = def.clone();
-            def.value = null;
-            return def;
-        });
+        this.definitions.forEach(function(def){ def.value = null });
     });
 
     AST_Definitions.DEFMETHOD("to_assignments", function(){