simple visitor API and code to figure out scope and references

lib/scope.js

@@ -0,0 +1,88 @@
+AST_Scope.DEFMETHOD("figure_out_scope", function(){
+    // step 1: handle definitions
+    var scope = null;
+    var tw = new TreeWalker(function(node, descend){
+        if (node instanceof AST_Scope) {
+            var save_scope = node.parent_scope = scope;
+            scope = node;
+            descend.call(node);
+            scope = save_scope;
+            return true;        // don't descend again in TreeWalker
+        }
+        if (node instanceof AST_With) {
+            for (var s = scope; s; s = s.parent_scope)
+                s.uses_with = true;
+            return;
+        }
+        if (node instanceof AST_SymbolDeclaration && !scope.parent_scope) {
+            node.global = true;
+        }
+        if (node instanceof AST_SymbolVar) {
+            scope.def_variable(node);
+        }
+        else if (node instanceof AST_SymbolLambda) {
+            scope.def_function(node);
+        }
+        else if (node instanceof AST_SymbolDefun) {
+            scope.parent_scope.def_function(node);
+        }
+        else if (node instanceof AST_Label) {
+            scope.def_label(node);
+        }
+        else if (node instanceof AST_SymbolCatch) {
+            // XXX: this is wrong according to ECMA-262 (12.4).  the
+            // `catch` argument name should be visible only inside the
+            // catch block.  For a quick fix AST_Catch should inherit
+            // from AST_Scope.
+            scope.def_variable(node);
+        }
+        else if (node instanceof AST_SymbolRef) {
+            node.scope = scope;
+        }
+    });
+    this.walk(tw);
+    // step 2: find back references and eval/with
+    var tw = new TreeWalker(function(node){
+        if (node instanceof AST_LabelRef) {
+            var sym = node.scope.find_label(node);
+            if (!sym) throw new Error("Undefined label " + node.name);
+            node.reference(sym);
+        }
+        else if (node instanceof AST_SymbolRef) {
+            var sym = node.scope.find_variable(node);
+            if (!sym) {
+                if (node.name == "eval") {
+                    for (var s = scope; s; s = s.parent_scope)
+                        s.uses_eval = true;
+                }
+            } else {
+                node.reference(sym);
+            }
+        }
+    });
+    this.walk(tw);
+});
+AST_Scope.DEFMETHOD("find_variable", function(name){
+    if (name instanceof AST_Symbol) name = name.name;
+    return this.variables[name] ||
+        (this.name && this.name.name == name && this.name) ||
+        (this.parent_scope && this.parent_scope.find_variable(name));
+});
+AST_Scope.DEFMETHOD("find_label", function(name){
+    if (name instanceof AST_Symbol) name = name.name;
+    return this.labels[name];
+});
+AST_Scope.DEFMETHOD("def_function", function(symbol){
+    this.def_variable(symbol);
+    this.functions[symbol.name] = symbol;
+    symbol.scope = this;
+});
+AST_Scope.DEFMETHOD("def_variable", function(symbol){
+    this.variables[symbol.name] = symbol;
+    delete this.functions[symbol.name];
+    symbol.scope = this;
+});
+AST_Scope.DEFMETHOD("def_label", function(symbol){
+    this.labels[symbol.name] = symbol;
+    symbol.scope = this;
+});