Parse and compress destructuring VarDefs

lib/ast.js

@@ -665,9 +665,12 @@ var AST_Const = DEFNODE("Const", null, {
 var AST_VarDef = DEFNODE("VarDef", "name value", {
     $documentation: "A variable declaration; only appears in a AST_Definitions node",
     $propdoc: {
-        name: "[AST_SymbolVar|AST_SymbolConst] name of the variable",
+        name: "[AST_SymbolVar|AST_SymbolConst|AST_Destructuring] name of the variable",
         value: "[AST_Node?] initializer, or null of there's no initializer"
     },
+    is_destructuring: function() {
+        return this.name instanceof AST_Destructuring;
+    },
     _walk: function(visitor) {
         return visitor._visit(this, function(){
             this.name._walk(visitor);