Use default params when --destructure-named-params + fix renaming of reserved destructured params

lib/src/js/nodes.dart

Index: lib/src/js/nodes.dart
diff --git a/lib/src/js/nodes.dart b/lib/src/js/nodes.dart
index 0ba181426578b19f97656189834b4847ce9d161d..5d0b3d172e7b5d96ae1e9cc0ee01b9290037217d 100644
--- a/lib/src/js/nodes.dart
+++ b/lib/src/js/nodes.dart
@@ -92,6 +92,7 @@ abstract class NodeVisitor<T> {
   T visitArrayBindingPattern(ArrayBindingPattern node);
   T visitObjectBindingPattern(ObjectBindingPattern node);
   T visitDestructuredVariable(DestructuredVariable node);
+  T visitSimpleBindingPattern(SimpleBindingPattern node);
 }
 
 class BaseVisitor<T> implements NodeVisitor<T> {
@@ -221,6 +222,7 @@ class BaseVisitor<T> implements NodeVisitor<T> {
   T visitObjectBindingPattern(ObjectBindingPattern node)
       => visitBindingPattern(node);
   T visitDestructuredVariable(DestructuredVariable node) => visitNode(node);
+  T visitSimpleBindingPattern(SimpleBindingPattern node) => visitNode(node);
 }
 
 abstract class Node {
@@ -777,7 +779,8 @@ abstract class VariableBinding extends Expression {
 }
 
 class DestructuredVariable extends Expression implements Parameter {
-  final Identifier name;
+  /// [LiteralString] or [Identifier].
+  final Expression name;
   final BindingPattern structure;
   final Expression defaultValue;
   DestructuredVariable({this.name, this.structure, this.defaultValue}) {
@@ -807,6 +810,17 @@ abstract class BindingPattern extends Expression implements VariableBinding {
   }
 }
 
+class SimpleBindingPattern extends BindingPattern {
+  final Identifier name;
+  SimpleBindingPattern(Identifier name)
+      : super([new DestructuredVariable(name: name)]), this.name = name;
+  accept(NodeVisitor visitor) => visitor.visitSimpleBindingPattern(this);
+
+  /// Avoid parenthesis when pretty-printing.
+  @override int get precedenceLevel => PRIMARY;
+  @override Node _clone() => new SimpleBindingPattern(name);
+}
+
 class ObjectBindingPattern extends BindingPattern {
   ObjectBindingPattern(List<DestructuredVariable> variables)
       : super(variables);