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

lib/src/js/printer.dart

Index: lib/src/js/printer.dart
diff --git a/lib/src/js/printer.dart b/lib/src/js/printer.dart
index bd8de3b40aa49c9bae41dc8051df78f5f84e9465..22186ebb47e79fe066916eb8f1941d02c269d9c7 100644
--- a/lib/src/js/printer.dart
+++ b/lib/src/js/printer.dart
@@ -621,8 +621,17 @@ class Printer implements NodeVisitor {
   }
 
   visitDestructuredVariable(DestructuredVariable node) {

[Jennifer Messerly, 2016/02/09 00:33:07]

this code looks a lot like propertyNameOut. Can they be unified cleanly?

if not, it may still be worth handling the invalid name issue on this side of
the world.

(Generally Printer is very easy to work with, unlike our Dart->JS transformer
where there's a lot of Dart->JS semantic knowledge we're trying to keep in
mind.)

[ochafik, 2016/02/09 01:51:20]

I agree in principle, but see the other comment: I think we need both a
LiteralString (for the matching pattern, with a computed / non computed printing
logic that differs from Printer's semantics of isValidJavaScriptId) and an
identifier. I think this + the different printing logic (add a ": identifier"
only if we printed the name in computed property style) makes it hard to unify.

-    var hasName = node.name != null;
-    if (hasName) visit(node.name);
+    var name = node.name;
+    var hasName = name != null;
+    if (hasName) {
+      if (name is LiteralString) {
+        out("[");
+        out(name.value);
+        out("]");
+      } else {
+        visit(name);
+      }
+    }
     if (node.structure != null) {
       if (hasName) {
         out(":");
@@ -639,6 +648,10 @@ class Printer implements NodeVisitor {
     }
   }
 
+  visitSimpleBindingPattern(SimpleBindingPattern node) {
+    visit(node.name);
+  }
+
   visitAssignment(Assignment assignment) {
     visitNestedExpression(assignment.leftHandSide, LEFT_HAND_SIDE,
                           newInForInit: inForInit,
@@ -1585,13 +1598,18 @@ abstract class VariableDeclarationVisitor<T> extends BaseVisitor<T> {
 
   _scanVariableBinding(VariableBinding d) {
     if (d is Identifier) declare(d);
-    if (d is RestParameter) _scanVariableBinding(d.parameter);
-    else if (d is BindingPattern) {
-      for (var v in d.variables) {
-        if (v.name != null) declare(v.name);
-        if (v.structure != null) _scanVariableBinding(v.structure);
-      }
-    }
+    else d.accept(this);
+  }
+
+  visitDestructuredVariable(DestructuredVariable node) {
+    var name = node.name;
+    if (name is Identifier) _scanVariableBinding(name);
+    super.visitDestructuredVariable(node);
+  }
+
+  visitSimpleBindingPattern(SimpleBindingPattern node) {
+    _scanVariableBinding(node.name);
+    super.visitSimpleBindingPattern(node);
   }
 
   visitVariableInitialization(VariableInitialization node) {