Add List.unmodifiable constructor.

sdk/lib/_internal/compiler/js_lib/js_array.dart

Index: sdk/lib/_internal/compiler/js_lib/js_array.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/js_array.dart b/sdk/lib/_internal/compiler/js_lib/js_array.dart
index 5763242e399206f4ecaa95aec1d96a3499233df7..ef8c0e606653c6ea33d858768c17232a4bee499b 100644
--- a/sdk/lib/_internal/compiler/js_lib/js_array.dart
+++ b/sdk/lib/_internal/compiler/js_lib/js_array.dart
@@ -77,6 +77,15 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
     return JS('JSFixedArray', '#', list);
   }
 
+  static List markUnmodifiableList(List list) {
+    // Functions are stored in the hidden class and not as properties in
+    // the object. We never actually look at the value, but only want
+    // to know if the property exists.
+    JS('void', r'#.fixed$length = Array', list);
+    JS('void', r'#.immutable$list = Array', list);
+    return JS('List', '#', list);

[sra1, 2015/04/22 21:17:31]

1. Change 'List' to 'JSArray'.

Leaving it as List means that the result of 'new List.unmodifiable(...)' will
never be optimized since it could be any implementation of List.

At least with JSArray we won't always be calling getInterceptor().

2. Open a bug against Dart2JS to recognize that unmodifiable lists have fixed
length.  Add a TODO here referencing the issue.

+  }
+
   checkMutable(reason) {
     if (this is !JSMutableArray) {
       throw new UnsupportedError(reason);
@@ -95,20 +104,20 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
   }
 
   E removeAt(int index) {
+    checkGrowable('removeAt');
     if (index is !int) throw new ArgumentError(index);
     if (index < 0 || index >= length) {
       throw new RangeError.value(index);
     }
-    checkGrowable('removeAt');
     return JS('var', r'#.splice(#, 1)[0]', this, index);
   }
 
   void insert(int index, E value) {
+    checkGrowable('insert');
     if (index is !int) throw new ArgumentError(index);
     if (index < 0 || index > length) {
       throw new RangeError.value(index);
     }
-    checkGrowable('insert');
     JS('void', r'#.splice(#, 0, #)', this, index, value);
   }
 
@@ -199,8 +208,9 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
   }
 
   void addAll(Iterable<E> collection) {
+    checkGrowable('addAll');
     for (E e in collection) {
-      this.add(e);
+      JS('void', r'#.push(#)', this, e);
     }
   }
 
@@ -564,9 +574,9 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
   int get length => JS('JSUInt32', r'#.length', this);
 
   void set length(int newLength) {
+    checkGrowable('set length');
     if (newLength is !int) throw new ArgumentError(newLength);
     if (newLength < 0) throw new RangeError.value(newLength);
-    checkGrowable('set length');
     JS('void', r'#.length = #', this, newLength);
   }