Start implementing checked mode and tools support for using it.

lib/compiler/implementation/lib/js_helper.dart

Index: lib/compiler/implementation/lib/js_helper.dart
===================================================================
--- lib/compiler/implementation/lib/js_helper.dart	(revision 7269)
+++ lib/compiler/implementation/lib/js_helper.dart	(working copy)
@@ -777,3 +777,91 @@
   if (target === null) return null;
   return JS('var', @'#.builtin$typeInfo', target);
 }
+
+/**
+ * The following methods are called by the runtime to implement
+ * checked mode. We specialize each primitive type (eg int, bool), and
+ * use the compiler's convention to do is checks on regular objects.
+ */
+stringTypeCheck(value) {
+  if (value === null) return value;
+  if (value is String) return value;
+  throw new TypeError('$value does not implement String');
+}
+
+doubleTypeCheck(value) {
+  if (value === null) return value;
+  if (value is double) return value;
+  throw new TypeError('$value does not implement double');
+}
+
+numTypeCheck(value) {
+  if (value === null) return value;
+  if (value is num) return value;
+  throw new TypeError('$value does not implement num');
+}
+
+boolTypeCheck(value) {
+  if (value === null) return value;
+  if (value is bool) return value;
+  throw new TypeError('$value does not implement bool');
+}
+
+functionTypeCheck(value) {
+  if (value === null) return value;
+  if (value is Function) return value;
+  throw new TypeError('$value does not implement Function');
+}
+
+intTypeCheck(value) {
+  if (value === null) return value;
+  if (value is int) return value;
+  throw new TypeError('$value does not implement int');
+}
+
+stringSuperTypeCheck(value, property) {
+  if (value === null) return value;
+  if (value is String) return value;
+  if (JS('bool', '!!#[#]', value, property)) return value;
+  String name = property.substring(3, property.length);

[floitsch, 2012/05/07 09:50:07]

explain what is cut off.
maybe assert that the property starts with the expected prefix.

[ahe, 2012/05/07 11:59:57]

Be careful about asserting anything in this code. The assertion will affect the
user's code.

[ngeoffray, 2012/05/07 13:15:42]

Very good point.

+  throw new TypeError('$value does not implement $name');
+}
+
+listTypeCheck(value) {
+  if (value === null) return value;
+  if (value is List) return value;
+  throw new TypeError('$value does not implement List');
+}
+
+listSuperTypeCheck(value, property) {
+  if (value === null) return value;
+  if (value is List) return value;
+  if (JS('bool', '!!#[#]', value, property)) return value;
+  String name = property.substring(3, property.length);
+  throw new TypeError('$value does not implement $name');
+}
+
+listSuperNativeTypeCheck(value, property) {

[floitsch, 2012/05/07 09:50:07]

Explain what this does.

[ngeoffray, 2012/05/07 13:15:42]

Done.

+  if (value === null) return value;
+  if (value is List) return value;
+  if (JS('bool', '#.#()', value, property)) return value;

[floitsch, 2012/05/07 11:06:56]

#.# won't work.

[ngeoffray, 2012/05/07 13:15:42]

Done.

+  String name = property.substring(3, property.length);
+  throw new TypeError('$value does not implement $name');
+}
+
+propertyTypeCheck(value, property) {

[floitsch, 2012/05/07 09:50:07]

ditto.

[ngeoffray, 2012/05/07 13:15:42]

Done.

+  if (value === null) return value;
+  if (JS('bool', '!!#[#]', value, property)) return value;
+  String name = property.substring(3, property.length);
+  throw new TypeError('$value does not implement $name');
+}
+
+callTypeCheck(value, property) {

[floitsch, 2012/05/07 09:50:07]

ditto.

[ngeoffray, 2012/05/07 13:15:42]

Done.

+  if (value === null) return value;
+  if ((JS('String', 'typeof #', value) === 'object')
+      && JS('bool', '#.#()', value, property)) {

[floitsch, 2012/05/07 11:06:56]

#.# won't work.

[ngeoffray, 2012/05/07 13:15:42]

Done.

+    return value;
+  }
+  String name = property.substring(3, property.length);
+  throw new TypeError('$value does not implement $name');
+}