Add additional hints to the analyzer to catch the 'x is double' dart2js bug.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java
index 736ceae5fb5b03f29ade79ed669738bab54e5b10..372059a4d0e26354233bf42f4a53366aae6e7bc7 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/HintCode.java
@@ -42,6 +42,27 @@ public enum HintCode implements ErrorCode {
       "Dead code, this on-catch block will never be executed since '%s' is a subtype of '%s'"),
 
   /**
+   * Hint for the {@code x is double} type checks.
+   */
+  IS_DOUBLE("When compiled to JS, this test will return true when the left hand side is an int"),
+
+  /**
+   * Hint for the {@code x is int} type checks.
+   */
+  IS_INT("When compiled to JS, this test will return true when the left hand side is a double"),

[karlklose, 2013/09/12 10:53:56]

It '*may* return true' (if the double is of the form 'x.0').

[jwren, 2013/09/12 20:45:07]

Agreed.  Sending a doc to you and the rest of the dart2js team shortly... we
were trying to keep the message short.  I realize that "will"->"may" would fix
it, but I'm not sure that having ambiguity in the message like that would be a
good thing.

+
+  /**
+   * Hint for the {@code x is! double} type checks.
+   */
+  IS_NOT_DOUBLE(
+      "When compiled to JS, this test will return false when the left hand side is an int"),
+
+  /**
+   * Hint for the {@code x is! int} type checks.

[karlklose, 2013/09/12 10:53:56]

Ditto.

+   */
+  IS_NOT_INT("When compiled to JS, this test will return false when the left hand side is a double"),

[karlklose, 2013/09/12 10:53:56]

Long line? (I am not sure which limit you use)

+
+  /**
    * Unused imports are imports which are never not used.
    */
   UNUSED_IMPORT("Unused import");