Inside the <mx:Script>, we usually need to put import statement, such as "import mx.controls.Alert" etc.
But for some classes, we do not need to import them. For example, mx.events.Event, mx.events.MouseEvent,
and flash.events.EventDispatcher, do not need to be explicitly imported. I am wondering whether there
is a list of known auto imported classes. If there is no such list that can't be edited, then what classes
are automatically imported by Flex 3?
Short answer: There is no list and it can't be edited.
Long answer: The compiler defines a set of implict imports in MXML. You can see the logic here in the compiler source code http://opensource.adobe.com/svn/opensource/flex/sdk/trunk/modules/compiler/src/java/flex2/ compiler/mxml/lang/StandardDefs.java.
It's probably worth a blog post.http://blogs.adobe.com/jasonsj/2010/03/implicit_imports_in_mxml.html
Jason San Jose
Software Engineer, Flash Builder