I want to step through some functions in UIComponent but in the debugger it just says 'mx.core::UIComponent/addChild [no source]'.
If I am just in the editor, I can control click on a UIComponent method and go directly to the method and everything.
What do I have to do in flash builder to attach the source for UIComponent in the debugger?
Debugger should be able to figure out source for UIComponent.
Are you using RSLs? If so, is "use debug RSLS" checked in Project properties -> Build path?