“could not resolve <mx:…> to a component implementation”

If you have ever tried to add mx.core.ToolTip (or certain other classes) as a mxml-tag to your Flex project then you might’ve run into the following compiler-error: “Could not resolve <mx:ToolTip> to a component implementation.” So why does Flex (or rather MXMLC, the compiler) let you write <mx:Button> and <mx:Canvas> and all those other Flex […]