The history of Ceylon support in NetBeans can be divided into three stages. In 2012, syntax coloring was created; in 2013, code completion was added; and yesterday, during Java2Days in Sofia in Bulgaria, where I ran into Ceylon lead Stephane Epardaud (@UnFroMage), i.e., in 2014, and under his guidance the Ceylon libraries in the NetBeans plugin were upgraded to the latest versions, syntax coloring was updated, the start of code folding has been implemented, and the Ceylon parser is partly integrated to check for syntax errors.
Above you see one of the Ceylon sample projects expanded to show one file, with syntax coloring, and the initial comment within a code fold.
And here you see the parser in action because a semi-colon has been omitted:
The message displayed when you hover over the red error icon or the red error mark is as follows, which comes from the Ceylon parser:
Here's the repo: