The documentation now describes various forms of syntactic sugar which, incidentally, make most of the code written at the time of XL2 acceptable again.

Most syntactic sugar transform a prefix notation using some particular word into an infix type annotation with possibly some additions. The words being considered include: type, class, module, function, method, procedure, to, operation, data, in, out, inout, io,
constant, variable, macro, generic, polymorphic, fast, small, global, thread and static.

The transformation are generally similar to the following, and might be implementable fully in the library:

{ type T is Impl } is { T as type is Impl }
{ type T with Interface } is { T as type with Interface }
{ type T inherits Base } is { T like Base }
{ type T like Base } is { T like Base }
{ T inherits Base } is { T like Base }
{ module M is Impl } is { M as module is Impl }
{ module M with Interface } is { M as module with Interface }  
{ procedure Proc is Impl } is { Proc as mayfail is Impl }

There are quite a few more, but the pattern is relatively general and simple.

More direct compiler analysis might be needed for a few cases, but that remains to be confirmed.