ANBF? Formal spec?

[clemensv]

I am missing a formal specification of TypeSpec, and a template for extension specs, along with an ABNF that can be used to build alternate parsers or generators.

[bterlson]

Can you say more about what you want to accomplish? Extending TypeSpec is done via libraries, where you can implement e.g. decorators and custom emitters. We do have a documented grammar, but it's important to note that TypeSpec is less of a format and more of a programming language. The type graph that emitters consume is not an AST but a data structure created from executing your TypeSpec program, so any custom implementation would have to implement these semantics as well.