libToffee.fx
libToffee.fx and its matching libToffee.a static library is an optional Toffee Base Library provided by the Elements compiler to facilitate some advanced language and compiler features.
It contains helper types that are crucial to the Elements compiler itself, such as internal support for Oxygene Future Types, generic versions of the NSArray<T> and NSDictionary<T> classes, extension methods to enable LINQ support, and more.
Source code for libToffee.fx is available on GitHub, with contributions being welcome.
Unlike rtl.fx, libToffee.fx is not automatically referenced by the Elements compiler, but new Cocoa projects created from templates will have the reference. The compiler will emit appropriate warnings if your code uses features that require libToffee.fx and it is not referenced.