This is amazing. Microsoft has made the inner workings of their IL compiler open to everyone by exposing the inner workings through an API. As the Overview describes, they’ve rewritten the IL compiler in managed code and in doing so have un-boxed the black box that was once the best IL compiler for Windows. It will be amazing to see how exposing this API will provide new development tools for increasing code-completion/style/correctness.
Traditionally, compilers are black boxes – source code goes in one end and object files or assemblies come out the other end. The Roslyn project changes that model by opening up the Visual Basic and C# compilers as APIs. These APIs allow tools and end-users to share in the wealth of information the compilers have about code. The Roslyn CTP previews the next generation of language object models for code generation, analysis, and refactoring, and the upcoming support for scripting and interactive use of VB and C#.
Original Source: MSDN Roslyn