I started searching for the same thing a couple of years ago after I saw the same Hejlsberg interview posted by sarosh. The only recommendation I was able to get was to read the Roslyn source code and the LSP reference. I could not get any reference regarding, for example, how would one build a parser that incrementally modifies the AST as you type. And regarding PLT, I would think those subjects have to do with the semantics of the language, and are orthogonal to the technology to build the compiler. But I'm not an expert, and could easily be wrong...