i have made a language that xompiles to c#. I wrote a lexer. then a parser. then a type checker (hindley milner, function local so that top level functions must have type signatures) a match compiler.

the hardest part was what came next: the code generation. despite producing c# instead of MSIL. The features I use are: static and dynamic traits, pattern matching, and a concurrentML.

It is actually quite simple when you don't have to do closure conversion yourself.