[javafu2]

F# team ask for modifications of the CLR (covariant delegates), porting a language on the CLR if you are not Microsoft is hard.

Scala never really run on the CLR, it's a vaporware, sorry a work in progress.

[adriaanm]

Yep, scala's .net back-end is discontinued, and one of the main challenges (I worked on it a bit) was indeed generating the proper generic signatures. (I hear people are using ikvm these days.)