If I ever develop a program language, the first action I will take is the clang approach and make it a library based architecture. That way, people can build tools for the language including IDE integration without having to reinvent the wheel.

Yes, this has been invaluable for us in Rust. One cool thing we've been able to do with this architecture is to write a fuzzer -- a tool that uses the Rust compiler itself to generate random Rust programs to test the compiler's correctness.

I think GHC does something like that. At the very least, it exposes an API that lets you do all sorts of fun things. There are projects like Scion[1] that let you integrate that into an editor.

[1]: https://github.com/nominolo/scion/

However, there is simply less drive to develop tooling like that for Haskell than there is for Java. Haskell is a much easier language to use given just a moderately intelligent text editor and a REPL than most others. Java, on the other hand, it verbose and annoying even with a very good IDE.

So Haskell can have good support, but since it isn't terribly necessary it isn't anything like a top priority.

Indeed, “the architecture of GHC” mentions some uses of GHC as a library: http://www.aosabook.org/en/ghc.html

Compiler As A Service. Microsoft are pushing this with Roslyn.

http://www.infoworld.com/d/application-development/microsoft...

What do you think of leksah?

I know of it, but haven't used it, yet. That's why my comment was a bit more guarded than it would have otherwise been. (Though re-reading that line, it doesn't come across as such to me now.)