[tikhonj]

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.

[obtu]

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