* [`hie-bios`](https://github.com/mpickering/hie-bios) for determining where your files are, what are their dependencies, what extensions are enabled and so on;
*`hie-core` (i.e. this library) for defining how to type check, when to type check, and producing diagnostic messages;
* A bunch of plugins that haven't yet been written, e.g. [`hie-hlint`](https://github.com/ndmitchell/hlint) and [`hie-ormolu`](https://github.com/tweag/ormolu) for your specific choices of plugin;
* [`haskell-lsp`](https://github.com/alanz/haskell-lsp) for sending those messages to a [Language Server Protocol (LSP)](https://microsoft.github.io/language-server-protocol/) server;
* An extension for your editor. We provide a [VS Code extension](https://code.visualstudio.com/api) as `extension` in this directory, although the components work in other LSP editors too (see below for instructions using Emacs).
The frst step is to install required Emacs packages. If you don't already have [Melpa](https://melpa.org/#/) package installation configured in your `.emacs`, put this stanza at the top.
When this is in your `.emacs` and evaluated, `M-x package-refresh-contents` to get the package database downloaded and then `M-x package-list-packages` to display the available packages. Click on a package to install it. You'll need to install the following packages:
For testing, I've been using the `ghc-lib-gen` target of the [`ghc-lib` project](https://github.com/digital-asset/ghc-lib). Navigate to the root of `ghc-lib` and create an `hie.yaml` file with contents
Invoke `cabal new-configure -w ~/.stack/programs/~/.stack/programs/x86_64-osx/ghc-8.6.5/bin/ghc` (this is the `ghc` used by `stack` to build `hie-core` - consult `//compiler/hie-core/stack.yaml` to help work out what you should write here). This last step will create a file `cabal.project.local` with contents pointing `cabal` to use the desired `ghc`. You can build `ghc-lib-gen` from the `ghc-lib` directory with the command `cabal new-build` as you like. After creating `cabal.project.local`, you should be all set. Open `ghc-lib/ghc-lib-gen/src/Main.hs` in a buffer and, for example, hover should bring up type/definition info.