This plugin is written mainly in Scala and is not mentioned to support GHC/Cabal directly. This plugin support sandbox projects and expects that the Cabal init/install/build is done on command-line.

Features
- Syntax highlighting (which can be customised);
- Error/warning highlighting;
- Find Usages of identifiers;
- Resolving references of identifiers (also to library code if library source code is added to project and resolves inside import declaration);
- Code completion by resolving references;
- Renaming variables (which first shows preview so refactoring scope can be adjusted);
- View type info from (selected) expression;
- View expression info;
- View quick documentation;
- View quick definition;
- Structure view;
- Navigate to declaration (called `Class` in IntelliJ menu);
- Navigate to identifier (called `Symbol` in IntelliJ menu);
- Code completion by looking to import declarations;
- Simple form of code formatting;

A lot of features are with the help of ghc-mod and ghc-modi. Documentation is provided by haskell-docs.

See for more information and getting started: https://github.com/rikvdkleij/intellij-haskell

Any feedback is welcome!

Regards,

Rik