Eliminating bugs with dependent Haskell (experience report)

Using dependent types in production code is a practical way to eliminate errors. While there are many examples of using dependent Haskell to prove invariants about code, few of these are applied to large scale production systems. Critics claim that dependent types are only useful in toy examples and that they are impractical for use in the real world. This experience report analyzes real world examples where dependent types have enabled us to find and eliminate bugs in production Haskell code.