[nextos]

Liquid Haskell is a bit different from Eiffel. On Eiffel, contracts were designed to be verified at runtime. There were some efforts to verify them at compile time, like Liquid Haskell does, but that's hard unless the whole language and type system are designed for that from the ground up.

As for my day to day job, I think the real difference with common software development was that requirements were very well understood right from the beginning. This allowed us to formalize them into axioms and then derive the implementation in a stepwise fashion using some Standard ML tooling.

I've also worked on proving theorems on existing software artifacts, but that's way harder both in terms of effort and number of defects.