To check the sources with LiquidHaskell: $ liquid Ceu/MODULE.hs References: https://liquid.kosmikus.org/ http://goto.ucsd.edu/~pmr/papers/rondon-liquid-types.pdf http://goto.ucsd.edu/~rjhala/papers/real_world_liquid.pdf https://nikivazou.github.io/static/Haskell17/a-tale.pdf https://www.cs.indiana.edu/~rrnewton/papers/refinement_reflection_draft.pdf