Right, exactly. I want guidance on whether code (new code or a modification to existing code) can make sense before I've written all of it. With modern Haskel

Right, exactly. I want guidance on whether code (new code or a modification to existing code) can make sense before I've written all of it. With modern Haskell I can start to ask those questions before I've written all of the term-level code and before I've written out all of the relevant types. I can start working with whichever is more convenient at the time, and feel ahead to where things might break down before I get there.