Yes, record accessors being partial functions is a big problem.

One way to deal with this is to not use fields at all together with algebraic data types (i.e. when you have more than one constructor), just pattern match. When you have some common field across all constructors, define a regular function to pull it out:

    someData :: MyData -> a

and use that instead. As to the second use case, if you need to access something common to A and B but not C, then:

    someOtherData :: MyData -> Maybe a

and pattern match on that. Or first pattern match on C and then have a catch all _ for A and B.

lens remedies a lot of Haskell's pain points when it comes to records, but I have to say that PureScripts record system is so much nicer.