It is very probable that data is an Either[Error, Result]. So you are forced to handle the error. You could also probably add a mapLeft and deal with an error at every step of computation.

Given the way fp-ts work, this library should be very type safe.

But of course, all of this looks much prettier and less verbose in haskell

The example actually does handle all errors, because the values are of type `Either` and the composition functions take this into account. If you would like to handle a particular error sitation explicitly, e.g. to enrich it with context or to transform one error into another, you may use `MapLeft` or `Swap`.