Comment by deredede

> E.g., requiring that a file have the correct MIME type, not be too large, and contain no EXIF metadata.

"Parse, don't validate" doesn't mean that you must encode everything in the type system -- in fact I'd argue you should usually only create new types for data (or pieces of data) that make sense for your business logic.

Here the type your business logic cares about is maybe "file valid for upload", and it is perfectly fine to have a function that takes a file, perform a bunch of checks on it, and returns a "file valid for upload" new type if it passes the checks.