So I thought this for a good long while - and then I started coding in Rust on a major project. Turns out that once I'd written my serialization/deserialization functions on the boundaries of my program, it's remarkably difficult to get the rest of my code to compile and not do what I was intending it to do.

It's not magic - the compiler doesn't guess at what I want - but it's close enough that I'm comfortable making larger changes than with Python.