Unexpected productivity boost of Rust

It's just so brittle. How can anyone think this is a good idea?

Like, how can anyone think that requiring the user to always remember to explicitly write `mutex.unlock()` or `defer mutex.unlock()` instead of just allowing optional explicit unlock and having it automatically unlock when it goes out of scope by default is a good idea? Both Go and Zig have this flaw. Or, how can anyone think that having a cast that can implicitly convert from any numeric type to any other in conjunction with pervasive type inference is a good idea, like Rust's terrible `as` operator? (I once spent a whole day debugging a bug due to this.)

As a side note, I hate the `as` cast in Rust. It's so brittle and dangerous it doesn't even feel like a part of the language. It's like a JavaScript developer snuck in and added it without anyone noticing. I hope they get rid of it in an edition.