Matt Godbolt sold me on Rust by showing me C++

This reminds me of SQL's constraints, or pydantic's custom types and validators, which can validate that a value should be an int, and between 0-999, and not exceed, e.g. -1 or 1000.

pydantic is a library for python, but I'm not aware of anything similar in rust or golang that can do this yet? (i.e. not just schema validation, but value range validation too)

The semantics are a little different in that you have to explicitly call .validate(), but Rust's "validator" crate[0] feels a lot like Pydantic to me.

[0]https://docs.rs/validator/latest/validator/

I'm aware of this as well as go(lang)'s https://github.com/go-playground/validator, so you are right, I'm wondering about a more implicit validator like what Pydantic does when a value is assigned, versus an explicit call to validate().