## What is nutype?

*nutype* is a procedural macro that adds sanitization and validation to newtypes, ensuring that values always meet your defined constraints.

## What’s new in v0.6.2

* *\[FEATURE]* Added `derive_unsafe(..)` for deriving arbitrary traits (requires enabling the `derive_unsafe` feature). * *\[FIX]* Upgraded Rust edition: *2021 → 2024*. * *\[FIX]* Improved error messages for `len_char_max` and `len_char_min`—they’re now clearer and easier to interpret.

## About `derive_unsafe`

With `derive_unsafe(..)`, you can now derive *any trait*, including third-party ones that nutype doesn’t recognize.

Unlike the safe `derive(..)`, this skips nutype’s internal checks. That means *you can accidentally break your validations at runtime*—for example, by enabling mutation via `DerefMut`.

To use this feature, add the `derive_unsafe` flag.

*Cautionary example:*

```rust use derive_more::{Deref, DerefMut}; use nutype::nutype;

#[nutype( derive(Debug, AsRef), derive_unsafe(Deref, DerefMut), validate(greater_or_equal = 0.0, less_or_equal = 2.0) )] struct LlmTemperature(f64);

fn main() { let mut temperature = LlmTemperature::try_new(1.5).unwrap();

    // This is exactly what you shouldn't do!
    *temperature = 2.5;

    // Validation rule? Violated.
    assert_eq!(temperature.as_ref(), &2.5);

} ```

*TL;DR:* `derive_unsafe` gives you freedom—but with that comes full responsibility. Use wisely.