Crate shrinkwraprs

shrinkwraprs

Making wrapper types allows us to give more compile-time guarantees about our code being correct:

// Now we can't mix up widths and heights; the compiler will yell at us!
struct Width(u64);
struct Height(u64);

But... they're kind of a pain to work with. If you ever need to get at that wrapped u64, you need to constantly pattern-match back and forth to wrap and unwrap the values.

shrinkwraprs aims to alleviate this pain by allowing you to derive implementations of various conversion traits by deriving Shrinkwrap and ShrinkwrapMut.

Traits implemented

Currently, using #[derive(Shrinkwrap)] will derive the following traits for all structs:

• AsRef<InnerType>
• Borrow<InnerType>
• Deref<Target=InnerType>

Additionally, using #[derive(Shrinkwrap, ShrinkwrapMut)] will additionally derive the following traits:

• AsMut<InnerType>
• BorrowMut<InnerType>
• DerefMut<Target=InnerType>

Cool, how do I use it?

#[macro_use] extern crate shrinkwraprs;

#[derive(Shrinkwrap)]
struct Email(String);

fn main() {
    let email = Email("chiya+snacks@natsumeya.jp".into());

    let is_discriminated_email =
        email.contains("+");  // Woohoo, we can use the email like a string!

    /* ... */
}

If you have multiple fields, but there's only one field you want to be able to deref/borrow as, mark it with #[shrinkwrap(main_field)]:

#[derive(Shrinkwrap)]
struct Email {
    spamminess: f64,
    #[shrinkwrap(main_field)] addr: String
}

#[derive(Shrinkwrap)]
struct CodeSpan(u32, u32, #[shrinkwrap(main_field)] Token);

If you also want to be able to modify the wrapped value directly, derive ShrinkwrapMut as well:

#[derive(Shrinkwrap, ShrinkwrapMut)]
struct InputBuffer {
    buffer: String
}

...
let mut input_buffer = /* ... */;
input_buffer.push_str("some values");
...

Functions

shrinkwrap
shrinkwrap_mut