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(i64);
struct Height(i64);

But... they're kind of a pain to work with. If you ever need to get at that wrapped i64, 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 attaching #[derive(Shrinkwrap)].

Traits implemented

Currently, shrinkwraprs derives the following traits for all structs:

• AsRef<InnerType>
• AsMut<InnerType>
• Borrow<InnerType>
• BorrowMut<InnerType>
• Deref<Target=InnerType>
• DerefMut<Target=InnerType>

Cool, how do I use it?

First, add shrinkwraprs as a dependency in your Cargo.toml:

[dependencies]

shrinkwraprs = "0.0.1"

Then, just slap a #[derive(Shrinkwrap)] on any structs you want convenient-ified:

#[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);