shrinkwraprs 0.0.2

Auto-derive for Rust conversion traits -- make working with newtypes a breeze


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:


shrinkwraprs = "0.0.2"

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

#[macro_use] extern crate shrinkwraprs;

struct Email(String);

fn main() {
  let email = Email("".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)]:

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

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