Newtype Index

A simplified copy of rustc's index crate.

Examples

```rust newtype_index! { pub struct MyIndex; }

// Shorthand for the above newtype_index!(pub MyIndex);

// Full example of all features newtype_index! { #[derive(SomeTrait)] pub struct MyIndex { pub const A = 5; pub const B = 999; } } ```

Serde can be enabled with the serde feature.