Macro rustc_index_macros::newtype_index

newtype_index!() { /* proc-macro */ }

Creates a struct type S that can be used as an index with IndexVec and so on.

There are two ways of interacting with these indices:

• The From impls are the preferred way. So you can do S::from(v) with a usize or u32. And you can convert back to an integer with u32::from(s).

• Alternatively, you can use the methods S::new(v) and s.index() to create/return a value.

Internally, the index uses a u32, so the index must not exceed u32::MAX.

The impls provided by default are Clone, Copy, PartialEq, Eq, and Hash.

Accepted attributes for customization:

• #[derive(HashStable_Generic)]/#[derive(HashStable)]: derives HashStable, as normal.
• #[encodable]: derives Encodable/Decodable.
• #[orderable]: derives PartialOrd/Ord, plus step-related methods.
• #[debug_format = "Foo({})"]: derives Debug with particular output.
• #[max = 0xFFFF_FFFD]: specifies the max value, which allows niche optimizations. The default max value is 0xFFFF_FF00.
• #[gate_rustc_only]: makes parts of the generated code nightly-only.