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41 lines
1.6 KiB
Rust
41 lines
1.6 KiB
Rust
// tidy-alphabetical-start
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#![cfg_attr(feature = "nightly", allow(internal_features))]
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#![cfg_attr(feature = "nightly", feature(allow_internal_unstable))]
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// tidy-alphabetical-end
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use proc_macro::TokenStream;
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mod newtype;
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/// Creates a struct type `S` that can be used as an index with
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/// `IndexVec` and so on.
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///
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/// There are two ways of interacting with these indices:
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///
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/// - The `From` impls are the preferred way. So you can do
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/// `S::from(v)` with a `usize` or `u32`. And you can convert back
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/// to an integer with `u32::from(s)`.
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///
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/// - Alternatively, you can use the methods `S::new(v)` and `s.index()`
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/// to create/return a value.
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///
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/// Internally, the index uses a u32, so the index must not exceed
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/// `u32::MAX`.
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///
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/// The impls provided by default are Clone, Copy, PartialEq, Eq, and Hash.
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///
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/// Accepted attributes for customization:
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/// - `#[derive(HashStable_Generic)]`/`#[derive(HashStable)]`: derives
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/// `HashStable`, as normal.
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/// - `#[encodable]`: derives `Encodable`/`Decodable`.
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/// - `#[orderable]`: derives `PartialOrd`/`Ord`, plus step-related methods.
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/// - `#[debug_format = "Foo({})"]`: derives `Debug` with particular output.
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/// - `#[max = 0xFFFF_FFFD]`: specifies the max value, which allows niche
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/// optimizations. The default max value is 0xFFFF_FF00.
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/// - `#[gate_rustc_only]`: makes parts of the generated code nightly-only.
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#[proc_macro]
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#[cfg_attr(feature = "nightly", allow_internal_unstable(step_trait, rustc_attrs, trusted_step))]
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pub fn newtype_index(input: TokenStream) -> TokenStream {
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newtype::newtype(input)
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}
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