73 lines
1.7 KiB
Rust
73 lines
1.7 KiB
Rust
use darling::{FromDeriveInput, FromMeta};
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#[derive(FromMeta, PartialEq, Eq, Debug)]
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enum Volume {
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Whisper,
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Talk,
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Shout,
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}
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/// A more complex example showing the ability to skip at a field or struct
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/// level while still tracking which type parameters need to be bounded.
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/// This can be seen by expanding this example using `cargo expand`.
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#[derive(FromMeta)]
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#[allow(dead_code)]
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enum Emphasis<T> {
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Constant(Volume),
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Variable(darling::util::PathList),
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#[darling(skip)]
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PerPhoneme(Option<T>),
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Strided {
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#[darling(skip)]
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step: Vec<T>,
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#[darling(multiple)]
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volume: Vec<Volume>,
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},
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}
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#[derive(FromDeriveInput)]
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#[darling(attributes(speak))]
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struct SpeakingOptions<T, U> {
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max_volume: U,
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#[darling(skip, default)]
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additional_data: Vec<T>,
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}
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#[derive(Default)]
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struct Phoneme {
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#[allow(dead_code)]
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first: String,
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}
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// This is probably the holy grail for `darling`'s own internal use-case:
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// Auto-apply `Default` bound to skipped *field* types in `where` clause.
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impl<T, U> Default for SpeakingOptions<T, U>
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where
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Vec<T>: Default,
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U: Default,
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{
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fn default() -> Self {
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Self {
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max_volume: Default::default(),
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additional_data: Default::default(),
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}
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}
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}
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fn main() {
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let derive_input = syn::parse_str(
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r#"
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#[derive(Speak)]
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#[speak(max_volume = "shout")]
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enum HtmlElement {
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Div(String)
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}
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"#,
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)
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.unwrap();
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let parsed: SpeakingOptions<Phoneme, Volume> =
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FromDeriveInput::from_derive_input(&derive_input).unwrap();
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assert_eq!(parsed.max_volume, Volume::Shout);
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assert_eq!(parsed.additional_data.len(), 0);
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}
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