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extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, Data, DataStruct, DeriveInput, Fields};
#[proc_macro_derive(CanTween)]
pub fn derive(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let struct_name = &input.ident;
let generics = &input.generics;
let where_clause = &input.generics.where_clause;
match &input.data {
Data::Struct(DataStruct { fields: Fields::Named(fields), .. }) => {
let field_name = fields.named.iter().map(|field| &field.ident);
TokenStream::from(quote! {
impl #generics keyframe::CanTween for #struct_name #generics #where_clause {
fn ease(mut from: Self, mut to: Self, time: impl keyframe::num_traits::Float) -> Self {
Self {
#(
#field_name: keyframe::CanTween::ease(from.#field_name, to.#field_name, time),
)*
}
}
}
})
}
Data::Struct(DataStruct { fields: Fields::Unnamed(fields), .. }) => {
let field_idx = fields.unnamed.iter().enumerate().map(|(i, _)| syn::Index::from(i));
TokenStream::from(quote! {
impl #generics keyframe::CanTween for #struct_name #generics #where_clause {
fn ease(mut from: Self, mut to: Self, time: impl keyframe::num_traits::Float) -> Self {
Self(
#(
keyframe::CanTween::ease(from.#field_idx, to.#field_idx, time),
)*
)
}
}
})
},
_ => panic!("Expected struct with fields!")
}
}