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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use animate::AnimationVariantAttrs;
use cg;
use quote::Tokens;
use syn::{DeriveInput, Path};
use synstructure;
pub fn derive(input: DeriveInput) -> Tokens {
let name = &input.ident;
let trait_path = parse_quote!(values::distance::ComputeSquaredDistance);
let (impl_generics, ty_generics, mut where_clause) =
cg::trait_parts(&input, &trait_path);
let input_attrs = cg::parse_input_attrs::<DistanceInputAttrs>(&input);
let s = synstructure::Structure::new(&input);
let mut append_error_clause = s.variants().len() > 1;
let mut match_body = s.variants().iter().fold(quote!(), |body, variant| {
let attrs = cg::parse_variant_attrs::<AnimationVariantAttrs>(&variant.ast());
if attrs.error {
append_error_clause = true;
return body;
}
let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
let sum = if this_info.is_empty() {
quote! { ::values::distance::SquaredDistance::Value(0.) }
} else {
let mut sum = quote!();
sum.append_separated(this_info.iter().zip(&other_info).map(|(this, other)| {
where_clause.add_trait_bound(&this.ast().ty);
quote! {
::values::distance::ComputeSquaredDistance::compute_squared_distance(#this, #other)?
}
}), quote!(+));
sum
};
quote! {
#body
(&#this_pattern, &#other_pattern) => {
Ok(#sum)
}
}
});
if append_error_clause {
if let Some(fallback) = input_attrs.fallback {
match_body.append_all(quote! {
(this, other) => #fallback(this, other)
});
} else {
match_body.append_all(quote! { _ => Err(()) });
}
}
quote! {
impl #impl_generics ::values::distance::ComputeSquaredDistance for #name #ty_generics #where_clause {
#[allow(unused_variables, unused_imports)]
#[inline]
fn compute_squared_distance(
&self,
other: &Self,
) -> Result<::values::distance::SquaredDistance, ()> {
match (self, other) {
#match_body
}
}
}
}
}
#[darling(attributes(distance), default)]
#[derive(Default, FromDeriveInput)]
struct DistanceInputAttrs {
fallback: Option<Path>,
}
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