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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 https://mozilla.org/MPL/2.0/. */
use crate::animate::{AnimationFieldAttrs, AnimationInputAttrs, AnimationVariantAttrs};
use derive_common::cg;
use proc_macro2::TokenStream;
use quote::TokenStreamExt;
use syn::{DeriveInput, WhereClause};
use synstructure;
pub fn derive(mut input: DeriveInput) -> TokenStream {
let animation_input_attrs = cg::parse_input_attrs::<AnimationInputAttrs>(&input);
let no_bound = animation_input_attrs.no_bound.unwrap_or_default();
let mut where_clause = input.generics.where_clause.take();
for param in input.generics.type_params() {
if !no_bound.iter().any(|name| name.is_ident(¶m.ident)) {
cg::add_predicate(
&mut where_clause,
parse_quote!(#param: crate::values::distance::ComputeSquaredDistance),
);
}
}
let (mut match_body, needs_catchall_branch) = {
let s = synstructure::Structure::new(&input);
let needs_catchall_branch = s.variants().len() > 1;
let match_body = s.variants().iter().fold(quote!(), |body, variant| {
let arm = derive_variant_arm(variant, &mut where_clause);
quote! { #body #arm }
});
(match_body, needs_catchall_branch)
};
input.generics.where_clause = where_clause;
if needs_catchall_branch {
// This ideally shouldn't be needed, but see:
// https://github.com/rust-lang/rust/issues/68867
match_body.append_all(quote! { _ => unsafe { debug_unreachable!() } });
}
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
quote! {
impl #impl_generics crate::values::distance::ComputeSquaredDistance for #name #ty_generics #where_clause {
#[allow(unused_variables, unused_imports)]
#[inline]
fn compute_squared_distance(
&self,
other: &Self,
) -> Result<crate::values::distance::SquaredDistance, ()> {
if std::mem::discriminant(self) != std::mem::discriminant(other) {
return Err(());
}
match (self, other) {
#match_body
}
}
}
}
}
fn derive_variant_arm(
variant: &synstructure::VariantInfo,
mut where_clause: &mut Option<WhereClause>,
) -> TokenStream {
let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
if variant_attrs.error {
return quote! {
(&#this_pattern, &#other_pattern) => Err(()),
};
}
let sum = if this_info.is_empty() {
quote! { crate::values::distance::SquaredDistance::from_sqrt(0.) }
} else {
let mut sum = quote!();
sum.append_separated(this_info.iter().zip(&other_info).map(|(this, other)| {
let field_attrs = cg::parse_field_attrs::<DistanceFieldAttrs>(&this.ast());
if field_attrs.field_bound {
let ty = &this.ast().ty;
cg::add_predicate(
&mut where_clause,
parse_quote!(#ty: crate::values::distance::ComputeSquaredDistance),
);
}
let animation_field_attrs =
cg::parse_field_attrs::<AnimationFieldAttrs>(&this.ast());
if animation_field_attrs.constant {
quote! {
{
if #this != #other {
return Err(());
}
crate::values::distance::SquaredDistance::from_sqrt(0.)
}
}
} else {
quote! {
crate::values::distance::ComputeSquaredDistance::compute_squared_distance(#this, #other)?
}
}
}), quote!(+));
sum
};
return quote! {
(&#this_pattern, &#other_pattern) => Ok(#sum),
};
}
#[derive(Default, FromField)]
#[darling(attributes(distance), default)]
struct DistanceFieldAttrs {
field_bound: bool,
}
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