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