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style: Make rust generate better code for derive(Animate) and derive(ComputeSquaredDistance).
See https://github.com/rust-lang/rust/issues/68867. This technically changes the semantics of #[animate(fallback)] and such when combined with #[animate(error)]. But no such combination exists and the new semantics are perfectly reasonable as well, IMHO. Differential Revision: https://phabricator.services.mozilla.com/D61761
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6876fed6e0
commit
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4 changed files with 105 additions and 89 deletions
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@ -107,7 +107,7 @@ pub fn animate_multiplicative_factor(
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/// be equal or an error is returned.
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///
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/// If a variant is annotated with `#[animation(error)]`, the corresponding
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/// `match` arm is not generated.
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/// `match` arm returns an error.
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///
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/// If the two values are not similar, an error is returned unless a fallback
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/// function has been specified through `#[animate(fallback)]`.
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@ -17,7 +17,7 @@ use std::ops::Add;
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/// on each fields of the values.
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///
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/// If a variant is annotated with `#[animation(error)]`, the corresponding
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/// `match` arm is not generated.
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/// `match` arm returns an error.
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///
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/// If the two values are not similar, an error is returned unless a fallback
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/// function has been specified through `#[distance(fallback)]`.
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@ -11,6 +11,8 @@ use synstructure::{Structure, VariantInfo};
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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 input_attrs = cg::parse_input_attrs::<AnimateInputAttrs>(&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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@ -21,39 +23,32 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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);
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}
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}
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let (mut match_body, append_error_clause) = {
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let (mut match_body, needs_catchall_branch) = {
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let s = Structure::new(&input);
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let mut append_error_clause = s.variants().len() > 1;
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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 = match derive_variant_arm(variant, &mut where_clause) {
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Ok(arm) => arm,
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Err(()) => {
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append_error_clause = true;
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return body;
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},
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};
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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, append_error_clause)
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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 append_error_clause {
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let input_attrs = cg::parse_input_attrs::<AnimateInputAttrs>(&input);
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if let Some(fallback) = input_attrs.fallback {
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match_body.append_all(quote! {
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(this, other) => #fallback(this, other, procedure)
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});
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} else {
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match_body.append_all(quote! { _ => Err(()) });
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}
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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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let fallback = match input_attrs.fallback {
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Some(fallback) => quote! { #fallback(self, other, procedure) },
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None => quote! { Err(()) },
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};
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quote! {
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impl #impl_generics crate::values::animated::Animate for #name #ty_generics #where_clause {
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#[allow(unused_variables, unused_imports)]
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@ -63,6 +58,9 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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other: &Self,
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procedure: crate::values::animated::Procedure,
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) -> Result<Self, ()> {
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if std::mem::discriminant(self) != std::mem::discriminant(other) {
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return #fallback;
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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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@ -74,13 +72,17 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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fn derive_variant_arm(
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variant: &VariantInfo,
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where_clause: &mut Option<WhereClause>,
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) -> Result<TokenStream, ()> {
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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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if variant_attrs.error {
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return Err(());
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}
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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 (result_value, result_info) = cg::value(&variant, "result");
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let mut computations = quote!();
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let iter = result_info.iter().zip(this_info.iter().zip(&other_info));
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@ -107,12 +109,13 @@ fn derive_variant_arm(
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}
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}
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}));
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Ok(quote! {
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quote! {
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(&#this_pattern, &#other_pattern) => {
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#computations
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Ok(#result_value)
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}
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})
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}
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}
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#[darling(attributes(animate), default)]
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@ -6,11 +6,12 @@ use crate::animate::{AnimationFieldAttrs, AnimationInputAttrs, AnimationVariantA
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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, Path};
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use syn::{DeriveInput, Path, 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 input_attrs = cg::parse_input_attrs::<DistanceInputAttrs>(&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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@ -22,76 +23,31 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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}
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}
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let (mut match_body, append_error_clause) = {
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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 mut append_error_clause = s.variants().len() > 1;
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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 attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
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if attrs.error {
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append_error_clause = true;
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return body;
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}
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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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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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quote! {
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#body
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(&#this_pattern, &#other_pattern) => {
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Ok(#sum)
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}
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}
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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, append_error_clause)
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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 append_error_clause {
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let input_attrs = cg::parse_input_attrs::<DistanceInputAttrs>(&input);
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if let Some(fallback) = input_attrs.fallback {
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match_body.append_all(quote! {
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(this, other) => #fallback(this, other)
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});
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} else {
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match_body.append_all(quote! { _ => Err(()) });
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}
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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 fallback = match input_attrs.fallback {
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Some(fallback) => quote! { #fallback(self, other) },
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None => quote! { Err(()) },
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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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@ -103,6 +59,9 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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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 #fallback;
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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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@ -111,6 +70,60 @@ pub fn derive(mut input: DeriveInput) -> TokenStream {
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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, FromDeriveInput)]
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struct DistanceInputAttrs {
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