stylo_derive/
compute_squared_distance.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use crate::animate::{AnimationFieldAttrs, AnimationInputAttrs, AnimationVariantAttrs};
6use crate::cg;
7use proc_macro2::TokenStream;
8use quote::TokenStreamExt;
9use syn::{DeriveInput, WhereClause};
10use synstructure;
11
12pub fn derive(mut input: DeriveInput) -> TokenStream {
13    let animation_input_attrs = cg::parse_input_attrs::<AnimationInputAttrs>(&input);
14    let no_bound = animation_input_attrs.no_bound.unwrap_or_default();
15    let mut where_clause = input.generics.where_clause.take();
16    for param in input.generics.type_params() {
17        if !no_bound.iter().any(|name| name.is_ident(&param.ident)) {
18            cg::add_predicate(
19                &mut where_clause,
20                parse_quote!(#param: crate::values::distance::ComputeSquaredDistance),
21            );
22        }
23    }
24
25    let (mut match_body, needs_catchall_branch) = {
26        let s = synstructure::Structure::new(&input);
27        let needs_catchall_branch = s.variants().len() > 1;
28
29        let match_body = s.variants().iter().fold(quote!(), |body, variant| {
30            let arm = derive_variant_arm(variant, &mut where_clause);
31            quote! { #body #arm }
32        });
33
34        (match_body, needs_catchall_branch)
35    };
36
37    input.generics.where_clause = where_clause;
38
39    if needs_catchall_branch {
40        // This ideally shouldn't be needed, but see:
41        // https://github.com/rust-lang/rust/issues/68867
42
43        match_body.append_all(quote! { _ => unsafe {
44            use ::debug_unreachable::debug_unreachable;
45            debug_unreachable!()
46        } });
47    }
48
49    let name = &input.ident;
50    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
51
52    quote! {
53        impl #impl_generics crate::values::distance::ComputeSquaredDistance for #name #ty_generics #where_clause {
54            #[allow(unused_variables, unused_imports)]
55            #[inline]
56            fn compute_squared_distance(
57                &self,
58                other: &Self,
59            ) -> Result<crate::values::distance::SquaredDistance, ()> {
60                if std::mem::discriminant(self) != std::mem::discriminant(other) {
61                    return Err(());
62                }
63                match (self, other) {
64                    #match_body
65                }
66            }
67        }
68    }
69}
70
71fn derive_variant_arm(
72    variant: &synstructure::VariantInfo,
73    mut where_clause: &mut Option<WhereClause>,
74) -> TokenStream {
75    let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
76    let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
77    let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
78
79    if variant_attrs.error {
80        return quote! {
81            (&#this_pattern, &#other_pattern) => Err(()),
82        };
83    }
84
85    let sum = if this_info.is_empty() {
86        quote! { crate::values::distance::SquaredDistance::from_sqrt(0.) }
87    } else {
88        let mut sum = quote!();
89        sum.append_separated(this_info.iter().zip(&other_info).map(|(this, other)| {
90            let field_attrs = cg::parse_field_attrs::<DistanceFieldAttrs>(&this.ast());
91            if field_attrs.field_bound {
92                let ty = &this.ast().ty;
93                cg::add_predicate(
94                    &mut where_clause,
95                    parse_quote!(#ty: crate::values::distance::ComputeSquaredDistance),
96                );
97            }
98
99            let animation_field_attrs =
100                cg::parse_field_attrs::<AnimationFieldAttrs>(&this.ast());
101
102            if animation_field_attrs.constant {
103                quote! {
104                    {
105                        if #this != #other {
106                            return Err(());
107                        }
108                        crate::values::distance::SquaredDistance::from_sqrt(0.)
109                    }
110                }
111            } else {
112                quote! {
113                    crate::values::distance::ComputeSquaredDistance::compute_squared_distance(#this, #other)?
114                }
115            }
116        }), quote!(+));
117        sum
118    };
119
120    return quote! {
121        (&#this_pattern, &#other_pattern) => Ok(#sum),
122    };
123}
124
125#[derive(Default, FromField)]
126#[darling(attributes(distance), default)]
127struct DistanceFieldAttrs {
128    field_bound: bool,
129}
stylo_derive/compute_squared_distance.rs

stylo_derive/
compute_squared_distance.rs
