stylo_derive/
animate.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::cg;
6use darling::util::PathList;
7use proc_macro2::TokenStream;
8use quote::TokenStreamExt;
9use syn::{DeriveInput, WhereClause};
10use synstructure::{Structure, VariantInfo};
11
12pub fn derive(mut input: DeriveInput) -> TokenStream {
13    let animation_input_attrs = cg::parse_input_attrs::<AnimationInputAttrs>(&input);
14
15    let no_bound = animation_input_attrs.no_bound.unwrap_or_default();
16    let mut where_clause = input.generics.where_clause.take();
17    for param in input.generics.type_params() {
18        if !no_bound.iter().any(|name| name.is_ident(&param.ident)) {
19            cg::add_predicate(
20                &mut where_clause,
21                parse_quote!(#param: crate::values::animated::Animate),
22            );
23        }
24    }
25    let (mut match_body, needs_catchall_branch) = {
26        let s = Structure::new(&input);
27        let needs_catchall_branch = s.variants().len() > 1;
28        let match_body = s.variants().iter().fold(quote!(), |body, variant| {
29            let arm = derive_variant_arm(variant, &mut where_clause);
30            quote! { #body #arm }
31        });
32        (match_body, needs_catchall_branch)
33    };
34
35    input.generics.where_clause = where_clause;
36
37    if needs_catchall_branch {
38        // This ideally shouldn't be needed, but see
39        // https://github.com/rust-lang/rust/issues/68867
40        match_body.append_all(quote! { _ => unsafe { debug_unreachable!() } });
41    }
42
43    let name = &input.ident;
44    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
45
46    quote! {
47        impl #impl_generics crate::values::animated::Animate for #name #ty_generics #where_clause {
48            #[allow(unused_variables, unused_imports)]
49            #[inline]
50            fn animate(
51                &self,
52                other: &Self,
53                procedure: crate::values::animated::Procedure,
54            ) -> Result<Self, ()> {
55                if std::mem::discriminant(self) != std::mem::discriminant(other) {
56                    return Err(());
57                }
58                match (self, other) {
59                    #match_body
60                }
61            }
62        }
63    }
64}
65
66fn derive_variant_arm(
67    variant: &VariantInfo,
68    where_clause: &mut Option<WhereClause>,
69) -> TokenStream {
70    let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
71    let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
72    let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
73
74    if variant_attrs.error {
75        return quote! {
76            (&#this_pattern, &#other_pattern) => Err(()),
77        };
78    }
79
80    let (result_value, result_info) = cg::value(&variant, "result");
81    let mut computations = quote!();
82    let iter = result_info.iter().zip(this_info.iter().zip(&other_info));
83    computations.append_all(iter.map(|(result, (this, other))| {
84        let field_attrs = cg::parse_field_attrs::<AnimationFieldAttrs>(&result.ast());
85        if field_attrs.field_bound {
86            let ty = &this.ast().ty;
87            cg::add_predicate(
88                where_clause,
89                parse_quote!(#ty: crate::values::animated::Animate),
90            );
91        }
92        if field_attrs.constant {
93            quote! {
94                if #this != #other {
95                    return Err(());
96                }
97                let #result = std::clone::Clone::clone(#this);
98            }
99        } else {
100            quote! {
101                let #result =
102                    crate::values::animated::Animate::animate(#this, #other, procedure)?;
103            }
104        }
105    }));
106
107    quote! {
108        (&#this_pattern, &#other_pattern) => {
109            #computations
110            Ok(#result_value)
111        }
112    }
113}
114
115#[derive(Default, FromDeriveInput)]
116#[darling(attributes(animation), default)]
117pub struct AnimationInputAttrs {
118    pub no_bound: Option<PathList>,
119}
120
121#[derive(Default, FromVariant)]
122#[darling(attributes(animation), default)]
123pub struct AnimationVariantAttrs {
124    pub error: bool,
125    // Only here because of structs, where the struct definition acts as a
126    // variant itself.
127    pub no_bound: Option<PathList>,
128}
129
130#[derive(Default, FromField)]
131#[darling(attributes(animation), default)]
132pub struct AnimationFieldAttrs {
133    pub constant: bool,
134    pub field_bound: bool,
135}
stylo_derive/animate.rs

stylo_derive/
animate.rs
