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 {
41            use ::debug_unreachable::debug_unreachable;
42            debug_unreachable!()
43        } });
44    }
45
46    let name = &input.ident;
47    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
48
49    quote! {
50        impl #impl_generics crate::values::animated::Animate for #name #ty_generics #where_clause {
51            #[allow(unused_variables, unused_imports)]
52            #[inline]
53            fn animate(
54                &self,
55                other: &Self,
56                procedure: crate::values::animated::Procedure,
57            ) -> Result<Self, ()> {
58                if std::mem::discriminant(self) != std::mem::discriminant(other) {
59                    return Err(());
60                }
61                match (self, other) {
62                    #match_body
63                }
64            }
65        }
66    }
67}
68
69fn derive_variant_arm(
70    variant: &VariantInfo,
71    where_clause: &mut Option<WhereClause>,
72) -> TokenStream {
73    let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
74    let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
75    let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
76
77    if variant_attrs.error {
78        return quote! {
79            (&#this_pattern, &#other_pattern) => Err(()),
80        };
81    }
82
83    let (result_value, result_info) = cg::value(&variant, "result");
84    let mut computations = quote!();
85    let iter = result_info.iter().zip(this_info.iter().zip(&other_info));
86    computations.append_all(iter.map(|(result, (this, other))| {
87        let field_attrs = cg::parse_field_attrs::<AnimationFieldAttrs>(&result.ast());
88        if field_attrs.field_bound {
89            let ty = &this.ast().ty;
90            cg::add_predicate(
91                where_clause,
92                parse_quote!(#ty: crate::values::animated::Animate),
93            );
94        }
95        if field_attrs.constant {
96            quote! {
97                if #this != #other {
98                    return Err(());
99                }
100                let #result = std::clone::Clone::clone(#this);
101            }
102        } else {
103            quote! {
104                let #result =
105                    crate::values::animated::Animate::animate(#this, #other, procedure)?;
106            }
107        }
108    }));
109
110    quote! {
111        (&#this_pattern, &#other_pattern) => {
112            #computations
113            Ok(#result_value)
114        }
115    }
116}
117
118#[derive(Default, FromDeriveInput)]
119#[darling(attributes(animation), default)]
120pub struct AnimationInputAttrs {
121    pub no_bound: Option<PathList>,
122}
123
124#[derive(Default, FromVariant)]
125#[darling(attributes(animation), default)]
126pub struct AnimationVariantAttrs {
127    pub error: bool,
128    // Only here because of structs, where the struct definition acts as a
129    // variant itself.
130    pub no_bound: Option<PathList>,
131}
132
133#[derive(Default, FromField)]
134#[darling(attributes(animation), default)]
135pub struct AnimationFieldAttrs {
136    pub constant: bool,
137    pub field_bound: bool,
138}
stylo_derive/animate.rs

stylo_derive/
animate.rs
