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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use darling::util::PathList;
use crate::cg;
use proc_macro2::TokenStream;
use quote::TokenStreamExt;
use syn::{DeriveInput, WhereClause};
use synstructure::{Structure, VariantInfo};
pub fn derive(mut input: DeriveInput) -> TokenStream {
let animation_input_attrs = cg::parse_input_attrs::<AnimationInputAttrs>(&input);
let no_bound = animation_input_attrs.no_bound.unwrap_or_default();
let mut where_clause = input.generics.where_clause.take();
for param in input.generics.type_params() {
if !no_bound.iter().any(|name| name.is_ident(¶m.ident)) {
cg::add_predicate(
&mut where_clause,
parse_quote!(#param: crate::values::animated::Animate),
);
}
}
let (mut match_body, needs_catchall_branch) = {
let s = Structure::new(&input);
let needs_catchall_branch = s.variants().len() > 1;
let match_body = s.variants().iter().fold(quote!(), |body, variant| {
let arm = derive_variant_arm(variant, &mut where_clause);
quote! { #body #arm }
});
(match_body, needs_catchall_branch)
};
input.generics.where_clause = where_clause;
if needs_catchall_branch {
// This ideally shouldn't be needed, but see
// https://github.com/rust-lang/rust/issues/68867
match_body.append_all(quote! { _ => unsafe { debug_unreachable!() } });
}
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
quote! {
impl #impl_generics crate::values::animated::Animate for #name #ty_generics #where_clause {
#[allow(unused_variables, unused_imports)]
#[inline]
fn animate(
&self,
other: &Self,
procedure: crate::values::animated::Procedure,
) -> Result<Self, ()> {
if std::mem::discriminant(self) != std::mem::discriminant(other) {
return Err(());
}
match (self, other) {
#match_body
}
}
}
}
}
fn derive_variant_arm(
variant: &VariantInfo,
where_clause: &mut Option<WhereClause>,
) -> TokenStream {
let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
if variant_attrs.error {
return quote! {
(&#this_pattern, &#other_pattern) => Err(()),
};
}
let (result_value, result_info) = cg::value(&variant, "result");
let mut computations = quote!();
let iter = result_info.iter().zip(this_info.iter().zip(&other_info));
computations.append_all(iter.map(|(result, (this, other))| {
let field_attrs = cg::parse_field_attrs::<AnimationFieldAttrs>(&result.ast());
if field_attrs.field_bound {
let ty = &this.ast().ty;
cg::add_predicate(
where_clause,
parse_quote!(#ty: crate::values::animated::Animate),
);
}
if field_attrs.constant {
quote! {
if #this != #other {
return Err(());
}
let #result = std::clone::Clone::clone(#this);
}
} else {
quote! {
let #result =
crate::values::animated::Animate::animate(#this, #other, procedure)?;
}
}
}));
quote! {
(&#this_pattern, &#other_pattern) => {
#computations
Ok(#result_value)
}
}
}
#[derive(Default, FromDeriveInput)]
#[darling(attributes(animation), default)]
pub struct AnimationInputAttrs {
pub no_bound: Option<PathList>,
}
#[derive(Default, FromVariant)]
#[darling(attributes(animation), default)]
pub struct AnimationVariantAttrs {
pub error: bool,
// Only here because of structs, where the struct definition acts as a
// variant itself.
pub no_bound: Option<PathList>,
}
#[derive(Default, FromField)]
#[darling(attributes(animation), default)]
pub struct AnimationFieldAttrs {
pub constant: bool,
pub field_bound: bool,
}
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