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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 http://mozilla.org/MPL/2.0/. */
use cg;
use darling::util::IdentList;
use quote::Tokens;
use syn::{DeriveInput, Path};
use synstructure::{Structure, VariantInfo};
pub fn derive(mut input: DeriveInput) -> Tokens {
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.contains(¶m.ident) {
cg::add_predicate(
&mut where_clause,
parse_quote!(#param: ::values::animated::Animate),
);
}
}
input.generics.where_clause = where_clause;
let s = Structure::new(&input);
let mut append_error_clause = s.variants().len() > 1;
let mut match_body = s.variants().iter().fold(quote!(), |body, variant| {
let arm = match derive_variant_arm(variant) {
Ok(arm) => arm,
Err(()) => {
append_error_clause = true;
return body;
}
};
quote! { #body #arm }
});
if append_error_clause {
let input_attrs = cg::parse_input_attrs::<AnimateInputAttrs>(&input);
if let Some(fallback) = input_attrs.fallback {
match_body.append_all(quote! {
(this, other) => #fallback(this, other, procedure)
});
} else {
match_body.append_all(quote! { _ => Err(()) });
}
}
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
quote! {
impl #impl_generics ::values::animated::Animate for #name #ty_generics #where_clause {
#[allow(unused_variables, unused_imports)]
#[inline]
fn animate(
&self,
other: &Self,
procedure: ::values::animated::Procedure,
) -> Result<Self, ()> {
match (self, other) {
#match_body
}
}
}
}
}
fn derive_variant_arm(variant: &VariantInfo) -> Result<Tokens, ()> {
let variant_attrs = cg::parse_variant_attrs_from_ast::<AnimationVariantAttrs>(&variant.ast());
if variant_attrs.error {
return Err(());
}
let (this_pattern, this_info) = cg::ref_pattern(&variant, "this");
let (other_pattern, other_info) = cg::ref_pattern(&variant, "other");
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.constant {
quote! {
if #this != #other {
return Err(());
}
let #result = ::std::clone::Clone::clone(#this);
}
} else {
quote! {
let #result =
::values::animated::Animate::animate(#this, #other, procedure)?;
}
}
}));
Ok(quote! {
(&#this_pattern, &#other_pattern) => {
#computations
Ok(#result_value)
}
})
}
#[darling(attributes(animate), default)]
#[derive(Default, FromDeriveInput)]
struct AnimateInputAttrs {
fallback: Option<Path>,
}
#[darling(attributes(animation), default)]
#[derive(Default, FromDeriveInput)]
pub struct AnimationInputAttrs {
pub no_bound: Option<IdentList>,
}
#[darling(attributes(animation), default)]
#[derive(Default, FromVariant)]
pub struct AnimationVariantAttrs {
pub error: bool,
// Only here because of structs, where the struct definition acts as a
// variant itself.
pub no_bound: Option<IdentList>,
}
#[darling(attributes(animation), default)]
#[derive(Default, FromField)]
pub struct AnimationFieldAttrs {
pub constant: bool,
}
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