tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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animate.rs (4621B)

      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 
      5 use crate::cg;
      6 use darling::util::PathList;
      7 use proc_macro2::TokenStream;
      8 use quote::TokenStreamExt;
      9 use syn::{DeriveInput, WhereClause};
     10 use synstructure::{Structure, VariantInfo};
     11 
     12 pub 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 
     69 fn 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)]
    120 pub struct AnimationInputAttrs {
    121    pub no_bound: Option<PathList>,
    122 }
    123 
    124 #[derive(Default, FromVariant)]
    125 #[darling(attributes(animation), default)]
    126 pub 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)]
    135 pub struct AnimationFieldAttrs {
    136    pub constant: bool,
    137    pub field_bound: bool,
    138 }