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https://github.com/mozilla/gecko-dev.git
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40a655a763
Signed-off-by: Nico Burns <nico@nicoburns.com> Differential Revision: https://phabricator.services.mozilla.com/D221815
80 lines
2.5 KiB
Rust
80 lines
2.5 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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use darling::{FromDeriveInput, FromField};
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use proc_macro2::{Span, TokenStream};
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use quote::{quote, TokenStreamExt};
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use syn::{self, parse_quote, DeriveInput, Field, Ident, WherePredicate};
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use synstructure::{self, BindStyle, BindingInfo, VariantInfo};
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pub(crate) fn parse_input_attrs<A>(input: &DeriveInput) -> A
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where
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A: FromDeriveInput,
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{
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match A::from_derive_input(input) {
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Ok(attrs) => attrs,
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Err(e) => panic!("failed to parse input attributes: {}", e),
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}
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}
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pub(crate) fn parse_field_attrs<A>(field: &Field) -> A
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where
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A: FromField,
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{
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match A::from_field(field) {
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Ok(attrs) => attrs,
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Err(e) => panic!("failed to parse field attributes: {}", e),
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}
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}
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pub(crate) fn add_predicate(where_clause: &mut Option<syn::WhereClause>, pred: WherePredicate) {
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where_clause
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.get_or_insert(parse_quote!(where))
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.predicates
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.push(pred);
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}
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pub(crate) fn fmap2_match<F, G>(
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input: &DeriveInput,
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bind_style: BindStyle,
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mut f: F,
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mut g: G,
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) -> TokenStream
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where
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F: FnMut(&BindingInfo) -> TokenStream,
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G: FnMut(&BindingInfo) -> Option<TokenStream>,
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{
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let mut s = synstructure::Structure::new(input);
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s.variants_mut().iter_mut().for_each(|v| {
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v.bind_with(|_| bind_style);
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});
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s.each_variant(|variant| {
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let (mapped, mapped_fields) = value(variant, "mapped");
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let fields_pairs = variant.bindings().iter().zip(mapped_fields.iter());
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let mut computations = quote!();
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computations.append_all(fields_pairs.map(|(field, mapped_field)| {
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let expr = f(field);
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quote! { let #mapped_field = #expr; }
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}));
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computations.append_all(
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mapped_fields
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.iter()
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.map(|mapped_field| match g(mapped_field) {
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Some(expr) => quote! { let #mapped_field = #expr; },
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None => quote!(),
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}),
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);
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computations.append_all(mapped);
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Some(computations)
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})
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}
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fn value<'a>(variant: &'a VariantInfo, prefix: &str) -> (TokenStream, Vec<BindingInfo<'a>>) {
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let mut v = variant.clone();
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v.bindings_mut().iter_mut().for_each(|b| {
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b.binding = Ident::new(&format!("{}_{}", b.binding, prefix), Span::call_site())
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});
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v.bind_with(|_| BindStyle::Move);
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(v.pat(), v.bindings().to_vec())
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}
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