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Derive the most trivial ToCss implementations 🌋
For now, all variants get serialised as the space-separated serialisations of their fields. Unit variants are not supported.
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18 changed files with 113 additions and 263 deletions
70
components/style_derive/to_css.rs
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70
components/style_derive/to_css.rs
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/* 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 http://mozilla.org/MPL/2.0/. */
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use quote;
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use syn;
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use synstructure;
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pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
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let name = &input.ident;
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let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
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let mut where_clause = where_clause.clone();
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for param in &input.generics.ty_params {
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where_clause.predicates.push(where_predicate(syn::Ty::Path(None, param.ident.clone().into())))
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}
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let style = synstructure::BindStyle::Ref.into();
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let match_body = synstructure::each_variant(&input, &style, |bindings, _| {
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if bindings.is_empty() {
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panic!("unit variants are not yet supported");
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}
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let (first, rest) = bindings.split_first().expect("unit variants are not yet supported");
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where_clause.predicates.push(where_predicate(first.field.ty.clone()));
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let mut expr = quote! {
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::style_traits::ToCss::to_css(#first, dest)
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};
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for binding in rest {
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where_clause.predicates.push(where_predicate(binding.field.ty.clone()));
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expr = quote! {
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#expr?;
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dest.write_str(" ")?;
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::style_traits::ToCss::to_css(#binding, dest)
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};
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}
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Some(expr)
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});
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quote! {
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impl #impl_generics ::style_traits::ToCss for #name #ty_generics #where_clause {
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#[allow(unused_variables, unused_imports)]
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#[inline]
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fn to_css<W>(&self, dest: &mut W) -> ::std::fmt::Result
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where
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W: ::std::fmt::Write
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{
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match *self {
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#match_body
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}
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}
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}
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}
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}
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/// `#ty: ::style_traits::ToCss`
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fn where_predicate(ty: syn::Ty) -> syn::WherePredicate {
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syn::WherePredicate::BoundPredicate(syn::WhereBoundPredicate {
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bound_lifetimes: vec![],
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bounded_ty: ty,
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bounds: vec![syn::TyParamBound::Trait(
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syn::PolyTraitRef {
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bound_lifetimes: vec![],
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trait_ref: syn::Path {
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global: true,
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segments: vec!["style_traits".into(), "ToCss".into()],
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},
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},
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syn::TraitBoundModifier::None
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)],
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})
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}
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