Revert "Backport several style changes from Gecko (5) (#30099)" (#30104)

This reverts commit 8e15389cae.

components/style_derive/to_css.rs

@@ -5,84 +5,15 @@
 use darling::util::Override;
 use darling::FromDeriveInput;
 use darling::FromField;
-use darling::FromMeta;
 use darling::FromVariant;
 use derive_common::cg;
-use proc_macro2::{Span, TokenStream};
+use proc_macro2::TokenStream;
 use quote::quote;
 use quote::{ToTokens, TokenStreamExt};
 use syn::parse_quote;
-use syn::{self, Data, Ident, Path, WhereClause};
+use syn::{self, Data, Path, WhereClause};
 use synstructure::{BindingInfo, Structure, VariantInfo};
 
-fn derive_bitflags(input: &syn::DeriveInput, bitflags: &CssBitflagAttrs) -> TokenStream {
-    let name = &input.ident;
-    let mut body = TokenStream::new();
-    for (rust_name, css_name) in bitflags.single_flags() {
-        let rust_ident = Ident::new(&rust_name, Span::call_site());
-        body.append_all(quote! {
-            if *self == Self::#rust_ident {
-                return dest.write_str(#css_name);
-            }
-        });
-    }
-
-    body.append_all(quote! {
-        let mut has_any = false;
-    });
-
-    if bitflags.overlapping_bits {
-        body.append_all(quote! {
-            let mut serialized = Self::empty();
-        });
-    }
-
-    for (rust_name, css_name) in bitflags.mixed_flags() {
-        let rust_ident = Ident::new(&rust_name, Span::call_site());
-        let serialize = quote! {
-            if has_any {
-                dest.write_char(' ')?;
-            }
-            has_any = true;
-            dest.write_str(#css_name)?;
-        };
-        if bitflags.overlapping_bits {
-            body.append_all(quote! {
-                if self.contains(Self::#rust_ident) && !serialized.intersects(Self::#rust_ident) {
-                    #serialize
-                    serialized.insert(Self::#rust_ident);
-                }
-            });
-        } else {
-            body.append_all(quote! {
-                if self.intersects(Self::#rust_ident) {
-                    #serialize
-                }
-            });
-        }
-    }
-
-    body.append_all(quote! {
-        Ok(())
-    });
-
-    quote! {
-        impl style_traits::ToCss for #name {
-            #[allow(unused_variables)]
-            #[inline]
-            fn to_css<W>(
-                &self,
-                dest: &mut style_traits::CssWriter<W>,
-            ) -> std::fmt::Result
-            where
-                W: std::fmt::Write,
-            {
-                #body
-            }
-        }
-    }
-}
-
 pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
     let mut where_clause = input.generics.where_clause.take();
     for param in input.generics.type_params() {
@@ -90,21 +21,12 @@ pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
     }
 
     let input_attrs = cg::parse_input_attrs::<CssInputAttrs>(&input);
-    if matches!(input.data, Data::Enum(..)) || input_attrs.bitflags.is_some() {
+    if let Data::Enum(_) = input.data {
         assert!(
             input_attrs.function.is_none(),
-            "#[css(function)] is not allowed on enums or bitflags"
+            "#[css(function)] is not allowed on enums"
         );
-        assert!(
-            !input_attrs.comma,
-            "#[css(comma)] is not allowed on enums or bitflags"
-        );
-    }
-
-    if let Some(ref bitflags) = input_attrs.bitflags {
-        assert!(!input_attrs.derive_debug, "Bitflags can derive debug on their own");
-        assert!(where_clause.is_none(), "Generic bitflags?");
-        return derive_bitflags(&input, bitflags);
+        assert!(!input_attrs.comma, "#[css(comma)] is not allowed on enums");
     }
 
     let match_body = {
@@ -327,36 +249,6 @@ fn derive_single_field_expr(
     expr
 }
 
-#[derive(Default, FromMeta)]
-pub struct CssBitflagAttrs {
-    /// Flags that can only go on their own, comma-separated.
-    pub single: String,
-    /// Flags that can go mixed with each other, comma-separated.
-    pub mixed: String,
-    /// Extra validation of the resulting mixed flags.
-    #[darling(default)]
-    pub validate_mixed: Option<Path>,
-    /// Whether there are overlapping bits we need to take care of when
-    /// serializing.
-    #[darling(default)]
-    pub overlapping_bits: bool,
-}
-
-impl CssBitflagAttrs {
-    /// Returns a vector of (rust_name, css_name) of a given flag list.
-    fn names(s: &str) -> Vec<(String, String)> {
-        s.split(',').map(|css_name| (cg::to_scream_case(css_name), css_name.to_owned())).collect()
-    }
-
-    pub fn single_flags(&self) -> Vec<(String, String)> {
-        Self::names(&self.single)
-    }
-
-    pub fn mixed_flags(&self) -> Vec<(String, String)> {
-        Self::names(&self.mixed)
-    }
-}
-
 #[derive(Default, FromDeriveInput)]
 #[darling(attributes(css), default)]
 pub struct CssInputAttrs {
@@ -365,7 +257,6 @@ pub struct CssInputAttrs {
     pub function: Option<Override<String>>,
     // Here because structs variants are also their whole type definition.
     pub comma: bool,
-    pub bitflags: Option<CssBitflagAttrs>,
 }
 
 #[derive(Default, FromVariant)]
@@ -375,7 +266,6 @@ pub struct CssVariantAttrs {
     // Here because structs variants are also their whole type definition.
     pub derive_debug: bool,
     pub comma: bool,
-    pub bitflags: Option<CssBitflagAttrs>,
     pub dimension: bool,
     pub keyword: Option<String>,
     pub skip: bool,