Opt out of bounds on type params for #[derive(ComputeSquaredDistance)]

components/style/values/generics/svg.rs

@@ -18,6 +18,7 @@ use values::distance::{ComputeSquaredDistance, SquaredDistance};
 #[animate(no_bound(UrlPaintServer))]
 #[derive(Animate, Clone, ComputeSquaredDistance, Debug, MallocSizeOf, PartialEq)]
 #[derive(ToAnimatedValue, ToComputedValue, ToCss)]
+#[distance(no_bound(UrlPaintServer))]
 pub struct SVGPaint<ColorType, UrlPaintServer> {
     /// The paint source
     pub kind: SVGPaintKind<ColorType, UrlPaintServer>,
@@ -33,6 +34,7 @@ pub struct SVGPaint<ColorType, UrlPaintServer> {
 #[animate(no_bound(UrlPaintServer))]
 #[derive(Animate, Clone, ComputeSquaredDistance, Debug, MallocSizeOf, PartialEq)]
 #[derive(ToAnimatedValue, ToAnimatedZero, ToComputedValue, ToCss)]
+#[distance(no_bound(UrlPaintServer))]
 pub enum SVGPaintKind<ColorType, UrlPaintServer> {
     /// `none`
     #[animation(error)]
@@ -205,7 +207,11 @@ pub enum SVGLength<LengthType> {
 pub enum SVGStrokeDashArray<LengthType> {
     /// `[ <length> | <percentage> | <number> ]#`
     #[css(comma)]
-    Values(#[css(if_empty = "none", iterable)] Vec<LengthType>),
+    Values(
+        #[css(if_empty = "none", iterable)]
+        #[distance(field_bound)]
+        Vec<LengthType>,
+    ),
     /// `context-value`
     ContextValue,
 }

components/style_derive/compute_squared_distance.rs

@@ -4,21 +4,29 @@
 
 use animate::AnimationVariantAttrs;
 use cg;
+use darling::util::IdentList;
 use quote::Tokens;
 use syn::{DeriveInput, Path};
 use synstructure;
 
-pub fn derive(input: DeriveInput) -> Tokens {
+pub fn derive(mut input: DeriveInput) -> Tokens {
-    let name = &input.ident;
-    let trait_path = parse_quote!(values::distance::ComputeSquaredDistance);
-    let (impl_generics, ty_generics, mut where_clause) =
-        cg::trait_parts(&input, &trait_path);
-
     let input_attrs = cg::parse_input_attrs::<DistanceInputAttrs>(&input);
+    let no_bound = 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(&param.ident) {
+            cg::add_predicate(
+                &mut where_clause,
+                parse_quote!(#param: ::values::distance::ComputeSquaredDistance),
+            );
+        }
+    }
+
+    let (mut match_body, append_error_clause) = {
         let s = synstructure::Structure::new(&input);
         let mut append_error_clause = s.variants().len() > 1;
 
-    let mut match_body = s.variants().iter().fold(quote!(), |body, variant| {
+        let match_body = s.variants().iter().fold(quote!(), |body, variant| {
             let attrs = cg::parse_variant_attrs::<AnimationVariantAttrs>(&variant.ast());
             if attrs.error {
                 append_error_clause = true;
@@ -32,7 +40,14 @@ pub fn derive(input: DeriveInput) -> Tokens {
             } else {
                 let mut sum = quote!();
                 sum.append_separated(this_info.iter().zip(&other_info).map(|(this, other)| {
-                where_clause.add_trait_bound(&this.ast().ty);
+                    let field_attrs = cg::parse_field_attrs::<DistanceFieldAttrs>(&this.ast());
+                    if field_attrs.field_bound {
+                        let ty = &this.ast().ty;
+                        cg::add_predicate(
+                            &mut where_clause,
+                            parse_quote!(#ty: ::values::distance::ComputeSquaredDistance),
+                        );
+                    }
                     quote! {
                         ::values::distance::ComputeSquaredDistance::compute_squared_distance(#this, #other)?
                     }
@@ -47,6 +62,10 @@ pub fn derive(input: DeriveInput) -> Tokens {
             }
         });
 
+        (match_body, append_error_clause)
+    };
+    input.generics.where_clause = where_clause;
+
     if append_error_clause {
         if let Some(fallback) = input_attrs.fallback {
             match_body.append_all(quote! {
@@ -57,6 +76,9 @@ pub fn derive(input: DeriveInput) -> Tokens {
         }
     }
 
+    let name = &input.ident;
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
     quote! {
         impl #impl_generics ::values::distance::ComputeSquaredDistance for #name #ty_generics #where_clause {
             #[allow(unused_variables, unused_imports)]
@@ -77,4 +99,11 @@ pub fn derive(input: DeriveInput) -> Tokens {
 #[derive(Default, FromDeriveInput)]
 struct DistanceInputAttrs {
     fallback: Option<Path>,
+    no_bound: Option<IdentList>,
+}
+
+#[darling(attributes(distance), default)]
+#[derive(Default, FromField)]
+struct DistanceFieldAttrs {
+    field_bound: bool,
 }