Don't use SmallVec<[T; 1]> for computed values with an empty default

components/style/properties/helpers.mako.rs

@@ -83,6 +83,7 @@
             delegate_animate=False, separator='Comma', **kwargs)">
     <%call expr="longhand(name, vector=True, **kwargs)">
         % if not gecko_only:
+            #[allow(unused_imports)]
             use smallvec::SmallVec;
             use std::fmt;
             #[allow(unused_imports)]
@@ -113,13 +114,23 @@
             pub mod computed_value {
                 pub use super::single_value::computed_value as single_value;
                 pub use self::single_value::T as SingleComputedValue;
+                % if allow_empty and allow_empty != "NotInitial":
+                use std::vec::IntoIter;
+                % else:
                 use smallvec::{IntoIter, SmallVec};
+                % endif
                 use values::computed::ComputedVecIter;
 
                 /// The computed value, effectively a list of single values.
                 #[derive(Debug, Clone, PartialEq)]
                 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-                pub struct T(pub SmallVec<[single_value::T; 1]>);
+                pub struct T(
+                    % if allow_empty and allow_empty != "NotInitial":
+                    pub Vec<single_value::T>,
+                    % else:
+                    pub SmallVec<[single_value::T; 1]>,
+                    % endif
+                );
 
                 % if delegate_animate:
                     use properties::animated_properties::Animatable;
@@ -149,7 +160,11 @@
 
                 impl IntoIterator for T {
                     type Item = single_value::T;
+                    % if allow_empty and allow_empty != "NotInitial":
+                    type IntoIter = IntoIter<single_value::T>;
+                    % else:
                     type IntoIter = IntoIter<[single_value::T; 1]>;
+                    % endif
                     fn into_iter(self) -> Self::IntoIter {
                         self.0.into_iter()
                     }
@@ -207,7 +222,7 @@
 
             pub fn get_initial_value() -> computed_value::T {
                 % if allow_empty and allow_empty != "NotInitial":
-                    computed_value::T(SmallVec::new())
+                    computed_value::T(vec![])
                 % else:
                     let mut v = SmallVec::new();
                     v.push(single_value::get_initial_value());

components/style/properties/helpers/animated_properties.mako.rs

@@ -808,7 +808,9 @@ pub trait RepeatableListAnimatable: Animatable {}
 impl RepeatableListAnimatable for LengthOrPercentage {}
 impl RepeatableListAnimatable for Either<f32, LengthOrPercentage> {}
 
-impl<T: RepeatableListAnimatable> Animatable for SmallVec<[T; 1]> {
+macro_rules! repeated_vec_impl {
+    ($($ty:ty),*) => {
+        $(impl<T: RepeatableListAnimatable> Animatable for $ty {
             fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64)
                 -> Result<Self, ()> {
                 use num_integer::lcm;
@@ -829,10 +831,14 @@ impl<T: RepeatableListAnimatable> Animatable for SmallVec<[T; 1]> {
                 let len = lcm(self.len(), other.len());
                 self.iter().cycle().zip(other.iter().cycle()).take(len).map(|(me, you)| {
                     me.compute_squared_distance(you)
-        }).collect::<Result<Vec<_>, _>>().map(|d| d.iter().sum())
+                }).sum()
             }
+        })*
+    };
 }
 
+repeated_vec_impl!(SmallVec<[T; 1]>, Vec<T>);
+
 /// https://drafts.csswg.org/css-transitions/#animtype-number
 impl Animatable for Au {
     #[inline]
@@ -3053,9 +3059,9 @@ pub struct IntermediateShadow {
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
 /// Intermediate type for box-shadow list and text-shadow list.
-pub struct IntermediateShadowList(pub SmallVec<[IntermediateShadow; 1]>);
+pub struct IntermediateShadowList(pub Vec<IntermediateShadow>);
 
-type ShadowList = SmallVec<[Shadow; 1]>;
+type ShadowList = Vec<Shadow>;
 
 impl From<IntermediateShadowList> for ShadowList {
     fn from(shadow_list: IntermediateShadowList) -> Self {
@@ -3172,11 +3178,7 @@ impl Animatable for IntermediateShadowList {
 
         let max_len = cmp::max(self.0.len(), other.0.len());
 
-        let mut result = if max_len > 1 {
-            SmallVec::from_vec(Vec::with_capacity(max_len))
-        } else {
-            SmallVec::new()
-        };
+        let mut result = Vec::with_capacity(max_len);
 
         for i in 0..max_len {
             let shadow = match (self.0.get(i), other.0.get(i)) {
@@ -3202,11 +3204,7 @@ impl Animatable for IntermediateShadowList {
     fn add(&self, other: &Self) -> Result<Self, ()> {
         let len = self.0.len() + other.0.len();
 
-        let mut result = if len > 1 {
-            SmallVec::from_vec(Vec::with_capacity(len))
-        } else {
-            SmallVec::new()
-        };
+        let mut result = Vec::with_capacity(len);
 
         result.extend(self.0.iter().cloned());
         result.extend(other.0.iter().cloned());