Auto merge of #16661 - emilio:alloc, r=bholley

style: Use SmallVec more in the style system.

I expect this to improve the situation significantly in https://bugzilla.mozilla.org/show_bug.cgi?id=1360881

This is worth doing on its own, though.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16661)
<!-- Reviewable:end -->

Cargo.lock

@@ -987,7 +987,7 @@ dependencies = [
  "servo_geometry 0.0.1",
  "servo_url 0.0.1",
  "simd 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "style_traits 0.0.1",
  "time 0.1.36 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1385,7 +1385,7 @@ dependencies = [
  "servo_config 0.0.1",
  "servo_geometry 0.0.1",
  "servo_url 0.0.1",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "style_traits 0.0.1",
  "unicode-bidi 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1966,7 +1966,7 @@ dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2293,7 +2293,7 @@ dependencies = [
  "servo_geometry 0.0.1",
  "servo_rand 0.0.1",
  "servo_url 0.0.1",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "style_traits 0.0.1",
  "time 0.1.36 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2389,7 +2389,7 @@ dependencies = [
  "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "precomputed-hash 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2685,8 +2685,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "smallvec"
-version = "0.3.2"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "heapsize 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "string_cache"
@@ -2762,7 +2765,7 @@ dependencies = [
  "servo_atoms 0.0.1",
  "servo_config 0.0.1",
  "servo_url 0.0.1",
- "smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "style_traits 0.0.1",
  "time 0.1.36 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-segmentation 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3520,7 +3523,7 @@ dependencies = [
 "checksum simd 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a94d14a2ae1f1f110937de5fb69e494372560181c7e1739a097fcc2cee37ba0"
 "checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
 "checksum slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "17b4fcaed89ab08ef143da37bc52adbcc04d4a69014f4c1208d6b51f0c47bc23"
-"checksum smallvec 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "dca03f2f42500a9ef8ac0d16183dff8bed40e3dcf98f9d4147928548d5c4236e"
+"checksum smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "4f8266519bc1d17d0b5b16f6c21295625d562841c708f6376f49028a43e9c11e"
 "checksum string_cache 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f55fba06c5e294108f22e8512eb598cb13388a117991e411a8df8f41a1219a75"
 "checksum string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "479cde50c3539481f33906a387f2bd17c8e87cb848c35b6021d41fb81ff9b4d7"
 "checksum string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b1884d1bc09741d466d9b14e6d37ac89d6909cbcac41dd9ae982d4d063bbedfc"

components/style/Cargo.toml

@@ -17,7 +17,7 @@ gecko = ["nsstring_vendor", "rayon/unstable", "num_cpus"]
 use_bindgen = ["bindgen", "regex"]
 servo = ["serde/unstable", "serde", "serde_derive", "heapsize", "heapsize_derive",
          "style_traits/servo", "servo_atoms", "servo_config", "html5ever-atoms",
-         "cssparser/heapsize", "cssparser/serde", "encoding",
+         "cssparser/heapsize", "cssparser/serde", "encoding", "smallvec/heapsizeof",
          "rayon/unstable", "servo_url"]
 testing = []
 gecko_debug = ["nsstring_vendor/gecko_debug"]
@@ -53,7 +53,7 @@ serde = {version = "0.9", optional = true}
 serde_derive = {version = "0.9", optional = true}
 servo_atoms = {path = "../atoms", optional = true}
 servo_config = {path = "../config", optional = true}
-smallvec = "0.3"
+smallvec = "0.3.3"
 style_traits = {path = "../style_traits"}
 servo_url = {path = "../url", optional = true}
 time = "0.1"

components/style/parser.rs

@@ -4,8 +4,6 @@
 
 //! The context within which CSS code is parsed.
 
-#![deny(missing_docs)]
-
 use context::QuirksMode;
 use cssparser::{Parser, SourcePosition, UnicodeRange};
 use error_reporting::ParseErrorReporter;

components/style/properties/helpers.mako.rs

@@ -15,6 +15,7 @@
         use app_units::Au;
         use cssparser::{Color as CSSParserColor, RGBA};
         use values::specified::AllowQuirks;
+        use smallvec::SmallVec;
         pub use values::specified::${type} as SpecifiedValue;
         pub mod computed_value {
             % if computed_type:
@@ -75,6 +76,7 @@
             delegate_animate=False, space_separated_allowed=False, **kwargs)">
     <%call expr="longhand(name, **kwargs)">
         % if not gecko_only:
+            use smallvec::SmallVec;
             use std::fmt;
             use values::HasViewportPercentage;
             use style_traits::ToCss;
@@ -100,10 +102,11 @@
             pub mod computed_value {
                 pub use super::single_value::computed_value as single_value;
                 pub use self::single_value::T as SingleComputedValue;
+                use smallvec::SmallVec;
                 /// The computed value, effectively a list of single values.
                 #[derive(Debug, Clone, PartialEq)]
                 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-                pub struct T(pub Vec<single_value::T>);
+                pub struct T(pub SmallVec<[single_value::T; 1]>);
 
                 % if delegate_animate:
                     use properties::animated_properties::Interpolate;
@@ -179,9 +182,11 @@
 
             pub fn get_initial_value() -> computed_value::T {
                 % if allow_empty:
-                    computed_value::T(vec![])
+                    computed_value::T(SmallVec::new())
                 % else:
-                    computed_value::T(vec![single_value::get_initial_value()])
+                    let mut v = SmallVec::new();
+                    v.push(single_value::get_initial_value());
+                    computed_value::T(v)
                 % endif
             }
 
@@ -193,19 +198,16 @@
                     if space_separated_allowed:
                         parse_func = "parse_space_or_comma_separated"
                 %>
+
                 % if allow_empty:
                     if input.try(|input| input.expect_ident_matching("none")).is_ok() {
-                        Ok(SpecifiedValue(Vec::new()))
+                        return Ok(SpecifiedValue(Vec::new()))
-                    } else {
-                        ${parse_func}(input, |parser| {
-                            single_value::parse(context, parser)
-                        }).map(SpecifiedValue)
                     }
-                % else:
-                    ${parse_func}(input, |parser| {
-                        single_value::parse(context, parser)
-                    }).map(SpecifiedValue)
                 % endif
+
+                ${parse_func}(input, |parser| {
+                    single_value::parse(context, parser)
+                }).map(SpecifiedValue)
             }
 
             pub use self::single_value::SpecifiedValue as SingleSpecifiedValue;
@@ -220,7 +222,7 @@
                 #[inline]
                 fn from_computed_value(computed: &computed_value::T) -> Self {
                     SpecifiedValue(computed.0.iter()
-                                       .map(|x| ToComputedValue::from_computed_value(x))
+                                       .map(ToComputedValue::from_computed_value)
                                        .collect())
                 }
             }

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

@@ -27,6 +27,7 @@ use properties::longhands::vertical_align::computed_value::T as VerticalAlign;
 use properties::longhands::visibility::computed_value::T as Visibility;
 #[cfg(feature = "gecko")] use properties::{PropertyDeclarationId, LonghandId};
 #[cfg(feature = "servo")] use servo_atoms::Atom;
+use smallvec::SmallVec;
 use std::cmp;
 #[cfg(feature = "gecko")] use std::collections::HashMap;
 use std::fmt;
@@ -612,7 +613,7 @@ pub trait Interpolate: Sized {
 /// https://drafts.csswg.org/css-transitions/#animtype-repeatable-list
 pub trait RepeatableListInterpolate: Interpolate {}
 
-impl<T: RepeatableListInterpolate> Interpolate for Vec<T> {
+impl<T: RepeatableListInterpolate> Interpolate for SmallVec<[T; 1]> {
     fn interpolate(&self, other: &Self, progress: f64) -> Result<Self, ()> {
         use num_integer::lcm;
         let len = lcm(self.len(), other.len());
@@ -1065,7 +1066,12 @@ impl Interpolate for ClipRect {
             };
 
             let max_len = cmp::max(self.0.len(), other.0.len());
-            let mut result = Vec::with_capacity(max_len);
+
+            let mut result = if max_len > 1 {
+                SmallVec::from_vec(Vec::with_capacity(max_len))
+            } else {
+                SmallVec::new()
+            };
 
             for i in 0..max_len {
                 let shadow = match (self.0.get(i), other.0.get(i)) {
@@ -2192,7 +2198,7 @@ pub trait ComputeDistance: Sized {
     }
 }
 
-impl<T: ComputeDistance> ComputeDistance for Vec<T> {
+impl<T: ComputeDistance> ComputeDistance for SmallVec<[T; 1]> {
     #[inline]
     fn compute_distance(&self, other: &Self) -> Result<f64, ()> {
         self.compute_squared_distance(other).map(|sd| sd.sqrt())
@@ -2848,7 +2854,7 @@ impl <'a> From<<&'a IntermediateColor> for CSSParserColor {
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
     #[allow(missing_docs)]
     /// Intermediate type for box-shadow list and text-shadow list.
-    pub struct Intermediate${type}ShadowList(pub Vec<Intermediate${type}Shadow>);
+    pub struct Intermediate${type}ShadowList(pub SmallVec<[Intermediate${type}Shadow; 1]>);
 
     impl <'a> From<<&'a Intermediate${type}ShadowList> for ${type}ShadowList {
         fn from(shadow_list: &Intermediate${type}ShadowList) -> ${type}ShadowList {

components/style/properties/longhand/border.mako.rs

@@ -145,7 +145,7 @@ ${helpers.gecko_keyword_conversion(Keyword('border-style',
                 match *computed {
                     computed_value::T(Some(ref vec)) => {
                         SpecifiedValue::Colors(vec.iter()
-                                                  .map(|c| ToComputedValue::from_computed_value((c)))
+                                                  .map(ToComputedValue::from_computed_value)
                                                   .collect())
                     },
                     computed_value::T(None) => {
@@ -675,7 +675,7 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
         #[derive(Debug, Clone, PartialEq)]
         #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
         pub struct T {
-            pub corners: Vec<NumberOrPercentage>,
+            pub corners: [NumberOrPercentage; 4],
             pub fill: bool,
         }
     }
@@ -721,10 +721,10 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
     #[inline]
     pub fn get_initial_value() -> computed_value::T {
         computed_value::T {
-            corners: vec![ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
+            corners: [ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
-                          ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
+                      ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
-                          ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
+                      ComputedNumberOrPercentage::Percentage(Percentage(1.0)),
-                          ComputedNumberOrPercentage::Percentage(Percentage(1.0))],
+                      ComputedNumberOrPercentage::Percentage(Percentage(1.0))],
             fill: false,
         }
     }
@@ -744,22 +744,22 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
         fn to_computed_value(&self, context: &Context) -> computed_value::T {
             let length = self.corners.len();
             let corners = match length {
-                4 => vec![self.corners[0].to_computed_value(context),
+                4 => [self.corners[0].to_computed_value(context),
-                          self.corners[1].to_computed_value(context),
+                      self.corners[1].to_computed_value(context),
-                          self.corners[2].to_computed_value(context),
+                      self.corners[2].to_computed_value(context),
-                          self.corners[3].to_computed_value(context)],
+                      self.corners[3].to_computed_value(context)],
-                3 => vec![self.corners[0].to_computed_value(context),
+                3 => [self.corners[0].to_computed_value(context),
-                          self.corners[1].to_computed_value(context),
+                      self.corners[1].to_computed_value(context),
-                          self.corners[2].to_computed_value(context),
+                      self.corners[2].to_computed_value(context),
-                          self.corners[1].to_computed_value(context)],
+                      self.corners[1].to_computed_value(context)],
-                2 => vec![self.corners[0].to_computed_value(context),
+                2 => [self.corners[0].to_computed_value(context),
-                          self.corners[1].to_computed_value(context),
+                      self.corners[1].to_computed_value(context),
-                          self.corners[0].to_computed_value(context),
+                      self.corners[0].to_computed_value(context),
-                          self.corners[1].to_computed_value(context)],
+                      self.corners[1].to_computed_value(context)],
-                1 => vec![self.corners[0].to_computed_value(context),
+                1 => [self.corners[0].to_computed_value(context),
-                          self.corners[0].to_computed_value(context),
+                      self.corners[0].to_computed_value(context),
-                          self.corners[0].to_computed_value(context),
+                      self.corners[0].to_computed_value(context),
-                          self.corners[0].to_computed_value(context)],
+                      self.corners[0].to_computed_value(context)],
                 _ => unreachable!(),
             };
             computed_value::T {
@@ -791,11 +791,11 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
             }
         }
 
-        if fill == false {
+        if !fill {
             fill = input.try(|input| input.expect_ident_matching("fill")).is_ok();
         }
 
-        if values.len() > 0 {
+        if !values.is_empty() {
             Ok(SpecifiedValue {
                 corners: values,
                 fill: fill

components/style/properties/longhand/inherited_text.mako.rs

@@ -753,10 +753,11 @@ ${helpers.single_keyword("text-align-last",
     pub mod computed_value {
         use app_units::Au;
         use cssparser::Color;
+        use smallvec::SmallVec;
 
         #[derive(Clone, PartialEq, Debug)]
         #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-        pub struct T(pub Vec<TextShadow>);
+        pub struct T(pub SmallVec<[TextShadow; 1]>);
 
         #[derive(Clone, PartialEq, Debug)]
         #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -833,7 +834,8 @@ ${helpers.single_keyword("text-align-last",
 
     #[inline]
     pub fn get_initial_value() -> computed_value::T {
-        computed_value::T(Vec::new())
+        use smallvec::SmallVec;
+        computed_value::T(SmallVec::new())
     }
 
     pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue,()> {

components/style/properties/shorthand/background.mako.rs

@@ -214,7 +214,7 @@
             }
             Ok(())
         }));
-        if any == false {
+        if !any {
             return Err(());
         }
 

components/style/values/computed/mod.rs

@@ -332,7 +332,7 @@ pub struct Shadow {
 /// A `<number>` value.
 pub type Number = CSSFloat;
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
 pub enum NumberOrPercentage {