Remove smallvec (#8)

c.f. #6

Cargo.lock

@@ -8,9 +8,9 @@ checksum = "739f4a8db6605981345c5654f3a85b056ce52f37a39d34da03f25bf2151ea16e"
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.10"
+version = "0.7.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8716408b8bc624ed7f65d223ddb9ac2d044c0547b6fa4b0d554f3a9540496ada"
+checksum = "7404febffaa47dac81aa44dba71523c9d069b1bdc50a77db41195149e17f68e5"
 dependencies = [
  "memchr",
 ]
@@ -37,7 +37,6 @@ dependencies = [
  "parking_lot",
  "serde",
  "servo_arc",
- "smallvec",
  "text-size",
 ]
 
@@ -109,9 +108,9 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.3.3"
+version = "2.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3728d817d99e5ac407411fa471ff9800a778d88a24685968b36824eaf4bee400"
+checksum = "0ee1c47aaa256ecabcaea351eae4a9b01ef39ed810004e298d2511ed284b1525"
 
 [[package]]
 name = "nodrop"
@@ -152,9 +151,9 @@ checksum = "41cc0f7e4d5d4544e8861606a285bb08d3e70712ccc7d2b84d7c0ccfaf4b05ce"
 
 [[package]]
 name = "regex"
-version = "1.3.6"
+version = "1.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f6946991529684867e47d86474e3a6d0c0ab9b82d5821e314b1ede31fa3a4b3"
+checksum = "d9251239e129e16308e70d853559389de218ac275b515068abc96829d05b948a"
 dependencies = [
  "aho-corasick",
  "memchr",
@@ -164,9 +163,9 @@ dependencies = [
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.17"
+version = "0.6.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fe5bd57d1d7414c6b5ed48563a2c855d995ff777729dcd91c369ec7fea395ae"
+checksum = "b5eb417147ba9860a96cfe72a0b93bf88fee1744b5636ec99ab20c1aa9376581"
 
 [[package]]
 name = "scopeguard"
@@ -176,9 +175,9 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "serde"
-version = "1.0.106"
+version = "1.0.119"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36df6ac6412072f67cf767ebbde4133a5b2e88e76dc6187fa7104cd16f783399"
+checksum = "9bdd36f49e35b61d49efd8aa7fc068fd295961fd2286d0b2ee9a4c7a14e99cc3"
 
 [[package]]
 name = "servo_arc"
@@ -202,18 +201,18 @@ checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
 [[package]]
 name = "text-size"
-version = "1.0.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f03e7efdedc3bc78cb2337f1e2785c39e45f5ef762d9e4ebb137fff7380a6d8a"
+checksum = "288cb548dbe72b652243ea797201f3d481a0609a967980fcc5b2315ea811560a"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "thread_local"
-version = "1.0.1"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d40c6d1b69745a6ec6fb1ca717914848da4b44ae29d9b3080cbee91d72a69b14"
+checksum = "bb9bc092d0d51e76b2b19d9d85534ffc9ec2db959a2523cdae0697e2972cd447"
 dependencies = [
  "lazy_static",
 ]

Cargo.toml

@@ -12,7 +12,6 @@ serde = { version = "1.0.89", optional = true, default-features = false }
 lasso = "0.4.1"
 text-size = "1.0.0"
 fxhash= "0.2.1"
-smallvec = "1.6.1"
 servo_arc = { path = "vendor/servo_arc" }
 parking_lot= "0.11.1"
 

src/green.rs

@@ -1,7 +1,7 @@
+mod builder;
+mod element;
 mod node;
 mod token;
-mod element;
-mod builder;
 
 pub(crate) use self::element::GreenElementRef;
 use self::element::{GreenElement, PackedGreenElement};

src/green/builder.rs

@@ -2,7 +2,6 @@ use std::{convert::TryFrom, num::NonZeroUsize};
 
 use fxhash::{FxBuildHasher, FxHashMap};
 use lasso::{Capacity, Rodeo, Spur};
-use smallvec::SmallVec;
 use text_size::TextSize;
 
 use crate::{
@@ -13,6 +12,12 @@ use crate::{
 
 use super::{node::GreenNodeHead, token::GreenTokenData};
 
+/// If `node.children() <= CHILDREN_CACHE_THRESHOLD`, we will not create
+/// a new [`GreenNode`], but instead lookup in the cache if this node is
+/// already present. If so we use the one in the cache, otherwise we insert
+/// this node into the cache.
+const CHILDREN_CACHE_THRESHOLD: usize = 3;
+
 #[derive(Debug)]
 pub struct NodeCache {
     nodes:    FxHashMap<GreenNodeHead, GreenNode>,
@@ -39,6 +44,7 @@ impl NodeCache {
         I::IntoIter: ExactSizeIterator,
     {
         let children = children.into_iter();
+
         // Green nodes are fully immutable, so it's ok to deduplicate them.
         // This is the same optimization that Roslyn does
         // https://github.com/KirillOsenkov/Bliki/wiki/Roslyn-Immutable-Trees
@@ -46,18 +52,69 @@ impl NodeCache {
         // For example, all `#[inline]` in this file share the same green node!
         // For `libsyntax/parse/parser.rs`, measurements show that deduping saves
         // 17% of the memory for green nodes!
-        if children.len() <= 3 {
-            let children: SmallVec<[_; 3]> = children.collect();
-            let head = GreenNodeHead::from_child_slice(kind, children.as_ref());
-            self.nodes
-                .entry(head.clone())
-                .or_insert_with(|| GreenNode::from_head_and_children(head, children))
-                .clone()
+        if children.len() <= CHILDREN_CACHE_THRESHOLD {
+            self.get_cached_node(kind, children)
         } else {
             GreenNode::new(kind, children)
         }
     }
 
+    /// Creates a [`GreenNode`] by looking inside the cache or inserting
+    /// a new node into the cache if it's a cache miss.
+    fn get_cached_node<I>(&mut self, kind: SyntaxKind, children: I) -> GreenNode
+    where
+        I: IntoIterator<Item = GreenElement>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        #[derive(Clone)]
+        struct ChildrenIter {
+            data: [Option<GreenElement>; CHILDREN_CACHE_THRESHOLD],
+            idx:  usize,
+            len:  usize,
+        }
+
+        impl ChildrenIter {
+            fn new(data: [Option<GreenElement>; CHILDREN_CACHE_THRESHOLD], count: usize) -> Self {
+                ChildrenIter {
+                    data,
+                    idx: 0,
+                    len: count,
+                }
+            }
+        }
+
+        impl Iterator for ChildrenIter {
+            type Item = GreenElement;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                let item = self.data.get_mut(self.idx)?;
+                self.idx += 1;
+                item.take()
+            }
+        }
+
+        impl ExactSizeIterator for ChildrenIter {
+            fn len(&self) -> usize {
+                self.len - self.idx
+            }
+        }
+
+        let mut data: [Option<GreenElement>; CHILDREN_CACHE_THRESHOLD] = [None, None, None];
+        let mut count = 0;
+
+        for child in children {
+            data[count] = Some(child);
+            count += 1;
+        }
+        let children = ChildrenIter::new(data, count);
+
+        let head = GreenNodeHead::from_child_iter(kind, children.clone());
+        self.nodes
+            .entry(head.clone())
+            .or_insert_with(|| GreenNode::from_head_and_children(head, children))
+            .clone()
+    }
+
     fn token(&mut self, kind: SyntaxKind, text: &str) -> GreenToken {
         let text_len = TextSize::try_from(text.len()).unwrap();
         let text = self.interner.get_or_intern(text);

src/green/node.rs

@@ -22,7 +22,10 @@ pub(super) struct GreenNodeHead {
 
 impl GreenNodeHead {
     #[inline]
-    pub(super) fn from_child_slice(kind: SyntaxKind, children: &[GreenElement]) -> Self {
+    pub(super) fn from_child_iter<I>(kind: SyntaxKind, children: I) -> Self
+    where
+        I: Iterator<Item = GreenElement>,
+    {
         let mut hasher = FxHasher32::default();
         let mut text_len: TextSize = 0.into();
         for child in children {

src/serde_impls.rs

@@ -1,10 +1,7 @@
 use serde::ser::{Serialize, SerializeMap, SerializeSeq, Serializer};
 use std::fmt;
 
-use crate::{
-    api::{Language, SyntaxNode, SyntaxToken},
-    NodeOrToken,
-};
+use crate::{Language, NodeOrToken, SyntaxNode, SyntaxToken};
 
 struct SerDisplay<T>(T);
 impl<T: fmt::Display> Serialize for SerDisplay<T> {

vendor/servo_arc/Cargo.lock

@@ -0,0 +1,28 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "nodrop"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+
+[[package]]
+name = "serde"
+version = "1.0.119"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9bdd36f49e35b61d49efd8aa7fc068fd295961fd2286d0b2ee9a4c7a14e99cc3"
+
+[[package]]
+name = "servo_arc"
+version = "0.1.1"
+dependencies = [
+ "nodrop",
+ "serde",
+ "stable_deref_trait",
+]
+
+[[package]]
+name = "stable_deref_trait"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"