WIP

Cargo.lock

@@ -245,6 +245,7 @@ dependencies = [
  "glob",
  "hashbrown 0.12.3",
  "humansize",
+ "id-arena",
  "itertools",
  "lazy_static",
  "libc",
@@ -383,6 +384,12 @@ dependencies = [
  "quick-error",
 ]
 
+[[package]]
+name = "id-arena"
+version = "2.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25a2bc672d1148e28034f176e01fffebb08b35768468cc954630da77a1449005"
+
 [[package]]
 name = "indexmap"
 version = "1.7.0"

Cargo.toml

@@ -66,6 +66,7 @@ hashbrown = "0.12.3"
 humansize = "2.1.3"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+id-arena = "2.2.1"
 
 [dev-dependencies]
 # assert_cmd 2.0.6 requires rust 1.60

src/diff/changes.rs

@@ -2,14 +2,14 @@
 
 use crate::{
     hash::DftHashMap,
-    parse::syntax::{Syntax, SyntaxId},
+    parse::syntax::{Syntax, SyntaxArena, SyntaxArenaId, SyntaxId},
 };
 
 #[derive(PartialEq, Eq, Clone, Copy)]
 pub enum ChangeKind<'a> {
-    Unchanged(&'a Syntax<'a>),
-    ReplacedComment(&'a Syntax<'a>, &'a Syntax<'a>),
-    ReplacedString(&'a Syntax<'a>, &'a Syntax<'a>),
+    Unchanged(SyntaxArenaId<'a>),
+    ReplacedComment(SyntaxArenaId<'a>, SyntaxArenaId<'a>),
+    ReplacedString(SyntaxArenaId<'a>, SyntaxArenaId<'a>),
     Novel,
 }
 
@@ -19,21 +19,36 @@ pub struct ChangeMap<'a> {
 }
 
 impl<'a> ChangeMap<'a> {
-    pub fn insert(&mut self, node: &'a Syntax<'a>, ck: ChangeKind<'a>) {
+    pub fn insert(
+        &mut self,
+        node_arena: &SyntaxArena<'a>,
+        node_id: SyntaxArenaId<'a>,
+        ck: ChangeKind<'a>,
+    ) {
+        let node = &node_arena[node_id];
         self.changes.insert(node.id(), ck);
     }
 
-    pub fn get(&self, node: &Syntax<'a>) -> Option<ChangeKind<'a>> {
+    pub fn get(
+        &self,
+        node_arena: &SyntaxArena<'a>,
+        node_id: SyntaxArenaId<'a>,
+    ) -> Option<ChangeKind<'a>> {
+        let node = &node_arena[node_id];
         self.changes.get(&node.id()).copied()
     }
 }
 
 pub fn insert_deep_unchanged<'a>(
-    node: &'a Syntax<'a>,
-    opposite_node: &'a Syntax<'a>,
+    node_arena: &SyntaxArena<'a>,
+    node_id: SyntaxArenaId<'a>,
+    opposite_node_id: SyntaxArenaId<'a>,
     change_map: &mut ChangeMap<'a>,
 ) {
-    change_map.insert(node, ChangeKind::Unchanged(opposite_node));
+    let node = &node_arena[node_id];
+    let opposite_node = &node_arena[opposite_node_id];
+
+    change_map.insert(node_arena, node_id, ChangeKind::Unchanged(opposite_node_id));
 
     match (node, opposite_node) {
         (
@@ -47,7 +62,7 @@ pub fn insert_deep_unchanged<'a>(
             },
         ) => {
             for (child, opposite_child) in node_children.iter().zip(opposite_children) {
-                insert_deep_unchanged(child, opposite_child, change_map);
+                insert_deep_unchanged(node_arena, *child, *opposite_child, change_map);
             }
         }
         (Syntax::Atom { .. }, Syntax::Atom { .. }) => {}
@@ -55,12 +70,17 @@ pub fn insert_deep_unchanged<'a>(
     }
 }
 
-pub fn insert_deep_novel<'a>(node: &'a Syntax<'a>, change_map: &mut ChangeMap<'a>) {
-    change_map.insert(node, ChangeKind::Novel);
+pub fn insert_deep_novel<'a>(
+    node_arena: &SyntaxArena<'a>,
+    node_id: SyntaxArenaId<'a>,
+    change_map: &mut ChangeMap<'a>,
+) {
+    let node = &node_arena[node_id];
+    change_map.insert(node_arena, node_id, ChangeKind::Novel);
 
     if let Syntax::List { children, .. } = node {
         for child in children.iter() {
-            insert_deep_novel(child, change_map);
+            insert_deep_novel(node_arena, *child, change_map);
         }
     }
 }

src/diff/dijkstra.rs

@@ -7,7 +7,7 @@ use crate::{
     diff::changes::ChangeMap,
     diff::graph::{populate_change_map, set_neighbours, Edge, Vertex},
     hash::DftHashMap,
-    parse::syntax::Syntax,
+    parse::syntax::{Syntax, SyntaxArena},
 };
 use bumpalo::Bump;
 use itertools::Itertools;
@@ -155,7 +155,7 @@ fn edge_between<'s, 'b>(before: &Vertex<'s, 'b>, after: &Vertex<'s, 'b>) -> Edge
 }
 
 /// What is the total number of AST nodes?
-fn node_count(root: Option<&Syntax>) -> u32 {
+fn node_count<'a>(node_arena: &SyntaxArena<'a>, root: Option<&Syntax>) -> u32 {
     let mut node = root;
     let mut count = 0;
     while let Some(current_node) = node {
@@ -167,38 +167,39 @@ fn node_count(root: Option<&Syntax>) -> u32 {
         };
         count += current_count;
 
-        node = current_node.next_sibling();
+        node = current_node.next_sibling().map(|id| &node_arena[id]);
     }
 
     count
 }
 
 /// How many top-level AST nodes do we have?
-fn tree_count(root: Option<&Syntax>) -> u32 {
+fn tree_count<'a>(node_arena: &SyntaxArena<'a>, root: Option<&Syntax>) -> u32 {
     let mut node = root;
     let mut count = 0;
     while let Some(current_node) = node {
         count += 1;
-        node = current_node.next_sibling();
+        node = current_node.next_sibling().map(|id| &node_arena[id]);
     }
 
     count
 }
 
 pub fn mark_syntax<'a>(
+    node_arena: &SyntaxArena<'a>,
     lhs_syntax: Option<&'a Syntax<'a>>,
     rhs_syntax: Option<&'a Syntax<'a>>,
     change_map: &mut ChangeMap<'a>,
     graph_limit: usize,
 ) -> Result<(), ExceededGraphLimit> {
-    let lhs_node_count = node_count(lhs_syntax) as usize;
-    let rhs_node_count = node_count(rhs_syntax) as usize;
+    let lhs_node_count = node_count(node_arena, lhs_syntax) as usize;
+    let rhs_node_count = node_count(node_arena, rhs_syntax) as usize;
     info!(
         "LHS nodes: {} ({} toplevel), RHS nodes: {} ({} toplevel)",
         lhs_node_count,
-        tree_count(lhs_syntax),
+        tree_count(node_arena, lhs_syntax),
         rhs_node_count,
-        tree_count(rhs_syntax),
+        tree_count(node_arena, rhs_syntax),
     );
 
     // When there are a large number of changes, we end up building a

src/diff/graph.rs

@@ -16,7 +16,7 @@ use crate::{
         stack::Stack,
     },
     hash::DftHashMap,
-    parse::syntax::{AtomKind, Syntax, SyntaxId},
+    parse::syntax::{AtomKind, Syntax, SyntaxArena, SyntaxArenaId, SyntaxId},
 };
 use Edge::*;
 
@@ -408,18 +408,22 @@ fn looks_like_punctuation(node: &Syntax) -> bool {
 /// Pop as many parents of `lhs_node` and `rhs_node` as
 /// possible. Return the new syntax nodes and parents.
 fn pop_all_parents<'s>(
-    lhs_node: Option<&'s Syntax<'s>>,
-    rhs_node: Option<&'s Syntax<'s>>,
+    node_arena: &SyntaxArena<'s>,
+    lhs_node_id: Option<SyntaxArenaId<'s>>,
+    rhs_node_id: Option<SyntaxArenaId<'s>>,
     lhs_parent_id: Option<SyntaxId>,
     rhs_parent_id: Option<SyntaxId>,
     parents: &Stack<EnteredDelimiter<'s>>,
 ) -> (
-    Option<&'s Syntax<'s>>,
-    Option<&'s Syntax<'s>>,
+    Option<SyntaxArenaId<'s>>,
+    Option<SyntaxArenaId<'s>>,
     Option<SyntaxId>,
     Option<SyntaxId>,
     Stack<EnteredDelimiter<'s>>,
 ) {
+    let lhs_node = lhs_node_id.map(|id| &node_arena[id]);
+    let rhs_node = rhs_node_id.map(|id| &node_arena[id]);
+
     let mut lhs_node = lhs_node;
     let mut rhs_node = rhs_node;
     let mut lhs_parent_id = lhs_parent_id;
@@ -432,8 +436,8 @@ fn pop_all_parents<'s>(
                 // Move to next after LHS parent.
 
                 // Continue from sibling of parent.
-                lhs_node = lhs_parent.next_sibling();
-                lhs_parent_id = lhs_parent.parent().map(Syntax::id);
+                lhs_node = lhs_parent.next_sibling().map(|id| &node_arena[id]);
+                lhs_parent_id = lhs_parent.parent().map(|id| node_arena[id].id());
                 parents = parents_next;
                 continue;
             }
@@ -444,8 +448,8 @@ fn pop_all_parents<'s>(
                 // Move to next after RHS parent.
 
                 // Continue from sibling of parent.
-                rhs_node = rhs_parent.next_sibling();
-                rhs_parent_id = rhs_parent.parent().map(Syntax::id);
+                rhs_node = rhs_parent.next_sibling().map(|id| &node_arena[id]);
+                rhs_parent_id = rhs_parent.parent().map(|id| node_arena[id].id());
                 parents = parents_next;
                 continue;
             }
@@ -457,10 +461,12 @@ fn pop_all_parents<'s>(
 
             // Continue from sibling of parent.
             if let Some((lhs_parent, rhs_parent, parents_next)) = try_pop_both(&parents) {
-                lhs_node = lhs_parent.next_sibling();
-                rhs_node = rhs_parent.next_sibling();
-                lhs_parent_id = lhs_parent.parent().map(Syntax::id);
-                rhs_parent_id = rhs_parent.parent().map(Syntax::id);
+                lhs_node = lhs_parent.next_sibling().map(|id| &node_arena[id]);
+                lhs_parent_id = lhs_parent.parent().map(|id| node_arena[id].id());
+
+                rhs_node = rhs_parent.next_sibling().map(|id| &node_arena[id]);
+                rhs_parent_id = rhs_parent.parent().map(|id| node_arena[id].id());
+
                 parents = parents_next;
                 continue;
             }
@@ -469,12 +475,19 @@ fn pop_all_parents<'s>(
         break;
     }
 
-    (lhs_node, rhs_node, lhs_parent_id, rhs_parent_id, parents)
+    (
+        lhs_node_id,
+        rhs_node_id,
+        lhs_parent_id,
+        rhs_parent_id,
+        parents,
+    )
 }
 
 /// Compute the neighbours of `v` if we haven't previously done so,
 /// and write them to the .neighbours cell inside `v`.
 pub fn set_neighbours<'s, 'b>(
+    node_arena: &SyntaxArena<'s>,
     v: &Vertex<'s, 'b>,
     alloc: &'b Bump,
     seen: &mut DftHashMap<&Vertex<'s, 'b>, Vec<&'b Vertex<'s, 'b>>>,
@@ -496,6 +509,7 @@ pub fn set_neighbours<'s, 'b>(
 
             // Both nodes are equal, the happy case.
             let (lhs_syntax, rhs_syntax, lhs_parent_id, rhs_parent_id, parents) = pop_all_parents(
+                node_arena,
                 lhs_syntax.next_sibling(),
                 rhs_syntax.next_sibling(),
                 v.lhs_parent_id,

src/parse/syntax.rs

@@ -4,6 +4,8 @@
 
 use std::{cell::Cell, env, fmt, hash::Hash, num::NonZeroU32};
 use typed_arena::Arena;
+use id_arena::Arena as IdArena;
+use id_arena::Id;
 
 use crate::{
     diff::changes::ChangeKind,
@@ -42,6 +44,9 @@ impl<'a> fmt::Debug for ChangeKind<'a> {
     }
 }
 
+pub type SyntaxArena<'a> = IdArena<Syntax<'a>>;
+pub type SyntaxArenaId<'a> = Id<Syntax<'a>>;
+
 pub type SyntaxId = NonZeroU32;
 
 /// Fields that are common to both `Syntax::List` and `Syntax::Atom`.
@@ -98,7 +103,7 @@ pub enum Syntax<'a> {
         info: SyntaxInfo<'a>,
         open_position: Vec<SingleLineSpan>,
         open_content: String,
-        children: Vec<&'a Syntax<'a>>,
+        children: Vec<SyntaxArenaId<'a>>,
         close_position: Vec<SingleLineSpan>,
         close_content: String,
         num_descendants: u32,
@@ -193,10 +198,10 @@ impl<'a> Syntax<'a> {
         arena: &'a Arena<Syntax<'a>>,
         open_content: &str,
         open_position: Vec<SingleLineSpan>,
-        children: Vec<&'a Syntax<'a>>,
+        children: Vec<SyntaxArenaId<'a>>,
         close_content: &str,
         close_position: Vec<SingleLineSpan>,
-    ) -> &'a Syntax<'a> {
+    ) -> SyntaxArenaId<'a> {
         // Skip empty atoms: they aren't displayed, so there's no
         // point making our syntax tree bigger. These occur when we're
         // parsing incomplete or malformed programs.
@@ -247,7 +252,7 @@ impl<'a> Syntax<'a> {
         mut position: Vec<SingleLineSpan>,
         mut content: &str,
         kind: AtomKind,
-    ) -> &'a Syntax<'a> {
+    ) -> SyntaxArenaId<'a> {
         // If a parser hasn't cleaned up \r on CRLF files with
         // comments, discard it.
         if content.ends_with('\r') {
@@ -273,11 +278,11 @@ impl<'a> Syntax<'a> {
         }
     }
 
-    pub fn parent(&self) -> Option<&'a Syntax<'a>> {
+    pub fn parent(&self) -> Option<SyntaxArenaId<'a>> {
         self.info().parent.get()
     }
 
-    pub fn next_sibling(&self) -> Option<&'a Syntax<'a>> {
+    pub fn next_sibling(&self) -> Option<SyntaxArenaId<'a>> {
         self.info().next_sibling.get()
     }
 
@@ -330,7 +335,7 @@ impl<'a> Syntax<'a> {
     }
 }
 
-pub fn comment_positions<'a>(nodes: &[&'a Syntax<'a>]) -> Vec<SingleLineSpan> {
+pub fn comment_positions<'a>(nodes: &[SyntaxArenaId<'a>]) -> Vec<SingleLineSpan> {
     fn walk_comment_positions(node: &Syntax<'_>, positions: &mut Vec<SingleLineSpan>) {
         match node {
             List { children, .. } => {
@@ -355,13 +360,13 @@ pub fn comment_positions<'a>(nodes: &[&'a Syntax<'a>]) -> Vec<SingleLineSpan> {
 }
 
 /// Initialise all the fields in `SyntaxInfo`.
-pub fn init_all_info<'a>(lhs_roots: &[&'a Syntax<'a>], rhs_roots: &[&'a Syntax<'a>]) {
+pub fn init_all_info<'a>(lhs_roots: &[SyntaxArenaId<'a>], rhs_roots: &[SyntaxArenaId<'a>]) {
     init_info(lhs_roots, rhs_roots);
     init_next_prev(lhs_roots);
     init_next_prev(rhs_roots);
 }
 
-fn init_info<'a>(lhs_roots: &[&'a Syntax<'a>], rhs_roots: &[&'a Syntax<'a>]) {
+fn init_info<'a>(lhs_roots: &[SyntaxArenaId<'a>], rhs_roots: &[SyntaxArenaId<'a>]) {
     let mut id = NonZeroU32::new(1).unwrap();
     init_info_on_side(lhs_roots, &mut id);
     init_info_on_side(rhs_roots, &mut id);
@@ -437,7 +442,7 @@ fn set_num_after(nodes: &[&Syntax], parent_num_after: usize) {
         }
     }
 }
-pub fn init_next_prev<'a>(roots: &[&'a Syntax<'a>]) {
+pub fn init_next_prev<'a>(roots: &[SyntaxArenaId<'a>]) {
     set_prev_sibling(roots);
     set_next_sibling(roots);
     set_prev(roots, None);
@@ -445,7 +450,7 @@ pub fn init_next_prev<'a>(roots: &[&'a Syntax<'a>]) {
 
 /// Set all the `SyntaxInfo` values for all the `roots` on a single
 /// side (LHS or RHS).
-fn init_info_on_side<'a>(roots: &[&'a Syntax<'a>], next_id: &mut SyntaxId) {
+fn init_info_on_side<'a>(roots: &[SyntaxArenaId<'a>], next_id: &mut SyntaxId) {
     set_parent(roots, None);
     set_num_ancestors(roots, 0);
     set_num_after(roots, 0);
@@ -492,7 +497,7 @@ fn set_content_is_unique(nodes: &[&Syntax]) {
     set_content_is_unique_from_counts(nodes, &counts);
 }
 
-fn set_prev_sibling<'a>(nodes: &[&'a Syntax<'a>]) {
+fn set_prev_sibling<'a>(nodes: &[SyntaxArenaId<'a>]) {
     let mut prev = None;
 
     for node in nodes {
@@ -505,7 +510,7 @@ fn set_prev_sibling<'a>(nodes: &[&'a Syntax<'a>]) {
     }
 }
 
-fn set_next_sibling<'a>(nodes: &[&'a Syntax<'a>]) {
+fn set_next_sibling<'a>(nodes: &[SyntaxArenaId<'a>]) {
     for (i, node) in nodes.iter().enumerate() {
         let sibling = nodes.get(i + 1).copied();
         node.info().next_sibling.set(sibling);
@@ -518,7 +523,7 @@ fn set_next_sibling<'a>(nodes: &[&'a Syntax<'a>]) {
 
 /// For every syntax node in the tree, mark the previous node
 /// according to a preorder traversal.
-fn set_prev<'a>(nodes: &[&'a Syntax<'a>], parent: Option<&'a Syntax<'a>>) {
+fn set_prev<'a>(nodes: &[SyntaxArenaId<'a>], parent: Option<SyntaxArenaId<'a>>) {
     for (i, node) in nodes.iter().enumerate() {
         let node_prev = if i == 0 { parent } else { Some(nodes[i - 1]) };
 
@@ -529,7 +534,7 @@ fn set_prev<'a>(nodes: &[&'a Syntax<'a>], parent: Option<&'a Syntax<'a>>) {
     }
 }
 
-fn set_parent<'a>(nodes: &[&'a Syntax<'a>], parent: Option<&'a Syntax<'a>>) {
+fn set_parent<'a>(nodes: &[SyntaxArenaId<'a>], parent: Option<SyntaxArenaId<'a>>) {
     for node in nodes {
         node.info().parent.set(parent);
         if let List { children, .. } = node {
@@ -928,7 +933,7 @@ impl MatchedPos {
 
 /// Walk `nodes` and return a vec of all the changed positions.
 pub fn change_positions<'a>(
-    nodes: &[&'a Syntax<'a>],
+    nodes: &[SyntaxArenaId<'a>],
     change_map: &ChangeMap<'a>,
 ) -> Vec<MatchedPos> {
     let mut positions = Vec::new();
@@ -937,7 +942,7 @@ pub fn change_positions<'a>(
 }
 
 fn change_positions_<'a>(
-    nodes: &[&'a Syntax<'a>],
+    nodes: &[SyntaxArenaId<'a>],
     change_map: &ChangeMap<'a>,
     positions: &mut Vec<MatchedPos>,
 ) {