Improves performance of bracket pair colorization.

Author: hediet

src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/ast.ts

@@ -3,6 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+import { BugIndicatingError } from 'vs/base/common/errors';
 import { CursorColumns } from 'vs/editor/common/core/cursorColumns';
 import { BracketKind } from 'vs/editor/common/languages/supports/languageBracketsConfiguration';
 import { ITextModel } from 'vs/editor/common/model';
@@ -125,7 +126,7 @@ export class PairAstNode extends BaseAstNode {
 	 * Avoid using this property, it allocates an array!
 	*/
 	public get children() {
-		const result = new Array<AstNode>();
+		const result: AstNode[] = [];
 		result.push(this.openingBracket);
 		if (this.child) {
 			result.push(this.child);
@@ -295,10 +296,19 @@ export abstract class ListAstNode extends BaseAstNode {
 			return false;
 		}
 
+		if (this.childrenLength === 0) {
+			// Don't reuse empty lists.
+			return false;
+		}
+
 		let lastChild: ListAstNode = this;
-		let lastLength: number;
-		while (lastChild.kind === AstNodeKind.List && (lastLength = lastChild.childrenLength) > 0) {
-			lastChild = lastChild.getChild(lastLength! - 1) as ListAstNode;
+		while (lastChild.kind === AstNodeKind.List) {
+			const lastLength = lastChild.childrenLength;
+			if (lastLength === 0) {
+				// Empty lists should never be contained in other lists.
+				throw new BugIndicatingError();
+			}
+			lastChild = lastChild.getChild(lastLength - 1) as ListAstNode;
 		}
 
 		return lastChild.canBeReused(openBracketIds);
@@ -324,7 +334,7 @@ export abstract class ListAstNode extends BaseAstNode {
 	}
 
 	public flattenLists(): ListAstNode {
-		const items = new Array<AstNode>();
+		const items: AstNode[] = [];
 		for (const c of this.children) {
 			const normalized = c.flattenLists();
 			if (normalized.kind === AstNodeKind.List) {

src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/concat23Trees.ts

@@ -108,7 +108,7 @@ function concat(node1: AstNode, node2: AstNode): AstNode {
 function append(list: ListAstNode, nodeToAppend: AstNode): AstNode {
 	list = list.toMutable() as ListAstNode;
 	let curNode: AstNode = list;
-	const parents = new Array<ListAstNode>();
+	const parents: ListAstNode[] = [];
 	let nodeToAppendOfCorrectHeight: AstNode | undefined;
 	while (true) {
 		// assert nodeToInsert.listHeight <= curNode.listHeight
@@ -157,7 +157,7 @@ function append(list: ListAstNode, nodeToAppend: AstNode): AstNode {
 function prepend(list: ListAstNode, nodeToAppend: AstNode): AstNode {
 	list = list.toMutable() as ListAstNode;
 	let curNode: AstNode = list;
-	const parents = new Array<ListAstNode>();
+	const parents: ListAstNode[] = [];
 	// assert nodeToInsert.listHeight <= curNode.listHeight
 	while (nodeToAppend.listHeight !== curNode.listHeight) {
 		// assert 0 <= nodeToInsert.listHeight < curNode.listHeight

src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/parser.ts

@@ -71,19 +71,24 @@ class Parser {
 	private parseList(
 		openedBracketIds: SmallImmutableSet<OpeningBracketId>,
 	): AstNode | null {
-		const items = new Array<AstNode>();
+		const items: AstNode[] = [];
 
 		while (true) {
-			const token = this.tokenizer.peek();
-			if (
-				!token ||
-				(token.kind === TokenKind.ClosingBracket &&
-					token.bracketIds.intersects(openedBracketIds))
-			) {
-				break;
+			let child = this.tryReadChildFromCache(openedBracketIds);
+
+			if (!child) {
+				const token = this.tokenizer.peek();
+				if (
+					!token ||
+					(token.kind === TokenKind.ClosingBracket &&
+						token.bracketIds.intersects(openedBracketIds))
+				) {
+					break;
+				}
+
+				child = this.parseChild(openedBracketIds);
 			}
 
-			const child = this.parseChild(openedBracketIds);
 			if (child.kind === AstNodeKind.List && child.childrenLength === 0) {
 				continue;
 			}
@@ -96,9 +101,7 @@ class Parser {
 		return result;
 	}
 
-	private parseChild(
-		openedBracketIds: SmallImmutableSet<number>,
-	): AstNode {
+	private tryReadChildFromCache(openedBracketIds: SmallImmutableSet<number>): AstNode | undefined {
 		if (this.oldNodeReader) {
 			const maxCacheableLength = this.positionMapper.getDistanceToNextChange(this.tokenizer.offset);
 			if (!lengthIsZero(maxCacheableLength)) {
@@ -119,7 +122,12 @@ class Parser {
 				}
 			}
 		}
+		return undefined;
+	}
 
+	private parseChild(
+		openedBracketIds: SmallImmutableSet<number>,
+	): AstNode {
 		this._itemsConstructed++;
 
 		const token = this.tokenizer.read()!;

src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/smallImmutableSet.ts

@@ -3,7 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-const emptyArr = new Array<number>();
+const emptyArr: number[] = [];
 
 /**
  * Represents an immutable set that works best for a small number of elements (less than 32).
@@ -86,7 +86,7 @@ export class SmallImmutableSet<T> {
 		}
 
 		// This can be optimized, but it's not a common case
-		const newItems = new Array<number>();
+		const newItems: number[] = [];
 		for (let i = 0; i < Math.max(this.additionalItems.length, other.additionalItems.length); i++) {
 			const item1 = this.additionalItems[i] || 0;
 			const item2 = other.additionalItems[i] || 0;

src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/tokenizer.ts

@@ -143,7 +143,9 @@ class NonPeekableTextBufferTokenizer {
 		// We must not jump into a token!
 		if (lineIdx === this.lineIdx) {
 			this.lineCharOffset = column;
-			this.lineTokenOffset = this.lineCharOffset === 0 ? 0 : this.lineTokens!.findTokenIndexAtOffset(this.lineCharOffset);
+			if (this.line !== null) {
+				this.lineTokenOffset = this.lineCharOffset === 0 ? 0 : this.lineTokens!.findTokenIndexAtOffset(this.lineCharOffset);
+			}
 		} else {
 			this.lineIdx = lineIdx;
 			this.lineCharOffset = column;
@@ -291,7 +293,7 @@ export class FastTokenizer implements Tokenizer {
 		let lastTokenEndOffset = 0;
 		let lastTokenEndLine = 0;
 
-		const smallTextTokens0Line = new Array<Token>();
+		const smallTextTokens0Line: Token[] = [];
 		for (let i = 0; i < 60; i++) {
 			smallTextTokens0Line.push(
 				new Token(
@@ -301,7 +303,7 @@ export class FastTokenizer implements Tokenizer {
 			);
 		}
 
-		const smallTextTokens1Line = new Array<Token>();
+		const smallTextTokens1Line: Token[] = [];
 		for (let i = 0; i < 60; i++) {
 			smallTextTokens1Line.push(
 				new Token(