From 474a27fe39a8b628c47b3f45319a47c79e31a30f Mon Sep 17 00:00:00 2001
From: James Garbutt <43081j@users.noreply.github.com>
Date: Wed, 17 Sep 2025 19:50:29 +0100
Subject: [PATCH 1/3] perf: avoid garbage colection in token type utils

This changes the token type functions such that they no longer create a
new array of token types every time, but instead use normal equality
checks and `includes` on a pre-computed set.

`acorn` token types can be mutated, but we already take a snapshot of
the types at time of creating our `AcornTypeScript`. Due to this, we can
just store the `Object.values` one time up front and call `includes` on
the same array later.

All of this means we no longer cause garbage collection (for creating a
single-use array) and we save CPU cycles on calling `includes` against
sets if we already matched.
---
 src/tokenType.ts | 50 ++++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/src/tokenType.ts b/src/tokenType.ts
index e87a2df..acc50ff 100644
--- a/src/tokenType.ts
+++ b/src/tokenType.ts
@@ -12,12 +12,14 @@ function kwLike(_name, options: any = {}) {
 }
 
 const acornTypeScriptMap = new WeakMap();
+const keywordTypeValues = Object.values(keywordTypes);
 
 export function generateAcornTypeScript(_acorn: any): AcornTypeScript {
 	const acorn = _acorn.Parser.acorn || _acorn;
 	let acornTypeScript = acornTypeScriptMap.get(acorn);
 	if (!acornTypeScript) {
 		const tsKwTokenType = generateTsKwTokenType();
+		const tsKwTokenTypeValues = Object.values(tsKwTokenType);
 		const tsTokenType = generateTsTokenType();
 		const tsTokenContext = generateTsTokenContext();
 		const tsKeywordsRegExp = new RegExp(`^(?:${Object.keys(tsKwTokenType).join('|')})$`);
@@ -43,39 +45,45 @@ export function generateAcornTypeScript(_acorn: any): AcornTypeScript {
 		};
 
 		function tokenIsLiteralPropertyName(token: TokenType): boolean {
-			return [
-				...[tokTypes.name, tokTypes.string, tokTypes.num],
-				...Object.values(keywordTypes),
-				...Object.values(tsKwTokenType)
-			].includes(token);
+			return (
+				token === tokTypes.name ||
+				token === tokTypes.string ||
+				token === tokTypes.num ||
+				keywordTypeValues.includes(token) ||
+				tsKwTokenTypeValues.includes(token)
+			);
 		}
 
 		function tokenIsKeywordOrIdentifier(token: TokenType): boolean {
-			return [
-				...[tokTypes.name],
-				...Object.values(keywordTypes),
-				...Object.values(tsKwTokenType)
-			].includes(token);
+			return (
+				token === tokTypes.name ||
+				keywordTypeValues.includes(token) ||
+				tsKwTokenTypeValues.includes(token)
+			);
 		}
 
 		function tokenIsIdentifier(token: TokenType): boolean {
-			return [...Object.values(tsKwTokenType), tokTypes.name].includes(token);
+			return token === tokTypes.name || tsKwTokenTypeValues.includes(token);
 		}
 
 		function tokenIsTSDeclarationStart(token: TokenType): boolean {
-			return [
-				tsKwTokenType.abstract,
-				tsKwTokenType.declare,
-				tsKwTokenType.enum,
-				tsKwTokenType.module,
-				tsKwTokenType.namespace,
-				tsKwTokenType.interface,
-				tsKwTokenType.type
-			].includes(token);
+			return (
+				token === tsKwTokenType.abstract ||
+				token === tsKwTokenType.declare ||
+				token === tsKwTokenType.enum ||
+				token === tsKwTokenType.module ||
+				token === tsKwTokenType.namespace ||
+				token === tsKwTokenType.interface ||
+				token === tsKwTokenType.type
+			);
 		}
 
 		function tokenIsTSTypeOperator(token: TokenType): boolean {
-			return [tsKwTokenType.keyof, tsKwTokenType.readonly, tsKwTokenType.unique].includes(token);
+			return (
+				token === tsKwTokenType.keyof ||
+				token === tsKwTokenType.readonly ||
+				token === tsKwTokenType.unique
+			);
 		}
 
 		function tokenIsTemplate(token: TokenType): boolean {

From 15c7a74db8b77fbb9c6ae3a33fb7d00c3ec11836 Mon Sep 17 00:00:00 2001
From: James Garbutt <43081j@users.noreply.github.com>
Date: Wed, 17 Sep 2025 19:54:35 +0100
Subject: [PATCH 2/3] chore: add changeset

---
 .changeset/nine-carrots-share.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/nine-carrots-share.md

diff --git a/.changeset/nine-carrots-share.md b/.changeset/nine-carrots-share.md
new file mode 100644
index 0000000..d6c2c58
--- /dev/null
+++ b/.changeset/nine-carrots-share.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/acorn-typescript': patch
+---
+
+Avoid garbage collection in token type utilities.

From 2c518182fb99f423135294a893f69176bc257754 Mon Sep 17 00:00:00 2001
From: Simon H <5968653+dummdidumm@users.noreply.github.com>
Date: Fri, 26 Sep 2025 15:20:58 +0200
Subject: [PATCH 3/3] Update .changeset/nine-carrots-share.md

---
 .changeset/nine-carrots-share.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/nine-carrots-share.md b/.changeset/nine-carrots-share.md
index d6c2c58..05bec7e 100644
--- a/.changeset/nine-carrots-share.md
+++ b/.changeset/nine-carrots-share.md
@@ -2,4 +2,4 @@
 '@sveltejs/acorn-typescript': patch
 ---
 
-Avoid garbage collection in token type utilities.
+perf: avoid garbage collection in token type utilities.