perf(concat-source): apply indexed-loop pattern to source(), size(), updateHash()

claude · claude · commit 086ac8cfa142 · 2026-04-29T10:54:05.000Z
Same V8 fast-path principle as the buffers() change in c29e061 — keep array iteration integer-indexed and the element type monomorphic so the optimizer doesn't fall off the cliff. A/B/A wall-clock medians (es6-promise.js fixture, 3 alternating runs so far; bg task still running): concat-source: source() (10 raw) 923 075 -> 971 196 ops/s (+5%) concat-source: size() 108 429 -> 692 935 ops/s (+6.4x) concat-source: updateHash() ~wash (within rme) The size() bench's 6.4x jump comes from the bench shape: it builds a fresh 4-child mixed ConcatSource per task and calls size() ten times. With for-of, each call allocates an iterator; the size() body itself is so cheap that the iterator setup dominates. for-i removes that overhead entirely. source() is more modest because the body work (string concat per child) outweighs iterator setup. updateHash() is wash for the same reason — `child.updateHash(hash)` is much heavier than the loop. Tests still green; lint clean. https://claude.ai/code/session_01EHhGq9PRFRGefVtwwasCqZ
diff --git a/lib/ConcatSource.js b/lib/ConcatSource.js
@@ -131,18 +131,22 @@ class ConcatSource extends Source {
 	 */
 	source() {
 		if (!this._isOptimized) this._optimize();
+		const children = /** @type {Source[]} */ (this._children);
+		const childCount = children.length;
 		let source = "";
-		for (const child of this._children) {
-			source += /** @type {Source} */ (child).source();
+		for (let ci = 0; ci < childCount; ci++) {
+			source += children[ci].source();
 		}
 		return source;
 	}
 
 	size() {
 		if (!this._isOptimized) this._optimize();
+		const children = /** @type {Source[]} */ (this._children);
+		const childCount = children.length;
 		let size = 0;
-		for (const child of this._children) {
-			size += /** @type {Source} */ (child).size();
+		for (let ci = 0; ci < childCount; ci++) {
+			size += children[ci].size();
 		}
 		return size;
 	}
@@ -315,10 +319,11 @@ class ConcatSource extends Source {
 	 */
 	updateHash(hash) {
 		if (!this._isOptimized) this._optimize();
+		const children = /** @type {Source[]} */ (this._children);
+		const childCount = children.length;
 		hash.update("ConcatSource");
-		for (const item of this._children) {
-			/** @type {Source} */
-			(item).updateHash(hash);
+		for (let ci = 0; ci < childCount; ci++) {
+			children[ci].updateHash(hash);
 		}
 	}
 
