@@ -974,7 +974,7 @@ const NO_NODE = /** @type {Node} */ (/** @type {Node | null} */ (null));
  * @internal
  * @typedef {PrintNode} CommentedNode
  */
-/** @typedef {{ type: "comment1" | "comment2" | "comment3" | "comment4", value: string, pos: number, line: number, col: number }} KeptComment a comment as a `comments` callback is handed it: terser's comment token, its offset, line from 1 and column from 0 */
+/** @typedef {{ type: "comment1" | "comment2" | "comment3" | "comment4", value: string, pos: number, line: number, col: number, file?: string }} KeptComment a comment as a `comments` callback is handed it: terser's comment token, its offset, line from 1 and column from 0, and the file it was read from */
 /** @typedef {(this: PrintNode, comment: Comment) => boolean} CommentFilter which comments are printed, `this` the node they are read off */
 /**
  * What the output stream reads off a node for comments, an ESTree node or a
@@ -20290,7 +20290,7 @@ const withCommentsDecidedOnce = (options) => {
 		result[key] = {
 			...group,
 			comments: (node, comment) => {
-				const id = `${comment.type}:${comment.pos}:${comment.line}:${comment.col}:${comment.value}`;
+				const id = `${comment.file}:${comment.type}:${comment.pos}:${comment.line}:${comment.col}:${comment.value}`;
 				let kept = decided.get(id);
 				if (kept === undefined) {
 					kept = callback(node, comment);
@@ -20319,7 +20319,7 @@ const withoutMapUrl = (text) => text.replace(MAP_URL_COMMENT, "");
  * @returns {number} their total length, or -1 unless a string, or an array or object of strings
  */
 const sourceTextLength = (files) => {
-	if (typeof files === "string") return withoutMapUrl(files).length;
+	if (typeof files === "string") return files.length;
 	const values = Array.isArray(files)
 		? files
 		: Object.getPrototypeOf(files) === Object.prototype
@@ -20328,7 +20328,7 @@ const sourceTextLength = (files) => {
 	let length = values.length > 0 ? 0 : -1;
 	for (const value of values) {
 		if (typeof value !== "string") return -1;
-		length += withoutMapUrl(value).length;
+		length += value.length;
 	}
 	return length;
 };
@@ -21029,7 +21029,14 @@ const installImprove = (modules) => {
 			}
 			names.add(parameter.name);
 		}
-		// A value naming a parameter would read the `let` in its dead zone,
+		// What the body declares the block declares, ahead of its `let`s.
+		A.walk(/** @type {Node} */ (fn.body), (/** @type {Node} */ node) => {
+			if (A.isSymbolDeclarationNode(node)) names.add(node.name);
+			if (!A.isLambdaNode(node)) return;
+			if (A.isDefunNode(node)) names.add(node.id.name);
+			return true;
+		});
+		// A value naming a parameter or one of those would read it there,
 		// and a spread passes values to more than one.
 		return !args.some(
 			(/** @type {Node} */ value) =>
 
@@ -9023,11 +9023,14 @@ describe("syntax-printer", () => {
 			for (const input of [
 				"var a = 8; (function (b, b) { b.toString(); })(--a, a |= 10); console.log(a);",
 				'var c = "FAIL"; (function (a, NaN) { switch (a) { case a: break; case (c = "PASS"), NaN: break; } })(NaN); console.log(c);',
-				"var values = [2, 3]; (function (large, e) { console.log(large, e); })({ large: 1 }, ...values);"
+				"var values = [2, 3]; (function (large, e) { console.log(large, e); })({ large: 1 }, ...values);",
+				"var x = 3; (function (a) { let x = String(a); console.log(a, x, x); })(x);",
+				"var g = 3; (function (a) { function g() {} console.log(a, typeof g, g.name); })(g);"
 			]) {
 				const { code } = await minify(input, { compress: { passes: 2 }, mangle: false });
 				expect(runProgram(/** @type {string} */ (code))).toBe(runProgram(input));
-				expect(code).not.toContain("{let");
+				// A block of `let`s opens a statement, where the function's body follows `)`.
+				expect(code).not.toMatch(/(^|[;}])\{let /);
 			}
 		});
 
@@ -12479,14 +12482,15 @@ const minifyCounted = async (input, options, fromTree) => {
 	};
 	treePrinting.enabled = fromTree;
 	// One run, as choosing a spelling by size prints the program again.
+	const choseBySize = choosesBySize.enabled;
 	choosesBySize.enabled = false;
 	try {
 		const { code, map } = await minify(input, options);
 		return { code, map, printedFromTree };
 	} finally {
 		modules.printTree = printTree;
 		treePrinting.enabled = true;
-		choosesBySize.enabled = true;
+		choosesBySize.enabled = choseBySize;
 	}
 };
 
 
@@ -17985,14 +17985,15 @@ declare class JsonpTemplatePlugin {
 }
 
 /**
- * a comment as a `comments` callback is handed it: terser's comment token, its offset, line from 1 and column from 0
+ * a comment as a `comments` callback is handed it: terser's comment token, its offset, line from 1 and column from 0, and the file it was read from
  */
 declare interface KeptComment {
 	type: "comment1" | "comment2" | "comment3" | "comment4";
 	value: string;
 	pos: number;
 	line: number;
 	col: number;
+	file?: string;
 }
 
 /**