fixes

Author: Rich-Harris

packages/svelte/src/compiler/phases/1-parse/acorn.js

@@ -76,7 +76,8 @@ export function parse_expression_at(source, comments, typescript, index) {
 
 	const { onComment, add_comments } = get_comment_handlers(
 		source,
-		/** @type {CommentWithLocation[]} */ (comments)
+		/** @type {CommentWithLocation[]} */ (comments),
+		index
 	);
 
 	const ast = parser.parseExpressionAt(source, index, {
@@ -97,8 +98,9 @@ export function parse_expression_at(source, comments, typescript, index) {
  * in JS code and so that `prettier-plugin-svelte` doesn't remove all comments when formatting.
  * @param {string} source
  * @param {CommentWithLocation[]} comments
+ * @param {number} index
  */
-function get_comment_handlers(source, comments) {
+function get_comment_handlers(source, comments, index = 0) {
 	return {
 		/**
 		 * @param {boolean} block
@@ -131,7 +133,9 @@ function get_comment_handlers(source, comments) {
 		add_comments(ast) {
 			if (comments.length === 0) return;
 
-			comments = comments.slice();
+			comments = comments
+				.filter((comment) => comment.start >= index)
+				.map(({ type, value, start, end }) => ({ type, value, start, end }));
 
 			walk(ast, null, {
 				_(node, { next, path }) {

packages/svelte/src/compiler/phases/1-parse/read/expression.js

@@ -34,6 +34,8 @@ export function get_loose_identifier(parser, opening_token) {
  */
 export default function read_expression(parser, opening_token, disallow_loose) {
 	try {
+		let comment_index = parser.root.comments.length;
+
 		const node = parse_expression_at(
 			parser.template,
 			parser.root.comments,
@@ -43,18 +45,23 @@ export default function read_expression(parser, opening_token, disallow_loose) {
 
 		let num_parens = 0;
 
-		if (node.leadingComments !== undefined && node.leadingComments.length > 0) {
-			parser.index = node.leadingComments.at(-1).end;
+		let i = parser.root.comments.length;
+		while (i-- > comment_index) {
+			const comment = parser.root.comments[i];
+			if (comment.end < node.start) {
+				parser.index = comment.end;
+				break;
+			}
 		}
 
 		for (let i = parser.index; i < /** @type {number} */ (node.start); i += 1) {
 			if (parser.template[i] === '(') num_parens += 1;
 		}
 
 		let index = /** @type {number} */ (node.end);
-		if (node.trailingComments !== undefined && node.trailingComments.length > 0) {
-			index = node.trailingComments.at(-1).end;
-		}
+
+		const last_comment = parser.root.comments.at(-1);
+		if (last_comment && last_comment.end > index) index = last_comment.end;
 
 		while (num_parens > 0) {
 			const char = parser.template[index];