Fix type error

src/util.js

@@ -7,8 +7,11 @@
 // Type Definitions
 //-----------------------------------------------------------------------------
 
-/** @typedef {import("css-tree").SyntaxReferenceError} SyntaxReferenceError */
-/** @typedef {import("css-tree").SyntaxMatchError} SyntaxMatchError */
+/*
+ * Note: Using `import()` in the JSDoc comments below because including them as
+ * typedef comments here caused Rollup to remove them. I couldn't figure out why
+ * this was happening so just working around for now.
+ */
 
 //-----------------------------------------------------------------------------
 // Helpers
@@ -17,7 +20,7 @@
 /**
  * Determines if an error is a reference error.
  * @param {Object} error The error object to check.
- * @returns {error is SyntaxReferenceError} True if the error is a reference error, false if not.
+ * @returns {error is import("css-tree").SyntaxReferenceError} True if the error is a reference error, false if not.
  */
 export function isSyntaxReferenceError(error) {
 	return typeof error.reference === "string";
@@ -26,7 +29,7 @@ export function isSyntaxReferenceError(error) {
 /**
  * Determines if an error is a syntax match error.
  * @param {Object} error The error object to check.
- * @returns {error is SyntaxMatchError} True if the error is a syntax match error, false if not.
+ * @returns {error is import("css-tree").SyntaxMatchError} True if the error is a syntax match error, false if not.
  */
 export function isSyntaxMatchError(error) {
 	return typeof error.syntax === "string";