fix: types (#19720)

lib/FileSystemInfo.js

@@ -2172,9 +2172,9 @@ class FileSystemInfo {
 
 	/**
 	 * @param {number | null | undefined} startTime when processing the files has started
-	 * @param {Iterable<string> | null} files all files
-	 * @param {Iterable<string> | null} directories all directories
-	 * @param {Iterable<string> | null} missing all missing files or directories
+	 * @param {Iterable<string> | null | undefined} files all files
+	 * @param {Iterable<string> | null | undefined} directories all directories
+	 * @param {Iterable<string> | null | undefined} missing all missing files or directories
 	 * @param {SnapshotOptions | null | undefined} options options object (for future extensions)
 	 * @param {(err: WebpackError | null, snapshot: Snapshot | null) => void} callback callback function
 	 * @returns {void}

types.d.ts

@@ -5656,9 +5656,9 @@ declare abstract class FileSystemInfo {
 	): void;
 	createSnapshot(
 		startTime: undefined | null | number,
-		files: null | Iterable<string>,
-		directories: null | Iterable<string>,
-		missing: null | Iterable<string>,
+		files: undefined | null | Iterable<string>,
+		directories: undefined | null | Iterable<string>,
+		missing: undefined | null | Iterable<string>,
 		options: undefined | null | SnapshotOptionsFileSystemInfo,
 		callback: (err: null | WebpackError, snapshot: null | Snapshot) => void
 	): void;