diff --git a/src/system/function.ts b/src/system/function.ts
index 3d2a317..0b937cf 100644
--- a/src/system/function.ts
+++ b/src/system/function.ts
@@ -2,9 +2,10 @@
 import { Disposable } from 'vscode';
 import { debounce as _debounce, once as _once } from 'lodash-es';
 
-export interface Deferrable {
+export interface Deferrable<T extends (...args: any[]) => any> {
+	(...args: Parameters<T>): ReturnType<T> | undefined;
 	cancel(): void;
-	flush(...args: any[]): void;
+	flush(): ReturnType<T> | undefined;
 	pending?(): boolean;
 }
 
@@ -38,7 +39,7 @@ export namespace Functions {
 		fn: T,
 		wait?: number,
 		options?: DebounceOptions,
-	): T & Deferrable {
+	): Deferrable<T> {
 		const { track, ...opts }: DebounceOptions = {
 			track: false,
 			...(options ?? {}),
@@ -55,12 +56,12 @@ export namespace Functions {
 			} as any) as T,
 			wait,
 			options,
-		) as T & Deferrable;
+		);
 
-		const tracked = (function (this: any, ...args: any[]) {
+		const tracked: Deferrable<T> = function (this: any, ...args: Parameters<T>) {
 			pending = true;
 			return debounced.apply(this, args);
-		} as any) as T & Deferrable;
+		} as any;
 
 		tracked.pending = function () {
 			return pending;
@@ -68,9 +69,8 @@ export namespace Functions {
 		tracked.cancel = function () {
 			return debounced.cancel.apply(debounced);
 		};
-		tracked.flush = function (...args: any[]) {
-			// eslint-disable-next-line prefer-spread
-			return debounced.flush.apply(debounced, args);
+		tracked.flush = function () {
+			return debounced.flush.apply(debounced);
 		};
 
 		return tracked;
diff --git a/src/trackers/documentTracker.ts b/src/trackers/documentTracker.ts
index 0a1dc4c..9f4f3aa 100644
--- a/src/trackers/documentTracker.ts
+++ b/src/trackers/documentTracker.ts
@@ -315,8 +315,8 @@ export class DocumentTracker<T> implements Disposable {
 		return doc;
 	}
 
-	private _dirtyIdleTriggeredDebounced: (((e: DocumentDirtyIdleTriggerEvent<T>) => void) & Deferrable) | undefined;
-	private _dirtyStateChangedDebounced: (((e: DocumentDirtyStateChangeEvent<T>) => void) & Deferrable) | undefined;
+	private _dirtyIdleTriggeredDebounced: Deferrable<(e: DocumentDirtyIdleTriggerEvent<T>) => void> | undefined;
+	private _dirtyStateChangedDebounced: Deferrable<(e: DocumentDirtyStateChangeEvent<T>) => void> | undefined;
 	private fireDocumentDirtyStateChanged(e: DocumentDirtyStateChangeEvent<T>) {
 		if (e.dirty) {
 			setImmediate(async () => {
diff --git a/src/trackers/lineTracker.ts b/src/trackers/lineTracker.ts
index 8b11ff6..d2ce299 100644
--- a/src/trackers/lineTracker.ts
+++ b/src/trackers/lineTracker.ts
@@ -199,7 +199,7 @@ export class LineTracker<T> implements Disposable {
 		this.onLinesChanged({ editor: this._editor, selections: this.selections, reason: reason });
 	}
 
-	private _linesChangedDebounced: (((e: LinesChangeEvent) => void) & Deferrable) | undefined;
+	private _linesChangedDebounced: Deferrable<(e: LinesChangeEvent) => void> | undefined;
 
 	private onLinesChanged(e: LinesChangeEvent) {
 		if (e.selections === undefined) {