Update implementation of FirstArgument

packages/utilities/src/index.ts

@@ -10,4 +10,4 @@ export {
 export {add, subtract} from './adjustment';
 export {CSS, Transform, Transition} from './css';
 export {canUseDOM} from './execution-context';
-export type {Arguments, ArgumentAtIndex, FirstArgument, Without} from './types';
+export type {Arguments, FirstArgument, Without} from './types';

packages/utilities/src/types.ts

@@ -1,10 +1,10 @@
 export type Arguments<T> = T extends (...args: infer U) => any ? U : never;
 
-export type ArgumentAtIndex<
-  Func,
-  Index extends keyof Arguments<Func>
-> = Arguments<Func>[Index];
-
-export type FirstArgument<T> = ArgumentAtIndex<T, 0>;
+export type FirstArgument<T> = T extends (
+  firstArg: infer U,
+  ...args: Array<any>
+) => any
+  ? U
+  : never;
 
 export type Without<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;