### Acknowledgement - [x] I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion. ### Comment code: ```ts interface I { } class J { } function X(arg1: number, arg2?: number, arg3: J = new J(), arg4?: I): number | null { return null; } (arg1: number, arg2?: number, arg3: J = 11.33, arg4?: I): number | null => { return null; } ``` the `arg3` in the lambda expression has type J, but its default value is a number. However, typescript engine gives no error. The version of `tsc` is 5.8.3