file2.ts(4,27): error TS9025: Declaration emit for this parameter requires implicitly adding undefined to its type. This is not supported with --isolatedDeclarations.


==== file1.ts (0 errors) ====
    type N = 1;
    export class Bar {
        c? = [2 as N] as const;
        c3? = 1 as N;
        readonly r = 1;
        f = 2;
    }
    
==== file2.ts (1 errors) ====
    export function foo(p = (ip = 10, v: number): void => {}): void{
    }
    type T = number
    export function foo2(p = (ip = 10 as T, v: number): void => {}): void{}
                              ~~~~~~~~~~~~
!!! error TS9025: Declaration emit for this parameter requires implicitly adding undefined to its type. This is not supported with --isolatedDeclarations.
!!! related TS9028 file2.ts:4:27: Add a type annotation to the parameter ip.
    export class Bar2 {
        readonly r = 1;
        f = 2;
    }