missingFunctionImplementation2_b.ts(1,17): error TS2391: Function implementation is missing or not immediately following the declaration.


==== missingFunctionImplementation2_a.ts (0 errors) ====
    export {};
    declare module "./missingFunctionImplementation2_b" {
      export function f(a, b): void;
    }
    
==== missingFunctionImplementation2_b.ts (1 errors) ====
    export function f(a?, b?);
                    ~
!!! error TS2391: Function implementation is missing or not immediately following the declaration.