Regarding - error: only virtual member functions can be marked 'override'

[David M]

Dear All,

1) i have added 2 interface classes and one struct in mojom and built.

2) it created virtual functions to override

3) in new_tab_page.h and cc i wrote override functions and implemented.

getting an error of:

A)

../..\chrome/browser/ui/webui/new_tab_page/new_tab_page_ui.h(166,64): error: only virtual member functions can be marked 'override'
  void SetCredentials(new_tab_page::mojom::Credentials login ) override;

B) here "new_tab_page::mojom::Credentials" is struct and i used raw_ptr to set the  memeber variables using interface. did i missed anything??

C) when we need to use raw_Ptr , Unique_ptr? and how to instantiate?

thanks in advance

David