For example:

class Foo {
 friend void bar(Foo*);
};

Currently there is no refactor option to generate void bar(Foo*), probably because it is not a member. However, that function would probably exist somewhere close by anyway so maybe it could offer an option to generate free function declaration and definition to the .cpp file.

For example it could end up as:

class Foo {
 friend void bar(Foo*);
};
void bar(Foo*);

in .cpp:

void bar(Foo*)
{}