foo.cpp:

namespace {
int foo;
}

void func1()
{
    foo = 42;
}

bar.cpp:

namespace {
int foo;
}

void func2()
{
    foo = 84;
}

baz.cpp:

enum {
    foo = 2
};

void func3()
{
    int boo = foo;
}

Find Usages on any foo in anon namespace finds all of them (including the enum). Find Usages on the foo enum (both the declaration and the usage) works as expected.