Would replacing ' :: ' with ' . ' create ambiguities in C++?

Due to attempts to make C++ mostly compatible with the existing C code (which allows name collisions between object names and struct tags), C++ allows name collisions between class names and object names.

Which means that:

struct data {
    static int member;
};

struct data2 {
    int member;
};

void f(data2& data) {
    data.member = data::member;
}

is legit code.

An example where both are valid, but refer to different objects:

#include <iostream>

struct A {
    int i;
};

struct B {
    int i;
    A B;
};

int main() {
    B x {0, 1};
    std::cout << x.B.i << '\n';
    std::cout << x.B::i << '\n';
}

See live on coliru.