We can get the compile time equivalent of a member function's
address by applying '&' to the function in a static context:

struct S {
     void foo() {}
}

enum pfoo = &S.foo; // ok

void main() {
     // now we can use the pointer to create, for example, a
delegate
     S s;
     void delegate() dg;
     dg.ptr = &s;
     dg.funcptr = pfoo;
     dg();
}

However, we can't do that to a nested function:

void main() {
     void foo() {
     }
     enum pfoo = &foo; // weird kind of an enum delegate;
pfoo.funcptr can't be accessed at compile time.
}

Is there a way to get a pointer to a non-static nested function?

import std.stdio;
void main() {
    void foo() {
        writeln("It works as expected");
    }
    enum pfoo = &foo;
       
    void delegate() dg;
    dg.ptr = pfoo.ptr;
    dg.funcptr = pfoo.funcptr;
    dg();