dmd.alias-instance-member.dd

[next edition] Aliasing a member of a type *instance* is now an error

Such an alias actually aliases a member of the instance's *type*, not
the instance member itself. That could be confusing, and is now an error.
Instead, alias a member of the type:

---
struct Foo
{
    int v;
    void test(Foo that) const
    {
        alias a = this.v; // OK
        alias b = that.v; // Error, use `typeof(that).v` instead
        assert(&a is &b); // passes
        assert(&b !is &that.v);
    }
}

struct Bar
{
    Foo f;
    alias v = f.v; // Error, use `typeof(f).v`
}
---