When to use typecons.proxy vs alias this?

[Adam D. Ruppe via Digitalmars-d-learn]

Use alias this if you want implicit conversions too.

Proxy keeps the types separate

void foo(Base b) { }

struct Modified {
    Base b;
    alias b this;
}

foo(Modified()); //works


That wouldn't work if it was proxied though, which you sometimes 
want to force everything to go through your modification.