Re: UFCS with constructors

[qznc]

On Wednesday, 6 November 2013 at 11:04:05 UTC, bearophile wrote:
import std.typecons: Typedef;
alias Foo = Typedef!double;
void main() {
    auto a1 = Foo(1);
    pragma(msg, typeof(a1));
    auto a2 = 1.Foo;
    pragma(msg, typeof(a2));
    auto a3 = Foo(-1);
    pragma(msg, typeof(a3));
    auto a4 = -1.Foo;
    pragma(msg, typeof(a4));
}

It prints:

Typedef!(double, nan)
Typedef!(double, nan)
Typedef!(double, nan)
double


Is this expected/acceptable/good?

Operator precedence of "." is higher than unary minus. That 
should be the explanation, why the fourth output is different 
than the others.

However, what is Typedef for?