Bug 12596 – Implement Typedef ctor that can take itself as a parameter

void main() { import std.typecons; alias TD = Typedef!double; TD x = TD(1.0); TD y = TD(x); // Error } DMD 2.066alpha gives: test.d(5,16): Error: constructor std.typecons.Typedef!(double, nan).Typedef.this (double init) is not callable using argument types (Typedef!(double, nan)) But I think "TD(x)" should be accepted, just like: void main() { auto x = double(1); auto y = double(x); }