I propose to add type inference (similar to one for functions) for constructor calls, that is to make the following program legal:

class C(T) {
  this(T) { }
}

void main() {
  immutable x = new C(0);
}

This would simplify programming eliminating the need to create a factory function or factory functions for each template class.

Pro: shorter programs.

Con: some consider it a good practice to make a factory function ALWAYS.

Pro: even if you create a factory function, the body of this function itself would be shortened.