dmd/changelog/dmd.deprecation-typesafe-variadic-class.dd

Typesafe variadic class parameters have been deprecated

This obscure feature allowed a limited form of implicit construction:

---
void check(bool x, Exception e...)
{
    if (!x)
        throw e;
}

void main(string[] args)
{
    check(args.length > 1, "missing argument");
}
---

However, few uses of this feature have been found, and one project was actually mistakenly using it instead of the more common Typesafe variadic array parameter.
Considering D doesn't support implicit construction and already has a confusing amount of different variadic parameter forms, it was decided to remove this feature.

As a corrective action, either call the constructor in the callee:

---
void check(string msg)
{
    if (!x)
        throw new Exception(msg);
}
---

Or let the caller construct the class instance:

---
void check(bool x, Exception e);

void main(string[] args)
{
    check(args.length > 1, new Exception("missing argument"));
}
---