Although it is a report on experimental support,

engine->SetEngineProperty(asEP_ALLOW_IMPLICIT_HANDLE_TYPES, 1);

First, set asEP_ALLOW_IMPLICIT_HANDLE_TYPES to true.

class@ A
{
  A(A@ a) {  }
}
class@ B : A
{
  B(A@ a) { super(a); }
}
class@ C : B
{
  C(A@ a) { super(a); }
}

int main()
{
  auto a = A(null);
  auto c = C(a);
  auto b = B(c);
  return 0;
}

Then prepare the above code and execute asrun, an error will be output.

$ ./asrun.exe script2.as
script2.as (18, 1) : INFO : Compiling int main()
script2.as (22, 8) : ERR  : No default constructor for object of type 'B'.
script2.as (22, 8) : ERR  : No appropriate opAssign method found in 'B' for value assignment
script2.as (0, 0) : ERR  : Script failed to build

If you change as follows, it works normally.

auto b = B(@c);

Alternatively,

B@ b = B(c);