Incorrectly expanded parameter pack crashes compiler

[bbartman]

Code:

<# Defining implicit utility function, macros, and builtins.  #>;
__throw_bad_alloc()<noreturn>:void

__STDCPP_DEFAULT_NEW_ALIGNMENT__<constexpr>:int = 8

addressof[T:type](x:ref T)<inline>:^T !
  return __builtin_addressof(x)

<# Defining Remove reference for perfect forwarding. #>;
remove_reference[T:type] = class { ty : type = T; }
remove_reference[T:type][ref T] = class { ty : type = T; }
remove_reference[T:type][rref T] = class { ty : type = T; }

<# Defining forwarding function. #>;
forward[T:type](t:ref remove_reference[T].ty)<constexpr>:rref T !{
  return static_cast[rref T](t);
}

forward[T:type](t:rref remove_reference[T].ty)<constexpr>:rref T !{
  return static_cast[rref remove_reference[T].ty](t);
}

move[T:type](t:rref T)<noexcept><constexpr>:rref remove_reference<T>.ty! {
  return static_cast[rref remove_reference[T].ty](t);
}

foo[T:type, Args:type...](x:^type, args:rrerf Args...):void! {
  x.construct(forward[Args](args...));
}

main():int !{
  subject:vector[int];
  return 0;
}```