The last constructor in variant.ctor is missing the Throws clause. I believe this inconsistency is a simple editorial issue, since the three preceeding (very similar!) constructors all explicitly say

Throws: Any exception thrown by calling the selected constructor of T(i)

This should be added to the constructor

template<size_t I, class U, class... Args>
  constexpr explicit variant(in_place_index_t<I>, initializer_list<U> il, Args&&... args);

as well.