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// PR c++/115378 // { dg-do compile { target c++20 } } struct tt {}; template<class Slot, auto Tag = []{}> constexpr auto __counter = 1; template <class Child, int Counter> using _as_base = tt; template <class... Envs> struct env : _as_base<Envs, __counter<int>>... {}; env<int> t;