Non default constructible object is created and returned, somehow

[fabiorossetto]

Expected Behavior

See the attached minimal reproducible example. SimpleCall returns an object of type NoDefaultCtor. Somehow, the code compiles. This doesn't make sense because how can NoDefaultCtor be constructed. value, which should be 7, is 0 instead.

Actual Behavior

Steps to Reproduce the Problem

#include <cstdio>
#include <https://raw.githubusercontent.com/boost-experimental/te/master/include/boost/te.hpp>
#include <cassert>

namespace te = boost::te;

struct NoDefaultCtor {
    NoDefaultCtor() = delete;

    int value{7};
};

struct SimpleCall {
  constexpr inline auto run() {
    return te::call<NoDefaultCtor>([](auto &self) {}, *this);
  }
};

struct Test {};

int main() {
  // Option 1 or 2 is required on some compilers
  te::poly<SimpleCall> f{Test{}};
  NoDefaultCtor s = f.run();
  return s.value;
}

Specifications

Tried on clang 16.0.0 and GCC 10