I´m trying to guess the syntax for reflecting operators and UDL´s, but failed :(

struct X {};
auto operator+(X,X) { return X{}; }
auto operator""_s(unsigned long long v)  { return v * 2; }
constexpr X x1, x2;

using r1 = reflexpr( operator+(X,X) );
using r2 = reflexpr( x1 + x2 );
using r3 = reflexpr( operator""_s(unsigned long long v) );
using r4 = reflexpr( 12_s );
https://compiler-explorer.com/z/hWP93dbW7

<source>:11:22: error: operator cannot be used as argument for the reflexpr operator
using r1 = reflexpr( operator+(X,X) );


Is any of these syntaxes right ?
Is this available already ?


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Cleiton