Using std::variant as YYSTYPE/yylval in gnu bison for C++

variant.yy

%{
#include <string>
#include <variant>
typedef std::variant<std::string, double> value_t;
#define YYSTYPE value_t
extern YYSTYPE yylval;
int yylex();
void yyerror(char const *s);
int main();
%}

%token FOO

%%

top:
  FOO { $$ = $1; }

%%

int yylex()
{
	yylval = std::string("hello");
	return FOO;
}

void yyerror(char const *s)
{
}

int main()
{
	return 0;
}