View Compilation Error

0_0_37995470_31049.cpp: In function 'Val operator+(const Val&, const Val&)':
0_0_37995470_31049.cpp:82:45: error: could not convert '{operator+((* & l.Val::a), (* & r.Val::a)), operator+((* & l.Val::b), (* & r.Val::b)), operator+((* & l.Val::len), (* & r.Val::len))}' from '<brace-enclosed initializer list>' to 'Val'
  return {l.a + r.a, l.b + r.b, l.len + r.len};
                                             ^