View Compilation Error

0_0_36328257_6784.cpp: In member function 'void Fenwick<T, M>::add(int, T)':
0_0_36328257_6784.cpp:54:10: error: expected '(' before 'constexpr'
       if constexpr (M)
          ^
0_0_36328257_6784.cpp:56:7: error: 'else' without a previous 'if'
       else c[x] += v;
       ^
0_0_36328257_6784.cpp:56:14: error: 'x' was not declared in this scope
       else c[x] += v;
              ^
0_0_36328257_6784.cpp: In member function 'T Fenwick<T, M>::ask(int) const':
0_0_36328257_6784.cpp:65:10: error: expected '(' before 'constexpr'
       if constexpr (M)
          ^
0_0_36328257_6784.cpp:67:7: error: 'else' without a previous 'if'
       else res += c[x];
       ^
0_0_36328257_6784.cpp:67:21: error: 'x' was not declared in this scope
       else res += c[x];
                     ^