non_constant_case_expression

Case expressions must be constant.

The analyzer produces this diagnostic when the expression in a case clause isn't a constant expression.

The following code produces this diagnostic because j isn't a constant:

void f(int i, int j) {
  switch (i) {
    case j:
      // ...
      break;
  }
}

Either make the expression a constant expression, or rewrite the switch statement as a sequence of if statements:

void f(int i, int j) {
  if (i == j) {
    // ...
  }
}