constant_pattern_with_non_constant_expression

The expression of a constant pattern must be a valid constant.

The analyzer produces this diagnostic when a constant pattern has an expression that isn't a valid constant.

The following code produces this diagnostic because the constant pattern i isn't a constant:

void f(int e, int i) {
  switch (e) {
    case i:
      break;
  }
}

If the value that should be matched is known, then replace the expression with a constant:

void f(int e, int i) {
  switch (e) {
    case 0:
      break;
  }
}

If the value that should be matched isn't known, then rewrite the code to not use a pattern:

void f(int e, int i) {
  if (e == i) {}
}