Inconsistent type or finality of pattern variable in logical-orDRT-W1395

The analyzer produces this diagnostic when a pattern variable that is declared on all branches of a logical-or pattern doesn't have the same type on every branch. It is also produced when the variable has a different finality on different branches. A pattern variable declared on multiple branches of a logical-or pattern is required to have the same type and finality in each branch, so that the type and finality of the variable can be known in code that's guarded by the logical-or pattern.

Examples

The following code produces this diagnostic because the variable a is defined to be an int on one branch and a double on the other:

void f(Object? x) {
  if (x case (int a) || (double a)) {
    print(a);
  }
}

The following code produces this diagnostic because the variable a is final in the first branch and isn't final in the second branch:

void f(Object? x) {
  if (x case (final int a) || (int a)) {
    print(a);
  }
}

Common fixes

If the finality of the variable is different, decide whether it should be final or not final and make the cases consistent:

void f(Object? x) {
  if (x case (int a) || (int a)) {
    print(a);
  }
}

If the type of the variable is different and the type isn't critical to the condition being matched, then ensure that the variable has the same type on both branches:

void f(Object? x) {
  if (x case (num a) || (num a)) {
    print(a);
  }
}

If the type of the variable is different and the type is critical to the condition being matched, then consider breaking the condition into multiple if statements or case clauses:

void f(Object? x) {
  if (x case int a) {
    print(a);
  } else if (x case double a) {
    print(a);
  }
}