assignment_to_final_local

The final variable '{0}' can only be set once.

The analyzer produces this diagnostic when a local variable that was declared to be final is assigned after it was initialized.

The following code produces this diagnostic because x is final, so it can't have a value assigned to it after it was initialized:

void f() {
  final x = 0;
  x = 3;
  print(x);
}

Remove the keyword final, and replace it with var if there's no type annotation:

void f() {
  var x = 0;
  x = 3;
  print(x);
}