Scoping with Dart's final keyword

All blocks have their own scope:

void main() {  if (true)  {    final x = 0;  }  final x = 10; //ok}

won't work:

void main() {  final x = 0;  for (var i = 0; i < 10; i++) {    x = i + 1; //NoSuchMethodError: cannot assign to final variable 'x'    print(x);  }}

but this one will:

void main() {  final x = 0;  for (var i = 0; i < 10; i++) {    final x = i + 1; //ok again    print(x);  }}

Because each iteration you say "i want a new final x"

They are block level finals and it's a new declaration each time. Since those are finals, not statics - it's expected behavior. At least, they can help you avoid some mistakes and provide code annotation that basically says: "won't change".

In short: yes.

Each block is its own scope. Every time you execute a block, it creates new instances of the variables in the block.

A "final" variable can only be initialized once, but every time you "execute" the declaration, a new unmodifiable variable is created. It doesn't matter whether the block is just a simple nested block, or it is a loop body, or even a function body.

main() {  foo(1);   foo(2);}void foo(final parameter) {  final local = parameter * 2;  for (final i in [1, 2]) {    final block1 = local + i;    {       final block2 = local + i * 2;       print(parameter * local * block1 * block2);    }  }}

In this example, all the final variables take more than one value during the life time of the program. Each time a final declaration is executed, the variable is introduced into the scope with a value, and when the block/scope is exited, the variable ceases to exist again.

The for(final i in ...) is handled specially, so the i variable is also created once for each loop iteration.