[rbehrends]

> Dart 1.0 has optional typing, but Dart 2.0 will be statically typed (with type inference though).

Not quite; it's more that compile time typing is getting cleaned up. You can still omit types, which will then either be inferred or set to `dynamic`. The following is valid strong mode Dart:

  f(n) {
    if (n <= 1)
      return 1;
    else
      return n * f(n - 1);
  }

The following will no longer work:

  int x = "foo";

In short, you can still omit types. It's just that if you declare them, they are enforced [1]. Dart will also infer them if possible, i.e. the following is illegal:

  var x = 1;
  x = "foo";

Here, x is inferred to be `int`, which makes the assignment of a string illegal. However, the following works:

  var x = true ? 0 : [];
  x = "foo";

Here, the type of `x` cannot be inferred, so it becomes `dynamic`, and therefore the assignment of "foo" becomes valid.

You can turn this off with --no-implicit-dynamic; with this option, all types must either be declared or have to be inferable.

[1] Sometimes not at compile time, though: Dart allows implicit downcasts and covariant generics at compile time and will insert runtime checks to catch those situations.