What functions and tools for working with null safety were introduced in Dart 2.12?

In Dart 2.12, support for null safety was introduced — a system that helps avoid errors related to null values. Main features and tools:

• Nullable and non-nullable types: by default, types cannot be null to prevent NullPointerException errors. To allow null, use ?, for example, String?.
• Null check operators: ! (assert non-null), ?? (if null, then), ?. (safe call for method or property).
• Compile-time analysis: the compiler checks that variables are not used without initialization or null checks.

Example:

String? name; // can be null

void greet() {
  if (name != null) {
    print('Hello, ${name!}'); // ! tells the compiler that name is not null
  } else {
    print('Hello, guest');
  }
}