What new features appeared in Dart 2.12?

• Null safety (null-soundness): It is guaranteed that variables cannot contain null unless their type is declared as nullable (with a ? suffix).
• Non-nullable by default: All types, except those explicitly declared as nullable (with ?), now do not allow null.
• Flow analysis: The code analyzer has become smarter in determining when a nullable variable is guaranteed not to contain null.
• Type inference improvements: Type inference has been improved, especially in the context of null safety.

// Null Safety example
String nonNullableString = 'hello'; // Cannot be null
String? nullableString = null;      // Can be null

void printLength(String? text) {
  if (text != null) {
    print(text.length); // flow analysis guarantees that text is not null here
  }
}