dart-modern-features

Use Records to bundle multiple values without defining a class, for example (String, int) fetchUser() returning ('Alice', 42). Access fields positionally with .$1 and .$2, avoiding boilerplate wrapper classes.

Use if-case with map patterns to combine type checking, validation, and assignment in one statement, such as if (json case {'name': String name, 'age': int age}). This replaces manual containsKey and is-type checks.

Sealed classes restrict subtypes to the same library, enabling the compiler to verify exhaustive switch expressions over all subtypes. Abstract classes allow unknown implementations anywhere, so the compiler cannot guarantee exhaustiveness.

Use extension types when you need type safety or domain-specific behavior without runtime allocation cost, since they compile down to the underlying type. Wrapper classes allocate new objects and are only needed for stateful behavior.

Records, patterns, and switch expressions were introduced in Dart 3.0. Later additions like null-aware elements and dot shorthands arrive in subsequent releases up to Dart 3.10, so check your SDK version before adopting them.