dart-use-pattern-matching

Use the syntax `switch (value) { pattern => expression}` where each case maps a pattern to a single expression. Switch expressions must be exhaustive and have no implicit fallthrough, making them ideal for producing values from sealed classes or enums.

Use Map and List patterns to validate structure and extract values simultaneously, for example `if (data case {'user': [String name, int age]})`. This checks the keys and types while binding name and age to local variables in one step.

Switch expressions produce a value, require exhaustiveness, and allow only single expressions per case. Switch statements execute side effects, allow fallthrough on empty cases, and implicitly break on non-empty cases without a break keyword.

Yes, switching over sealed classes or enums requires all subtypes to be handled. Run `dart analyze` to find errors like 'not exhaustively matched', then add the missing Object patterns or a Wildcard case as a fallback.

Use a `when` clause after a pattern to evaluate arbitrary conditions that patterns cannot express, such as `case Square(size: var s) when s > 0`. Guards run only after the pattern matches and can reference bound variables.