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avoid-bottom-type-in-patterns

added in: 1.5.0
warning
Dart 3.0+
Pro+

Warns when a pattern contains a void, Never or Null type.

Presence of these types inside a pattern is most likely a bug.

Example​

❌ Bad:

final object = WithField('hello');

if (object case Null()) {} // LINT: Avoid the 'Null' type inside patterns. Try using a different type.
if (object case Never()) {} // LINT: Avoid the 'Never' type inside patterns. Try using a different type.

if (object case final Null value) {} // LINT: Avoid the 'Null' type inside patterns. Try using a different type.
if (object case final Never value) {} // LINT: Avoid the 'Never' type inside patterns. Try using a different type.

final value = switch (object) {
  Null() => 'bad', // LINT: Avoid the 'Null' type inside patterns. Try using a different type.
  Never() => 'bad', // LINT: Avoid the 'Never' type inside patterns. Try using a different type.
};

✅ Good:

final object = WithField('hello');

if (object == null) {}
if (object case == null) {} // Correct, 'null' instead of 'Null'

if (object case WithField()) {}

final value = switch (object) {
  == null => 'good',
  _ => 'good',
};

Additional Resources​