prefer_wildcard_pattern

v0.4.0 Warning Fix Pattern Matching

Using Object() as a catch-all pattern in switch expressions, switch statements, or if-case conditions is functionally equivalent to the wildcard pattern _. The wildcard is more idiomatic in Dart and instantly recognizable as “match anything.”

Why use this rule

_ is the standard Dart idiom for “I don’t care about the value.” Using Object() instead adds visual noise and may confuse readers into thinking the pattern is doing something specific. The wildcard pattern is shorter, clearer, and universally understood.

See also: Dart patterns

Don’t

// Using Object() as a catch-all pattern
String classify(Object object) {
  return switch (object) {
    int() => 'int',
    Object() => 'other',
  };
}

void statement(Object object) {
  switch (object) {
    case int():
      break;
    case Object():
      break;
  }
}

void ifCase(Object object) {
  if (object case Object()) {}
}

Do

// Using the wildcard pattern _
String classify(Object object) {
  return switch (object) {
    int() => 'int',
    _ => 'other',
  };
}

void statement(Object object) {
  switch (object) {
    case int():
      break;
    case _:
      break;
  }
}

// Object() with field destructuring is fine — it extracts values
String withFields(Object object) {
  return switch (object) {
    int() => 'int',
    Object(hashCode: final h) => 'hash: $h',
    _ => 'other',
  };
}

Configuration

This rule is in the recommended preset, so it is on with preset: recommended or preset: opinionated. Add it to preset: core with prefer_wildcard_pattern: true.

To turn it off:

many_lints.yaml

rules:
  prefer_wildcard_pattern: false

To keep the rule on but skip certain paths, use per-rule exclude.

Related rules

• avoid_wildcard_cases_with_enums — Opposing convention. Keep exhaustiveness checking by listing enum cases explicitly.
• prefer_switch_with_enums — Use a switch instead of an if-else chain over enum constants.
• avoid_single_field_destructuring — Avoid destructuring a single field when direct property access is simpler.
• use_existing_destructuring — Add properties to an existing destructuring instead of accessing them directly.