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avoid-unused-generics

added in: 1.4.0
warning
⚙️🛠
Pro+
preset: recommended

Warns when a function or method declares unused generic types.

Unused generics are usually a sign of a bug or can appear after code refactoring.

⚙️ Config​

Set ignore-overridden (default is false) to ignore methods that have the @override annotation (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-generics:
        ignore-overridden: false

Example​

❌ Bad:

class SomeClass {
  // LINT: This generic type is not used. Try removing it or referencing it in code.
  String unused<T extends num>() {
    // ...
  }

  // LINT: This generic type is not used. Try removing it or referencing it in code.
  String multiple<T, U>(U param) {
    // ...
  }
}

// LINT: This generic type is not used. Try removing it or referencing it in code.
void function<T>() {
  return;
}

✅ Good:

class SomeClass {
  String used<T extends num>() { // Correct, 'T' is used
    return (value as T).toString();
  }

  T multiple<T, U>(U param) { // Correct, both generics are used
    // ...
  }
}

void function() {
  return;
}

Example with "ignore-overridden"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-generics:
        ignore-overridden: true

✅ Good:

abstract class Abstract {
  void fn<T>();
}

class Child extends Abstract {
  @override
  void fn<T>() { // Correct, overridden declaration
    return;
  }
}

Additional Resources​