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avoid-unused-instances

added in: 1.8.0
warning
⚙️
Pro+
preset: recommended

Warns when a newly created object is not being used.

Unused newly created objects are usually a sign of a bug and are expected to be returned, assigned or thrown.

⚙️ Config​

Set ignored-instances (default is [Timer, Debounce, Catcher]) to ignore instances that are intended to be unused (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-instances:
        ignored-instances:
          - Timer
          - SomeOtherClass

Example​

❌ Bad:

class SomeClass {
  ...
}

SomeClass function() {
  if (someCondition) {
    SomeClass(); // LINT: This instance is not used. Try removing it or referencing it in code.
  }

  return SomeClass();
}

✅ Good:

SomeClass function() {
  if (someCondition) {
    return SomeClass();
  }

  return SomeClass();
}

Example with "ignored-instances"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-instances:
        ignored-instances:
          - Timer

✅ Good:

SomeClass function() {
  if (someCondition) {
    Timer(); // Correct, ignored
  }

  return SomeClass();
}