avoid_constant_conditions

v0.4.0 Warning Control Flow

Warns when a binary comparison has constant operands on both sides, meaning the result is always the same at compile time. This usually indicates a typo, a copy-paste error, or dead code that should be cleaned up.

Why use this rule

A condition like 4 == 11 or Config.channel == 'stable' (where Config.channel is a static const) always evaluates to the same boolean. One branch becomes unreachable dead code while the other always executes. This is almost never intentional and typically signals a mistake where one operand should have been a variable.

See also: Effective Dart: Usage

Don’t

const _retryLimit = 4;

abstract final class Config {
  static const channel = 'stable';
}

void bad() {
  // Two integer literals compared
  if (4 == 11) {
    print('unreachable');
  }

  // Static const field compared to a string literal
  if (Config.channel == 'stable') {
    print('always true');
  }

  // Top-level const compared to a literal
  final result = _retryLimit != 4;

  // Boolean literals compared
  final b = true == false;
}

Do

void good(String value, int count) {
  // Variable compared to literal
  if (value == 'stable') {
    print('hello');
  }

  // Variable compared to const
  if (count > _retryLimit) {
    print('big');
  }

  // Two variables
  final a = count;
  if (a == count) {
    print('same');
  }
}

Configuration

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

To turn it off:

many_lints.yaml

rules:
  avoid_constant_conditions: false

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

Related rules

• avoid_contradictory_expressions — Detect logical AND conditions that always evaluate to false.
• avoid_equal_expressions — Both operands of a binary expression should not be identical.
• avoid_self_compare — Flag a value compared against itself with compareTo.
• avoid_constant_switches — Detect switch statements on constant expressions.