void _check()

in lib/src/rules/prefer_is_empty.dart [95:170]
65 lines of code
32 McCabe index (conditional complexity)

  void _check(BinaryExpression expression, int value,
      {required bool constantOnRight}) {
    // Don't lint if we're in a const constructor initializer.
    var constructorInitializer =
        expression.thisOrAncestorOfType<ConstructorInitializer>();
    if (constructorInitializer != null) {
      var constructorDecl = constructorInitializer.parent;
      if (constructorDecl is! ConstructorDeclaration ||
          constructorDecl.constKeyword != null) {
        return;
      }
    }

    // Or in a const context.
    // See: https://github.com/dart-lang/linter/issues/1719
    if (expression.inConstantContext) {
      return;
    }

    var operator = expression.operator;
    if (value == 0) {
      if (operator.type == TokenType.EQ_EQ ||
          operator.type == TokenType.LT_EQ) {
        rule.reportLint(expression, errorCode: PreferIsEmpty.useIsEmpty);
      } else if (operator.type == TokenType.GT ||
          operator.type == TokenType.BANG_EQ) {
        rule.reportLint(expression, errorCode: PreferIsEmpty.useIsNotEmpty);
      } else if (operator.type == TokenType.LT) {
        rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysFalse);
      } else if (operator.type == TokenType.GT_EQ) {
        rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysTrue);
      }
    } else if (value == 1) {
      if (constantOnRight) {
        // 'length >= 1' is same as 'isNotEmpty',
        // and 'length < 1' is same as 'isEmpty'
        if (operator.type == TokenType.GT_EQ) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.useIsNotEmpty);
        } else if (operator.type == TokenType.LT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.useIsEmpty);
        }
      } else {
        // '1 <= length' is same as 'isNotEmpty',
        // and '1 > length' is same as 'isEmpty'
        if (operator.type == TokenType.LT_EQ) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.useIsNotEmpty);
        } else if (operator.type == TokenType.GT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.useIsEmpty);
        }
      }
    } else if (value < 0) {
      if (constantOnRight) {
        // 'length' is always >= 0, so comparing with negative makes no sense.
        if (operator.type == TokenType.EQ_EQ ||
            operator.type == TokenType.LT_EQ ||
            operator.type == TokenType.LT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysFalse);
        } else if (operator.type == TokenType.BANG_EQ ||
            operator.type == TokenType.GT_EQ ||
            operator.type == TokenType.GT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysTrue);
        }
      } else {
        // 'length' is always >= 0, so comparing with negative makes no sense.
        if (operator.type == TokenType.EQ_EQ ||
            operator.type == TokenType.GT_EQ ||
            operator.type == TokenType.GT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysFalse);
        } else if (operator.type == TokenType.BANG_EQ ||
            operator.type == TokenType.LT_EQ ||
            operator.type == TokenType.LT) {
          rule.reportLint(expression, errorCode: PreferIsEmpty.alwaysTrue);
        }
      }
    }
  }