E0297: abstract properties are not allowed in interfaces

TypeScript abstract classes can contain abstract methods and fields. Interface methods and fields are automatically abstract. It is a syntax error to write abstract for an interface method or field:

interface Logger {
  abstract log(
    severity: LogLevel,
    message: string,
  );
}

class ConsoleLogger implements Logger {
  log(
    severity: LogLevel,
    message: string,
  ) {
    console.log(`${severity}: ${message}`);
  }
}

To fix this error, remove the abstract keyword:

interface Logger {
  log(
    severity: LogLevel,
    message: string,
  );
}

Alternatively, convert the interface into an abstract class:

abstract class Logger {
  abstract log(
    severity: LogLevel,
    message: string,
  );
}

class ConsoleLogger extends Logger {
  log(
    severity: LogLevel,
    message: string,
  ) {
    console.log(`${severity}: ${message}`);
  }
}

Introduced in quick-lint-js version 2.10.0.

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