prefer_final_parameters

The parameter '{0}' should be final.

The analyzer produces this diagnostic when a parameter of a constructor, method, function, or closure isn't marked as being final.

The following code produces this diagnostic because the parameter s isn't a final parameter:

String f(String s) => s;

Add the modifier final to the parameter:

String f(final String s) => s;

Unless stated otherwise, the documentation on this site reflects Dart 3.7.3. Page last updated on 2025-05-08. View source or report an issue.