# prefer_final_parameters

> Details about the prefer_final_parameters diagnostic produced by the Dart analyzer.



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_The parameter '{0}' should be final._

## Description

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

## Example

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

```dart
String f([!String s!]) => s;
```

## Common fixes

Add the modifier `final` to the parameter:

```dart
String f(final String s) => s;
```

