unused_field_from_primary_constructor

The value of the field '{0}' isn't used.

The analyzer produces this diagnostic when a private field is declared in a primary constructor but never read, even if it's written in one or more places.

The following code produces this diagnostic because the field _i isn't read anywhere in the library:

class C(final int _i);

The primary constructor declares a field because the keyword final is used. (Using the var keyword also declares a field.)

If the parameter is still necessary, but the associated field is not, then remove the final or var keyword:

class C(int _i);

If the parameter is also unnecessary, then remove it (which also removes the associated field).

class C {}

If the field was intended to be used, then add the missing code.