missing_required_param

The parameter '{0}' is required.

The parameter '{0}' is required. {1}.

The analyzer produces this diagnostic when a method or function with a named parameter that is annotated as being required is invoked without providing a value for the parameter.

The following code produces this diagnostic because the named parameter x is required:

import 'package:meta/meta.dart';

void f({@required int? x}) {}

void g() {
  f();
}

Provide the required value:

import 'package:meta/meta.dart';

void f({@required int? x}) {}

void g() {
  f(x: 2);
}