not_initialized_non_nullable_variable

The non-nullable variable '{0}' must be initialized.

The analyzer produces this diagnostic when a static field or top-level variable has a type that's non-nullable and doesn't have an initializer. Fields and variables that don't have an initializer are normally initialized to null, but the type of the field or variable doesn't allow it to be set to null, so an explicit initializer must be provided.

The following code produces this diagnostic because the field f can't be initialized to null:

class C {
  static int f;
}

Similarly, the following code produces this diagnostic because the top-level variable v can't be initialized to null:

int v;

If the field or variable can't be initialized to null, then add an initializer that sets it to a non-null value:

class C {
  static int f = 0;
}

If the field or variable should be initialized to null, then change the type to be nullable:

int? v;

If the field or variable can't be initialized in the declaration but will always be initialized before it's referenced, then mark it as being late:

class C {
  static late int f;
}