void_checks 
            
            Don’t assign to void.
This rule is available as of Dart 2.0.0.
Rule sets: core, recommended, flutter
Details
DON’T assign to void.
BAD:
class A<T> {
  T value;
  void test(T arg) { }
}
void main() {
  A<void> a = A<void>();
  a.value = 1; // LINT
  a.test(1); // LINT
}
Usage
To enable the void_checks rule,
add void_checks under linter > rules in your
analysis_options.yaml
file:
linter:
  rules:
    - void_checks