avoid_annotating_with_dynamic   
              
Avoid annotating with dynamic when not required.
Details
#AVOID annotating with dynamic when not required.
As dynamic is the assumed return value of a function or method, it is usually
not necessary to annotate it.
BAD:
dart
dynamic lookUpOrDefault(String name, Map map, dynamic defaultValue) {
  var value = map[name];
  if (value != null) return value;
  return defaultValue;
}GOOD:
dart
lookUpOrDefault(String name, Map map, defaultValue) {
  var value = map[name];
  if (value != null) return value;
  return defaultValue;
}
Enable
#To enable the avoid_annotating_with_dynamic rule,
add avoid_annotating_with_dynamic under linter > rules in your
analysis_options.yaml file:
analysis_options.yaml
yaml
linter:
  rules:
    - avoid_annotating_with_dynamicIf you're instead using the YAML map syntax to configure linter rules,
add avoid_annotating_with_dynamic: true under linter > rules:
analysis_options.yaml
yaml
linter:
  rules:
    avoid_annotating_with_dynamic: true