concrete_class_with_abstract_member

'{0}' must have a method body because '{1}' isn't abstract.

The analyzer produces this diagnostic when a member of a concrete class is found that doesn't have a concrete implementation. Concrete classes aren't allowed to contain abstract members.

The following code produces this diagnostic because m is an abstract method but C isn't an abstract class:

class C {
  void m();
}

If it's valid to create instances of the class, provide an implementation for the member:

class C {
  void m() {}
}

If it isn't valid to create instances of the class, mark the class as being abstract:

abstract class C {
  void m();
}