```
@Retention(RUNTIME)
@Target({TYPE_USE,TYPE_PARAMETER})
@SubtypeOf({})
public @interface MustCallUnknown
```
The top qualifier in the Must Call type hierarchy. It represents a type that might have an obligation to call any set (even an infinite set!) of methods. This type contains every object. This type should rarely be written by a programmer.
The Object Construction Checker cannot verify that the property represented by this annotation is enforced; that is, the Object Construction Checker will always issue a warning when the value of an expression with this type might be de-allocated.

See the Checker Framework Manual:
Must Call Checker

Annotation Type MustCallUnknown