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// The test cases GenericNull, FieldAccess, and InferTypeArgs often fail together.
// Here are some things that might be wrong if they are failing.
// * If you have overridden AnnotatedTypeFactory.createTreeAnnotator(), the body should return a
// list that contains the result of running the overridden implementation, as in:
// public TreeAnnotator createTreeAnnotator() {
// return new ListTreeAnnotator(super.createTreeAnnotator(), new MyOwnTreeAnnotator(this));
// }
// * If 'null' is intentionally not the bottom type in your type hierarchy, then you may suppress
// this warning for your particular type system.
//
// * The standard defaulting rules set the qualifier of type variable lower
// bounds to bottom. (https://checkerframework.org/manual/#climb-to-top) If
// you change this default to top, then this error will go away. (Add the
// meta-annotation @DefaultFor(LOWER_BOUNDS) to the top annotation class.)
// This will make types like List<@Bottom Object> illegal, so carefully
// consider if this is desirable.
//
class GenericNull {
/**
* In most type systems, null's type is bottom and therefore the generic return type T is a
* supertype of null's type.
*
* <p>However, in the nullness and lock type systems, null's type is not bottom, so they exclude
* this test. For the Lock Checker, null's type is bottom for the @GuardedByUnknown hierarchy
* but not for the @LockPossiblyHeld hierarchy.
*/
@SuppressWarnings({"nullness", "lock"})
<T> T f() {
return null;
}
}
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