Holds if this function is deleted.
This may be because it was explicitly deleted with an = delete
definition, or because the compiler was unable to auto-generate a
definition for it.
Most implicitly deleted functions are omitted from the database.
Class.implicitCopyConstructorDeleted and
Class.implicitCopyAssignmentOperatorDeleted can be used to find
whether a class would have had those members implicitly deleted.
predicate isDeleted()