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!standard 11.05 (11)          98-04-01 AI95-00176/03
!class binding interpretation 97-03-19
!status ARG Approved 11-0-0 98-04-01
!status ARG Approved (with changes) 13-0-0 95-11-01
!status work item 97-03-19
!status received 97-03-19
!priority Low
!difficulty Easy
!subject Access_Check is performed for access discriminants
!summary 98-03-19
The check that an access discriminant is non-null is an Access_Check.
!question 98-03-19
Is the null check that occurs when evaluating a discriminant association for an access discriminant considered to be an Access_Check?
!recommendation 98-03-19
(See summary.)
!wording 98-04-01
(See summary.)
!discussion 98-03-19
It was an oversight to omit the null check that occurs on discriminant association for an access discriminant from the list of checks associated with Access_Check in 11.5(11).
!appendix

!section 11.5(11)
!subject Access_Check is performed for access discriminants
!reference RM95-11.5(11)
!from Norman Cohen
!reference 96-5781.a Norman H. Cohen 96-12-20>>
!discussion

RM 11.5(11) purports to list the circumstances under which an Access_Check
is performed, but omits the check performed during elaboration of a
discriminant constraint that the discriminant value is not null.

(It follows from 3.7.1(12) that the elaboration of a discriminant
constraint entails conversion of each value in the constraint to the
corresponding discriminant subtype, and it follows from 4.6(49) that
conversion to an anonymous access type entails a check that the operand
value is not null.)

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