CVS difference for ai05s/ai05-0008-1.txt

--- ai05s/ai05-0008-1.txt	2006/03/18 07:38:01	1.1
+++ ai05s/ai05-0008-1.txt	2006/03/23 03:30:57	1.2
@@ -1,4 +1,4 @@
-!standard 3.10.2(26/2)                                 06-03-17    AI05-0008-1/01
+!standard 3.10.2(26/2)                                 06-03-18    AI05-0008-1/02
 !standard 4.1(9)
 !standard 8.5.1(5/2)
 !class binding interpretation 06-03-17
@@ -68,14 +68,114 @@
 
 !wording
 
-(TBD.)
+Replace 3.10.2(26/2):
 
+    The view shall not be a subcomponent that depends on discriminants
+    of a variable whose nominal subtype is unconstrained, unless this
+    subtype is indefinite, or the variable is constrained by its initial
+    value.
+
+  with the following:
+
+    The view shall not be a subcomponent that depends on discriminants
+    of an enclosing composite object (view) C whose nominal subtype is
+    unconstrained, unless C is known to be constrained by its initial value,
+    as follows:
+
+     * the subtype of C is indefinite;
+
+     * C is part of a stand-alone constant (including a generic formal
+       object of mode IN);
+
+     * C is a stand-alone variable constrained by its initial value; or
+
+     * C is a dereference of a pool-specific access type, and there is
+       no partial view of the type of C that is constrained.
+
+    AARM NOTE: We disallow dereferences of general access types because
+      they might denote stand-alone aliased unconstrained variables.
+
+    In addition to the places where Legality Rules normally apply, these rules
+    apply also in the private part of an instance of a generic unit. For the
+    purposes of determining within a generic body whether C is known to be
+    constrained by its initial value, a subtype is not considered indefinite if
+    it is a descendant of an untagged generic formal derived type, nor is an
+    access type considered pool-specific if it is a descendant of a formal access
+    type.
+
+Modify 4.1(9) as follows:
+
+    If the type of the name in a dereference is some access-to-object type T,
+    then the dereference denotes a view of an object, the nominal subtype of the
+    view being the designated subtype of T.  {If the designated subtype has
+    unconstrained discriminants, the (actual) subtype of the view is constrained
+    by the values of the discriminants of the designated object, except when
+    there is a partial view of the type of the designated subtype that does not
+    have discriminants, in which case the dereference is not constrained by its
+    discriminant values.}
+
+  AARM NOTE (added after the Ada 95 ones): 
+    The last sentence is different from Ada 95; it is necessary because general
+    access types can designated unconstrained objects in Ada 2005 (that was not
+    possible in Ada 95). Thus, the rules that had this effect in Ada 95 (the object
+    being constrained by its initial value) don't work in Ada 2005 and we have to
+    say this explicitly.
+
+    The "except" part of the last sentence prevents privacy "breaking", so that
+    if a private type has discriminants only in the full view, they don't
+    interfere with freely interassigning values between objects the type, even
+    when the objects live in the heap.
+
+  Retain the AARM note 4.1(9.d/2) from Draft 16 of the Ada 2005 AARM.
+
+Replace 8.5.1(5/2):
+
+    The renamed entity shall not be a subcomponent that depends on discriminants
+    of a variable whose nominal subtype is unconstrained, unless this subtype is
+    indefinite, or the variable is constrained by its initial value. A slice of
+    an array shall not be renamed if this restriction disallows renaming of the
+    array. In addition to the places where Legality Rules normally apply, these
+    rules apply also in the private part of an instance of a generic unit. These
+    rules also apply for a renaming that appears in the body of a generic unit,
+    with the additional requirement that even if the nominal subtype of the
+    variable is indefinite, its type shall not be a descendant of an untagged
+    generic formal derived type.
+
+  with the following:
+
+    The renamed entity shall not be a subcomponent that depends on discriminants
+    of an enclosing composite object (view) C whose nominal subtype is
+    unconstrained, unless C is known to be constrained by its initial value,
+    as follows:
+
+     * the subtype of C is indefinite;
+
+     * C is part of a stand-alone constant (including a generic formal
+       object of mode IN);
+
+     * C is a stand-alone variable constrained by its initial value; or
+
+     * C is a dereference of a pool-specific access type, and there is
+       no partial view of the type of C that is constrained.
+
+    AARM NOTE: We disallow dereferences of general access types because
+      they might denote stand-alone aliased unconstrained variables.
+
+    A slice of an array shall not be renamed if these rules disallow renaming of
+    the array. In addition to the places where Legality Rules normally apply,
+    these rules apply also in the private part of an instance of a generic unit.
+    For the purposes of determining within a generic body whether C is known to
+    be constrained by its initial value, a subtype is not considered indefinite
+    if it is a descendant of an untagged generic formal derived type, nor is an
+    access type considered pool-specific if it is a descendant of a formal access
+    type.
+
 !discussion
 
 3.10.2(26/2) and 8.5.1(5/2) are not really wrong, because they both say the operation
 is illegal "unless the variable is constrained by its initial value". That's not
 true here; we only know that it *might* be constrained, and that is not enough as
-legality rules require certainty. But it would be best to improve the wording so this
+legality rules require certainty. But it is best to improve the wording so this
 is clear.
 
 !ACATS test