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J.11 The Class Attribute of Untagged Incomplete Types

Static Semantics

{AI95-00326-01} For the first subtype S of a type T declared by an incomplete_type_declaration that is not tagged, the following attribute is defined: 
{AI95-00326-01} S'Class

Denotes the first subtype of the incomplete class-wide type rooted at T. The completion of T shall declare a tagged type. Such an attribute reference shall occur in the same library unit as the incomplete_type_declaration.
Reason: {AI95-00326-01} This must occur in the same unit to prevent children from imposing requirements on their ancestor library units for deferred incomplete types. 

Wording Changes from Ada 95

{AI95-00326-01} {AI05-0299-1} This subclause clause is new. This feature was moved here because the tagged incomplete type provides a better way to provide this capability (it doesn't put requirements on the completion based on uses that could be anywhere). Pity we didn't think of it in 1994. 

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