4.3 Aggregates

An aggregate combines component values into a composite value of an array type, record type, or record extension.

The expected type for an aggregate shall be a single array type, a single type with the Aggregate aspect specified (or a class-wide type rooted at such a type), or a single descendant of a record type or of a record extension. 

A record_aggregate or extension_aggregate shall not be of a class-wide type. 

For the evaluation of an aggregate, an anonymous object is created and values for the components or ancestor part are obtained (as described in the subsequent subclause for each kind of the aggregate) and assigned into the corresponding components or ancestor part of the anonymous object. Obtaining the values and the assignments occur in an arbitrary order. The value of the aggregate is the value of this object. 

If an aggregate is of a tagged type, a check is made that its value belongs to the first subtype of the type. Constraint_Error is raised if this check fails. Any discriminant check is performed before the initialization of any nondiscriminant component of the aggregate object.