8.5.1 Object Renaming Declarations

object_renaming_declaration ::=
   defining_identifier : subtype_mark renames object_name;

Name Resolution Rules

The type of the object_name shall resolve to the type determined by the subtype_mark.
Legality Rules
The renamed entity shall be an object.
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 aliased. A slice of an array shall not be renamed if this restriction disallows renaming of the array.
Static Semantics
An object_renaming_declaration declares a new view of the renamed object whose properties are identical to those of the renamed view. Thus, the properties of the renamed object are not affected by the renaming_declaration. In particular, its value and whether or not it is a constant are unaffected; similarly, the constraints that apply to an object are not affected by renaming (any constraint implied by the subtype_mark of the object_renaming_declaration is ignored).
Examples
Example of renaming an object:

declare
   L : Person renames Leftmost_Person;  -- See section 3.10.1 Incomplete Type Declarations
begin
   L.Age := L.Age + 1;
end;