8.2 Scope of Declarations
For each declaration, the language rules define a certain portion of the program text called the scope of the declaration. The scope of a declaration is also called the scope of any view or entity declared by the declaration. Within the scope of an entity, and only there, there are places where it is legal to refer to the declared entity. These places are defined by the rules of visibility and overloading.
The immediate scope of a declaration is a portion of the declarative region immediately enclosing the declaration. The immediate scope starts at the beginning of the declaration, except in the case of an overloadable declaration, in which case the immediate scope starts just after the place where the profile of the callable entity is determined (which is at the end of the _specification for the callable entity, or at the end of the generic_instantiation if an instance). The immediate scope extends to the end of the declarative region, with the following exceptions:
- The immediate scope of a library_item includes only its semantic dependents.
- The immediate scope of a declaration in the private part of a library unit does not include the visible part of any public descendant of that library unit.
The visible part of (a view of) an entity is a portion of the text of its declaration containing declarations that are visible from outside. The private part of (a view of) an entity that has a visible part contains all declarations within the declaration of (the view of) the entity, except those in the visible part; these are not visible from outside. Visible and private parts are defined only for these kinds of entities: callable entities, other program units, and composite types.
- The visible part of a view of a callable entity is its profile.
- The visible part of a composite type other than a task or protected type consists of the declarations of all components declared (explicitly or implicitly) within the type_declaration.
- The visible part of a generic unit includes the generic_formal_part. For a generic package, it also includes the first list of basic_declarative_items of the package_specification. For a generic subprogram, it also includes the profile.
- The visible part of a package, task unit, or protected unit consists of declarations in the program unit's declaration other than those following the reserved word private, if any; see 7.1 and 12.7 for packages, 9.1 for task units, and 9.4 for protected units.
The scope of a declaration always contains the immediate scope of the declaration. In addition, for a given declaration that occurs immediately within the visible part of an outer declaration, or is a public child of an outer declaration, the scope of the given declaration extends to the end of the scope of the outer declaration, except that the scope of a library_item includes only its semantic dependents.
The immediate scope of a declaration is also the immediate scope of the entity or view declared by the declaration. Similarly, the scope of a declaration is also the scope of the entity or view declared by the declaration.
4 There are notations for denoting visible declarations that are not directly visible. For example, parameter_specifications are in the visible part of a subprogram_declaration so that they can be used in named-notation calls appearing outside the called subprogram. For another example, declarations of the visible part of a package can be denoted by expanded names appearing outside the package, and can be made directly visible by a use_clause.
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Copyright © 2000 The MITRE Corporation, Inc. Ada Reference Manual