Ada 95 RM - 10.1.6 Environment-Level Visibility Rules

(1): The normal visibility rules do not apply within a parent_unit_name or a context_clause, nor within a pragma that appears at the place of a compilation unit. The special visibility rules for those contexts are given here.

(2): Within the parent_unit_name at the beginning of a library_item, and within a with_clause, the only declarations that are visible are those that are library_items of the environment, and the only declarations that are directly visible are those that are root library_items of the environment. Notwithstanding the rules of 4.1.3, an expanded name in a with_clause may consist of a prefix that denotes a generic package and a selector_name that denotes a child of that generic package. (The child is necessarily a generic unit; see 10.1.1.)
(3): Within a use_clause or pragma that is within a context_clause, each library_item mentioned in a previous with_clause of the same context_clause is visible, and each root library_item so mentioned is directly visible. In addition, within such a use_clause, if a given declaration is visible or directly visible, each declaration that occurs immediately within the given declaration's visible part is also visible. No other declarations are visible or directly visible.
(4): Within the parent_unit_name of a subunit, library_items are visible as they are in the parent_unit_name of a library_item; in addition, the declaration corresponding to each body_stub in the environment is also visible.
(5): Within a pragma that appears at the place of a compilation unit, the immediately preceding library_item and each of its ancestors is visible. The ancestor root library_item is directly visible.

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