8.1 Declarative Region

Reason: This is so that the component_declarations can be directly visible in the record_representation_clause.

Reason: The constructs that have declarative regions are the constructs that can have declarations nested inside them. Nested declarations are declared in that declarative region. The one exception is for enumeration literals; although they are nested inside an enumeration type declaration, they behave as if they were declared at the same level as the type. 

To be honest: A declarative region does not include parent_unit_names.

Ramification: A declarative region does not include context_clauses.

Discussion: Don't confuse the declarative region of a declaration with the declarative region in which it immediately occurs. 

Ramification: "Occurs immediately within" and "local to" are synonyms (when referring to declarations).

Thus, “local to” applies to both declarations and entities, whereas “occurs immediately within” only applies to declarations. We use this term only informally; for cases where precision is required, we use the term "occurs immediately within", since it is less likely to cause confusion. 

Discussion: It is necessary for the things that have a declarative region to include anything that contains declarations (except for enumeration type declarations). This includes any declaration that has a profile (that is, subprogram_declaration, subprogram_body, entry_declaration, subprogram_renaming_declaration, formal_subprogram_declaration, access-to-subprogram type_declaration), anything that has a discriminant_part (that is, various kinds of type_declaration), anything that has a component_list (that is, record type_declaration and record extension type_declaration), and finally the declarations of task and protected units and packages.

It was necessary to extend Ada 83's definition of declarative region to take the following Ada 95 features into account: 

Discriminated and access-to-subprogram type declarations need a declarative region. Enumeration type declarations cannot have one, because you don't have to say "Color.Red" to refer to the literal Red of Color. For other type declarations, it doesn't really matter whether or not there is an associated declarative region, so for simplicity, we give one to all types except enumeration types.

We now say that an accept_statement has its own declarative region, rather than being part of the declarative region of the entry_declaration, so that declarative regions are properly nested regions of text, so that it makes sense to talk about "inner declarative regions", and "...extends to the end of a declarative region". Inside an accept_statement, the name of one of the parameters denotes the parameter_specification of the accept_statement, not that of the entry_declaration. If the accept_statement is nested within a block_statement, these parameter_specifications can hide declarations of the block_statement. The semantics of such cases was unclear in RM83. 

To be honest: Unfortunately, we have the same problem for the entry name itself — it should denote the accept_statement, but accept_statements are not declarations. They should be, and they should hide the entry from all visibility within themselves. 

Note that we can't generalize this to entry_bodies, or other bodies, because the declarative_part of a body is not supposed to contain (explicit) homographs of things in the declaration. It works for accept_statements only because an accept_statement does not have a declarative_part.

To avoid confusion, we use the term “local to” only informally in Ada 95. Even RM83 used the term incorrectly (see, for example, RM83-12.3(13)).

In Ada 83, (root) library units were inside Standard; it was not clear whether the declaration or body of Standard was meant. In Ada 95, they are children of Standard, and so occur immediately within Standard's declarative region, but not within either the declaration or the body. (See RM83-8.6(2) and RM83-10.1.1(5).) 

{AI95-00318-02} Extended_return_statement (see 6.5) is added to the list of constructs that have a declarative region. 

{AI12-0094-1} Corrigendum: access_definition is added to the list of constructs that have a declarative region. This allows parameter names declared in anonymous access type subprogram types to be the same as other names declared outside. For instance: 

{AI12-0005-1} This is now legal, as one would expect; it was illegal in previous versions of Ada as the parameter A and the component A were homographs in the same declarative region (see 8.3). Note that some implementations already allow this common sense interpretation, so this extension might in fact already be used in existing code. 

{AI12-0061-1} {AI12-0236-1} {AI12-0308-1} Added iterated_component_association, iterated_element_association, and declare_expression to the rapidly expanding list of constructs that have a declarative region.