!ASIS Issue #097
!topic  Names for components of derived records
!reference  ASIS 95-17.6,17.36
!from  Sergey Rybin  98-07-25
!keywords  derived records types components
!discussion

I'm afraid I've found one more thing in the current ASIS definition
which needs clarification.

Consider 17.6, "function Corresponding_Name_Definition". It says:

--  - Record component references, return the defining name of the
--    record discriminant or component_declaration.  For derived types, the
--    result is an Is_Part_Of_Implicit structural (syntactic)
--    component from the declaration of the parent type definition.

Suppose we have X as a reference to a component of a derived record
type.  According to this paragraph, the result of applying
Corresponding_Name_Definition to it should be an implicit component
"from the declaration of the parent type definition". Let

   Y := Corresponding_Name_Definition (X);

The question is: what is Enclosing_Element (Y)? It looks like it
should be a component definition "of the parent type
definition". Well, let

   Z := Enclosing_Element (Y);

Is Z implicit or explicit? And the next question - what is
Enclosing_Element (Z)? Is it "the parent type definition"? And what
kind of Element should we get on this stage of applying
Enclosing_Element - Implicit or explicit?

ASIS 17.6 says, that in case of a reference to a component of a
derived record type the result of Corresponding_Name_Definition should
be a component defining name from the declaration of the _PARENT_ type
definition. But from the other side, RM 95 says in 3.4(14), that all
the components of a derived record type are implicitly declared
"within the declarative region of the [_derived_] type".

Probably, more logical approach for the references of the components
of derived record types would be:

- Corresponding_Name_Definition returns Is_Part_Of_Implicit defining
  name of a component;

- Enclosing_Element, when applied to such a defining name, returns
  Is_Part_Of_Implicit A_Component_Declaration/A_Discriminant_Specification;

- When applied again to this implicit component/discriminant
  declaration, Enclosing_Element returns an _explicit_ declaration of
  this _derived_ type (but not of the _parent_ type)

Sergey

!resolution  Accept, with Modification
!date 98-07-29

Change Clause 17.6, function Corresponding_Name_Definition, from:

--  - Record component references, return the defining name of the
--    record discriminant or component_declaration.  For derived types, the
--    result is an Is_Part_Of_Implicit structural (syntactic)
--    component from the declaration of the parent type definition.

To:

--  - Record component references return the defining name of the
--    record discriminant or component_declaration.  For references
--    to inherited declarations of derived types, the
--    Corresponding_Name_Definition returns the defining name of the
--    implicit inherited declaration.