To:        J3                                                J3/15-167
Subject:   Procedure overriding unnecessarily restrictive
From:      Van Snyder
Reference: 15-007r1
Date: 2015 June 07

1. Introduction
===============

All arguments of an overriding type-bound procedure, other than the
passed-object dummy argument are required to have the same
characteristics.

This is unhelpful, and is unnecessary if the parent type is abstract,
because an object of abstract type cannot exist, and therefore cannot be
the designator in the <data-ref> in a <procedure-designator>.

An overriding type-bound procedure is not permitted to have additional
arguments.

This is unhelpful, and is unnecessary if the parent type is abstract,
because an object of abstract type cannot exist, and therefore cannot be
the designator in the <data-ref> in a <procedure-designator>.

The result characteristics of an overriding function are required to be
the same as those of the overridden function.

This is unhelpful, and is unnecessary if the parent type is abstract,
because an object of abstract type cannot exist, and therefore cannot be
the designator in the <data-ref> in a <procedure-designator>.

2. Proposal
===========

Revise the fourth item of the list in 4.5.7.3p2 to allow additional
optional arguments if the parent type is abstract.

Revise the sixth item of the list in 4.5.7.3p2 to require the
characteristics of a dummy argument of an overriding procedure to be the
same as those of the corresponding dummy variable of the overridden
procedure only if the parent type is not abstract.

Revise the seventh item of the list to allow the result type of an
overriding function to be different from the result type of an
overridden function if the parent type is abstract.

3. Edits
========

[81:3 4.5.7.3p2] Replace the fourth list item with

"  o  If the parent type is not abstract, they shall have the same
      number of dummy arguments.  Otherwise, the overriding procedure
      shall not have fewer dummy arguments than the overridden
      procedure."

[81:5-6 4.5.7.3p2] Replace the sixth list item with

"  o  Named dummy arguments that correspond by position shall have the
      same names.

{Don't require alternate return indicators to have names.}

"  o  If the parent type is not abstract, dummy arguments that
      correspond by position, other than the passed-object dummy
      variable, shall have the same characteristics.

[81:7 4.5.7.3p2] In the seventh list item replace "having" with ". If
the parent type is not abstract, and they are functions, they shall
have".