To:        J3                                                J3/15-165
Subject:   Is it intended to allow TYPE(*) in SELECT TYPE?
From:      Van Snyder
Reference: 15-007r1
Date: 2015 June 07

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

C837, on SELECT TYPE, says the <selector> shall be polymorphic.

4.3.2.2p3 says an assumed-type entity -- one declared using TYPE(*) --
is unlimited polymorphic.

C410 prohibits an assumed-type entity from appearing in a designator or
expression, except as a dummy argument in a few cases.  This prohibits
it from being a subscript, cosubscript, or substring designator (which
are already prohibited because these are required to be integers).

Therefore, an assumed-type entity is allowed to be the <selector> in a
SELECT TYPE statement.  But (apparently), the dynamic type of an
assumed-type entity is unknowable.

Either assumed-type entities should not be unlimited polymorphic, the
<selector> in a SELECT TYPE statement should be prohibited to be of
assumed type, or an assumed-type entity should be prohibited _AS_ a
designator, not just _IN_ a designator.

2. Edits
========

{The specification that assumed-type entities are polymorphic came from
subclause 9.4 on page 34 of N1904, TS 29113, "Further Interoperability
of Fortran with C."  We don't do interps or publish corrigenda on
Technical Specifications.  Should this difference from TS 29113 be
brought to readers' attention?}

[xviii Introduction under "Data usage and computation"] Insert a
sentence: "An assumed-type entity is not allowed as the <selector> in a
SELECT TYPE statement; assumed type was introduced in ISO/IEC TS 29113,
not ISO/IEC 1539-1:2010."

[54:13 C410] Replace "in a designator or expression" with "as a
designator or in an expression,"

Alternatively

[54:13 C410] Delete "in a designator or expression".

Alternatively

[186:7 C837] After "polymorphic" insert "and not of assumed type".