J3/13-267
To: J3
From: Malcolm Cohen
Subject: Interp f08/92 on derived type parameters
Date: 2013 June 23

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NUMBER: F08/0092
TITLE: Derived type parameter requirements
KEYWORD: Derived type parameter
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider

  Type t1(a,a)
    Integer,Kind :: a
    Integer,Len :: a
  End Type
  Type t2(a)
    Integer,Kind :: a,a,a
  End Type

These type definition appears to valid, in that
(a) there is no requirement that a type parameter appears only once in
    the <type-param-name-list>;
(b) there is no requirement that a type parameter appears in only one
    <type-param-def-stmt>, and only once.

Were these intended to be valid?  What is their meaning?

ANSWER:

These were not intended to be valid, and they are not valid because
the standard does not establish an interpretation for them.  Unique
names for type parameters can possibly be deduced from the scoping
rules.

Edits are supplied to make the requirements explicit.

EDITS to 10-007r1:

[61:19+] In 4.5.2.1, after C427 insert new constraint
  "C427a (R426) The same <type-param-name> shall not appear more than
         once in a <derived-type-stmt>."
{Require unique names for type parameters.}

[64:9] In 4.5.3.1, C438, after "shall appear" insert "exactly once".
{Forbid multiple declarations of a type parameter, whether in the same
 <type-param-def-stmt> or more than one.}

SUBMITTED BY: Malcolm Cohen

HISTORY: m201  13-nnn  Submitted

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