J3/11-221
To: J3
From: Malcolm Cohen
Subject: Duplicate specific procedures in generic interface blocks
Date: 2011 June 30

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NUMBER: F03/0019
TITLE: Multiple identical specific procedures in generic interface
       blocks
KEYWORDS: Type-bound generics
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider
  Module m12
    Interface g1
      Subroutine s
      End
    End Interface
    Interface g2
      Procedure s
    End Interface
  End Module
  Program p12
    Use m12
    Interface g1     ! (1)
      Procedure s
    End Interface
    Interface g2     ! (2)
      Procedure s
    End Interface
    Call g1
    Call g2
  End Program

It is clear that the interface block marked (2) is not conforming,
since it violates C1209 which says
  "A procedure-name shall not specify a procedure that is specified
   previously in any procedure-stmt in any accessible interface with
   the same generic identifier."

However, it is not clear whether the interface block marked (1) is
conforming, since s was specified previously by an interface-body not
a procedure-stmt, even though both (1) and (2) attempt to do the same
thing, viz create a generic interface with a duplicate specific.

An even more obscure example is
  Module mx12
    Interface g3
      Subroutine s
      End
    End Interface
    Private s
  End
  Program px12
    Use mx12
    Interface g3
      Subroutine s
      End
    End Interface
    Call g3
  End Program

Here there is clearly no violation of C1209 but it is not obvious
whether the ambiguity rules are applied or not.

ANSWER:

These examples were not intended to be conforming.
An edit is supplied to clarify.

EDIT:

[281:11-12] Replace C1209 entirely by
  "C1209 (R1201) An <interface-specification> in a generic interface
         block shall not specify a procedure that is specified
         previously in any accessible interface with the same generic
         identifier."

SUBMITTED BY:  Van Snyder

HISTORY: 04-406    m170  F03/0019 submitted
         04-406r1  m170  Passed by J3 meeting
         05-146    m171  Passed J3 letter ballot #10
         N1658     m176  Failed WG5 ballot N1657
         11-nnn    m195  Revised answer.

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