To: J3                                                     J3/26-150
From: Brad Richardson & Generics
Subject: Response to UTI025
Date: 2026-May-26

Reference: 26-007r1

UTI 025 states:

    "Why is the that constraint needed?

    One immediately wonders if a nonintrinsic procedure can appear
    where it is not valid...

    Perhaps a NOTE is in order explaining this, because otherwise
    vendors might omit the checks it must be requiring.

    This seems like a very ad-hoc extra requirement on the
    instantiation argument, requiring analysis of the entire template
    not just the declarations.

    It contrasts strongly with the deferred types, where we have put
    onerous limitations on the instantiation argument just so that the
    compiler does not need to say something like "oh, you can't have
    this type here, because an object of this type was assigned to
    somewhere in the template"."

Subgroup agrees that constraint C1635 is not correctly stated. The
intent is to enable the use of intrinsic procedures as instantiation
arguments, but it is not well defined what specifics exist, or what
the interfaces of those specifics exactly are.

[413:4] At the beginning of the sentence insert "If it is not an
        intrinsic procedure, " such that the constraint now reads
        "The instantiation procedure corresponding to a deferred
        procedure shall not be a procedure pointer. If it is not an
        intrinsic procedure, it shall have the same characteristics
        as the deferred procedure, except that a pure procedure may
        correspond to a deferred procedure that is not pure, a simple
        procedure may correspond to a deferred procedure that is not
        simple, and an elemental procedure may correspond to a deferred
        procedure that is not elemental."

[413:8-10] Delete constraint C1635.

[413:10+] Insert the following paragraph.
          "If an intrinsic procedure could be used as if it had the
          interface specified for a deferred procedure, it is valid
          to use as an instantiation argument corresponding to that
          deferred argument."

[413:10+] Insert the following as a NOTE.
          "Despite it not being entirely clear whether there exists
           a specific intrisic procedure with the exact
           characteristics of a particular interface, the following
           example is still considered valid.

           TEMPLATE DEMO{T, REDUCTION}
               DEFERRED TYPE :: T
               DEFERRED INTERFACE
                   PURE FUNCTION REDUCTION(A)
                       TYPE(T), INTERFACE(IN) :: A(:)
                       TYPE(T) :: REDUCTION
                   END FUNCTION
               END INTERFACE
           END TEMPLATE

           INSTANTIATE DEMO{REAL, SUM}
           INSTANTIATE DEMO{INTEGER, PRODUCT}"

[413:10+] Delete UTI 025

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