CLASS question

[OP1]

The code below does not compile with XE 17 (probably justly so). It compiles if U and V are not declared as allocatable arrays.The help for CLASS in the provided documentation does not seem to cover this case, maybe I am missing something here?

PROGRAM P
IMPLICIT NONE
TYPE,ABSTRACT :: T
END TYPE T
TYPE,EXTENDS(T) :: T1
END TYPE T1
TYPE(T1),ALLOCATABLE :: U(:)
CALL S(U)
CONTAINS
SUBROUTINE S(V)
IMPLICIT NONE
CLASS(T),ALLOCATABLE :: V(:)
END SUBROUTINE S
END PROGRAM P

[IanH]

This isn't permitted.  Inside `S`, you could (re-)allocate the `V` dummy argument to be some other extension of `T`, that was incompatible with the declared type of the actual argument `U`.  To avoid this there is a requirement that the declared type and polymorphic/non-polymorphic nature of the actual and dummy arguments must match if the dummy has the pointer or allocatable attribute (F2008 12.5.2.5p2).

I found a hint of an incomplete mention of this in the ifort documentation for allocatable arrays under "Array arguments", but it applies to scalar dummy arguments and pointer dummy arguments too.

[OP1]

Ah, I understand now. Thanks for the clear explanation!