[flang] Defined assignment issue.

[DanielCChen]

Consider the following reducer:

module m
    type base
        real, allocatable :: data
        contains

        procedure :: uncommonAssgn
        generic :: assignment(=) => uncommonAssgn
    end type

    contains

    !! this is rather unusual way to do assignment: choose the larger value
    !between LHS and RHS for components
    subroutine uncommonAssgn (b1, b2)
        class(base), intent(inout) :: b1
        class(base), intent(in) :: b2

print*, b1%data                     !! Should print 10.1
    end subroutine
end module

module m1
use m
    type container
        type(base) data
    end type

    contains

    subroutine assgnCo (co1, co2)
        type(container), allocatable :: co1
        type(container) co2

        co1 = co2
    end subroutine
end module

program dummyArg009
use m1
    type(container), allocatable :: co1, co2

    allocate (co1,co2)

    co1%data%data = 10.1

    !! test 2
    call assgnCo (co1, co2)
end

Flang's output

> a.out
 0.

Expected output:

>a.out
10.1

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following reducer: ``` module m type base real, allocatable :: data contains

    procedure :: uncommonAssgn
    generic :: assignment(=) => uncommonAssgn
end type

contains

!! this is rather unusual way to do assignment: choose the larger value
!between LHS and RHS for components
subroutine uncommonAssgn (b1, b2)
    class(base), intent(inout) :: b1
    class(base), intent(in) :: b2

print*, b1%data !! Should print 10.1
end subroutine
end module

module m1
use m
type container
type(base) data
end type

contains

subroutine assgnCo (co1, co2)
    type(container), allocatable :: co1
    type(container) co2

    co1 = co2
end subroutine

end module

program dummyArg009
use m1
type(container), allocatable :: co1, co2

allocate (co1,co2)

co1%data%data = 10.1

!! test 2
call assgnCo (co1, co2)

end

Flang's output

> a.out
0.

Expected output:

>a.out
10.1

</details>

[klausler]

This is working as intended. Although compilers vary widely on their interpretations here, the text in F'2023 9.7.3.2 paragraph 7 is pretty clear: "When an intrinsic assignment statement (10.2.1.3) is executed, any noncoarray allocated allocatable subobject of the variable is deallocated before the assignment takes place." At the top level, the assignment co1 = co2 is an intrinsic assignment, and that text makes no exception for nested components with defined assignments.