[Bug fortran/86100] New: Spurious error with -fcheck=bounds and allocatable class(*) array components

[neil.n.carlson at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86100

            Bug ID: 86100
           Summary: Spurious error with -fcheck=bounds and allocatable
                    class(*) array components
           Product: gcc
           Version: 8.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: neil.n.carlson at gmail dot com
  Target Milestone: ---

When compiled with -fcheck=bounds, the following example gives a spurious
runtime bound mismatch error on the 'b=a' assignment statement:

type any_matrix
  class(*), allocatable :: m(:,:)
end type
type(any_matrix) :: a, b
allocate(a%m, source=reshape([3,5],shape=[1,2]))
b = a ! SPURIOUS RUNTIME ERROR with -fcheck=bounds
end

At line 6 of file gfortran-20180610.f90
Fortran runtime error: Array bound mismatch for dimension 1 of array
'<<unknown>>' (2/1)

Without the -fcheck=bounds option the assignment executes correctly (checked
via adding code to examine b%m).

There are no problems if the array component is rank-1, or if it is declared
integer instead of class(*). So this issue seems confined to allocatable
class(*) components of rank 2 (or greater?)