Full line comments before the first CASE in a CASE block are dropped

[raehik]

We attempt to store comments in our AST as statements. Mostly, the places where statements are valid and (full line) comments are valid are the same, so this isn't a problem. However, in the case of the CASE block

select case
  case (expr1)
    statement
  case (expr2)
    statement
end select

the user is able to insert comments between the SELECT CASE statement, and the first CASE statement.

These comments are currently thrown away. I wonder if there's a way we could keep them instead.

---

Production code does use this pattern: the open source WRF-Chem project uses it a number of times (extract):

       tracer_select: SELECT CASE(config_flags%tracer_opt)
!
! only mixing one fire(smoke) scalar array
!
       CASE (TRACER_SMOKE,TRACER_TEST1,TRACER_TEST2)
        CALL wrf_debug(15,'DOING TRACER MIXING, 1 SPECIE ONLY')
        do nv=2,num_tracer
         do k=kts,kte
            pblst(k)=max(epsilc,tracer(i,k,j,nv))
         enddo

               call vertmx(dtstep,pblst,ekmfull,dryrho_1d, &
                           zzfull,zz,0.,kts,kte)
         do k=kts,kte-1
            tracer(i,k,j,nv)=max(epsilc,pblst(k))
         enddo
        enddo
       CASE DEFAULT
!        CALL wrf_debug(15,'NOT YET DEFINED')
       END SELECT tracer_select

[raehik]

Could throw a Maybe Comment (or Maybe [Comment]?) field into BlCase. Should be straightforward enough to parse.