Odd LINENO behaviour in 'eval'

[Martijn Dekker]

Test script:
printf "$LINENO "
printf "$LINENO "
eval '  printf "$LINENO "
        printf "$LINENO "
        printf "$LINENO " '
printf "$LINENO\n"

Output on various shells:
            bash: 1 2 5 6 7 6  (?!)
     {m,l,pd}ksh: 1 2 0 0 0 6  (?)
      AT&T ksh88: 1 2 3 3 3 6
      AT&T ksh93: 1 2 1 2 3 6
      FreeBSD sh: 1 2 1 2 3 6
            dash: 1 2 1 2 3 6
            yash: 1 2 1 2 3 6
    zsh (native): 1 2 1 2 3 6
        zsh (sh): 1 2 3 3 3 6  (like ksh88)

It is unclear to me why bash starts counting the 'eval' lines at 5. Is
this a bug?

- M.