Unexpected "!$" history expansion after use of here-document

[Viktor Dukhovni]

Configuration Information [Automatically generated, do not change]:
Machine: amd64
OS: freebsd11.1
Compiler: cc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='amd64' 
-DCONF_OSTYPE='freebsd11.1' -DCONF_MACHTYPE='amd64-portbld-freebsd11.1' 
-DCONF_VENDOR='portbld' -DLOCALEDIR='/usr/local/share/locale' -DPACKAGE='bash' 
-DSHELL  -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  
-DDEFAULT_PATH_VALUE='/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin'
  -DSTANDARD_UTILS_PATH='/sbin:/bin:/usr/sbin:/usr/bin' -DLIBICONV_PLUG 
-I/usr/local/include -O2 -pipe  -DLIBICONV_PLUG -fstack-protector 
-fno-strict-aliasing -Wno-parentheses -Wno-format-security
uname output: FreeBSD straasha.imrryr.org 11.1-RELEASE-p10 FreeBSD 
11.1-RELEASE-p10 #1 r333375M: Sat Jun 23 17:50:31 EDT 2018     
root@straasha.imrryr.org:/usr/obj/usr/src/sys/GENERIC  amd64
Machine Type: amd64-portbld-freebsd11.1

Bash Version: 4.4
Patch Level: 23
Release Status: release

Description:
        Intuitevely, (and confirmed behaviour of "csh" whose history
        substitution bash emulates), after a command of the form:

                $ grep foo <<EOF > /tmp/bar
                foobar
                abcdef
                EOF

        One would expect "!$" to be /tmp/bar, so that an immediate:

                $ wc -l !$

        should expand to "wc -l /tmp/bar" and output "1".

        Instead we get:

            $ PS1='$ '
            $ PS2=" "
            $ grep foo <<EOF > /tmp/bar
             foobar
             abcdef
             EOF
            $ cat !$ > /dev/tty
            cat 
             > /dev/tty
            abc
            abc
            123
            123
            <CTRL-D>
            $ history 3
                3  grep foo <<EOF > /tmp/bar
            foobar
            abcdef
            EOF

                4  cat 
             > /dev/tty
                5  history 3

        It looks like "!$" expands to the newline after the EOF in history 
entry 3.
        The expansion (as in "csh") should be "/tmp/bar".

Repeat-By:

        In interactive shell, expand "!$" after a command that uses a 
here-document:

        $ grep foo <<EOF > /tmp/bar
        foo
        EOF
        $ echo "--!$++"
        echo "--
        ++"
        --
        ++