variables vs. TAB

[jidanni]

$ mkdir /tmp/some_dir
$ touch /tmp/some_dir/file
$ a=/tmp
$ cat $a/some<TAB> /tmp/some<TAB>

Note how the former TAB just gives
$a/some_dir<SPACE>            BUG!
Which SPACE one must replace with a / by hand to continue expanding like the 
latter.

Whilst the latter gives
/tmp/some_dir/
correctly.

bash:
  Installed: 4.2-5

Indeed,
$ aaaaaaa=/tmp
$ $aaa<TAB> also gives the bad behavior. It's as if it never occurred to
the authors these might be directories.