Variable casts from string to array but silently fails in reverse

[Jonathan Doull]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib
 -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4
-Wformat -Wformat-security -Werror=format-security -Wall
uname output: Linux moriarty 3.2.0-58-generic #88-Ubuntu SMP Tue Dec 3
17:37:58 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.2
Patch Level: 25
Release Status: release

Description:

Variables can be automatically cast from string to array.
However when cast from array to string, the cast silently fails.

Repeat-By:

Demonstraction script:

#-------------    SCRIPT START   ---------------
#!/bin/bash
function demonstrate_fail() {

    local something

    something=""                  # setting something to a string
    declare -p something

    something=(hello world now)   # setting something to an array
    declare -p something

    something=""                  # setting something to a string
    declare -p something          # UNEXPECTED BEHAVIOUR : something is
still an array

    something=1                   # setting something to an integer
    declare -p something          # UNEXPECTED BEHAVIOUR : first array
element is updated

}

demonstrate_fail
#-------------    SCRIPT END   ---------------

Fix:
 Using unset seems only workaround.