time keyword evaluates following command's (builtin) argument

[Anti Räis]

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../. -I.././include -I.././lib
-Wdate-time -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat
-Werror=format-security -Wall
uname output: Linux x 4.13.0-26-generic #29~16.04.2-Ubuntu SMP Tue Jan 9
22:00:44 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.3
Patch Level: 48
Release Status: release

Description:
    Bash unexpectedly evaluates a builtin command argument when it is
executed after `time` keyword. This does not happen when the builtin
command is executed at later time or with different type of argument.

Repeat-By:
    Following bash script will trigger the issue.

    --------------------[script start]--------------------
    #!/bin/bash

    if [ "$0" = "$BASH_SOURCE" ]; then
            echo "source $0 <cmd>"
            exit
    fi

    if [ ! "$#" = 1 ]; then
            echo "[*] missing argument"
            return
    fi

    alias exp='"$($1)"'
    echo "[*] type exp: $(type exp)"
    echo "[*] executing command: $1"
    set -o xtrace

    echo exp
    time
    echo exp
    echo exp
    --------------------[script end  ]--------------------

    Example output when the issue occurs:

    --------------------[output start]--------------------
    $ source ./bashexp.sh "date"
    [*] type exp: exp is aliased to `"$($1)"'
    [*] executing command: date
    ++ echo exp
    exp

    real    0m0.000s
    user    0m0.000s
    sys     0m0.000s
    +++ date
    ++ echo 'T jaan  16 10:29:24 EET 2018'
    T jaan  16 10:29:24 EET 2018
    ++ echo exp
    exp
    --------------------[output end  ]--------------------

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