语法正确的函数定义失败 (alias 的陷阱)

引用:

-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=0] ; cat rc-2
foo()
{
    echo This is function foo
}
-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=0] ; source rc-2
-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=0] ; foo
This is function foo
-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=0] ; cat rc-1
ls()
{
    echo This is function ls
}
-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=0] ; source rc-1
bash: rc-1: line 1: syntax error near unexpected token `('
bash: rc-1: line 1: `ls()'
-(dearvoid@LinuxEden:Forum)-(~/tmp)-
[$$=6362 $?=1] ; bye

引用:

-(dearvoid@LinuxEden:Forum)-(~/void/bash)-
[$$=7463 $?=0] ; cat confusing-aliases-2.sh
#!/bin/bash

shopt -s expand_aliases

alias foo='echo hello world'

#
# The following definition is the same as this:
#
#   echo hello world()
#   {
#       builtin echo 'this is a function'
#   }
#
# It will cause syntax error.
#
foo()
{
    builtin echo 'this is a function'
}

foo
-(dearvoid@LinuxEden:Forum)-(~/void/bash)-
[$$=7463 $?=0] ; ./confusing-aliases-2.sh
./confusing-aliases-2.sh: line 17: syntax error near unexpected token `('
./confusing-aliases-2.sh: line 17: `foo()'
-(dearvoid@LinuxEden:Forum)-(~/void/bash)-
[$$=7463 $?=2] ; bye