POSIX: reserved words should not expand into aliases

POSIX: reserved words should not expand into aliases

[Ravi (Tom) Hale]

The [POSIX Shell Command Language section 
2.3.1](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_03_01) 
says:

 > However, reserved words in correct grammatical context shall not be 
candidates for alias substitution.

It seems that both `{ba,z}sh` have a bug here.

How do I access a reserved word if an alias is hiding it?

Here `if` works normally:

     % if : ; then echo true; fi
     true

After aliasing `if`:

     % alias if=date
     % if : ; then echo true; fi
     zsh: parse error near `then'

Prefixing with `builtin` or `\` doesn't help:

     % builtin if : ; then echo true; fi
     zsh: parse error near `then'
     % \if : ; then echo true; fi
     zsh: parse error near `then'

How do I access a reserved word in the pathological case that it hidden 
by an alias?


Prior art: https://unix.stackexchange.com/q/456408/143394

Re: POSIX: reserved words should not expand into aliases

[dana]

On 15 Jul 2018, at 07:16, Ravi (Tom) Hale <ravi@hale.ee> wrote:
>It seems that both `{ba,z}sh` have a bug here.
>
>How do I access a reserved word if an alias is hiding it?

http://zsh.sourceforge.net/Doc/Release/Options.html#Shell-Emulation

>POSIX_ALIASES <K> <S>
>When this option is set, reserved words are not candidates for alias expansion:
>it is still possible to declare any of them as an alias, but the alias will
>never be expanded. Reserved words are described in Reserved Words.

dana