Keyword Aliasing Behaviour

Keyword Aliasing Behaviour

[Sean B. Palmer]

Using zsh 4.2.6, I note that keywords can be aliased. For example:

    alias in='test'

But then this gets expanded when the "in" keyword is used in a case:

   $ case $HOME in *) :;; esac
   zsh: parse error near `test'

I asked the #zsh IRC channel on Freenode, and a member there thought
it sounded like a bug and directed me to this mailing list. Can anyone
confirm that this is a bug, or is it a feature? If it's a bug, is it
fixed in a later version? If a feature, what is the rationale for it?

I notice that man zshall states that unless alias is provided with a
-g flag, making the alias global, the alias will only be expanded in a
command position. Since the "in" keyword in a case statement is not in
a command position, the behaviour I'm seeing appears to be erroneous.

The case $var { ... } syntax was suggested to me on #zsh, and is
useful but I probably shouldn't be rebinding keywords anyway.
Nevertheless, this was surprising behaviour.

Thanks,

--
Sean B. Palmer, http://inamidst.com/sbp/

Re: Keyword Aliasing Behaviour

[Peter Stephenson]

"Sean B. Palmer" wrote:
> Using zsh 4.2.6, I note that keywords can be aliased. For example:
> 
>     alias in='test'
> 
> But then this gets expanded when the "in" keyword is used in a case:
> 
>    $ case $HOME in *) :;; esac
>    zsh: parse error near `test'

This was certainly considered an error in the case of "for X in", so the
behaviour is inconsistent.  This fixes the case of "case".

Index: Src/parse.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/parse.c,v
retrieving revision 1.52
diff -u -r1.52 parse.c
--- Src/parse.c	7 Mar 2006 21:31:22 -0000	1.52
+++ Src/parse.c	26 Mar 2006 18:52:11 -0000
@@ -1023,6 +1023,7 @@
 par_case(int *complex)
 {
     int oecused = ecused, brflag, p, pp, n = 1, type;
+    int ona, onc;
 
     p = ecadd(0);
 
@@ -1033,14 +1034,23 @@
     ecstr(tokstr);
 
     incmdpos = 1;
+    ona = noaliases;
+    onc = nocorrect;
+    noaliases = nocorrect = 1;
     yylex();
     while (tok == SEPER)
 	yylex();
     if (!(tok == STRING && !strcmp(tokstr, "in")) && tok != INBRACE)
+    {
+	noaliases = ona;
+	nocorrect = onc;
 	YYERRORV(oecused);
+    }
     brflag = (tok == INBRACE);
     incasepat = 1;
     incmdpos = 0;
+    noaliases = ona;
+    nocorrect = onc;
     yylex();
 
     for (;;) {

-- 
Peter Stephenson <p.w.stephenson@ntlworld.com>
Web page still at http://www.pwstephenson.fsnet.co.uk/