Re: [BUG] emulate sh: arith assignment assigns variable type

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

On Fri, 01 Jan 2016 21:03:33 +0100
Martijn Dekker <martijn@inlv.org> wrote:
> When an assignment is done to an unset variable using an arithmetic
> expression, zsh assigns a numerical or arithmetic type to that variable,
> causing subsequent normal shell assignments to be interpreted as
> arithmetic expressions.

Yes, it does.

Does this need a special option?  The linkage is a bit tenouous.

diff --git a/Doc/Zsh/options.yo b/Doc/Zsh/options.yo
index f377539..b5e9100 100644
--- a/Doc/Zsh/options.yo
+++ b/Doc/Zsh/options.yo
@@ -2098,6 +2098,12 @@ When it is unset, zsh allows expressions of the form tt($#)var(name)
 to refer to the length of tt($)var(name), even for special variables,
 for example in expressions such as tt($#-) and tt($#*).
 
+Another difference is that with the option set assignment to an
+unset variable in artihmetic context causes the variable to be created
+as a scalar rather than a numeric type.  So after `tt(unset t; (( t = 3
+)))'. without tt(POSIX_IDENTIFIERS) set tt(t) has integer type and with
+it set it has scalar type.
+
 When the option is unset and multibyte character support is enabled (i.e. it
 is compiled in and the option tt(MULTIBYTE) is set), then additionally any
 alphanumeric characters in the local character set may be used in
diff --git a/Src/params.c b/Src/params.c
index 8cab969..054fb1f 100644
--- a/Src/params.c
+++ b/Src/params.c
@@ -3061,6 +3061,7 @@ setnparam(char *s, mnumber val)
 	if (ss)
 	    *ss = '\0';
 	pm = createparam(t, ss ? PM_ARRAY :
+			 isset(POSIXIDENTIFIERS) ? PM_SCALAR :
 			 (val.type & MN_INTEGER) ? PM_INTEGER : PM_FFLOAT);
 	if (!pm)
 	    pm = (Param) paramtab->getnode(paramtab, t);
diff --git a/Test/C01arith.ztst b/Test/C01arith.ztst
index c7bd81f..61da763 100644
--- a/Test/C01arith.ztst
+++ b/Test/C01arith.ztst
@@ -409,3 +409,14 @@
 >2
 >(eval):6: bad math expression: unexpected ')'
 >(eval):7: bad math expression: unexpected ')'
+
+  unset number
+  (( number = 3 ))
+  print ${(t)number}
+  unset number
+  (setopt posix_identifiers
+  (( number = 3 ))
+  print ${(t)number})
+0:type of variable when created in arithmetic context
+>integer
+>scalar