[sv-ac] substituting arguments with parentheses

Hi Folks:

One technical glitch that I have run into with 1549 involves
parenthesizing actual arguments before substituting them.

I wrote something about this in the Clause 16 changes for 
1549.  At that time I was thinking about whether adding parentheses
around "$" would result in illegal syntax.

I have since realized that we must not add parentheses around
an actual that is substituted for a variable_lvalue in a local 
variable update.

Here are some questions:

1. Are there actual arguments (like "$", for example) for which
   it is illegal to add parenthesize?  If so, are other delimiters
   appropriate?

2. What about "$"?  Is it really illegal to write

      a[*0:($)]

   ?

If the cases of "$" and substitution for the variable_lvalue are
the only exceptions, we can separate them out.  I am worried about
others that we are missing.

J.H.

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