Opinions wanted: What should (.list pmacro-name 42) do?

[Doug Evans]

Doug Evans wrote:
> Hi.
>
> What should the output of
>
> (define-pmacro (foo a) (add a 1))
> (.list foo 42)
>
> be?
>
> Currently the result is (<pmacro> 42)
> where <pmacro> is the pmacro object for "foo".
>
> It's not ideal because it means that a pmacro object "escapes" 
> pmacro-processing and can be seen by, for example, rtl compilation.
>
> However, it's not that unexpected.  The user asked for a list 
> containing two objects, the pmacro and 42.
> This is akin to saying (list + 42) in Scheme.
>
> We *could* have the pmacro evaluator re-examine the result and if it 
> sees (<pmacro> mumble) then re-expand it.  That's what we do for 
> symbols today (i.e. if the result of pmacro-expansion is a symbol that 
> names a pmacro, we re-evaluate it), but that has problems, e.g.
> http://sourceware.org/ml/cgen/2009-q3/msg00052.html
> and I'm leaning toward removing that behavior.
>
> It's not clear to me what The Right Thing to do is.
> Opinions?
>

[For completeness' sake ...]
An alternative is of course to flag any pmacros that "escape" as 
errors.  We need to do that anyway for cases like (.list 42 foo).