[bug#53878] [PATCH v3 09/15] gnu: Add racket-vm-cgc.

[Philip McGrath <philip@philipmcgrath.com>]

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Hi,

On Sunday, February 20, 2022 4:03:26 AM EST Liliana Marie Prikler wrote:
> So here's my suggestion:
> 
> Inside chez-and-racket-bootstrap, define (make-<package>) functions for
> the following:
> - chez-bootstrap-bootfiles, chez-for-racket-bootstrap-bootfiles:
>   Taking version and origin.
> - racket-vm-cgc: Taking version and origin.
> - racket-vm-bc: Taking racket-vm-cgc.
> - racket-vm-cs: Taking racket-vm-bc.
> 
> Inside chez, define chez-scheme, as well as non-bootstrapped versions
> of stex et al.
> Also define make-chez-scheme-for-racket, taking version and origin as
> parameter.  Finally, define chez-scheme-for-system, which uses
> (resolve-interface '(gnu packages racket)) to get racket's version and
> origin.
> 
> Inside racket, define %racket-version, %racket-origin, racket-minimal
> and racket.  It'd also be good if you made local definitions
> (define racket-vm-cgc (make-racket-vm-cgc %racket-version %racket-
> origin))
> (define racket-vm-bc (make-racket-vm-bc racket-vm-cgc))
> ...
> in this file.

My understanding—which is not very good!—is that this would have the same 
problem we do currently. It would be analogous to my example from
<https://issues.guix.gnu.org/53878#93>:

> But  Ludo’'s examples show that's wrong: those uses of `chez scheme` are in
> what the "expansion contexts" model would call "expression contexts".
> 
> Instead, I think rule № 2 prohibits any reference to a variable imported
> from
> another (gnu packages ...) module that will be evaluated when the (gnu
> packages ...) modules are—visited? instantiated? [2][3]—IDK when exactly,
> but, for practical purposes, any variable reference that is not underneath
> a lambda abstraction.
> 
> If that's right, IIUC, it would mean that:
>
>     (define chez-scheme-for-racket
>       (make-chez-scheme-for-racket ...))
> 
> would also be prohibited.
> 
> On the other hand, uses of `(racket-vm-for-system)` and `(chez-scheme-for-
> system)` in an `imports` field should still be fine, thanks to the implicit
> thunks.

The reference to `make-chez-scheme-for-racket` or `make-racket-vm-cs` or any 
such procedure defined in "chez-and-racket-bootstrap.scm" would be evaluated 
when "racket.scm" is instantiated—or whenever precisely it is that causes the 
problem.

-Philip

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