Re: question regarding substitute* and #t

[Arun Isaac <arunisaac@systemreboot.net>]

Mark H Weaver <mhw@netris.org> writes:

> After we switch to using 'invoke' everywhere, or more precisely, after
> we arrange to never return #false from any phase or snippet, then
> there should be one more step before removing the vestigial #true
> returns: we should change the code that calls phases or snippets to
> ignore the value(s) returned by those procedures.  When that is done,
> then the #t's will truly be vestigial.  Does that make sense?

I think we should start removing the vestigial #true right away. Why
wait until we can make the code that calls phases ignore the values
returned by those phases? As it stands, that code errors out only when a
phase returns #false, not when it returns any other value (even
unspecified). WDYT?

The #true is already vestigial. In fact, #true being vestigial is what
annoyed me and made me start the original thread discussing ways to get
rid of it.

https://lists.gnu.org/archive/html/guix-devel/2017-12/msg00235.html

And, it so happened that we concluded the best way to go forward was to
deprecate boolean results altogether and transition to an exception
based system.