bug#42601: Guix install bug: error: Unbound variable: ~S

[Ricardo Wurmus]

Jan Wielkiewicz <tona_kosmicznego_smiecia@interia.pl> writes:

> Dnia 2020-07-29, o godz. 22:17:01
> Ricardo Wurmus <rekado@elephly.net> napisał(a):
>
>> 
>> “avr-toolchain” is a procedure, not a package.  Use
>> “avr-toolchain-4.9” or “avr-toolchain-5”.
>> 
>
> Success!
>
> What about the strange message though?
> "incorrect package definition" would be better.

“Unbound variable: ~S” looks like a format string with a placeholder
that didn’t get replaced with an actual value.  It would be marginally
better if it said “Unbound variable: avr-toolchain”.

We should, I think, take advantage of the fact that the type of inputs
is known: it can only be an origin or a package value.  Perhaps we can
catch unbound variables in inputs and print a more valuable error
message.

-- 
Ricardo