Re: wrong variable name in error message about unbound variable?

[Christoph Anton Mitterer]

On Tue, 2023-10-17 at 00:26 -0400, Grisha Levit wrote:
> The array subscript can an arbitrary arithmetic expression with side
> effects, so it makes sense to perform the expansion even if the array
> whose subscript is being expanded is unset:

Okay... that's all pretty convoluted. I assume it boils down to the
idea that a variable that's not an associative array may become
automatically an indexed array, right?


As Lawrence pointed out:
$ set -u 
$ declare -A a
$ echo ${a[k]}
bash: a[k]: unbound variable

Here it actually looks first at a (which turns out to be an associative
array) and thus doesn't even bother to evaluate k, which makes sense of
course, in order to avoid any side effects.


Here, when a is still undeclared it still makes "sense" to evaluate the
subscript, as a may even become a declared indexed array while doing
so:
$ set -u
$ declare -p a
bash: declare: a: not found
$ echo ${a[a[4]=0]}
bash: a[a[4]=0]: unbound variable
$ declare -p a
declare -a a=([4]="0")

okay, makes sense to me. But:
$ set -u
$ declare -p a
bash: declare: a: not found
$ echo ${a[a[4]=4]}
bash: a[a[4]=4]: unbound variable
$ declare -p a
declare -a a=([4]="4")

Why does it say unbound here?
a[4]=4 should evaluate to 4 and also set the index 4, right?



Cheers,
Chris.