Re: RFE: Fix the name collision issues and typing issues with namerefs, improve various issues for function libraries

[tetsujin]

I should add the related problem:

$ f() { declare -n x=$1; echo "x=$x"; declare y="local Y"; echo
"x=$x"; }
$ y="global Y"
$ f y
x=global Y
x=local Y

In other words, even if you do get a nameref to point to something in
the caller's scope, as soon as you shadow that variable with another
local variable, the nameref points to that one instead.
(As Greg pointed out, the name ref basically fails if the referenced
name is shared with any local variable in the function.)
This is arguably in line with the name of the feature ("nameref", i.e.
referencing the variable by name rather than by specific identity) but
I feel it's much more useful for a variable reference, once
established, to be stable.

To sum up a bit:

- There should be a way to declare a nameref locally in a function
which reliably refers to a variable in the caller's scope - IMO this
is the whole point of having a reference type, to get around the fact
that the language is otherwise pass-by-value.

- A nameref, once established, should refer to a particular name _in a
particular scope_. Shadowing the referenced variable with a new local
should not cause the nameref to switch to the new definition.

- Because Bash can create global namerefs from within a function,
creating a global nameref to a function-local variable should not be
allowed (because the global nameref would outlive the declaration it
references)