Bash local nameref declaration does not work

Question

I am trying to set a local variable in a function with nameref.

The script code is the following:

#!/usr/bin/bash
msg=hello
myparam=''

superfunc () {
productfile=$1
local -n refmyparam=$2
}

superfunc $msg $myparam
echo $myparam

When running it I get the error:

 line 7: local: `': not a valid identifier

We use GNU bash, version 5.2.21

Answer 1

local -n and declare -n need a variable name as their value, not its value.

Also, creating a local reference variable doesn't change the original variable. You need to change the reference variable to see how the change propagates back to the original:

#!/bin/bash
msg=hello
myparam=''

superfunc () {
    productfile=$1
    local -n refmyparam=$2
    refmyparam=changed     # Modify the local variable.
}

superfunc $msg myparam     # No dollar sign for $2!
echo $myparam              # Changed!