"local -g" declaration references local var in enclosing scope

[Adrian Ho]

[Apologies, an earlier edition of this bug report was sent from the address
aho@lex.03s.net, which can only be replied to from my internal network.
Please ignore that report. Thanks much!]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc-11
Compilation CFLAGS: -DSSH_SOURCE_BASHRC
uname output: Linux lex 6.5.0-25-generic #25-Ubuntu SMP PREEMPT_DYNAMIC Wed
Feb  7 14:58:39 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.2
Patch Level: 26
Release Status: release

Description:
        "local -g var" incorrectly references a local variable in an
enclosing scope, while "local -g var=val" correctly references and modifies
the global variable.

Repeat-By:
        Test script:

#!/usr/bin/env bash
echo "Bash version: $BASH_VERSION"

b() {
  local -g a=2
  c
}
c() {
  local -g a
  a=3
}

y() {
  local z=1
  x
}
x() {
  local -g z=2
  w
}
w() {
  local -g z
  echo "w: z=$z"
  z=3
}

b; y
echo "a=$a z=$z"

        Expected output:

Bash version: 5.2.26(1)-release
w: z=2
a=3 z=3

        Actual output:

Bash version: 5.2.26(1)-release
w: z=1
a=3 z=2