Completion with -W fails if words contain ':'

[Keith Thompson]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2 -Werror=implicit-function-declaration
-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -flto=auto
-ffat-lto-objects -fstack-protector-strong -fstack-clash-protection
-Wformat -Werror=format-security -fcf-protection -Wall
uname output: Linux sal 6.11.0-9-generic #9-Ubuntu SMP PREEMPT_DYNAMIC
Mon Oct 14 13:19:59 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.2
Patch Level: 32
Release Status: release

Description:
If the wordlist given to `complete -W` includes words
    containing the ':' character, completion misbehaves.

    The problem seems to occur if two or more words in the wordlist
    share a common prefix ending with ':'.  The problem does not
    occur with other characters; I've tried '/' and '_'.

Repeat-By:
    Execute the following commands:

    say() { echo "$@" ; }
    complete -W "abc:abc abc:xyz" say

    Type "say " at the prompt, then type <TAB> repeatedly.

    Each <TAB> character appends "abc:" to the argument.

    It should append "abc:" the first time, then offer a choice
    between "abc:abc" and "abc:xyz".