unclear error message about already registered struct

[kbkpbot]

Describe the bug

User don't known where is the previous defined struct's location.

Related to PR #26482

Reproduction Steps

err.v

module main

struct Error{}

v err.v

Expected Behavior

User should get some error message about that the Error is already defined in vlib/builtin/chan_option_result.v

Current Behavior

$ v err.v
err.v:3:8: error cannot register struct `Error`, another type with this name exists
    1 | module main
    2 |
    3 | struct Error{}
      |        ~~~~~
    4 |

Possible Solution

Fix error system

Additional Information/Context

No response

V version

V 0.5.0 ad9d912.30bfae1

Environment details (OS name and version, etc.)

V full version	V 0.5.0 ad9d912.30bfae1
OS	linux, Ubuntu 24.04.3 LTS
Processor	8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-9700 CPU @ 3.00GHz
Memory	12.06GB/15.51GB
V executable	/media/HD/github/kbkpbot/v/v
V last modified time	2026-02-01 06:02:06
V home dir	OK, value: /media/HD/github/kbkpbot/v
VMODULES	OK, value: /home/mars/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/mars/v/bug/err
Git version	git version 2.43.0
V git status	weekly.2025.52-352-gc53013b4
.git/config present	true
cc version	cc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
gcc version	gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
clang version	Ubuntu clang version 18.1.3 (1ubuntu1)
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.39-0ubuntu8.6) 2.39

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.