referencing interface object causes c error: pointer expected

[daansystems]

V version: V 0.4.9 535b04f, press to see full `v doctor` output

V full version	V 0.4.9 5c65e58.535b04f
OS	windows, Microsoft Windows 11 Pro 26100 64-bit
Processor	24 cpus, 64bit, little endian, AMD Ryzen 9 3900X 12-Core Processor
Memory	20.53GB/31.9GB
V executable	C:\v\v.exe
V last modified time	2025-02-02 09:32:13
V home dir	OK, value: C:\v
VMODULES	OK, value: C:\Users\info.vmodules
VTMP	OK, value: C:\Users\info\AppData\Local\Temp\v_0
Current working dir	OK, value: D:\vbug2
Git version	git version 2.42.0.windows.2
V git status	weekly.2025.1-155-g535b04f4-dirty
.git/config present	true
cc version	N/A
gcc version	N/A
clang version	clang version 17.0.1
msvc version	N/A
tcc version	tcc version 0.9.27 (x86_64 Windows)
tcc git status	thirdparty-windows-amd64 b425ac82
emcc version	N/A
glibc version	ldd (cygwin) 3.4.7

What did you do?
./v -g -o vdbg cmd/v && ./vdbg main.v && D:\vbug2\main.exe

module main

@[heap]
interface IGameObject {
mut:
	name     string
	parent   ?&IGameObject
	children []&IGameObject
	add_child(mut o IGameObject)
}

@[heap]
struct GameObject implements IGameObject {
mut:
	name     string
	parent   ?&IGameObject
	children []&IGameObject
}

fn (mut gameobject GameObject) add_child(mut o IGameObject) {
	o.parent = gameobject
	gameobject.children << o
}

fn main() {
	mut v1 := &GameObject{
		name: 'v1'
	}
	mut v2 := &GameObject{
		name: 'v2'
	}
	v1.add_child(mut v2)
	for child in v1.children {
		if child.parent != none {
			eprintln('parent: ${child.parent.name}')
		}
	}
}

What did you see?

================== C compilation error (from tcc): ==============
cc: C:/Users/info/AppData/Local/Temp/v_0/main.01JK329G1WXGW8DEKSJER12Z08.tmp.c:4117: warning: implicit declaration of function 'tcc_backtrace'
cc: C:/Users/info/AppData/Local/Temp/v_0/main.01JK329G1WXGW8DEKSJER12Z08.tmp.c:6898: error: pointer expected
... (the original output was 3 lines long, and was truncated to 2 lines)
=================================================================
(You can pass `-cg`, or `-show-c-output` as well, to print all the C error messages).
builder error: 
==================
C error found. It should never happen, when compiling pure V code.
This is a V compiler bug, please report it using `v bug file.v`,
or goto https://github.com/vlang/v/issues/new/choose .
You can also use #help on Discord: https://discord.gg/vlang .

What did you expect to see?

no c error

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[huly-for-github]

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