C error when setting an optional alias type

[bbodi]

V doctor:

OS: windows, Microsoft Windows 11 Pro v22000 64-bit
Processor: 12 cpus, 64bit, little endian, Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz  

CC version: tcc version 0.9.27 (x86_64 Windows)

getwd: C:\dev\in_progress\vmarkdown
vmodules: C:\Users\sharp\.vmodules
vroot: C:\dev\misc\v
vexe: C:\dev\misc\v\v.exe
vexe mtime: 2022-08-22 14:59:54
is vroot writable: true
is vmodules writable: true
V full version: V 0.3.0 a689641

Git version: git version 2.34.1.windows.1
Git vroot status: Error: fatal: not a git repository (or any of the parent directories): .git
.git/config present: false
thirdparty/tcc: N/A

What did you do? v -g -o vdbg cmd/v && vdbg src/bug.v

type TreeIndex = usize

struct Node {
mut:
    next ?TreeIndex
}

fn main() {
	mut node := Node {}
	node.next = 0
}

What did you expect to see?

no C error

What did you see instead?

==================
C:/Users/sharp/AppData/Local/Temp/v_0/bug.2555758640680499064.tmp.c:7391: warning: cast between pointer and integer of different size
C:/Users/sharp/AppData/Local/Temp/v_0/bug.2555758640680499064.tmp.c:12283: error: cannot convert 'int' to 'struct _option_main__TreeIndex'
...
==================
(Use `v -cg` to print the entire error message)

builder error: 
==================
C error. This should never happen.

This is a compiler bug, please report it using `v bug file.v`.

https://github.com/vlang/v/issues/new/choose

You can also use #help on Discord: https://discord.gg/vlang

[bbodi]

The same happens when I use a struct instead of a type alias:

struct TreeIndex {index usize}

struct Node {
mut:
    next ?TreeIndex
}

fn main() {
	mut node := Node {}
	node.next = TreeIndex{0}
}

[JulienLecoq]

This is similar to: #14185 This does not work for any optional type. You can maybe rename your issue since it's not really about optional alias type.

[ghost]

struct Node {
mut:
	next ?usize
}

fn main() {
	mut node := Node {}
	node.next = 0
}

==================
/tmp/v_1000/bug.17695358547426339078.tmp.c:12107: error: cannot convert 'int' to 'struct _option_usize'
...
==================