cgen: direct assigning string to ?string with -autofree

[MCausc78]

Describe the bug

title

Reproduction Steps

struct Attr {
	name    string
	has_arg bool
	arg     string
}

fn main() {
	mut m := ?string(none)
	attrs := [Attr{'foo', false, 'bar'}, Attr{'baz', true, 'qux'}]
	for attr in attrs {
		if attr.name == 'baz' && attr.has_arg {
			m = attr.arg
		}
	}
	println(m)
}

run with -autofree

Expected Behavior

PS D:\Games\Proekti\V\interactions> v -autofree run test.v
Option('qux')

Current Behavior

PS D:\Games\Proekti\V\interactions> v -autofree test.v
==================
C:/Users/mclr/AppData/Local/Temp/v_0/test.01HQXW2JYMT0R4K06RTW1Q7TDN.tmp.c:6771: warning: implicit declaration of function 'tcc_backtrace'
C:/Users/mclr/AppData/Local/Temp/v_0/test.01HQXW2JYMT0R4K06RTW1Q7TDN.tmp.c:13028: error: cannot convert 'struct string' to 'struct _option_string'
...
==================
(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

PS D:\Games\Proekti\V\interactions> 

Possible Solution

No response

Additional Information/Context

generated C code with -autofree:

VV_LOCAL_SYMBOL void main__main(void) {
	_option_string m = (_option_string){ .state=2, .err=_const_none__, .data={EMPTY_STRUCT_INITIALIZATION} };
	Array_main__Attr attrs = new_array_from_c_array(2, 2, sizeof(main__Attr), _MOV((main__Attr[2]){((main__Attr){.name = /*clone1*/_SLIT("foo"),.has_arg = false,.arg = /*clone1*/_SLIT("bar"),}), ((main__Attr){.name = /*clone1*/_SLIT("baz"),.has_arg = true,.arg = /*clone1*/_SLIT("qux"),})}));
	for (int _t1 = 0; _t1 < attrs.len; ++_t1) {
		main__Attr attr = ((main__Attr*)attrs.data)[_t1];
		if (string__eq(attr.name, _SLIT("baz")) && attr.has_arg) {
			m =  string_clone_static(attr.arg);
		}
	}
	println(_option_string_str(m));
	array_free(&attrs); // autofreed var main false
}

Without:

VV_LOCAL_SYMBOL void main__main(void) {
	_option_string m = (_option_string){ .state=2, .err=_const_none__, .data={EMPTY_STRUCT_INITIALIZATION} };
	Array_main__Attr attrs = new_array_from_c_array(2, 2, sizeof(main__Attr), _MOV((main__Attr[2]){((main__Attr){.name = _SLIT("foo"),.has_arg = false,.arg = _SLIT("bar"),}), ((main__Attr){.name = _SLIT("baz"),.has_arg = true,.arg = _SLIT("qux"),})}));
	for (int _t1 = 0; _t1 < attrs.len; ++_t1) {
		main__Attr attr = ((main__Attr*)attrs.data)[_t1];
		if (string__eq(attr.name, _SLIT("baz")) && attr.has_arg) {
			_option_string _t2;
			_option_ok(&(string[]) { attr.arg }, (_option*)(&_t2), sizeof(string));
			m = _t2;
		}
	}
	println(_option_string_str(m));
}

V version

V 0.4.4 febc4a7

Environment details (OS name and version, etc.)

V full version: V 0.4.4 57a33c3.febc4a7
OS: windows, Microsoft Windows 11 Pro v22000 64-bit
Processor: 12 cpus, 64bit, little endian, 

getwd: D:\Games\Proekti\V\interactions
vexe: D:\Games\Proekti\V\v\v.exe
vexe mtime: 2024-03-01 20:41:30

vroot: OK, value: D:\Games\Proekti\V\v
VMODULES: OK, value: C:\Users\mclr\.vmodules
VTMP: OK, value: C:\Users\mclr\AppData\Local\Temp\v_0

Git version: git version 2.37.0.windows.1
Git vroot status: weekly.2024.07-80-gfebc4a7e
.git/config present: true

CC version:
thirdparty/tcc status: thirdparty-windows-amd64 a39eb79b

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