Optional type matches incorrectly in $for field

[jcweaver997]

Describe the bug

Accessing optional field in compile time code causes C error

Reproduction Steps

module main

interface TestInterface {
	test_func() f64
}

struct Struct1 {
	num f64
}

fn (o &Struct1) test_func() f64 {
	return o.num
}

struct Struct2 {
	s1 ?&Struct1
}

fn do_thing[T]() T {
	t := T{}
	$for field in T.fields {
		$if field.typ is TestInterface {
			i := TestInterface(t.$(field.name))
			println('${i.test_func()}')
		}
	}
	return t
}

pub fn main() {
	do_thing[Struct2]()
}

Expected Behavior

no C error

Current Behavior

C error:

PS C:\Users\jcwea\Documents\git\vtest> v run .
==================
C:/Users/jcwea/AppData/Local/Temp/v_0/vtest.01HQPQ5SW9NC7GKNV47M8KWAVT.tmp.c:6995: warning: implicit declaration of function 'tcc_backtrace'
C:/Users/jcwea/AppData/Local/Temp/v_0/vtest.01HQPQ5SW9NC7GKNV47M8KWAVT.tmp.c:13239: error: cannot convert 'struct _option_main__Struct1_ptr' to 'struct main__Struct1 *'
...
==================
(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

Possible Solution

The best solution is probably to not match ?T's with $if field.typ is T, thus never calling the code in the $if statement. But we would likely still want to be able to match these optional field types somehow, maybe with a $if field.underlying_typ is T or something similar. I image it could work the same way as unwrapping an alias or a sum type during compile time.

Additional Information/Context

affects vgdextension

V version

V 0.4.4 7df5646

Environment details (OS name and version, etc.)

V full version: V 0.4.4 1733dab.7df5646
OS: windows, Microsoft Windows 11 Pro v26058 64-bit
Processor: 24 cpus, 64bit, little endian, 

getwd: C:\Users\jcwea\Documents\git\vtest
vexe: C:\Users\jcwea\Documents\git\v\v.exe
vexe mtime: 2024-02-27 22:26:52

vroot: OK, value: C:\Users\jcwea\Documents\git\v
VMODULES: OK, value: C:\Users\jcwea\.vmodules
VTMP: OK, value: C:\Users\jcwea\AppData\Local\Temp\v_0

Git version: git version 2.40.0.windows.1
Git vroot status: weekly.2024.09-4-g7df56462
.git/config present: true

CC version: Error: 'cc' is not recognized as an internal or external command,
operable program or batch file.

thirdparty/tcc status: thirdparty-windows-amd64 b99a453d

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