Optional Function returns break everything

[shininglove]

V doctor:

V full version: V 0.4.7 63957f2.3307340
OS: linux, Ubuntu 24.04.1 LTS

getwd: ~/vlang/option_bug_maybe
vexe: ~/vlang/v/v
vexe mtime: 2024-09-21 23:21:32

vroot: OK, value: ~/vlang/v
VMODULES: OK, value: ~/.vmodules
VTMP: OK, value: /tmp/v_1000

Git version: git version 2.43.0
Git vroot status: weekly.2024.37-36-g33073407
.git/config present: true

CC version: cc (Ubuntu 13.2.0-23ubuntu4) 13.2.0
thirdparty/tcc status: thirdparty-linux-amd64 0134e9b9

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

module main

type DataFn = fn (name string) string

fn which_lang(name string) string {
	return name
}

fn find_func(name string) ?DataFn {
	return match name {
		'vlang' { which_lang }
		else { none }
	}
}

fn main() {
	req := find_func('vlang')
	fun := req('options')
	println(fun)
}

What did you expect to see?

a print of 'options'

What did you see instead?

================== C compilation error (from tcc): ==============
cc: /tmp/v_1000/main.01J8BE9J6F2YCCRKS27WSRJ220.tmp.c:13346: error: lvalue expected
=================================================================
(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 .

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[spytheman]

A workaround could be:

module main

type DataFn = fn (name string) string

struct Wrapper {
    f DataFn = unsafe { nil }
}

fn which_lang(name string) string {
    return name
}

fn find_func(name string) ?Wrapper {
    return match name {
        'vlang' { Wrapper{ f: which_lang } }
        else { none }
    }
}

fn main() {
    req := find_func('vlang')
    fun := req?.f('options')
    println(fun)
}