cgen error - unwrapping an option field in a struct doesn't seem to unwrap it correctly

[el-gringo]

Describe the bug

Unwrapping an option field in a struct doesn't seem to be correctly unwrapped.

Reproduction Steps

Code: https://play.vlang.io/p/5b48070739

struct LayoutTree {
    mut:
        root ?usize
}

fn LayoutTree.new() LayoutTree {
    return LayoutTree {
        root: ?usize(none)
    }
}

fn test1() {
	root := usize(1)
	mut list := []usize {}
	list << root
	println("list: ${list}")
}

fn test2() {
	mut tree := LayoutTree.new()
	mut list := []usize {}
	tree.root = ?usize(1)
	println("tree.root: ${tree.root}")
	if tree.root != none {
		println("is not none: ${tree.root}")
    	list << tree.root
		println("parents ${list}")
	}
}

fn test3() {
	mut tree := LayoutTree.new()
	mut list := []usize {}
	tree.root = ?usize(1)
	// extract root in an other variable before unwrapping
    root := tree.root
	println("tree.root: ${root}")
	if root != none {
		println("is not none: ${root}")
    	list << root
		println("parents ${list}")
	}
}

fn main() {
	test1() // pass
	test2() // fail
	test3() // pass
}

Expected Behavior

Unwrapping an option field in a struct with if should not ask to unwrap it again

Current Behavior

Output:

code.v:26:11: error: unwrapped Option cannot be used in an infix expression
   24 |     if tree.root != none {
   25 |         println("is not none: ${tree.root}")
   26 |         list << tree.root
      |              ~~
   27 |         println("parents ${list}")
   28 |     }
Exited with error status 1

Possible Solution

Extracting the struct option field in a variable, then unwrap it with a if.

struct LayoutTree {
    mut:
        root ?usize
}

fn LayoutTree.new() LayoutTree {
    return LayoutTree {
        root: ?usize(none)
    }
}

fn main() {
	mut tree := LayoutTree.new()
	mut list := []usize {}
	tree.root = ?usize(1)
	// extract root in an other variable before unwrapping
    root := tree.root
	println("tree.root: ${root}")
	if root != none {
		println("is not none: ${root}")
    	list << root
		println("parents ${list}")
	}
}

Additional Information/Context

No response

V version

V 0.4.8 f1333be.5bba92a

Environment details (OS name and version, etc.)

V full version: V 0.4.8 f1333be.5bba92a
OS: linux, Debian GNU/Linux 12 (bookworm) (VM)
Processor: 2 cpus, 64bit, little endian, Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz

getwd: /home/admin/playground
vexe: /home/admin/v/v
vexe mtime: 2024-11-17 18:25:30

vroot: OK, value: /home/admin/v
VMODULES: OK, value: .vmodules
VTMP: OK, value: /tmp/v_0

Git version: git version 2.39.5
Git vroot status: Error: fatal: detected dubious ownership in repository at '/home/admin/v'
To add an exception for this directory, call:

	git config --global --add safe.directory /home/admin/v
.git/config present: true

CC version: cc (Debian 12.2.0-14) 12.2.0
emcc version: N/A
thirdparty/tcc status: Error: fatal: detected dubious ownership in repository at '/home/admin/v/thirdparty/tcc'
To add an exception for this directory, call:

	git config --global --add safe.directory /home/admin/v/thirdparty/tcc
 Error: fatal: detected dubious ownership in repository at '/home/admin/v/thirdparty/tcc'
To add an exception for this directory, call:

	git config --global --add safe.directory /home/admin/v/thirdparty/tcc

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_{Huly®: V_0.6-21335}

[spytheman]

The original cgen error was caused by this code:

import datatypes { DoublyLinkedList }

pub type LayoutBoxId = usize;
pub struct LayoutBox {
}

pub struct LayoutTree {
    mut:
        root ?LayoutBoxId
        boxes []LayoutBox
}


pub fn LayoutTree.new() LayoutTree {
    return LayoutTree {
        root: ?LayoutBoxId(none),
        boxes: []LayoutBox {},
    }
}

fn main() {
	mut tree := LayoutTree.new()
	tree.root = 1
	println("tree: ${tree}")
	if tree.root != none {
		println("is not none")
		mut parents := DoublyLinkedList[LayoutBoxId] {}
    	parents.push_back(tree.root)
		println("parents ${parents}")
	}
}

From: https://play.vlang.io/p/7fc4324df7

[felipensp]

The selector option unwrap was not implemented yet.