c error while trying to map it.wait() on a thread of arrays

[not-ivy]

V doctor:

V full version: V 0.4.4 ac2dcc2
OS: linux, "Arch Linux"
Processor: 16 cpus, 64bit, little endian, 12th Gen Intel(R) Core(TM) i7-1260P

getwd: /home/nora/Documents/foxglove-world/fox
vexe: /usr/lib/vlang/v
vexe mtime: 2024-03-16 22:23:00

vroot: NOT writable, value: /usr/lib/vlang
VMODULES: OK, value: /home/nora/.vmodules
VTMP: OK, value: /tmp/v_60271

Git version: git version 2.44.0
Git vroot status: Error: fatal: not a git repository (or any of the parent directories): .git
.git/config present: false

CC version: cc (GCC) 13.2.1 20230801
thirdparty/tcc: N/A

What did you do?
v run .

module cmds

import os
import cli
import net.urllib

pub fn sync() cli.Command {
	return cli.Command{
		name: 'sync'
		description: 'sync local dens from remote'
		execute: execsync
	}
}

fn execsync(cmd cli.Command) ! {
	dens := os.read_lines('/etc/fox/dens')!.map(urllib.parse(it)!)
	mut threads := []thread !{}
	for den in dens {
		threads << spawn update(den)
	}
	threads.map(it.wait()!)
}

fn update(den urllib.URL) ! {
	println(den.str())
	return
}

What did you expect to see?

code works as expected

What did you see instead?

==================
/tmp/v_60271/fox.6109388202681245468.tmp.c:24611: error: declaration of void object
...
==================
(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

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[not-ivy]

using regular for..in loop works fine, like the following

fn execsync(cmd cli.Command) ! {
	dens := os.read_lines('/etc/fox/dens')!.map(urllib.parse(it)!)
	mut threads := []thread !{}
	for den in dens {
		threads << spawn update(den)
	}
	for t in threads {
		t.wait()!
	}
}

[felipensp]

It looks like the issue treated in the PR #21011 @Delta456

[not-ivy]

still reproducible on bedaf4f

$ v version
V 0.4.4 bedaf4f
$ v run .
==================
/tmp/v_60271/fox.01HS74DVJRND7H5QXD8NTT79NT.tmp.c:25208: error: declaration of void object
...
==================
(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

[Delta456]

It looks like the issue treated in the PR #21011 @Delta456

My PR handles for ast.LambdaExpr

[Delta456]

I assume this should be a checker error because Result needs an or value right? @felipensp

[JalonSolov]

Yes. Since Result type can be no return at all, it cannot work in .map() calls. Just like the other error where someone was trying to use .map(println('something')). That one was easier to see, but it's the same type of problem - if there's no return value (which there isn't if an error happens), then you can't use it in .map().

The only way to do this is to force a valid type using an or block.