Compiler bug: math operation with number|string|any with a function that return void causes C error instead of type error

[AQMpolyface]

V version: V 0.4.9 87b1de8, press to see full `v doctor` output

V full version	V 0.4.9 f83af8a.87b1de8
OS	linux, "CachyOS"
Processor	16 cpus, 64bit, little endian, AMD Ryzen 7 Pro 7735U with Radeon Graphics
Memory	2.82GB/30.12GB
V executable	/home/polyface/git/v/v
V last modified time	2025-03-19 15:28:03
V home dir	OK, value: /home/polyface/git/v
VMODULES	OK, value: /home/polyface/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/polyface/Documents/v/bug
Git version	git version 2.49.0
V git status	weekly.2025.12-6-g87b1de82
.git/config present	true
cc version	cc (GCC) 14.2.1 20250207
gcc version	gcc (GCC) 14.2.1 20250207
clang version	clang version 19.1.7
tcc version	tcc version 0.9.28rc 2024-07-31 HEAD@1cee0908 (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 0134e9b9
emcc version	N/A
glibc version	ldd (GNU libc) 2.41

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

module main

fn main() {
	a := 1 / println('')
}

What did you see?

src/main.v:4:2: warning: unused variable: `a`
    2 | 
    3 | fn main() {
    4 |     a := 1 / println('')
      |     ^
    5 | }
================== C compilation error (from tcc): ==============
cc: /tmp/v_1000/main.01JPQG9QA1CVBXSRKHXKXJNW00.tmp.c:1897: error: declaration of void object
=================================================================
(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 .

What did you expect to see?

compiler: mismatched types int literal and void

notes:
this also gets an error, so its not only bultin functions, or ints.

module main

fn main() {
	a := 1 - do_somth()
}

fn do_somth() {
	println('as')
}

You get a correct error when puttinf the function before 1 like

	a := do_somth() - 1 

give the correct error

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[huly-for-github]

Connected to Huly®: V_0.6-22371

[JalonSolov]

V should definitely give you a better error message.

The problem is that println is a void function (it doesn't return anything at all), so you are essentially dividing by 0.

[jorgeluismireles]

As I understand the problem is that while println('') + 1 gives V error (void + int) as it should, reversing the sum as 1 + println('') gives C error instead V's (int + void).

fn main() {
	//_ := println('') + 1 // gives V error
	_ := 1 + println('') // gives C error
}

[AQMpolyface]

exactly. Sorry if it wasnt clear

[Delta456]

This is the only with inbuilt functions like println.

It can be replicated with all void types