cgen error for generic fn with `mut x ?Type` argument, when an array is passed

[spytheman]

V version: V 0.4.10 a8a4507, press to see full `v doctor` output

V full version	V 0.4.10 dd083e7.a8a4507
OS	linux, Ubuntu 20.04.6 LTS
Processor	4 cpus, 64bit, little endian, Intel(R) Core(TM) i3-3225 CPU @ 3.30GHz
Memory	4.84GB/15.05GB
V executable	/home/delian/v/v
V last modified time	2025-04-01 11:15:55
V home dir	OK, value: /home/delian/v
VMODULES	OK, value: /home/delian/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/delian/v
env VFLAGS	"-no-parallel"
Git version	git version 2.48.1
V git status	weekly.2025.13-40-ga8a45072
.git/config present	true
cc version	cc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
gcc version	gcc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
clang version	clang version 10.0.0-4ubuntu1
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.31-0ubuntu9.16) 2.31

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

fn main() {
	mut arr := []int{}
	mut bbb := unwrap(mut arr)
	bbb << 1
	dump(bbb)
}
fn unwrap[T](mut t ?T) T {
	return t or { panic('unexpected `none`') }
}

What did you see?

================== C compilation error (from tcc): ==============
cc: /tmp/v_1000/xx.01JQRH1JDP41ZXN4HD3KAKE80K.tmp.c:6008: error: cannot convert 'struct array *' to 'struct _option_Array_int_ptr'
=================================================================
(You can pass `-cg`, or `-show-c-output` as well, to print all the C error messages).

What did you expect to see?

a compiled program

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[huly-for-github]

Connected to Huly®: V_0.6-22492

[jorgeluismireles]

Running the same code in playground V 0.4.12 6cbd1e3 gives this error:

Running code...
Can't run code. The server returned an error:
/box/code.v:4: warning: implicit declaration of function 'builtin___option_ok'
/box/code.v:3: warning: assignment from incompatible pointer type
/home/admin/v/thirdparty/tcc/lib/libgc.a: error: 'GC_noop1_ptr' defined twice
tcc: error: undefined symbol 'builtin___option_ok'
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 .
Exited with error status 1
Please try again.

[felipensp]

File an issue case you can reproduce it on latest V.

…

On Mon, Oct 13, 2025 at 9:24 PM Jorge Mireles ***@***.***> wrote: *jorgeluismireles* left a comment (vlang/v#24101) <#24101 (comment)> Running the same code in playground V 0.4.12 6cbd1e3 <6cbd1e3> gives this error: Running code... Can't run code. The server returned an error: /box/code.v:4: warning: implicit declaration of function 'builtin___option_ok' /box/code.v:3: warning: assignment from incompatible pointer type /home/admin/v/thirdparty/tcc/lib/libgc.a: error: 'GC_noop1_ptr' defined twice tcc: error: undefined symbol 'builtin___option_ok' 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 . Exited with error status 1 Please try again. — Reply to this email directly, view it on GitHub <#24101 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAF46O6CQ6QLRSOEJT275E33XQ7DVAVCNFSM6AAAAAB2GTZDDKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJZGUYDEMRRGQ> . You are receiving this because you were assigned.Message ID: ***@***.***>

-- Att, Felipe Pena