`checker`: `?&T` cannot be compared to `nil` even inside a comptime `$if T.indirections != 0` branch

[enghitalo]

Describe the bug

The checker rejects a comptime-guarded val == unsafe { nil } comparison when val has type ?&T, even though the $if T.indirections != 0 branch only fires because the option's payload is a pointer. The diagnostic says "unwrap the option first", but inside the comptime branch the program already knows the payload is a pointer — the option wrapper should not block the nil comparison.

Reproduction Steps

struct Tag {
	id     string
	parent ?&Tag
}

fn is_nil_field[T](val T) bool {
	$if T.indirections != 0 {
		return val == unsafe { nil }
	}
	return false
}

fn main() {
	t := Tag{}
	$for f in Tag.fields {
		println(is_nil_field(t.$(f.name)))
	}
}

Expected Behavior

Compiles. Prints false for id (string is not pointer-typed, falls into return false) and true for parent (option is none).

Current Behavior

error: `?Tag` cannot be used as `nil`, unwrap the option first
   8 |         return val == unsafe { nil }
     |                ~~~

Possible Solution

Either (a) distinguish ?&T from ?T in T.indirections so the comptime guard maps to the actual pointer-ness of the payload, or (b) teach the ==-with-nil checker to look through the option wrapper when T.indirections != 0. Alternatively, generalize isnil(val) in builtin to accept ?&T so user code has a clean escape hatch.

V version

V 0.5.1 (40b3711)

Environment details (OS name and version, etc.)

|V full version      |V 0.5.1 1b3385cc34ff783e793d1a26a8ec5be587c80fe0.40b3711
|:-------------------|:-------------------
|OS                  |linux, Ubuntu 24.04 LTS
|Processor           |16 cpus, 64bit, little endian, AMD Ryzen 7 5800H with Radeon Graphics
|Memory              |10.02GB/30.7GB
|                    |
|V executable        |/home/hitalo/Documents/v/v
|V last modified time|2026-04-18 09:18:00
|                    |
|V home dir          |OK, value: /home/hitalo/Documents/v
|VMODULES            |OK, value: /home/hitalo/.vmodules
|VTMP                |OK, value: /tmp/v_1000
|Current working dir |OK, value: /home/hitalo/Documents/v
|                    |
|Git version         |git version 2.43.0
|V git status        |0.5.1-1006-g40b3711b-dirty
|.git/config present |true
|                    |
|cc version          |cc (GCC) 14.2.0
|gcc version         |gcc (GCC) 14.2.0
|clang version       |Ubuntu clang version 18.1.3 (1)
|tcc version         |tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
|tcc git status      |thirdparty-linux-amd64 696c1d84
|emcc version        |emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.6 ()
|glibc version       |ldd (Ubuntu GLIBC 2.39-0ubuntu8.3) 2.39

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.