@[heap] flag in wrapper struct does not make the error disappear

[lv37]

Describe the bug

module main

@[heap]
struct Wrapper {
    a &int = unsafe { nil }
}

fn test[T](a &T) Wrapper {
    $if T is int {
        return Wrapper{a}
    }
    return Wrapper{}
}

fn main() {
    a := 123
    println(test(a).a)
}

Reproduction Steps

Compile the above code.

Expected Behavior

Compile successfully.

Current Behavior

main.v:10:24: error: `a` cannot be assigned outside `unsafe` blocks as it might refer to an object stored on stack. Consider wrapping the `T` object in a `struct` declared as `[heap]`.
    8 | fn test[T](a &T) Wrapper {
    9 |     $if T is int {
   10 |         return Wrapper{a}
      |                        ^
   11 |     }
   12 |     return Wrapper{}

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.5 58a8fc6

Environment details (OS name and version, etc.)

V full version: V 0.4.5 b347f54.58a8fc6
OS: linux, Linux version 6.8.9-300.fc40.x86_64 (mockbuild@5f5c14101bdf4cb8942130379360ff7d) (gcc (GCC) 14.0.1 20240411 (Red Hat 14.0.1-0), GNU ld version 2.41-34.fc40) #1 SMP PREEMPT_DYNAMIC Thu May  2 18:59:06 UTC 2024
Processor: 4 cpus, 64bit, little endian, Intel(R) Core(TM) i5-4310U CPU @ 2.00GHz

getwd: /home/user/Projects/learncpp
vexe: /home/user/.local/lib/v/v
vexe mtime: 2024-05-13 20:51:27

vroot: OK, value: /home/user/.local/lib/v
VMODULES: OK, value: /home/user/.vmodules
VTMP: OK, value: /tmp/v_1002

Git version: git version 2.45.0
Git vroot status: weekly.2024.14-312-g58a8fc6c
.git/config present: true

CC version: cc (GCC) 14.1.1 20240507 (Red Hat 14.1.1-1)
thirdparty/tcc status: thirdparty-linux-amd64 12f392c3

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