Required explicit cast to empty interface

[einar-hjortdal]

Describe the bug

Explicit cast of variable to empty interface is required, but I believe it shouldn't be required, an implicit cast should be allowed.

Rationale: all types implement an empty interface, they do not need to be made implement an empty interface.

Reproduction Steps

module main

struct Null {}

interface Values {}

fn main() {
	mut a := []Values{len: 10, init: Null{}}
	for i := 0; i < a.len; i++ {
		a[i] = 69
	}
}

v run array-of-interfaces.v 
array-of-interfaces.v:8:35: error: expected `Values`, not `Null`
    6 | 
    7 | fn main() {
    8 |     mut a := []Values{len: 10, init: Null{}}
      |                                      ~~~~~~
    9 |     for i := 0; i < a.len; i++ {
   10 |         a[i] = 69

Expected Behavior

No error is thrown

Current Behavior

module main

struct Null {}

interface Values {}

fn main() {
	mut a := []Values{len: 10, init: Values(Null{})} // bruh.
	for i := 0; i < a.len; i++ {
		a[i] = 69
	}
}

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.10 a298fb8

Environment details (OS name and version, etc.)

|V full version      |V 0.4.10 537605a.a298fb8
|:-------------------|:-------------------
|OS                  |linux, "openmamba release 2024.6 for x86_64 (rolling)"
|Processor           |8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
|Memory              |7.83GB/31.16GB
|                    |
|V executable        |/home/einar/.local/lib64/v/v
|V last modified time|2025-04-02 08:51:46
|                    |
|V home dir          |OK, value: /home/einar/.local/lib64/v
|VMODULES            |OK, value: /home/einar/.vmodules
|VTMP                |OK, value: /tmp/v_1000
|Current working dir |OK, value: /home/einar/Documents/projects/vlang/active/firebird
|                    |
|Git version         |git version 2.49.0
|V git status        |weekly.2025.13-45-ga298fb8a
|.git/config present |true
|                    |
|cc version          |cc (GCC) 14.2.1 20240909
|gcc version         |gcc (GCC) 14.2.1 20240909
|clang version       |N/A
|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

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[huly-for-github]

Connected to Huly®: V_0.6-22507

[jorgeluismireles]

You have a point since a[i] = 69 is accepted instead of explicit cast a[i] = Values(69).

[einar-hjortdal]

You have a point since a[i] = 69 is accepted instead of explicit cast a[i] = Values(69).

That used to be a problem last year and it was fixed, I am guessing this also needs to be taken care of