Static method on generic type is not supported

[blackshirt]

Describe the bug

This bug/missing feautures is already discussed on discord before this submitted, see missing feature of support static method on generic type thanks @spytheman

Code: https://vosca.dev/p/db03a26fcd

module main 

type Tag = int
type Octet = string

fn (o Octet) tag() Tag {
	return Tag(1)
}

fn (o Octet) pack() ![]u8 {
	return o.bytes()
}

fn (o Octet) bytes() []u8 {
	s := string(o)
	return s.bytes()
}

// static method on concrete type 
fn Octet.unpack(b []u8) Octet {
	return Octet(b.bytestr())
}

// This is generic type 
struct Elm[T] {
mut:
	val T
}

fn Elm.new[T](val T) Elm[T] {
	return Elm[T]{
		val: val
	}
}

fn (el Elm[T]) the_t() T {
	return el.val
}

//  static method on generic type, this not working
fn Elm.unpack[T](src []u8) !Elm[T] {
	t := T.unpack[T](src)
	return Elm[T]{t}
}

fn (el Elm[T]) tag() Tag {
	return el.val.tag()
}

fn (el Elm[T]) pack() ![]u8 {
	return el.val.pack()!
}

fn main() {
	b := Octet('xx')
	mut el := Elm.new[Octet](b)
	dump(el)
	bytes := el.pack()!
	dump(bytes)

	// unpack
	ab := Elm.unpack[Octet](bytes)!
	dump(ab)
	dump(el == ab)
	
	dump(el.the_t())
}

Reproduction Steps

Use above snippet to reproduce the results

Expected Behavior

Define static method on generic type should be supported.

Current Behavior

Output:

code.v:37:7: error: unknown function: T.unpack
   35 | 
   36 | fn Elm.unpack[T](src []u8) !Elm[T] {
   37 |     t := T.unpack[T](src)
      |          ~~~~~~~~~~~~~~~~
   38 |     return Elm[T]{t}
   39 | }
code.v:37:4: error: assignment mismatch: 1 variable(s) but `T.unpack()` returns 0 value(s)
   35 | 
   36 | fn Elm.unpack[T](src []u8) !Elm[T] {
   37 |     t := T.unpack[T](src)
      |       ~~
   38 |     return Elm[T]{t}
   39 | }
code.v:38:16: error: `t` (no value) used as value
   36 | fn Elm.unpack[T](src []u8) !Elm[T] {
   37 |     t := T.unpack[T](src)
   38 |     return Elm[T]{t}
      |                   ^
   39 | }
   40 |
If the code of your project is in multiple files, try with `v .` instead of `v code.v`
Exited with error status 1

Possible Solution

No response

Additional Information/Context

when its changed to instance based method,

// changes static to instance method
fn (mut o Octet) unpack(b []u8) Octet {
    return Octet(b.bytestr())
}

// // changes static to instance method
fn (mut el Elm[T]) unpack[T](src []u8) !Elm[T] {
    t := el.val.unpack(src)
    out := Elm.new[T](t)
    return out
}

its produces expected behavour

[code.v:49] el: Elm[Octet]{
    val:     Octet(xx)
}
[code.v:51] bytes: [120, 120]
[code.v:55] ab: Elm[Octet]{
    val:     Octet(xx)
}

### V version

V 0.4.3 c3cf9ee.cc220e6

### Environment details (OS name and version, etc.)

V full version: V 0.4.4 c3cf9ee.a36c693
OS: linux, Ubuntu 22.04.2 LTS
Processor: 2 cpus, 64bit, little endian, Intel(R) Xeon(R) CPU E5-2670 v2 @ 2.50GHz

getwd: /home/pmakhnev/playground
vexe: /home/pmakhnev/v/v
vexe mtime: 2024-03-18 12:00:08

vroot: OK, value: /home/pmakhnev/v
VMODULES: OK, value: /root/.vmodules
VTMP: OK, value: /tmp/v_0

Git version: git version 2.34.1
Git vroot status: weekly.2024.11-45-ga36c693f
.git/config present: true

CC version: cc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
thirdparty/tcc status: thirdparty-linux-amd64 12f392c3

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