Structs in other modules should not be able to implement private interfaces

[Trakis196]

Describe the feature

Private structs are not able to be initialized or have their fields accessed from another module, however private interfaces are able to be implemented from another module and used in function arguments for that interface. For example:

// main.v
module main
import baz

fn main() {
	b := Bar{10}
	baz.print_foo(b) // prints 10
}

struct Bar {
	a int
}

// sub module
module baz

interface Foo {
	a int
}

pub fn print_foo(f Foo) {
	println(f.a)
}

Use Case

To be consistent with private structs, and to constrain interfaces to a specific module they are in if they are private.

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Version used

V 0.4.2 48a1d6c

Environment details (OS name and version, etc.)

OS: linux, "Arch Linux"
Processor: 8 cpus, 64bit, little endian, 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
Git version: git version 2.42.0
Git vroot status: weekly.2023.23-837-g48a1d6cc-dirty
.git/config present: true
CC version: cc (GCC) 13.2.1 20230801
thirdparty/tcc status: thirdparty-linux-amd64 12f392c3

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