Traits should allow methods with generic return types

[grasshopper47]

Aim

Currently it is possible to use generics within a trait:

trait Extensions
{
    fn generic<N>(self : [u8], right : [u8; N]) -> bool;   // OK
}

Expected Behavior

A trait allows methods with a generic return type:

trait Extensions
{
    fn generic<N>(self) -> [u8; N];                    
}

Bug

When creating the implementation the compiler throws a confusing error:

impl Extensions for [u8]
{
    pub fn generic<N>(self) -> [u8; N] // error: Expected type [u8; N], found type [u8; N]
    {
        // .. //
    }
}

Linked issue: #3502

To Reproduce

Compile the following:

trait Extensions
{
    fn generic<N>(self) -> [u8; N];                    
}

impl Extensions for [u8]
{
    pub fn generic<N>(self) -> [u8; N] // error: Expected type [u8; N], found type [u8; N]
    {
        // .. //
    }
}

Installation Method

Binary

Nargo Version

0.19.2

Additional Context

No response

Would you like to submit a PR for this Issue?

No

Support Needs

No response

[TomAFrench]

Closing as duplicate of #3479

[TomAFrench]

Reopening as they're actually slightly different.