Incorrect codegen for trait methods

[kvinwang]

Describe the bug
I am trying out the ink 4.0-beta.

Given the following trait definition:

#[ink::trait_definition(namespace = "pink_system")]
pub trait System {
    #[ink(message)]
    fn version(&self) -> (u16, u16);
}

The generated forwarder is:

impl<E> System for __ink_TraitCallBuilderSystem<E>
where
    E: ::ink::env::Environment,
{
    fn version(&self) -> Self::versionOutput {
        ::ink::env::call::build_call::<Self::Env>()
            .call_type(
                ::ink::env::call::Call::new()
                    .callee(::ink::ToAccountId::to_account_id(self)),
            )
            .exec_input(::ink::env::call::ExecutionInput::new(
                ::ink::env::call::Selector::new([0x87_u8, 0xC9_u8, 0x8A_u8, 0x8D_u8]),
            ))
            .returns::<(u16, u16)>()
    }
}

And also the metadata.json:

{
  "args": [],
  "docs": [],
  "label": "System::version",
  "mutates": false,
  "payable": false,
  "returnType": {
    "displayName": [],
    "type": 6
  },
  "selector": "0x87c98a8d"
},
...
{
"id": 6,
"type": {
  "def": {
    "tuple": [
      7,
      7
    ]
  }
}
},

Expected behavior
It should be:
.returns::<Result<(u16, u16),LangError>>()
and ditto in the metadata.

[ascjones]

I see the handling of LangError for traits was left as a follow-up in the @HCastano's original PR: #1450.

[kvinwang]

Hey guys,

I've noticed that 4.0.0-rc has been released.
Have the follow-ups in #1450 been done yet? This issue is definitely blocking us to upgrade to ink-4.0.

[ascjones]

Yes I believe the issues you have raised here are now fixed via #1525 (call builder return type) and #1531 (metadata). Can you double check and then we can close this issue?

[kvinwang]

Great, it works with 4.0.0-rc.