Into::into needs From impl or turbofish

[michaeljklein]

Aim

Attempted to compile a program with an Into<Field> that's called like let _: Field = T.into():

struct Foo {
    inner: Field,
}

impl Into<Field> for Foo {
    fn into(self) -> Field {
        self.inner
    }
}

fn main() {
    let foo = Foo {
        inner: 0,
    };

    // This works:
    // let _: Field = Into::<Field>::into(foo);

    // This fails with 'No matching impl':
    //
    // error: No matching impl found for `Field: From<Foo>`
    //     ┌─ main.nr:439:20
    //     │
    // 439 │     let _: Field = foo.into();
    //     │                    -------- No impl for `Field: From<Foo>`
    //     │
    let _: Field = foo.into();
}

Expected Behavior

Expected that, given impl Into<Field> for Foo and the following definition for Into:

pub trait Into<T> {
    fn into(self) -> T;
}

For any foo: Foo, calling foo.into() when the return type is known to be Field would convert Foo -> Field.

Bug

foo.into() fails with the following error:

error: No matching impl found for `Field: From<Foo>`
    ┌─ main.nr:439:20
    │
439 │     let _: Field = foo.into();
    │                    -------- No impl for `Field: From<Foo>`
    │

It appears to be "getting stuck" on the following impl for Into:

impl<T, U> Into<T> for U
where
    T: From<U>,
{
    fn into(self) -> T {
        T::from(self)
    }
}

However, it's unclear why this is happening since the turbofish version works: Into::<Field>::into(foo)

To Reproduce

Workaround

Yes

Workaround Description

Use turbofish

Additional Context

No response

Project Impact

Nice-to-have

Blocker Context

No response

Nargo Version

nargo version = 0.38.0 noirc version = 0.38.0+0fc0c53ec183890370c69aa4148952b3123cb055 (git version hash: 0fc0c53, is dirty: false)

NoirJS Version

No response

Proving Backend Tooling & Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[asterite]

It seems this works in master, probably fixed by #7041