Cannot access trait type methods from built-in types.

[Thunkar]

Aim

Define a trait for all numeric types:

trait FromField {
    fn from_field(x: Field) -> Self;
}

impl FromField for u8 {
    fn from_field(x: Field) -> Self {
        x as u8
    }
}

fn main(x: Field) {
    u8::from_field(x);
}

Expected Behavior

It should compile

Bug

Compiler errors out:

error: Unexpected u8, expected one of for, }, expression, statement ┌─ /mnt/user-data/grego/repos/noir-experiments/traits_on_u/src/main.nr:12:5 │ 12 │ u8::from_field(x); │ -- │

To Reproduce

Try to compile the provided example

Project Impact

Nice-to-have

Impact Context

No response

Workaround

None

Workaround Description

No response

Additional Context

No response

Installation Method

Binary (noirup default)

Nargo Version

No response

NoirJS Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[jfecher]

This is because u8 is a keyword where the Foo::method syntax currently expects an identifier for Foo.

If anyone reading is encountering this issue, the workaround is to use the static trait method syntax FromField::from_field(x). If type annotations are needed, you can add a let binding:

let y: u8 = FromField::from_field(x);