`deduce_closure_signature` bails on aliases referencing self

[lcnr]

pub trait Fn0: Fn(i32) -> Self::Out {
    type Out;
}

impl<F: Fn(i32) -> ()> Fn0 for F {
    type Out = ();
}

pub fn closure_typer(_: impl Fn0) {}

fn main() {
    closure_typer(move |x| {
        let _: i64 = x.into();
    });
}

affected tests

• tests/ui/closures/supertrait-hint-references-assoc-ty.rs
• tests/ui/borrowck/issue-103095.rs

[lcnr]

this is similar to the occurs check: we should instead try to normalize these aliases