type inference breaks if there is more than one IntoIterator bound.

[jhgg]

With this code, the B: IntoIterator<Item = Foo>, bound added breaks inference on a.

struct Foo {
    bar: u64,
}

fn what<A, B>(a: A, b: B)
where
    A: IntoIterator<Item = Foo>,
    B: IntoIterator<Item = Foo>,
{
    a.into_iter().map(|x| x.bar).count();
}

rust-analyzer version: dd43f3f 2021-10-27 nightly

[flodiebold]

Likely the same issue as #9990

[flodiebold]

rust-lang/chalk#750 is the Chalk root cause. #11242 has a reproduction in a hir-ty test.