incomplete normalization in implied bounds

[aliemjay]

The following fails to compile:

pub trait Iter {
    type Item;
}

impl<'x, I> Iter for I
where
    I: IntoIterator<Item = &'x str>,
{
    type Item = &'x str;
}

pub struct Map<I>(I)
where
    I: Iter,
    I::Item: 'static;

fn test(_: Map<Vec<&str>>) {}
//~^ ERROR needs to satisfy a `'static` lifetime requirement

while changing the Iter impl to use a paramter type X instead of the lifetime 'x makes it compile:

// ...

impl<X, I> Iter for I
where
    I: IntoIterator<Item = X>,
{
    type Item = X;
}

// ...

This is because we are ignoring projection predicates that constrain region variables while using those that constrain type variables:

rust/compiler/rustc_traits/src/implied_outlives_bounds.rs

Lines 86 to 94 in 8a7ca93

	if obligation.predicate.has_non_region_infer() {
	match obligation.predicate.kind().skip_binder() {
	ty::PredicateKind::Clause(ty::Clause::Projection(..))
	| ty::PredicateKind::AliasRelate(..) => {
	ocx.register_obligation(obligation.clone());
	}
	_ => {}
	}
	}

Should be fixed by #109482.