Don't project to RPITIT that has no default value

[compiler-errors]

Replicates this behavior, but for RPITIT projection logic (which currently is separate)

rust/compiler/rustc_trait_selection/src/traits/project.rs

Lines 2105 to 2115 in b171953

	if !assoc_ty.item.defaultness(tcx).has_value() {
	// This means that the impl is missing a definition for the
	// associated type. This error will be reported by the type
	// checker method `check_impl_items_against_trait`, so here we
	// just return Error.
	debug!(
	"confirm_impl_candidate: no associated type {:?} for {:?}",
	assoc_ty.item.name, obligation.predicate
	);
	return Progress { term: tcx.ty_error_misc().into(), obligations: nested };
	}

Fixes #108738

[rustbot]

r? @cjgillot

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[cjgillot]

@bors r+

[bors]

📌 Commit 7634c59 has been approved by cjgillot

It is now in the queue for this repository.