servo/servo

@nikomatsakis I tried to quickly write down the HIR check in meantime, but I stopped at the problem with converting hir::Ty to ty::TyS (haven't investigated it though).
Anyway, my MIR check:

    fn visit_constant(&mut self, constant: &mir::Constant<'tcx>, location: mir::Location) {
        self.super_constant(constant, location);

        let ur_cx = &self.unrooted_cx;
        if ur_cx.is_unrooted_ty(constant.ty, false) {
            ur_cx.late_cx.span_lint(UNROOTED_MUST_ROOT, constant.span, "error visit_constant")
        }
    }

Where ur_cx is like in PR right know. What I mean by "doesn't seem to work" is that it doesn't fail at

   fn foo<#[must_root] T>(val: &T) {
        bar(val);
    }
    fn bar<T>(val: T) {}

Now everything just mixed up in my head if it goes what I tried to check with visit_constant.

So, do I understand you right, that visit_constant should be enough?

PS this week I focused mainly on this PR postponing all of my university assignments, so I'd like to focus more on them in the first place if this PR requires a lot of additional work.