More polishing

compiler/rustc_hir/src/hir.rs

@@ -2568,6 +2568,11 @@ pub enum PreciseCapturingArg<'hir> {
     Param(PreciseCapturingNonLifetimeArg),
 }
 
+/// We need to have a [`Node`] for the [`HirId`] that we attach the type/const param
+/// resolution to. Lifetimes don't have this problem, and for them, it's actually
+/// kind of detrimental to use a custom node type versus just using [`Lifetime`],
+/// since resolve_bound_vars operates on `Lifetime`s.
+// FIXME(precise_capturing): Investigate storing this as a path instead?
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub struct PreciseCapturingNonLifetimeArg {
     pub hir_id: HirId,