Make Voldemort comments less cryptic

compiler/rustc_lint/src/traits.rs

@@ -96,7 +96,7 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
             };
             let def_id = trait_predicate.trait_ref.def_id;
             if cx.tcx.lang_items().drop_trait() == Some(def_id) {
-                // Explicitly allow `impl Drop`, a drop-guards-as-Voldemort-type pattern.
+                // Explicitly allow `impl Drop`, a drop-guards-as-unnameable-type pattern.
                 if trait_predicate.trait_ref.self_ty().is_impl_trait() {
                     continue;
                 }

compiler/rustc_middle/src/ty/sty.rs

@@ -2857,7 +2857,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Uint(..)
             | ty::Float(..) => true,
 
-            // The voldemort ZSTs are fine.
+            // ZST which can't be named are fine.
             ty::FnDef(..) => true,
 
             ty::Array(element_ty, _len) => element_ty.is_trivially_pure_clone_copy(),

tests/ui/drop-bounds/drop-bounds-impl-drop.rs

@@ -2,6 +2,7 @@
 #![deny(drop_bounds)]
 // As a special exemption, `impl Drop` in the return position raises no error.
 // This allows a convenient way to return an unnamed drop guard.
+// Voldemort here refers to types that are unnameable.
 fn voldemort_type() -> impl Drop {
   struct Voldemort;
   impl Drop for Voldemort {