Rollup merge of #120270 - compiler-errors:randos, r=lcnr

A bunch of random modifications

r? oli-obk

Kitchen sink of changes that I didn't know where to put elsewhere. Documentation tweaks mostly, but also removing some unreachable code and simplifying the pretty printing for closures/coroutines.

compiler/rustc_hir_analysis/src/autoderef.rs

@@ -12,7 +12,9 @@ use rustc_trait_selection::traits::StructurallyNormalizeExt;
 
 #[derive(Copy, Clone, Debug)]
 pub enum AutoderefKind {
+    /// A true pointer type, such as `&T` and `*mut T`.
     Builtin,
+    /// A type which must dispatch to a `Deref` implementation.
     Overloaded,
 }
 
@@ -83,6 +85,7 @@ impl<'a, 'tcx> Iterator for Autoderef<'a, 'tcx> {
                 (AutoderefKind::Builtin, ty)
             }
         } else if let Some(ty) = self.overloaded_deref_ty(self.state.cur_ty) {
+            // The overloaded deref check already normalizes the pointee type.
             (AutoderefKind::Overloaded, ty)
         } else {
             return None;

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -254,7 +254,7 @@ fn compare_method_predicate_entailment<'tcx>(
     // checks. For the comparison to be valid, we need to
     // normalize the associated types in the impl/trait methods
     // first. However, because function types bind regions, just
-    // calling `normalize_associated_types_in` would have no effect on
+    // calling `FnCtxt::normalize` would have no effect on
     // any associated types appearing in the fn arguments or return
     // type.