Simplify an iterator search in borrowck diag

Rather than `.into_iter().rev().find_position(...)`, this case can
simply call `.iter().rposition(...)`.

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -4,7 +4,6 @@ use crate::session_diagnostics::{
     CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause,
     CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
 };
-use itertools::Itertools;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
@@ -226,16 +225,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         }
                     } else {
                         if autoderef_index.is_none() {
-                            autoderef_index =
-                                match place.projection.into_iter().rev().find_position(|elem| {
-                                    !matches!(
-                                        elem,
-                                        ProjectionElem::Deref | ProjectionElem::Downcast(..)
-                                    )
-                                }) {
-                                    Some((index, _)) => Some(place.projection.len() - index),
-                                    None => Some(0),
-                                };
+                            autoderef_index = match place.projection.iter().rposition(|elem| {
+                                !matches!(
+                                    elem,
+                                    ProjectionElem::Deref | ProjectionElem::Downcast(..)
+                                )
+                            }) {
+                                Some(index) => Some(index + 1),
+                                None => Some(0),
+                            };
                         }
                         if index >= autoderef_index.unwrap() {
                             buf.insert(0, '*');