clippy_utils: make peel_*_ty_refs class of functions a bit more consistent

clippy_lints/src/dereference.rs

@@ -1,10 +1,9 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::has_enclosing_paren;
-use clippy_utils::ty::{adjust_derefs_manually_drop, implements_trait, is_manually_drop};
+use clippy_utils::ty::{adjust_derefs_manually_drop, implements_trait, is_manually_drop, peel_and_count_ty_refs};
 use clippy_utils::{
     DefinedTy, ExprUseNode, expr_use_ctxt, get_parent_expr, is_block_like, is_lint_allowed, path_to_local,
-    peel_middle_ty_refs,
 };
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_data_structures::fx::FxIndexMap;
@@ -942,7 +941,7 @@ fn report<'tcx>(
             let (expr_str, expr_is_macro_call) =
                 snippet_with_context(cx, expr.span, data.first_expr.span.ctxt(), "..", &mut app);
             let ty = typeck.expr_ty(expr);
-            let (_, ref_count) = peel_middle_ty_refs(ty);
+            let (_, ref_count, _) = peel_and_count_ty_refs(ty);
             let deref_str = if ty_changed_count >= ref_count && ref_count != 0 {
                 // a deref call changing &T -> &U requires two deref operators the first time
                 // this occurs. One to remove the reference, a second to call the deref impl.
@@ -1045,7 +1044,7 @@ fn report<'tcx>(
             if let ty::Ref(_, dst, _) = data.adjusted_ty.kind()
                 && dst.is_slice()
             {
-                let (src, n_src_refs) = peel_middle_ty_refs(ty);
+                let (src, n_src_refs, _) = peel_and_count_ty_refs(ty);
                 if n_src_refs >= 2 && src.is_array() {
                     return;
                 }

clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs

@@ -4,7 +4,7 @@ use rustc_middle::ty;
 use rustc_span::def_id::LocalDefId;
 
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::ty::type_is_unsafe_function;
+use clippy_utils::ty::is_unsafe_fn;
 use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{iter_input_pats, path_to_local};
 
@@ -51,7 +51,7 @@ fn check_raw_ptr<'tcx>(
             let typeck = cx.tcx.typeck_body(body.id());
             let _: Option<!> = for_each_expr(cx, body.value, |e| {
                 match e.kind {
-                    hir::ExprKind::Call(f, args) if type_is_unsafe_function(cx, typeck.expr_ty(f)) => {
+                    hir::ExprKind::Call(f, args) if is_unsafe_fn(cx, typeck.expr_ty(f)) => {
                         for arg in args {
                             check_arg(cx, &raw_ptrs, arg);
                         }

clippy_lints/src/manual_abs_diff.rs

@@ -4,8 +4,8 @@ use clippy_utils::higher::If;
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::HasSession as _;
 use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::{eq_expr_value, peel_blocks, peel_middle_ty_refs, span_contains_comment};
+use clippy_utils::ty::{is_type_diagnostic_item, peel_and_count_ty_refs};
+use clippy_utils::{eq_expr_value, peel_blocks, span_contains_comment};
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
@@ -107,7 +107,7 @@ impl ManualAbsDiff {
             |ty| is_type_diagnostic_item(cx, ty, sym::Duration) && self.msrv.meets(cx, msrvs::DURATION_ABS_DIFF);
 
         let a_ty = cx.typeck_results().expr_ty(a).peel_refs();
-        let (b_ty, b_n_refs) = peel_middle_ty_refs(cx.typeck_results().expr_ty(b));
+        let (b_ty, b_n_refs, _) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(b));
 
         (a_ty == b_ty && (is_int(a_ty) || is_duration(a_ty))).then_some((a_ty, b_n_refs))
     }

clippy_lints/src/manual_slice_size_calculation.rs

@@ -2,6 +2,7 @@ use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::snippet_with_context;
+use clippy_utils::ty::peel_and_count_ty_refs;
 use clippy_utils::{expr_or_init, is_in_const_context, std_or_core};
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Expr, ExprKind};
@@ -102,7 +103,7 @@ fn simplify_half<'tcx>(
         && let ExprKind::MethodCall(method_path, receiver, [], _) = expr1.kind
         && method_path.ident.name == sym::len
         && let receiver_ty = cx.typeck_results().expr_ty(receiver)
-        && let (receiver_ty, refs_count) = clippy_utils::ty::walk_ptrs_ty_depth(receiver_ty)
+        && let (receiver_ty, refs_count, _) = peel_and_count_ty_refs(receiver_ty)
         && let ty::Slice(ty1) = receiver_ty.kind()
         // expr2 is `size_of::<T2>()`?
         && let ExprKind::Call(func, []) = expr2.kind

clippy_lints/src/matches/manual_ok_err.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::{indent_of, reindent_multiline};
 use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::{option_arg_ty, peel_mid_ty_refs_is_mutable};
+use clippy_utils::ty::{option_arg_ty, peel_and_count_ty_refs};
 use clippy_utils::{get_parent_expr, is_res_lang_ctor, path_res, peel_blocks, span_contains_comment};
 use rustc_ast::{BindingMode, Mutability};
 use rustc_errors::Applicability;
@@ -135,15 +135,11 @@ fn apply_lint(cx: &LateContext<'_>, expr: &Expr<'_>, scrutinee: &Expr<'_>, is_ok
     let scrut = Sugg::hir_with_applicability(cx, scrutinee, "..", &mut app).maybe_paren();
 
     let scrutinee_ty = cx.typeck_results().expr_ty(scrutinee);
-    let (_, n_ref, mutability) = peel_mid_ty_refs_is_mutable(scrutinee_ty);
-    let prefix = if n_ref > 0 {
-        if mutability == Mutability::Mut {
-            ".as_mut()"
-        } else {
-            ".as_ref()"
-        }
-    } else {
-        ""
+    let (_, _, mutability) = peel_and_count_ty_refs(scrutinee_ty);
+    let prefix = match mutability {
+        Some(Mutability::Mut) => ".as_mut()",
+        Some(Mutability::Not) => ".as_ref()",
+        None => "",
     };
 
     let sugg = format!("{scrut}{prefix}.{method}()");

clippy_lints/src/matches/manual_utils.rs

@@ -2,7 +2,7 @@ use crate::map_unit_fn::OPTION_MAP_UNIT_FN;
 use crate::matches::MATCH_AS_REF;
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::{is_copy, is_type_diagnostic_item, peel_mid_ty_refs_is_mutable, type_is_unsafe_function};
+use clippy_utils::ty::{is_copy, is_type_diagnostic_item, is_unsafe_fn, peel_and_count_ty_refs};
 use clippy_utils::{
     CaptureKind, can_move_expr_to_closure, expr_requires_coercion, is_else_clause, is_lint_allowed, is_res_lang_ctor,
     path_res, path_to_local_id, peel_blocks, peel_hir_expr_refs, peel_hir_expr_while,
@@ -30,8 +30,9 @@ pub(super) fn check_with<'tcx, F>(
 where
     F: Fn(&LateContext<'tcx>, &'tcx Pat<'_>, &'tcx Expr<'_>, SyntaxContext) -> Option<SomeExpr<'tcx>>,
 {
-    let (scrutinee_ty, ty_ref_count, ty_mutability) =
-        peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
+    let (scrutinee_ty, ty_ref_count, ty_mutability) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(scrutinee));
+    let ty_mutability = ty_mutability.unwrap_or(Mutability::Mut);
+
     if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::Option)
         && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::Option))
     {
@@ -191,7 +192,7 @@ fn can_pass_as_func<'tcx>(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Ex
         ExprKind::Call(func, [arg])
             if path_to_local_id(arg, binding)
                 && cx.typeck_results().expr_adjustments(arg).is_empty()
-                && !type_is_unsafe_function(cx, cx.typeck_results().expr_ty(func).peel_refs()) =>
+                && !is_unsafe_fn(cx, cx.typeck_results().expr_ty(func).peel_refs()) =>
         {
             Some(func)
         },

clippy_lints/src/matches/single_match.rs

@@ -2,10 +2,8 @@ use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::{
     SpanRangeExt, expr_block, snippet, snippet_block_with_context, snippet_with_applicability, snippet_with_context,
 };
-use clippy_utils::ty::implements_trait;
-use clippy_utils::{
-    is_lint_allowed, is_unit_expr, peel_blocks, peel_hir_pat_refs, peel_middle_ty_refs, peel_n_hir_expr_refs,
-};
+use clippy_utils::ty::{implements_trait, peel_and_count_ty_refs};
+use clippy_utils::{is_lint_allowed, is_unit_expr, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs};
 use core::ops::ControlFlow;
 use rustc_arena::DroplessArena;
 use rustc_errors::{Applicability, Diag};
@@ -133,7 +131,7 @@ fn report_single_pattern(
 
     let (pat, pat_ref_count) = peel_hir_pat_refs(arm.pat);
     let (msg, sugg) = if let PatKind::Expr(_) = pat.kind
-        && let (ty, ty_ref_count) = peel_middle_ty_refs(cx.typeck_results().expr_ty(ex))
+        && let (ty, ty_ref_count, _) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(ex))
         && let Some(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait()
         && let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait()
         && (ty.is_integral()

clippy_lints/src/methods/implicit_clone.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_context;
-use clippy_utils::ty::implements_trait;
-use clippy_utils::{is_diag_item_method, is_diag_trait_item, peel_middle_ty_refs, sym};
+use clippy_utils::ty::{implements_trait, peel_and_count_ty_refs};
+use clippy_utils::{is_diag_item_method, is_diag_trait_item, sym};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
@@ -14,7 +14,7 @@ pub fn check(cx: &LateContext<'_>, method_name: Symbol, expr: &hir::Expr<'_>, re
         && is_clone_like(cx, method_name, method_def_id)
         && let return_type = cx.typeck_results().expr_ty(expr)
         && let input_type = cx.typeck_results().expr_ty(recv)
-        && let (input_type, ref_count) = peel_middle_ty_refs(input_type)
+        && let (input_type, ref_count, _) = peel_and_count_ty_refs(input_type)
         && !(ref_count > 0 && is_diag_trait_item(cx, method_def_id, sym::ToOwned))
         && let Some(ty_name) = input_type.ty_adt_def().map(|adt_def| cx.tcx.item_name(adt_def.did()))
         && return_type == input_type

clippy_lints/src/methods/inefficient_to_string.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::{is_type_lang_item, walk_ptrs_ty_depth};
+use clippy_utils::ty::{is_type_lang_item, peel_and_count_ty_refs};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
@@ -24,7 +24,7 @@ pub fn check(
         && let Some(args) = cx.typeck_results().node_args_opt(expr.hir_id)
         && let arg_ty = cx.typeck_results().expr_ty_adjusted(receiver)
         && let self_ty = args.type_at(0)
-        && let (deref_self_ty, deref_count) = walk_ptrs_ty_depth(self_ty)
+        && let (deref_self_ty, deref_count, _) = peel_and_count_ty_refs(self_ty)
         && deref_count >= 1
         && specializes_tostring(cx, deref_self_ty)
     {

clippy_lints/src/methods/mut_mutex_lock.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::expr_custom_deref_adjustment;
-use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
+use clippy_utils::ty::{is_type_diagnostic_item, peel_and_count_ty_refs};
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, Mutability};
 use rustc_lint::LateContext;
@@ -10,8 +10,7 @@ use super::MUT_MUTEX_LOCK;
 
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'tcx>, recv: &'tcx Expr<'tcx>, name_span: Span) {
     if matches!(expr_custom_deref_adjustment(cx, recv), None | Some(Mutability::Mut))
-        && let (_, ref_depth, Mutability::Mut) = peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(recv))
-        && ref_depth >= 1
+        && let (_, _, Some(Mutability::Mut)) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(recv))
         && let Some(method_id) = cx.typeck_results().type_dependent_def_id(ex.hir_id)
         && let Some(impl_id) = cx.tcx.impl_of_assoc(method_id)
         && is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::Mutex)

clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -3,11 +3,12 @@ use super::unnecessary_iter_cloned::{self, is_into_iter};
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::{SpanRangeExt, snippet};
-use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item, is_type_lang_item};
+use clippy_utils::ty::{
+    get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item, is_type_lang_item, peel_and_count_ty_refs,
+};
 use clippy_utils::visitors::find_all_ret_expressions;
 use clippy_utils::{
-    fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, is_expr_temporary_value, peel_middle_ty_refs,
-    return_ty, sym,
+    fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, is_expr_temporary_value, return_ty, sym,
 };
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
@@ -119,8 +120,8 @@ fn check_addr_of_expr(
                 },
             ] = adjustments[..]
         && let receiver_ty = cx.typeck_results().expr_ty(receiver)
-        && let (target_ty, n_target_refs) = peel_middle_ty_refs(*target_ty)
-        && let (receiver_ty, n_receiver_refs) = peel_middle_ty_refs(receiver_ty)
+        && let (target_ty, n_target_refs, _) = peel_and_count_ty_refs(*target_ty)
+        && let (receiver_ty, n_receiver_refs, _) = peel_and_count_ty_refs(receiver_ty)
         // Only flag cases satisfying at least one of the following three conditions:
         // * the referent and receiver types are distinct
         // * the referent/receiver type is a copyable array
@@ -385,7 +386,7 @@ fn check_other_call_arg<'tcx>(
         && let fn_sig = cx.tcx.fn_sig(callee_def_id).instantiate_identity().skip_binder()
         && let Some(i) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == maybe_arg.hir_id)
         && let Some(input) = fn_sig.inputs().get(i)
-        && let (input, n_refs) = peel_middle_ty_refs(*input)
+        && let (input, n_refs, _) = peel_and_count_ty_refs(*input)
         && let (trait_predicates, _) = get_input_traits_and_projections(cx, callee_def_id, input)
         && let Some(sized_def_id) = cx.tcx.lang_items().sized_trait()
         && let Some(meta_sized_def_id) = cx.tcx.lang_items().meta_sized_trait()

clippy_lints/src/methods/useless_asref.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::{implements_trait, should_call_clone_as_function, walk_ptrs_ty_depth};
+use clippy_utils::ty::{implements_trait, peel_and_count_ty_refs, should_call_clone_as_function};
 use clippy_utils::{get_parent_expr, is_diag_trait_item, path_to_local_id, peel_blocks, strip_pat_refs};
 use rustc_errors::Applicability;
 use rustc_hir::{self as hir, LangItem};
@@ -50,8 +50,8 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, call_name: Symbo
         // check if the type after `as_ref` or `as_mut` is the same as before
         let rcv_ty = cx.typeck_results().expr_ty(recvr);
         let res_ty = cx.typeck_results().expr_ty(expr);
-        let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
-        let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
+        let (base_res_ty, res_depth, _) = peel_and_count_ty_refs(res_ty);
+        let (base_rcv_ty, rcv_depth, _) = peel_and_count_ty_refs(rcv_ty);
         if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
             if let Some(parent) = get_parent_expr(cx, expr) {
                 // allow the `as_ref` or `as_mut` if it is followed by another method call

clippy_lints/src/redundant_clone.rs

@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::{span_lint_hir, span_lint_hir_and_then};
 use clippy_utils::fn_has_unsatisfiable_preds;
 use clippy_utils::mir::{LocalUsage, PossibleBorrowerMap, visit_local_usage};
 use clippy_utils::source::SpanRangeExt;
-use clippy_utils::ty::{has_drop, is_copy, is_type_lang_item, walk_ptrs_ty_depth};
+use clippy_utils::ty::{has_drop, is_copy, is_type_lang_item, peel_and_count_ty_refs};
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{Body, FnDecl, LangItem, def_id};
@@ -263,7 +263,7 @@ fn is_call_with_ref_arg<'tcx>(
         && args.len() == 1
         && let mir::Operand::Move(mir::Place { local, .. }) = &args[0].node
         && let ty::FnDef(def_id, _) = *func.ty(mir, cx.tcx).kind()
-        && let (inner_ty, 1) = walk_ptrs_ty_depth(args[0].node.ty(mir, cx.tcx))
+        && let (inner_ty, 1, _) = peel_and_count_ty_refs(args[0].node.ty(mir, cx.tcx))
         && !is_copy(cx, inner_ty)
     {
         Some((def_id, *local, inner_ty, destination.as_local()?))

clippy_lints/src/redundant_slicing.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::get_parent_expr;
 use clippy_utils::source::snippet_with_context;
-use clippy_utils::ty::is_type_lang_item;
-use clippy_utils::{get_parent_expr, peel_middle_ty_refs};
+use clippy_utils::ty::{is_type_lang_item, peel_and_count_ty_refs};
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_errors::Applicability;
 use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
@@ -82,8 +82,8 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing {
             && let ExprKind::Index(indexed, range, _) = addressee.kind
             && is_type_lang_item(cx, cx.typeck_results().expr_ty_adjusted(range), LangItem::RangeFull)
         {
-            let (expr_ty, expr_ref_count) = peel_middle_ty_refs(cx.typeck_results().expr_ty(expr));
-            let (indexed_ty, indexed_ref_count) = peel_middle_ty_refs(cx.typeck_results().expr_ty(indexed));
+            let (expr_ty, expr_ref_count, _) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(expr));
+            let (indexed_ty, indexed_ref_count, _) = peel_and_count_ty_refs(cx.typeck_results().expr_ty(indexed));
             let parent_expr = get_parent_expr(cx, expr);
             let needs_parens_for_prefix =
                 parent_expr.is_some_and(|parent| cx.precedence(parent) > ExprPrecedence::Prefix);

clippy_lints/src/size_of_ref.rs

@@ -1,5 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::{path_def_id, peel_middle_ty_refs};
+use clippy_utils::path_def_id;
+use clippy_utils::ty::peel_and_count_ty_refs;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
@@ -59,7 +60,7 @@ impl LateLintPass<'_> for SizeOfRef {
             && let Some(def_id) = path_def_id(cx, path)
             && cx.tcx.is_diagnostic_item(sym::mem_size_of_val, def_id)
             && let arg_ty = cx.typeck_results().expr_ty(arg)
-            && peel_middle_ty_refs(arg_ty).1 > 1
+            && peel_and_count_ty_refs(arg_ty).1 > 1
         {
             span_lint_and_help(
                 cx,

clippy_lints/src/unused_peekable.rs

@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
-use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
+use clippy_utils::ty::{is_type_diagnostic_item, peel_and_count_ty_refs};
 use clippy_utils::{fn_def_id, is_trait_method, path_to_local_id, peel_ref_operators, sym};
 use rustc_ast::Mutability;
 use rustc_hir::intravisit::{Visitor, walk_expr};
@@ -61,7 +61,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedPeekable {
                 && let Some(init) = local.init
                 && !init.span.from_expansion()
                 && let Some(ty) = cx.typeck_results().expr_ty_opt(init)
-                && let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty)
+                && let (ty, _, None | Some(Mutability::Mut)) = peel_and_count_ty_refs(ty)
                 && is_type_diagnostic_item(cx, ty, sym::IterPeekable)
             {
                 let mut vis = PeekableVisitor::new(cx, binding);
@@ -211,7 +211,7 @@ impl<'tcx> Visitor<'tcx> for PeekableVisitor<'_, 'tcx> {
 
 fn arg_is_mut_peekable(cx: &LateContext<'_>, arg: &Expr<'_>) -> bool {
     if let Some(ty) = cx.typeck_results().expr_ty_opt(arg)
-        && let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty)
+        && let (ty, _, None | Some(Mutability::Mut)) = peel_and_count_ty_refs(ty)
         && is_type_diagnostic_item(cx, ty, sym::IterPeekable)
     {
         true