From 49c7ee2d1cdb5052dddf152c8507e1157190e1ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sosth=C3=A8ne=20Gu=C3=A9don?= <sosthene@guedon.gdn>
Date: Sat, 16 Jul 2022 12:44:33 +0200
Subject: [PATCH] Fix the lint in clippy itself

---
 clippy_lints/src/dereference.rs                             | 1 +
 clippy_lints/src/derive.rs                                  | 5 ++++-
 clippy_lints/src/redundant_slicing.rs                       | 4 +++-
 clippy_lints/src/types/mod.rs                               | 1 +
 clippy_lints/src/utils/conf.rs                              | 2 +-
 clippy_lints/src/utils/internal_lints/metadata_collector.rs | 2 +-
 6 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/clippy_lints/src/dereference.rs b/clippy_lints/src/dereference.rs
index 8c7cf7748be1..cee7ec44f5b9 100644
--- a/clippy_lints/src/dereference.rs
+++ b/clippy_lints/src/dereference.rs
@@ -778,6 +778,7 @@ fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, &
                                     .and_then(|subs| subs.get(1..))
                                 {
                                     Some(subs) => cx.tcx.mk_substs(subs.iter().copied()),
+                                    #[allow(clippy::iter_empty)]
                                     None => cx.tcx.mk_substs([].iter()),
                                 } && let impl_ty = if cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref() {
                                     // Trait methods taking `&self`
diff --git a/clippy_lints/src/derive.rs b/clippy_lints/src/derive.rs
index a982990e4186..9ca443b7dff6 100644
--- a/clippy_lints/src/derive.rs
+++ b/clippy_lints/src/derive.rs
@@ -516,7 +516,10 @@ fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) ->
         tcx.mk_predicates(ty_predicates.iter().map(|&(p, _)| p).chain(
             params.iter().filter(|&&(_, needs_eq)| needs_eq).map(|&(param, _)| {
                 tcx.mk_predicate(Binder::dummy(PredicateKind::Trait(TraitPredicate {
-                    trait_ref: TraitRef::new(eq_trait_id, tcx.mk_substs([tcx.mk_param_from_def(param)].into_iter())),
+                    trait_ref: TraitRef::new(
+                        eq_trait_id,
+                        tcx.mk_substs(std::iter::once(tcx.mk_param_from_def(param))),
+                    ),
                     constness: BoundConstness::NotConst,
                     polarity: ImplPolarity::Positive,
                 })))
diff --git a/clippy_lints/src/redundant_slicing.rs b/clippy_lints/src/redundant_slicing.rs
index db6c97f3739c..8693ca9af830 100644
--- a/clippy_lints/src/redundant_slicing.rs
+++ b/clippy_lints/src/redundant_slicing.rs
@@ -11,6 +11,8 @@ use rustc_middle::ty::adjustment::{Adjust, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::subst::GenericArg;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
+use std::iter;
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for redundant slicing expressions which use the full range, and
@@ -134,7 +136,7 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing {
                 } else if let Some(target_id) = cx.tcx.lang_items().deref_target() {
                     if let Ok(deref_ty) = cx.tcx.try_normalize_erasing_regions(
                         cx.param_env,
-                        cx.tcx.mk_projection(target_id, cx.tcx.mk_substs([GenericArg::from(indexed_ty)].into_iter())),
+                        cx.tcx.mk_projection(target_id, cx.tcx.mk_substs(iter::once(GenericArg::from(indexed_ty)))),
                     ) {
                         if deref_ty == expr_ty {
                             let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0;
diff --git a/clippy_lints/src/types/mod.rs b/clippy_lints/src/types/mod.rs
index 353a6f6b899e..f3ba096237f5 100644
--- a/clippy_lints/src/types/mod.rs
+++ b/clippy_lints/src/types/mod.rs
@@ -490,6 +490,7 @@ impl Types {
                         }
                     }
                 }
+                #[allow(clippy::iter_empty)]
                 match *qpath {
                     QPath::Resolved(Some(ty), p) => {
                         context.is_nested_call = true;
diff --git a/clippy_lints/src/utils/conf.rs b/clippy_lints/src/utils/conf.rs
index 38e5c5e5b736..8cceaae8359f 100644
--- a/clippy_lints/src/utils/conf.rs
+++ b/clippy_lints/src/utils/conf.rs
@@ -327,7 +327,7 @@ define_Conf! {
     /// Lint: DISALLOWED_SCRIPT_IDENTS.
     ///
     /// The list of unicode scripts allowed to be used in the scope.
-    (allowed_scripts: Vec<String> = ["Latin"].iter().map(ToString::to_string).collect()),
+    (allowed_scripts: Vec<String> = vec!["Latin".to_string()]),
     /// Lint: NON_SEND_FIELDS_IN_SEND_TY.
     ///
     /// Whether to apply the raw pointer heuristic to determine if a type is `Send`.
diff --git a/clippy_lints/src/utils/internal_lints/metadata_collector.rs b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
index 92934c16d4b4..27658ebcc6f8 100644
--- a/clippy_lints/src/utils/internal_lints/metadata_collector.rs
+++ b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
@@ -797,7 +797,7 @@ fn get_lint_group_and_level_or_lint(
     let result = cx.lint_store.check_lint_name(
         lint_name,
         Some(sym::clippy),
-        &[Ident::with_dummy_span(sym::clippy)].into_iter().collect(),
+        &std::iter::once(Ident::with_dummy_span(sym::clippy)).collect(),
     );
     if let CheckLintNameResult::Tool(Ok(lint_lst)) = result {
         if let Some(group) = get_lint_group(cx, lint_lst[0]) {