Auto merge of #11953 - Jarcho:issue_11952, r=Alexendoo

Fix binder handling in `unnecessary_to_owned`

fixes #11952

The use of `rebind` instead of `EarlyBinder::bind` isn't technically needed, but it is the semantically correct operation.

changelog: None

4 files changed, 150 insertions, 103 deletions

diff --git a/clippy_lints/src/methods/unnecessary_to_owned.rs b/clippy_lints/src/methods/unnecessary_to_owned.rs
index 395b22ebc5d..c4775b6bd04 100644
--- a/clippy_lints/src/methods/unnecessary_to_owned.rs
+++ b/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -15,8 +15,7 @@ use rustc_lint::LateContext;
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
 use rustc_middle::ty::{
-    self, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, GenericArgsRef, ParamTy, ProjectionPredicate,
-    TraitPredicate, Ty,
+    self, ClauseKind, GenericArg, GenericArgKind, GenericArgsRef, ParamTy, ProjectionPredicate, TraitPredicate, Ty,
 };
 use rustc_span::{sym, Symbol};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
@@ -359,6 +358,7 @@ fn get_input_traits_and_projections<'tcx>(
     (trait_predicates, projection_predicates)
 }
 
+#[expect(clippy::too_many_lines)]
 fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<'a>) -> bool {
     for (_, node) in cx.tcx.hir().parent_iter(expr.hir_id) {
         match node {
@@ -387,22 +387,21 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                 if let Some((callee_def_id, call_generic_args, recv, call_args)) =
                     get_callee_generic_args_and_args(cx, parent_expr)
                 {
-                    // FIXME: the `instantiate_identity()` below seems incorrect, since we eventually
-                    // call `tcx.try_instantiate_and_normalize_erasing_regions` further down
-                    // (i.e., we are explicitly not in the identity context).
-                    let fn_sig = cx.tcx.fn_sig(callee_def_id).instantiate_identity().skip_binder();
+                    let bound_fn_sig = cx.tcx.fn_sig(callee_def_id);
+                    let fn_sig = bound_fn_sig.skip_binder();
                     if let Some(arg_index) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == expr.hir_id)
-                        && let Some(param_ty) = fn_sig.inputs().get(arg_index)
-                        && let ty::Param(ParamTy { index: param_index , ..}) = param_ty.kind()
+                        && let param_ty = fn_sig.input(arg_index).skip_binder()
+                        && let ty::Param(ParamTy { index: param_index , ..}) = *param_ty.kind()
                         // https://github.com/rust-lang/rust-clippy/issues/9504 and https://github.com/rust-lang/rust-clippy/issues/10021
-                        && (*param_index as usize) < call_generic_args.len()
+                        && (param_index as usize) < call_generic_args.len()
                     {
                         if fn_sig
+                            .skip_binder()
                             .inputs()
                             .iter()
                             .enumerate()
                             .filter(|(i, _)| *i != arg_index)
-                            .any(|(_, ty)| ty.contains(*param_ty))
+                            .any(|(_, ty)| ty.contains(param_ty))
                         {
                             return false;
                         }
@@ -414,7 +413,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                                 .iter()
                                 .filter(|predicate| {
                                     if let ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder()
-                                        && trait_predicate.trait_ref.self_ty() == *param_ty
+                                        && trait_predicate.trait_ref.self_ty() == param_ty
                                     {
                                         true
                                     } else {
@@ -425,7 +424,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                         let new_subst = cx
                             .tcx
                             .mk_args_from_iter(call_generic_args.iter().enumerate().map(|(i, t)| {
-                                if i == (*param_index as usize) {
+                                if i == param_index as usize {
                                     GenericArg::from(ty)
                                 } else {
                                     t
@@ -433,7 +432,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                             }));
 
                         if trait_predicates.any(|predicate| {
-                            let predicate = EarlyBinder::bind(predicate).instantiate(cx.tcx, new_subst);
+                            let predicate = bound_fn_sig.rebind(predicate).instantiate(cx.tcx, new_subst);
                             let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate);
                             !cx.tcx
                                 .infer_ctxt()
@@ -443,12 +442,12 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                             return false;
                         }
 
-                        let output_ty = fn_sig.output();
-                        if output_ty.contains(*param_ty) {
+                        let output_ty = cx.tcx.instantiate_bound_regions_with_erased(fn_sig.output());
+                        if output_ty.contains(param_ty) {
                             if let Ok(new_ty) = cx.tcx.try_instantiate_and_normalize_erasing_regions(
                                 new_subst,
                                 cx.param_env,
-                                EarlyBinder::bind(output_ty),
+                                bound_fn_sig.rebind(output_ty),
                             ) {
                                 expr = parent_expr;
                                 ty = new_ty;
diff --git a/tests/ui/unnecessary_to_owned.fixed b/tests/ui/unnecessary_to_owned.fixed
index 67faabc53cb..2dd1d746626 100644
--- a/tests/ui/unnecessary_to_owned.fixed
+++ b/tests/ui/unnecessary_to_owned.fixed
@@ -1,4 +1,10 @@
-#![allow(clippy::needless_borrow, clippy::needless_borrows_for_generic_args, clippy::ptr_arg)]
+#![allow(
+    clippy::needless_borrow,
+    clippy::needless_borrows_for_generic_args,
+    clippy::ptr_arg,
+    clippy::manual_async_fn,
+    clippy::needless_lifetimes
+)]
 #![warn(clippy::unnecessary_to_owned, clippy::redundant_clone)]
 
 use std::borrow::Cow;
@@ -506,3 +512,18 @@ mod issue_10033 {
         }
     }
 }
+
+mod issue_11952 {
+    use core::future::{Future, IntoFuture};
+
+    fn foo<'a, T: AsRef<[u8]>>(x: T, y: &'a i32) -> impl 'a + Future<Output = Result<(), ()>> {
+        async move {
+            let _y = y;
+            Ok(())
+        }
+    }
+
+    fn bar() {
+        IntoFuture::into_future(foo([], &0));
+    }
+}
diff --git a/tests/ui/unnecessary_to_owned.rs b/tests/ui/unnecessary_to_owned.rs
index 99f9136427d..17fad33402b 100644
--- a/tests/ui/unnecessary_to_owned.rs
+++ b/tests/ui/unnecessary_to_owned.rs
@@ -1,4 +1,10 @@
-#![allow(clippy::needless_borrow, clippy::needless_borrows_for_generic_args, clippy::ptr_arg)]
+#![allow(
+    clippy::needless_borrow,
+    clippy::needless_borrows_for_generic_args,
+    clippy::ptr_arg,
+    clippy::manual_async_fn,
+    clippy::needless_lifetimes
+)]
 #![warn(clippy::unnecessary_to_owned, clippy::redundant_clone)]
 
 use std::borrow::Cow;
@@ -506,3 +512,18 @@ mod issue_10033 {
         }
     }
 }
+
+mod issue_11952 {
+    use core::future::{Future, IntoFuture};
+
+    fn foo<'a, T: AsRef<[u8]>>(x: T, y: &'a i32) -> impl 'a + Future<Output = Result<(), ()>> {
+        async move {
+            let _y = y;
+            Ok(())
+        }
+    }
+
+    fn bar() {
+        IntoFuture::into_future(foo([].to_vec(), &0));
+    }
+}
diff --git a/tests/ui/unnecessary_to_owned.stderr b/tests/ui/unnecessary_to_owned.stderr
index d8971b51dca..ad6fa422b8c 100644
--- a/tests/ui/unnecessary_to_owned.stderr
+++ b/tests/ui/unnecessary_to_owned.stderr
@@ -1,11 +1,11 @@
 error: redundant clone
-  --> $DIR/unnecessary_to_owned.rs:148:64
+  --> $DIR/unnecessary_to_owned.rs:154:64
    |
 LL |     require_c_str(&CString::from_vec_with_nul(vec![0]).unwrap().to_owned());
    |                                                                ^^^^^^^^^^^ help: remove this
    |
 note: this value is dropped without further use
-  --> $DIR/unnecessary_to_owned.rs:148:20
+  --> $DIR/unnecessary_to_owned.rs:154:20
    |
 LL |     require_c_str(&CString::from_vec_with_nul(vec![0]).unwrap().to_owned());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -13,55 +13,55 @@ LL |     require_c_str(&CString::from_vec_with_nul(vec![0]).unwrap().to_owned())
    = help: to override `-D warnings` add `#[allow(clippy::redundant_clone)]`
 
 error: redundant clone
-  --> $DIR/unnecessary_to_owned.rs:149:40
+  --> $DIR/unnecessary_to_owned.rs:155:40
    |
 LL |     require_os_str(&OsString::from("x").to_os_string());
    |                                        ^^^^^^^^^^^^^^^ help: remove this
    |
 note: this value is dropped without further use
-  --> $DIR/unnecessary_to_owned.rs:149:21
+  --> $DIR/unnecessary_to_owned.rs:155:21
    |
 LL |     require_os_str(&OsString::from("x").to_os_string());
    |                     ^^^^^^^^^^^^^^^^^^^
 
 error: redundant clone
-  --> $DIR/unnecessary_to_owned.rs:150:48
+  --> $DIR/unnecessary_to_owned.rs:156:48
    |
 LL |     require_path(&std::path::PathBuf::from("x").to_path_buf());
    |                                                ^^^^^^^^^^^^^^ help: remove this
    |
 note: this value is dropped without further use
-  --> $DIR/unnecessary_to_owned.rs:150:19
+  --> $DIR/unnecessary_to_owned.rs:156:19
    |
 LL |     require_path(&std::path::PathBuf::from("x").to_path_buf());
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant clone
-  --> $DIR/unnecessary_to_owned.rs:151:35
+  --> $DIR/unnecessary_to_owned.rs:157:35
    |
 LL |     require_str(&String::from("x").to_string());
    |                                   ^^^^^^^^^^^^ help: remove this
    |
 note: this value is dropped without further use
-  --> $DIR/unnecessary_to_owned.rs:151:18
+  --> $DIR/unnecessary_to_owned.rs:157:18
    |
 LL |     require_str(&String::from("x").to_string());
    |                  ^^^^^^^^^^^^^^^^^
 
 error: redundant clone
-  --> $DIR/unnecessary_to_owned.rs:152:39
+  --> $DIR/unnecessary_to_owned.rs:158:39
    |
 LL |     require_slice(&[String::from("x")].to_owned());
    |                                       ^^^^^^^^^^^ help: remove this
    |
 note: this value is dropped without further use
-  --> $DIR/unnecessary_to_owned.rs:152:20
+  --> $DIR/unnecessary_to_owned.rs:158:20
    |
 LL |     require_slice(&[String::from("x")].to_owned());
    |                    ^^^^^^^^^^^^^^^^^^^
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:57:36
+  --> $DIR/unnecessary_to_owned.rs:63:36
    |
 LL |     require_c_str(&Cow::from(c_str).into_owned());
    |                                    ^^^^^^^^^^^^^ help: remove this
@@ -70,415 +70,415 @@ LL |     require_c_str(&Cow::from(c_str).into_owned());
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_to_owned)]`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:58:19
+  --> $DIR/unnecessary_to_owned.rs:64:19
    |
 LL |     require_c_str(&c_str.to_owned());
    |                   ^^^^^^^^^^^^^^^^^ help: use: `c_str`
 
 error: unnecessary use of `to_os_string`
-  --> $DIR/unnecessary_to_owned.rs:60:20
+  --> $DIR/unnecessary_to_owned.rs:66:20
    |
 LL |     require_os_str(&os_str.to_os_string());
    |                    ^^^^^^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:61:38
+  --> $DIR/unnecessary_to_owned.rs:67:38
    |
 LL |     require_os_str(&Cow::from(os_str).into_owned());
    |                                      ^^^^^^^^^^^^^ help: remove this
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:62:20
+  --> $DIR/unnecessary_to_owned.rs:68:20
    |
 LL |     require_os_str(&os_str.to_owned());
    |                    ^^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `to_path_buf`
-  --> $DIR/unnecessary_to_owned.rs:64:18
+  --> $DIR/unnecessary_to_owned.rs:70:18
    |
 LL |     require_path(&path.to_path_buf());
    |                  ^^^^^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:65:34
+  --> $DIR/unnecessary_to_owned.rs:71:34
    |
 LL |     require_path(&Cow::from(path).into_owned());
    |                                  ^^^^^^^^^^^^^ help: remove this
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:66:18
+  --> $DIR/unnecessary_to_owned.rs:72:18
    |
 LL |     require_path(&path.to_owned());
    |                  ^^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `to_string`
-  --> $DIR/unnecessary_to_owned.rs:68:17
+  --> $DIR/unnecessary_to_owned.rs:74:17
    |
 LL |     require_str(&s.to_string());
    |                 ^^^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:69:30
+  --> $DIR/unnecessary_to_owned.rs:75:30
    |
 LL |     require_str(&Cow::from(s).into_owned());
    |                              ^^^^^^^^^^^^^ help: remove this
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:70:17
+  --> $DIR/unnecessary_to_owned.rs:76:17
    |
 LL |     require_str(&s.to_owned());
    |                 ^^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_string`
-  --> $DIR/unnecessary_to_owned.rs:71:17
+  --> $DIR/unnecessary_to_owned.rs:77:17
    |
 LL |     require_str(&x_ref.to_string());
    |                 ^^^^^^^^^^^^^^^^^^ help: use: `x_ref.as_ref()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:73:19
+  --> $DIR/unnecessary_to_owned.rs:79:19
    |
 LL |     require_slice(&slice.to_vec());
    |                   ^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:74:36
+  --> $DIR/unnecessary_to_owned.rs:80:36
    |
 LL |     require_slice(&Cow::from(slice).into_owned());
    |                                    ^^^^^^^^^^^^^ help: remove this
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:75:19
+  --> $DIR/unnecessary_to_owned.rs:81:19
    |
 LL |     require_slice(&array.to_owned());
    |                   ^^^^^^^^^^^^^^^^^ help: use: `array.as_ref()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:76:19
+  --> $DIR/unnecessary_to_owned.rs:82:19
    |
 LL |     require_slice(&array_ref.to_owned());
    |                   ^^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref.as_ref()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:77:19
+  --> $DIR/unnecessary_to_owned.rs:83:19
    |
 LL |     require_slice(&slice.to_owned());
    |                   ^^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `into_owned`
-  --> $DIR/unnecessary_to_owned.rs:80:42
+  --> $DIR/unnecessary_to_owned.rs:86:42
    |
 LL |     require_x(&Cow::<X>::Owned(x.clone()).into_owned());
    |                                          ^^^^^^^^^^^^^ help: remove this
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:83:25
+  --> $DIR/unnecessary_to_owned.rs:89:25
    |
 LL |     require_deref_c_str(c_str.to_owned());
    |                         ^^^^^^^^^^^^^^^^ help: use: `c_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:84:26
+  --> $DIR/unnecessary_to_owned.rs:90:26
    |
 LL |     require_deref_os_str(os_str.to_owned());
    |                          ^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:85:24
+  --> $DIR/unnecessary_to_owned.rs:91:24
    |
 LL |     require_deref_path(path.to_owned());
    |                        ^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:86:23
+  --> $DIR/unnecessary_to_owned.rs:92:23
    |
 LL |     require_deref_str(s.to_owned());
    |                       ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:87:25
+  --> $DIR/unnecessary_to_owned.rs:93:25
    |
 LL |     require_deref_slice(slice.to_owned());
    |                         ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:89:30
+  --> $DIR/unnecessary_to_owned.rs:95:30
    |
 LL |     require_impl_deref_c_str(c_str.to_owned());
    |                              ^^^^^^^^^^^^^^^^ help: use: `c_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:90:31
+  --> $DIR/unnecessary_to_owned.rs:96:31
    |
 LL |     require_impl_deref_os_str(os_str.to_owned());
    |                               ^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:91:29
+  --> $DIR/unnecessary_to_owned.rs:97:29
    |
 LL |     require_impl_deref_path(path.to_owned());
    |                             ^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:92:28
+  --> $DIR/unnecessary_to_owned.rs:98:28
    |
 LL |     require_impl_deref_str(s.to_owned());
    |                            ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:93:30
+  --> $DIR/unnecessary_to_owned.rs:99:30
    |
 LL |     require_impl_deref_slice(slice.to_owned());
    |                              ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:95:29
+  --> $DIR/unnecessary_to_owned.rs:101:29
    |
 LL |     require_deref_str_slice(s.to_owned(), slice.to_owned());
    |                             ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:95:43
+  --> $DIR/unnecessary_to_owned.rs:101:43
    |
 LL |     require_deref_str_slice(s.to_owned(), slice.to_owned());
    |                                           ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:96:29
+  --> $DIR/unnecessary_to_owned.rs:102:29
    |
 LL |     require_deref_slice_str(slice.to_owned(), s.to_owned());
    |                             ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:96:47
+  --> $DIR/unnecessary_to_owned.rs:102:47
    |
 LL |     require_deref_slice_str(slice.to_owned(), s.to_owned());
    |                                               ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:98:26
+  --> $DIR/unnecessary_to_owned.rs:104:26
    |
 LL |     require_as_ref_c_str(c_str.to_owned());
    |                          ^^^^^^^^^^^^^^^^ help: use: `c_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:99:27
+  --> $DIR/unnecessary_to_owned.rs:105:27
    |
 LL |     require_as_ref_os_str(os_str.to_owned());
    |                           ^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:100:25
+  --> $DIR/unnecessary_to_owned.rs:106:25
    |
 LL |     require_as_ref_path(path.to_owned());
    |                         ^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:101:24
+  --> $DIR/unnecessary_to_owned.rs:107:24
    |
 LL |     require_as_ref_str(s.to_owned());
    |                        ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:102:24
+  --> $DIR/unnecessary_to_owned.rs:108:24
    |
 LL |     require_as_ref_str(x.to_owned());
    |                        ^^^^^^^^^^^^ help: use: `&x`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:103:26
+  --> $DIR/unnecessary_to_owned.rs:109:26
    |
 LL |     require_as_ref_slice(array.to_owned());
    |                          ^^^^^^^^^^^^^^^^ help: use: `array`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:104:26
+  --> $DIR/unnecessary_to_owned.rs:110:26
    |
 LL |     require_as_ref_slice(array_ref.to_owned());
    |                          ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:105:26
+  --> $DIR/unnecessary_to_owned.rs:111:26
    |
 LL |     require_as_ref_slice(slice.to_owned());
    |                          ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:107:31
+  --> $DIR/unnecessary_to_owned.rs:113:31
    |
 LL |     require_impl_as_ref_c_str(c_str.to_owned());
    |                               ^^^^^^^^^^^^^^^^ help: use: `c_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:108:32
+  --> $DIR/unnecessary_to_owned.rs:114:32
    |
 LL |     require_impl_as_ref_os_str(os_str.to_owned());
    |                                ^^^^^^^^^^^^^^^^^ help: use: `os_str`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:109:30
+  --> $DIR/unnecessary_to_owned.rs:115:30
    |
 LL |     require_impl_as_ref_path(path.to_owned());
    |                              ^^^^^^^^^^^^^^^ help: use: `path`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:110:29
+  --> $DIR/unnecessary_to_owned.rs:116:29
    |
 LL |     require_impl_as_ref_str(s.to_owned());
    |                             ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:111:29
+  --> $DIR/unnecessary_to_owned.rs:117:29
    |
 LL |     require_impl_as_ref_str(x.to_owned());
    |                             ^^^^^^^^^^^^ help: use: `&x`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:112:31
+  --> $DIR/unnecessary_to_owned.rs:118:31
    |
 LL |     require_impl_as_ref_slice(array.to_owned());
    |                               ^^^^^^^^^^^^^^^^ help: use: `array`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:113:31
+  --> $DIR/unnecessary_to_owned.rs:119:31
    |
 LL |     require_impl_as_ref_slice(array_ref.to_owned());
    |                               ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:114:31
+  --> $DIR/unnecessary_to_owned.rs:120:31
    |
 LL |     require_impl_as_ref_slice(slice.to_owned());
    |                               ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:116:30
+  --> $DIR/unnecessary_to_owned.rs:122:30
    |
 LL |     require_as_ref_str_slice(s.to_owned(), array.to_owned());
    |                              ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:116:44
+  --> $DIR/unnecessary_to_owned.rs:122:44
    |
 LL |     require_as_ref_str_slice(s.to_owned(), array.to_owned());
    |                                            ^^^^^^^^^^^^^^^^ help: use: `array`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:117:30
+  --> $DIR/unnecessary_to_owned.rs:123:30
    |
 LL |     require_as_ref_str_slice(s.to_owned(), array_ref.to_owned());
    |                              ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:117:44
+  --> $DIR/unnecessary_to_owned.rs:123:44
    |
 LL |     require_as_ref_str_slice(s.to_owned(), array_ref.to_owned());
    |                                            ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:118:30
+  --> $DIR/unnecessary_to_owned.rs:124:30
    |
 LL |     require_as_ref_str_slice(s.to_owned(), slice.to_owned());
    |                              ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:118:44
+  --> $DIR/unnecessary_to_owned.rs:124:44
    |
 LL |     require_as_ref_str_slice(s.to_owned(), slice.to_owned());
    |                                            ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:119:30
+  --> $DIR/unnecessary_to_owned.rs:125:30
    |
 LL |     require_as_ref_slice_str(array.to_owned(), s.to_owned());
    |                              ^^^^^^^^^^^^^^^^ help: use: `array`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:119:48
+  --> $DIR/unnecessary_to_owned.rs:125:48
    |
 LL |     require_as_ref_slice_str(array.to_owned(), s.to_owned());
    |                                                ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:120:30
+  --> $DIR/unnecessary_to_owned.rs:126:30
    |
 LL |     require_as_ref_slice_str(array_ref.to_owned(), s.to_owned());
    |                              ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:120:52
+  --> $DIR/unnecessary_to_owned.rs:126:52
    |
 LL |     require_as_ref_slice_str(array_ref.to_owned(), s.to_owned());
    |                                                    ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:121:30
+  --> $DIR/unnecessary_to_owned.rs:127:30
    |
 LL |     require_as_ref_slice_str(slice.to_owned(), s.to_owned());
    |                              ^^^^^^^^^^^^^^^^ help: use: `slice`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:121:48
+  --> $DIR/unnecessary_to_owned.rs:127:48
    |
 LL |     require_as_ref_slice_str(slice.to_owned(), s.to_owned());
    |                                                ^^^^^^^^^^^^ help: use: `s`
 
 error: unnecessary use of `to_string`
-  --> $DIR/unnecessary_to_owned.rs:123:20
+  --> $DIR/unnecessary_to_owned.rs:129:20
    |
 LL |     let _ = x.join(&x_ref.to_string());
    |                    ^^^^^^^^^^^^^^^^^^ help: use: `x_ref`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:125:13
+  --> $DIR/unnecessary_to_owned.rs:131:13
    |
 LL |     let _ = slice.to_vec().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `slice.iter().copied()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:126:13
+  --> $DIR/unnecessary_to_owned.rs:132:13
    |
 LL |     let _ = slice.to_owned().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `slice.iter().copied()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:127:13
+  --> $DIR/unnecessary_to_owned.rs:133:13
    |
 LL |     let _ = [std::path::PathBuf::new()][..].to_vec().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `[std::path::PathBuf::new()][..].iter().cloned()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:128:13
+  --> $DIR/unnecessary_to_owned.rs:134:13
    |
 LL |     let _ = [std::path::PathBuf::new()][..].to_owned().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `[std::path::PathBuf::new()][..].iter().cloned()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:130:13
+  --> $DIR/unnecessary_to_owned.rs:136:13
    |
 LL |     let _ = IntoIterator::into_iter(slice.to_vec());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `slice.iter().copied()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:131:13
+  --> $DIR/unnecessary_to_owned.rs:137:13
    |
 LL |     let _ = IntoIterator::into_iter(slice.to_owned());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `slice.iter().copied()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:132:13
+  --> $DIR/unnecessary_to_owned.rs:138:13
    |
 LL |     let _ = IntoIterator::into_iter([std::path::PathBuf::new()][..].to_vec());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `[std::path::PathBuf::new()][..].iter().cloned()`
 
 error: unnecessary use of `to_owned`
-  --> $DIR/unnecessary_to_owned.rs:133:13
+  --> $DIR/unnecessary_to_owned.rs:139:13
    |
 LL |     let _ = IntoIterator::into_iter([std::path::PathBuf::new()][..].to_owned());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `[std::path::PathBuf::new()][..].iter().cloned()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:195:14
+  --> $DIR/unnecessary_to_owned.rs:201:14
    |
 LL |     for t in file_types.to_vec() {
    |              ^^^^^^^^^^^^^^^^^^^
@@ -494,28 +494,34 @@ LL +         let path = match get_file_path(t) {
    |
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:218:14
+  --> $DIR/unnecessary_to_owned.rs:224:14
    |
 LL |     let _ = &["x"][..].to_vec().into_iter();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `["x"][..].iter().cloned()`
 
 error: unnecessary use of `to_vec`
-  --> $DIR/unnecessary_to_owned.rs:223:14
+  --> $DIR/unnecessary_to_owned.rs:229:14
    |
 LL |     let _ = &["x"][..].to_vec().into_iter();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `["x"][..].iter().copied()`
 
 error: unnecessary use of `to_string`
-  --> $DIR/unnecessary_to_owned.rs:270:24
+  --> $DIR/unnecessary_to_owned.rs:276:24
    |
 LL |         Box::new(build(y.to_string()))
    |                        ^^^^^^^^^^^^^ help: use: `y`
 
 error: unnecessary use of `to_string`
-  --> $DIR/unnecessary_to_owned.rs:378:12
+  --> $DIR/unnecessary_to_owned.rs:384:12
    |
 LL |         id("abc".to_string())
    |            ^^^^^^^^^^^^^^^^^ help: use: `"abc"`
 
-error: aborting due to 79 previous errors
+error: unnecessary use of `to_vec`
+  --> $DIR/unnecessary_to_owned.rs:527:37
+   |
+LL |         IntoFuture::into_future(foo([].to_vec(), &0));
+   |                                     ^^^^^^^^^^^ help: use: `[]`
+
+error: aborting due to 80 previous errors