Test array into_iter with more wrapper types

src/test/ui/iterators/into-iter-on-arrays-2018.rs

@@ -2,6 +2,8 @@
 // edition:2018
 
 use std::array::IntoIter;
+use std::ops::Deref;
+use std::rc::Rc;
 use std::slice::Iter;
 
 fn main() {
@@ -17,6 +19,21 @@ fn main() {
     //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
     //~| WARNING this was previously accepted by the compiler but is being phased out
 
+    // The `array_into_iter` lint doesn't cover other wrappers that deref to an array.
+    let _: Iter<'_, i32> = Rc::new(array).into_iter();
+    let _: Iter<'_, i32> = Array(array).into_iter();
+
     // But you can always use the trait method explicitly as an array.
     let _: IntoIter<i32, 10> = IntoIterator::into_iter(array);
 }
+
+/// User type that dereferences to an array.
+struct Array([i32; 10]);
+
+impl Deref for Array {
+    type Target = [i32; 10];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}

src/test/ui/iterators/into-iter-on-arrays-2018.stderr

@@ -1,5 +1,5 @@
 warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
-  --> $DIR/into-iter-on-arrays-2018.rs:12:34
+  --> $DIR/into-iter-on-arrays-2018.rs:14:34
    |
 LL |     let _: Iter<'_, i32> = array.into_iter();
    |                                  ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
@@ -9,7 +9,7 @@ LL |     let _: Iter<'_, i32> = array.into_iter();
    = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
 
 warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
-  --> $DIR/into-iter-on-arrays-2018.rs:16:44
+  --> $DIR/into-iter-on-arrays-2018.rs:18:44
    |
 LL |     let _: Iter<'_, i32> = Box::new(array).into_iter();
    |                                            ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
@@ -21,7 +21,7 @@ warning: 2 warnings emitted
 
 Future incompatibility report: Future breakage date: None, diagnostic:
 warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
-  --> $DIR/into-iter-on-arrays-2018.rs:12:34
+  --> $DIR/into-iter-on-arrays-2018.rs:14:34
    |
 LL |     let _: Iter<'_, i32> = array.into_iter();
    |                                  ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
@@ -32,7 +32,7 @@ LL |     let _: Iter<'_, i32> = array.into_iter();
 
 Future breakage date: None, diagnostic:
 warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
-  --> $DIR/into-iter-on-arrays-2018.rs:16:44
+  --> $DIR/into-iter-on-arrays-2018.rs:18:44
    |
 LL |     let _: Iter<'_, i32> = Box::new(array).into_iter();
    |                                            ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`

src/test/ui/iterators/into-iter-on-arrays-2021.rs

@@ -3,6 +3,8 @@
 // compile-flags: -Zunstable-options
 
 use std::array::IntoIter;
+use std::ops::Deref;
+use std::rc::Rc;
 
 fn main() {
     let array = [0; 10];
@@ -11,6 +13,21 @@ fn main() {
     let _: IntoIter<i32, 10> = array.into_iter();
     let _: IntoIter<i32, 10> = Box::new(array).into_iter();
 
-    // And you can always use the trait method explicitly as an array.
+    // The `array_into_iter` lint doesn't cover other wrappers that deref to an array.
+    let _: IntoIter<i32, 10> = Rc::new(array).into_iter();
+    let _: IntoIter<i32, 10> = Array(array).into_iter();
+
+    // You can always use the trait method explicitly as an array.
     let _: IntoIter<i32, 10> = IntoIterator::into_iter(array);
 }
+
+/// User type that dereferences to an array.
+struct Array([i32; 10]);
+
+impl Deref for Array {
+    type Target = [i32; 10];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}