From fabd77201abacd200379c67cda44b3a4e743e754 Mon Sep 17 00:00:00 2001
From: Konrad Borowski <konrad@borowski.pw>
Date: Tue, 29 Jan 2019 12:40:16 +0100
Subject: [PATCH] Remove TrustedRandomAccess specialization for Cloned<T: Copy>

For incorrect Clone implementations, this exposes specialization.
---
 src/libcore/iter/adapters/mod.rs | 18 ++----------------
 src/libcore/tests/iter.rs        | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/src/libcore/iter/adapters/mod.rs b/src/libcore/iter/adapters/mod.rs
index f8d6bedeace25..1b0f471d71013 100644
--- a/src/libcore/iter/adapters/mod.rs
+++ b/src/libcore/iter/adapters/mod.rs
@@ -314,27 +314,13 @@ impl<'a, I, T: 'a> FusedIterator for Cloned<I>
 #[doc(hidden)]
 unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I>
     where I: TrustedRandomAccess<Item=&'a T>, T: Clone
-{
-    default unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
-        self.it.get_unchecked(i).clone()
-    }
-
-    #[inline]
-    default fn may_have_side_effect() -> bool { true }
-}
-
-#[doc(hidden)]
-unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I>
-    where I: TrustedRandomAccess<Item=&'a T>, T: Copy
 {
     unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
-        *self.it.get_unchecked(i)
+        self.it.get_unchecked(i).clone()
     }
 
     #[inline]
-    fn may_have_side_effect() -> bool {
-        I::may_have_side_effect()
-    }
+    fn may_have_side_effect() -> bool { true }
 }
 
 #[unstable(feature = "trusted_len", issue = "37572")]
diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs
index 0fa99745d9065..a94bd1af07d17 100644
--- a/src/libcore/tests/iter.rs
+++ b/src/libcore/tests/iter.rs
@@ -1,6 +1,7 @@
 use core::cell::Cell;
 use core::iter::*;
 use core::{i8, i16, isize};
+use core::sync::atomic::{AtomicUsize, Ordering};
 use core::usize;
 
 #[test]
@@ -1305,6 +1306,24 @@ fn test_cloned_side_effects() {
     assert_eq!(count, 2);
 }
 
+#[test]
+fn test_cloned_side_effects_with_incorrect_clone_implementation() {
+    #[derive(Copy)]
+    struct X;
+
+    static CALL_COUNT: AtomicUsize = AtomicUsize::new(0);
+
+    impl Clone for X {
+        fn clone(&self) -> X {
+            CALL_COUNT.store(CALL_COUNT.load(Ordering::Relaxed) + 1, Ordering::Relaxed);
+            X
+        }
+    }
+
+    for _ in [X; 3].iter().cloned().zip(&[1]) {}
+    assert_eq!(CALL_COUNT.load(Ordering::Relaxed), 2);
+}
+
 #[test]
 fn test_double_ended_map() {
     let xs = [1, 2, 3, 4, 5, 6];