std: Remove #[old_orphan_check] from PartialEq

This is a deprecated attribute that is slated for removal, and it also affects
all implementors of the trait. This commit removes the attribute and fixes up
implementors accordingly. The primary implementation which was lost was the
ability to compare `&[T]` and `Vec<T>` (in that order).

This change also modifies the `assert_eq!` macro to not consider both directions
of equality, only the one given in the left/right forms to the macro. This
modification is motivated due to the fact that `&[T] == Vec<T>` no longer
compiles, causing hundreds of errors in unit tests in the standard library (and
likely throughout the community as well).

cc #19470
[breaking-change]

src/doc/trpl/macros.md

@@ -37,7 +37,7 @@ number of elements.
 
 ```rust
 let x: Vec<u32> = vec![1, 2, 3];
-# assert_eq!(&[1,2,3], &x);
+# assert_eq!(x, [1, 2, 3]);
 ```
 
 This can't be an ordinary function, because it takes any number of arguments.
@@ -51,7 +51,7 @@ let x: Vec<u32> = {
     temp_vec.push(3);
     temp_vec
 };
-# assert_eq!(&[1,2,3], &x);
+# assert_eq!(x, [1, 2, 3]);
 ```
 
 We can implement this shorthand, using a macro: [^actual]
@@ -73,7 +73,7 @@ macro_rules! vec {
     };
 }
 # fn main() {
-#     assert_eq!([1,2,3], vec![1,2,3]);
+#     assert_eq!(vec![1,2,3], [1, 2, 3]);
 # }
 ```
 

src/libcollections/linked_list.rs

@@ -1079,7 +1079,7 @@ mod test {
         thread::spawn(move || {
             check_links(&n);
             let a: &[_] = &[&1,&2,&3];
-            assert_eq!(a, n.iter().collect::<Vec<_>>());
+            assert_eq!(a, &n.iter().collect::<Vec<_>>()[..]);
         }).join().ok().unwrap();
     }
 

src/libcollections/vec.rs

@@ -1533,22 +1533,22 @@ impl<T> Extend<T> for Vec<T> {
 }
 
 __impl_slice_eq1! { Vec<A>, Vec<B> }
-__impl_slice_eq2! { Vec<A>, &'b [B] }
-__impl_slice_eq2! { Vec<A>, &'b mut [B] }
-__impl_slice_eq2! { Cow<'a, [A]>, &'b [B], Clone }
-__impl_slice_eq2! { Cow<'a, [A]>, &'b mut [B], Clone }
-__impl_slice_eq2! { Cow<'a, [A]>, Vec<B>, Clone }
+__impl_slice_eq1! { Vec<A>, &'b [B] }
+__impl_slice_eq1! { Vec<A>, &'b mut [B] }
+__impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
+__impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
+__impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
 
 macro_rules! array_impls {
     ($($N: expr)+) => {
         $(
             // NOTE: some less important impls are omitted to reduce code bloat
-            __impl_slice_eq2! { Vec<A>, [B; $N] }
-            __impl_slice_eq2! { Vec<A>, &'b [B; $N] }
-            // __impl_slice_eq2! { Vec<A>, &'b mut [B; $N] }
-            // __impl_slice_eq2! { Cow<'a, [A]>, [B; $N], Clone }
-            // __impl_slice_eq2! { Cow<'a, [A]>, &'b [B; $N], Clone }
-            // __impl_slice_eq2! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
+            __impl_slice_eq1! { Vec<A>, [B; $N] }
+            __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
+            // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
+            // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
+            // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
+            // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
         )+
     }
 }

src/libcollectionstest/enum_set.rs

@@ -153,19 +153,19 @@ fn test_iterator() {
 
     e1.insert(A);
     let elems: Vec<_> = e1.iter().collect();
-    assert_eq!([A], elems);
+    assert_eq!(elems, [A]);
 
     e1.insert(C);
     let elems: Vec<_> = e1.iter().collect();
-    assert_eq!([A,C], elems);
+    assert_eq!(elems, [A,C]);
 
     e1.insert(C);
     let elems: Vec<_> = e1.iter().collect();
-    assert_eq!([A,C], elems);
+    assert_eq!(elems, [A,C]);
 
     e1.insert(B);
     let elems: Vec<_> = e1.iter().collect();
-    assert_eq!([A,B,C], elems);
+    assert_eq!(elems, [A,B,C]);
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -183,35 +183,35 @@ fn test_operators() {
 
     let e_union = e1 | e2;
     let elems: Vec<_> = e_union.iter().collect();
-    assert_eq!([A,B,C], elems);
+    assert_eq!(elems, [A,B,C]);
 
     let e_intersection = e1 & e2;
     let elems: Vec<_> = e_intersection.iter().collect();
-    assert_eq!([C], elems);
+    assert_eq!(elems, [C]);
 
     // Another way to express intersection
     let e_intersection = e1 - (e1 - e2);
     let elems: Vec<_> = e_intersection.iter().collect();
-    assert_eq!([C], elems);
+    assert_eq!(elems, [C]);
 
     let e_subtract = e1 - e2;
     let elems: Vec<_> = e_subtract.iter().collect();
-    assert_eq!([A], elems);
+    assert_eq!(elems, [A]);
 
     // Bitwise XOR of two sets, aka symmetric difference
     let e_symmetric_diff = e1 ^ e2;
     let elems: Vec<_> = e_symmetric_diff.iter().collect();
-    assert_eq!([A,B], elems);
+    assert_eq!(elems, [A,B]);
 
     // Another way to express symmetric difference
     let e_symmetric_diff = (e1 - e2) | (e2 - e1);
     let elems: Vec<_> = e_symmetric_diff.iter().collect();
-    assert_eq!([A,B], elems);
+    assert_eq!(elems, [A,B]);
 
     // Yet another way to express symmetric difference
     let e_symmetric_diff = (e1 | e2) - (e1 & e2);
     let elems: Vec<_> = e_symmetric_diff.iter().collect();
-    assert_eq!([A,B], elems);
+    assert_eq!(elems, [A,B]);
 }
 
 #[test]

src/libcollectionstest/str.rs

@@ -83,7 +83,7 @@ fn test_collect() {
 fn test_into_bytes() {
     let data = String::from_str("asdf");
     let buf = data.into_bytes();
-    assert_eq!(b"asdf", buf);
+    assert_eq!(buf, b"asdf");
 }
 
 #[test]

src/libcollectionstest/vec_deque.rs

@@ -821,7 +821,7 @@ fn test_as_slices() {
 
         let (left, right) = ring.as_slices();
         let expected: Vec<_> = (0..i+1).collect();
-        assert_eq!(left, expected);
+        assert_eq!(left, &expected[..]);
         assert_eq!(right, []);
     }
 
@@ -830,8 +830,8 @@ fn test_as_slices() {
         let (left, right) = ring.as_slices();
         let expected_left: Vec<_> = (-last..j+1).rev().collect();
         let expected_right: Vec<_> = (0..first).collect();
-        assert_eq!(left, expected_left);
-        assert_eq!(right, expected_right);
+        assert_eq!(left, &expected_left[..]);
+        assert_eq!(right, &expected_right[..]);
     }
 
     assert_eq!(ring.len() as i32, cap);
@@ -849,7 +849,7 @@ fn test_as_mut_slices() {
 
         let (left, right) = ring.as_mut_slices();
         let expected: Vec<_> = (0..i+1).collect();
-        assert_eq!(left, expected);
+        assert_eq!(left, &expected[..]);
         assert_eq!(right, []);
     }
 
@@ -858,8 +858,8 @@ fn test_as_mut_slices() {
         let (left, right) = ring.as_mut_slices();
         let expected_left: Vec<_> = (-last..j+1).rev().collect();
         let expected_right: Vec<_> = (0..first).collect();
-        assert_eq!(left, expected_left);
-        assert_eq!(right, expected_right);
+        assert_eq!(left, &expected_left[..]);
+        assert_eq!(right, &expected_right[..]);
     }
 
     assert_eq!(ring.len() as i32, cap);

src/libcore/cmp.rs

@@ -64,7 +64,6 @@ use option::Option::{self, Some, None};
 /// inverse of `ne`; that is, `!(a == b)` if and only if `a != b`.
 #[lang="eq"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[old_orphan_check]
 pub trait PartialEq<Rhs: ?Sized = Self> {
     /// This method tests for `self` and `other` values to be equal, and is used by `==`.
     #[stable(feature = "rust1", since = "1.0.0")]

src/libcore/cmp_macros.rs

@@ -15,8 +15,11 @@
 #[macro_export]
 macro_rules! __impl_slice_eq1 {
     ($Lhs: ty, $Rhs: ty) => {
+        __impl_slice_eq1! { $Lhs, $Rhs, Sized }
+    };
+    ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
         #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, 'b, A, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
+        impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
             #[inline]
             fn eq(&self, other: &$Rhs) -> bool { &self[..] == &other[..] }
             #[inline]
@@ -31,13 +34,7 @@ macro_rules! __impl_slice_eq2 {
         __impl_slice_eq2! { $Lhs, $Rhs, Sized }
     };
     ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
-        #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
-            #[inline]
-            fn eq(&self, other: &$Rhs) -> bool { &self[..] == &other[..] }
-            #[inline]
-            fn ne(&self, other: &$Rhs) -> bool { &self[..] != &other[..] }
-        }
+        __impl_slice_eq1!($Lhs, $Rhs, $Bound);
 
         #[stable(feature = "rust1", since = "1.0.0")]
         impl<'a, 'b, A: $Bound, B> PartialEq<$Lhs> for $Rhs where B: PartialEq<A> {

src/libcore/iter.rs

@@ -530,10 +530,9 @@ pub trait Iterator {
     /// # Examples
     ///
     /// ```
-    /// # #![feature(core)]
-    /// let a = [1, 2, 3, 4, 5];
-    /// let b: Vec<_> = a.iter().cloned().collect();
-    /// assert_eq!(a, b);
+    /// let expected = [1, 2, 3, 4, 5];
+    /// let actual: Vec<_> = expected.iter().cloned().collect();
+    /// assert_eq!(actual, expected);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -927,8 +926,8 @@ pub trait Iterator {
     /// # #![feature(core)]
     /// let a = [(1, 2), (3, 4)];
     /// let (left, right): (Vec<_>, Vec<_>) = a.iter().cloned().unzip();
-    /// assert_eq!([1, 3], left);
-    /// assert_eq!([2, 4], right);
+    /// assert_eq!(left, [1, 3]);
+    /// assert_eq!(right, [2, 4]);
     /// ```
     #[unstable(feature = "core", reason = "recent addition")]
     fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where

src/libcore/macros.rs

@@ -66,10 +66,10 @@ macro_rules! assert {
     );
 }
 
-/// Asserts that two expressions are equal to each other, testing equality in
-/// both directions.
+/// Asserts that two expressions are equal to each other.
 ///
-/// On panic, this macro will print the values of the expressions.
+/// On panic, this macro will print the values of the expressions with their
+/// debug representations.
 ///
 /// # Examples
 ///
@@ -84,10 +84,8 @@ macro_rules! assert_eq {
     ($left:expr , $right:expr) => ({
         match (&($left), &($right)) {
             (left_val, right_val) => {
-                // check both directions of equality....
-                if !((*left_val == *right_val) &&
-                     (*right_val == *left_val)) {
-                    panic!("assertion failed: `(left == right) && (right == left)` \
+                if !(*left_val == *right_val) {
+                    panic!("assertion failed: `(left == right)` \
                            (left: `{:?}`, right: `{:?}`)", *left_val, *right_val)
                 }
             }

src/libcoretest/mem.rs

@@ -103,7 +103,7 @@ fn test_transmute() {
     }
 
     unsafe {
-        assert_eq!([76], transmute::<_, Vec<u8>>("L".to_string()));
+        assert_eq!(transmute::<_, Vec<u8>>("L".to_string()), [76]);
     }
 }
 

src/libfmt_macros/lib.rs

@@ -446,7 +446,7 @@ mod tests {
 
     fn same(fmt: &'static str, p: &[Piece<'static>]) {
         let parser = Parser::new(fmt);
-        assert!(p == parser.collect::<Vec<Piece<'static>>>());
+        assert!(parser.collect::<Vec<Piece<'static>>>() == p);
     }
 
     fn fmtdflt() -> FormatSpec<'static> {

src/librustc_driver/test.rs

@@ -808,12 +808,11 @@ fn walk_ty() {
         let tup2_ty = ty::mk_tup(tcx, vec!(tup1_ty, tup1_ty, uint_ty));
         let uniq_ty = ty::mk_uniq(tcx, tup2_ty);
         let walked: Vec<_> = uniq_ty.walk().collect();
-        assert_eq!([uniq_ty,
-                    tup2_ty,
-                    tup1_ty, int_ty, uint_ty, int_ty, uint_ty,
-                    tup1_ty, int_ty, uint_ty, int_ty, uint_ty,
-                    uint_ty],
-                   walked);
+        assert_eq!(walked, [uniq_ty,
+                            tup2_ty,
+                            tup1_ty, int_ty, uint_ty, int_ty, uint_ty,
+                            tup1_ty, int_ty, uint_ty, int_ty, uint_ty,
+                            uint_ty]);
     })
 }
 

src/libstd/collections/hash/set.rs

@@ -1192,7 +1192,7 @@ mod test_set {
         };
 
         let v = hs.into_iter().collect::<Vec<char>>();
-        assert!(['a', 'b'] == v || ['b', 'a'] == v);
+        assert!(v == ['a', 'b'] || v == ['b', 'a']);
     }
 
     #[test]

src/libstd/old_io/buffered.rs

@@ -548,7 +548,7 @@ mod test {
         let mut w = BufferedWriter::with_capacity(3, Vec::new());
         w.write_all(&[0, 1]).unwrap();
         let a: &[_] = &[];
-        assert_eq!(a, &w.get_ref()[..]);
+        assert_eq!(&w.get_ref()[..], a);
         let w = w.into_inner();
         let a: &[_] = &[0, 1];
         assert_eq!(a, &w[..]);