Rollup of 5 pull requests

src/liballoc/collections/btree/map.rs

@@ -200,7 +200,7 @@ impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
             }
         }
 
-        if self.len() == 0 {
+        if self.is_empty() {
             // Ideally we'd call `BTreeMap::new` here, but that has the `K:
             // Ord` constraint, which this method lacks.
             BTreeMap {
@@ -759,12 +759,12 @@ impl<K: Ord, V> BTreeMap<K, V> {
     #[stable(feature = "btree_append", since = "1.11.0")]
     pub fn append(&mut self, other: &mut Self) {
         // Do we have to append anything at all?
-        if other.len() == 0 {
+        if other.is_empty() {
             return;
         }
 
         // We can just swap `self` and `other` if `self` is empty.
-        if self.len() == 0 {
+        if self.is_empty() {
             mem::swap(self, other);
             return;
         }

src/liballoc/collections/linked_list.rs

@@ -237,15 +237,15 @@ impl<T> LinkedList<T> {
 
         // Not creating new mutable (unique!) references overlapping `element`.
         match node.prev {
-            Some(prev) => (*prev.as_ptr()).next = node.next.clone(),
+            Some(prev) => (*prev.as_ptr()).next = node.next,
             // this node is the head node
-            None => self.head = node.next.clone(),
+            None => self.head = node.next,
         };
 
         match node.next {
-            Some(next) => (*next.as_ptr()).prev = node.prev.clone(),
+            Some(next) => (*next.as_ptr()).prev = node.prev,
             // this node is the tail node
-            None => self.tail = node.prev.clone(),
+            None => self.tail = node.prev,
         };
 
         self.len -= 1;

src/liballoc/collections/vec_deque.rs

@@ -9,6 +9,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
+use core::array::LengthAtMost32;
 use core::cmp::{self, Ordering};
 use core::fmt;
 use core::iter::{repeat_with, FromIterator, FusedIterator};
@@ -2571,13 +2572,14 @@ impl<A: PartialEq> PartialEq for VecDeque<A> {
 impl<A: Eq> Eq for VecDeque<A> {}
 
 macro_rules! __impl_slice_eq1 {
-    ($Lhs: ty, $Rhs: ty) => {
-        __impl_slice_eq1! { $Lhs, $Rhs, Sized }
-    };
-    ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
+    ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => {
         #[stable(feature = "vec_deque_partial_eq_slice", since = "1.17.0")]
-        impl<A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
-            fn eq(&self, other: &$Rhs) -> bool {
+        impl<A, B, $($vars)*> PartialEq<$rhs> for $lhs
+        where
+            A: PartialEq<B>,
+            $($constraints)*
+        {
+            fn eq(&self, other: &$rhs) -> bool {
                 if self.len() != other.len() {
                     return false;
                 }
@@ -2589,26 +2591,12 @@ macro_rules! __impl_slice_eq1 {
     }
 }
 
-__impl_slice_eq1! { VecDeque<A>, Vec<B> }
-__impl_slice_eq1! { VecDeque<A>, &[B] }
-__impl_slice_eq1! { VecDeque<A>, &mut [B] }
-
-macro_rules! array_impls {
-    ($($N: expr)+) => {
-        $(
-            __impl_slice_eq1! { VecDeque<A>, [B; $N] }
-            __impl_slice_eq1! { VecDeque<A>, &[B; $N] }
-            __impl_slice_eq1! { VecDeque<A>, &mut [B; $N] }
-        )+
-    }
-}
-
-array_impls! {
-     0  1  2  3  4  5  6  7  8  9
-    10 11 12 13 14 15 16 17 18 19
-    20 21 22 23 24 25 26 27 28 29
-    30 31 32
-}
+__impl_slice_eq1! { [] VecDeque<A>, Vec<B>, }
+__impl_slice_eq1! { [] VecDeque<A>, &[B], }
+__impl_slice_eq1! { [] VecDeque<A>, &mut [B], }
+__impl_slice_eq1! { [const N: usize] VecDeque<A>, [B; N], [B; N]: LengthAtMost32 }
+__impl_slice_eq1! { [const N: usize] VecDeque<A>, &[B; N], [B; N]: LengthAtMost32 }
+__impl_slice_eq1! { [const N: usize] VecDeque<A>, &mut [B; N], [B; N]: LengthAtMost32 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: PartialOrd> PartialOrd for VecDeque<A> {

src/liballoc/lib.rs

@@ -78,6 +78,8 @@
 #![feature(cfg_target_has_atomic)]
 #![feature(coerce_unsized)]
 #![cfg_attr(not(bootstrap), feature(const_in_array_repeat_expressions))]
+#![feature(const_generic_impls_guard)]
+#![feature(const_generics)]
 #![feature(dispatch_from_dyn)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]

src/liballoc/rc.rs

@@ -815,7 +815,7 @@ impl<T> Rc<[T]> {
                     let slice = from_raw_parts_mut(self.elems, self.n_elems);
                     ptr::drop_in_place(slice);
 
-                    Global.dealloc(self.mem, self.layout.clone());
+                    Global.dealloc(self.mem, self.layout);
                 }
             }
         }

src/liballoc/sync.rs

@@ -703,7 +703,7 @@ impl<T> Arc<[T]> {
                     let slice = from_raw_parts_mut(self.elems, self.n_elems);
                     ptr::drop_in_place(slice);
 
-                    Global.dealloc(self.mem.cast(), self.layout.clone());
+                    Global.dealloc(self.mem.cast(), self.layout);
                 }
             }
         }

src/liballoc/vec.rs

@@ -56,6 +56,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
+use core::array::LengthAtMost32;
 use core::cmp::{self, Ordering};
 use core::fmt;
 use core::hash::{self, Hash};
@@ -2171,47 +2172,36 @@ impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
 }
 
 macro_rules! __impl_slice_eq1 {
-    ($Lhs: ty, $Rhs: ty) => {
-        __impl_slice_eq1! { $Lhs, $Rhs, Sized }
-    };
-    ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
+    ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => {
         #[stable(feature = "rust1", since = "1.0.0")]
-        impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
+        impl<A, B, $($vars)*> PartialEq<$rhs> for $lhs
+        where
+            A: PartialEq<B>,
+            $($constraints)*
+        {
             #[inline]
-            fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
+            fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] }
             #[inline]
-            fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
+            fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] }
         }
     }
 }
 
-__impl_slice_eq1! { Vec<A>, Vec<B> }
-__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 }
+__impl_slice_eq1! { [] Vec<A>, Vec<B>, }
+__impl_slice_eq1! { [] Vec<A>, &[B], }
+__impl_slice_eq1! { [] Vec<A>, &mut [B], }
+__impl_slice_eq1! { [] Cow<'_, [A]>, &[B], A: Clone }
+__impl_slice_eq1! { [] Cow<'_, [A]>, &mut [B], A: Clone }
+__impl_slice_eq1! { [] Cow<'_, [A]>, Vec<B>, A: Clone }
+__impl_slice_eq1! { [const N: usize] Vec<A>, [B; N], [B; N]: LengthAtMost32 }
+__impl_slice_eq1! { [const N: usize] Vec<A>, &[B; N], [B; N]: LengthAtMost32 }
 
-macro_rules! array_impls {
-    ($($N: expr)+) => {
-        $(
-            // NOTE: some less important impls are omitted to reduce code bloat
-            __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 }
-        )+
-    }
-}
-
-array_impls! {
-     0  1  2  3  4  5  6  7  8  9
-    10 11 12 13 14 15 16 17 18 19
-    20 21 22 23 24 25 26 27 28 29
-    30 31 32
-}
+// NOTE: some less important impls are omitted to reduce code bloat
+// FIXME(Centril): Reconsider this?
+//__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], [B; N]: LengthAtMost32 }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], [B; N]: LengthAtMost32 }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], [B; N]: LengthAtMost32 }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], [B; N]: LengthAtMost32 }
 
 /// Implements comparison of vectors, lexicographically.
 #[stable(feature = "rust1", since = "1.0.0")]

src/libcore/alloc.rs

@@ -827,11 +827,11 @@ pub unsafe trait Alloc {
         let old_size = layout.size();
 
         if new_size >= old_size {
-            if let Ok(()) = self.grow_in_place(ptr, layout.clone(), new_size) {
+            if let Ok(()) = self.grow_in_place(ptr, layout, new_size) {
                 return Ok(ptr);
             }
         } else if new_size < old_size {
-            if let Ok(()) = self.shrink_in_place(ptr, layout.clone(), new_size) {
+            if let Ok(()) = self.shrink_in_place(ptr, layout, new_size) {
                 return Ok(ptr);
             }
         }

src/libcore/str/lossy.rs

@@ -46,7 +46,7 @@ impl<'a> Iterator for Utf8LossyChunksIter<'a> {
     type Item = Utf8LossyChunk<'a>;
 
     fn next(&mut self) -> Option<Utf8LossyChunk<'a>> {
-        if self.source.len() == 0 {
+        if self.source.is_empty() {
             return None;
         }
 
@@ -141,7 +141,7 @@ impl fmt::Display for Utf8Lossy {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // If we're the empty string then our iterator won't actually yield
         // anything, so perform the formatting manually
-        if self.bytes.len() == 0 {
+        if self.bytes.is_empty() {
             return "".fmt(f)
         }
 

src/librustc_mir/borrow_check/conflict_errors.rs

@@ -1140,19 +1140,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 bug!("try_report_cannot_return_reference_to_local: not a local")
             };
             match self.body.local_kind(*local) {
-                LocalKind::ReturnPointer | LocalKind::Temp => {
-                    (
-                        "temporary value".to_string(),
-                        "temporary value created here".to_string(),
-                    )
-                }
-                LocalKind::Arg => {
-                    (
-                        "function parameter".to_string(),
-                        "function parameter borrowed here".to_string(),
-                    )
-                },
-                LocalKind::Var => bug!("local variable without a name"),
+                LocalKind::ReturnPointer | LocalKind::Temp => (
+                    "temporary value".to_string(),
+                    "temporary value created here".to_string(),
+                ),
+                LocalKind::Arg => (
+                    "function parameter".to_string(),
+                    "function parameter borrowed here".to_string(),
+                ),
+                LocalKind::Var => (
+                    "local binding".to_string(),
+                    "local binding introduced here".to_string(),
+                ),
             }
         };
 

src/libstd/io/mod.rs

@@ -1923,7 +1923,7 @@ impl<T: Read, U: Read> Read for Chain<T, U> {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
         if !self.done_first {
             match self.first.read(buf)? {
-                0 if buf.len() != 0 => self.done_first = true,
+                0 if !buf.is_empty() => self.done_first = true,
                 n => return Ok(n),
             }
         }
@@ -1955,7 +1955,7 @@ impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
     fn fill_buf(&mut self) -> Result<&[u8]> {
         if !self.done_first {
             match self.first.fill_buf()? {
-                buf if buf.len() == 0 => { self.done_first = true; }
+                buf if buf.is_empty() => { self.done_first = true; }
                 buf => return Ok(buf),
             }
         }

src/libstd/sys/unix/alloc.rs

@@ -29,7 +29,7 @@ unsafe impl GlobalAlloc for System {
         if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
             libc::calloc(layout.size(), 1) as *mut u8
         } else {
-            let ptr = self.alloc(layout.clone());
+            let ptr = self.alloc(layout);
             if !ptr.is_null() {
                 ptr::write_bytes(ptr, 0, layout.size());
             }

src/libstd/sys/unix/process/process_unix.rs

@@ -277,7 +277,7 @@ impl Command {
         if self.get_gid().is_some() ||
             self.get_uid().is_some() ||
             self.env_saw_path() ||
-            self.get_closures().len() != 0 {
+            !self.get_closures().is_empty() {
             return Ok(None)
         }
 

src/test/ui/borrowck/return-local-binding-from-desugaring.rs

@@ -0,0 +1,33 @@
+// To avoid leaking the names of local bindings from expressions like for loops, #60984
+// explicitly ignored them, but an assertion that `LocalKind::Var` *must* have a name would
+// trigger an ICE. Before this change, this file's output would be:
+// ```
+// error[E0515]: cannot return value referencing local variable `__next`
+//   --> return-local-binding-from-desugaring.rs:LL:CC
+//    |
+// LL |     for ref x in xs {
+//    |         ----- `__next` is borrowed here
+// ...
+// LL |     result
+//    |     ^^^^^^ returns a value referencing data owned by the current function
+// ```
+// FIXME: ideally `LocalKind` would carry more information to more accurately explain the problem.
+
+use std::collections::HashMap;
+use std::hash::Hash;
+
+fn group_by<I, F, T>(xs: &mut I, f: F) -> HashMap<T, Vec<&I::Item>>
+where
+    I: Iterator,
+    F: Fn(&I::Item) -> T,
+    T: Eq + Hash,
+{
+    let mut result = HashMap::new();
+    for ref x in xs {
+        let key = f(x);
+        result.entry(key).or_insert(Vec::new()).push(x);
+    }
+    result //~ ERROR cannot return value referencing local binding
+}
+
+fn main() {}

src/test/ui/borrowck/return-local-binding-from-desugaring.stderr

@@ -0,0 +1,12 @@
+error[E0515]: cannot return value referencing local binding
+  --> $DIR/return-local-binding-from-desugaring.rs:30:5
+   |
+LL |     for ref x in xs {
+   |                  -- local binding introduced here
+...
+LL |     result
+   |     ^^^^^^ returns a value referencing data owned by the current function
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0515`.

src/test/ui/const-generics/array-impls/alloc-traits-impls-length-32.rs

@@ -0,0 +1,40 @@
+// check-pass
+
+pub fn yes_vec_partial_eq_array<A, B>() -> impl PartialEq<[B; 32]>
+where
+    A: PartialEq<B>,
+{
+    Vec::<A>::new()
+}
+
+pub fn yes_vec_partial_eq_ref_array<'a, A, B>() -> impl PartialEq<&'a [B; 32]>
+where
+    A: PartialEq<B>,
+{
+    Vec::<A>::new()
+}
+
+use std::collections::VecDeque;
+
+pub fn yes_vecdeque_partial_eq_array<A, B>() -> impl PartialEq<[B; 32]>
+where
+    A: PartialEq<B>,
+{
+    VecDeque::<A>::new()
+}
+
+pub fn yes_vecdeque_partial_eq_ref_array<'a, A, B>() -> impl PartialEq<&'a [B; 32]>
+where
+    A: PartialEq<B>,
+{
+    VecDeque::<A>::new()
+}
+
+pub fn yes_vecdeque_partial_eq_ref_mut_array<'a, A, B>() -> impl PartialEq<&'a mut [B; 32]>
+where
+    A: PartialEq<B>,
+{
+    VecDeque::<A>::new()
+}
+
+fn main() {}