Auto merge of #51319 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 6 pull requests

Successful merges:

 - #51143 (Specify that packed types must derive, not implement, Copy)
 - #51226 (Make Layout's align a NonZeroUsize)
 - #51297 (Fix run button style)
 - #51306 (impl Default for &mut str)
 - #51312 (Clarify the difference between get_mut and into_mut for OccupiedEntry)
 - #51313 (use type name in E0599 enum variant suggestion)

Failed merges:

14 files changed, 99 insertions, 57 deletions

diff --git a/src/liballoc/btree/map.rs b/src/liballoc/btree/map.rs
index 28c42144b2a..9b6f91c039f 100644
--- a/src/liballoc/btree/map.rs
+++ b/src/liballoc/btree/map.rs
@@ -2369,6 +2369,11 @@ impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
 
     /// Gets a mutable reference to the value in the entry.
     ///
+    /// If you need a reference to the `OccupiedEntry` which may outlive the
+    /// destruction of the `Entry` value, see [`into_mut`].
+    ///
+    /// [`into_mut`]: #method.into_mut
+    ///
     /// # Examples
     ///
     /// ```
@@ -2380,9 +2385,13 @@ impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
     ///
     /// assert_eq!(map["poneyland"], 12);
     /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
-    ///      *o.get_mut() += 10;
+    ///     *o.get_mut() += 10;
+    ///     assert_eq!(*o.get(), 22);
+    ///
+    ///     // We can use the same Entry multiple times.
+    ///     *o.get_mut() += 2;
     /// }
-    /// assert_eq!(map["poneyland"], 22);
+    /// assert_eq!(map["poneyland"], 24);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut V {
@@ -2391,6 +2400,10 @@ impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
 
     /// Converts the entry into a mutable reference to its value.
     ///
+    /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
+    ///
+    /// [`get_mut`]: #method.get_mut
+    ///
     /// # Examples
     ///
     /// ```
diff --git a/src/liballoc/tests/str.rs b/src/liballoc/tests/str.rs
index 03d295d16e6..75306ac82df 100644
--- a/src/liballoc/tests/str.rs
+++ b/src/liballoc/tests/str.rs
@@ -1326,6 +1326,7 @@ fn test_str_default() {
 
     t::<&str>();
     t::<String>();
+    t::<&mut str>();
 }
 
 #[test]
diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 6172a98bca6..229758803c8 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -20,6 +20,7 @@ use fmt;
 use mem;
 use usize;
 use ptr::{self, NonNull};
+use num::NonZeroUsize;
 
 extern {
     /// An opaque, unsized type. Used for pointers to allocated memory.
@@ -66,7 +67,7 @@ fn size_align<T>() -> (usize, usize) {
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Layout {
     // size of the requested block of memory, measured in bytes.
-    size: usize,
+    size_: usize,
 
     // alignment of the requested block of memory, measured in bytes.
     // we ensure that this is always a power-of-two, because API's
@@ -75,17 +76,12 @@ pub struct Layout {
     //
     // (However, we do not analogously require `align >= sizeof(void*)`,
     //  even though that is *also* a requirement of `posix_memalign`.)
-    align: usize,
+    align_: NonZeroUsize,
 }
 
-
-// FIXME: audit default implementations for overflow errors,
-// (potentially switching to overflowing_add and
-//  overflowing_mul as necessary).
-
 impl Layout {
     /// Constructs a `Layout` from a given `size` and `align`,
-    /// or returns `None` if either of the following conditions
+    /// or returns `LayoutErr` if either of the following conditions
     /// are not met:
     ///
     /// * `align` must be a power of two,
@@ -126,23 +122,23 @@ impl Layout {
     ///
     /// # Safety
     ///
-    /// This function is unsafe as it does not verify that `align` is
-    /// a power-of-two nor `size` aligned to `align` fits within the
-    /// address space (i.e. the `Layout::from_size_align` preconditions).
+    /// This function is unsafe as it does not verify the preconditions from
+    /// [`Layout::from_size_align`](#method.from_size_align).
     #[inline]
     pub unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self {
-        Layout { size: size, align: align }
+        Layout { size_: size, align_: NonZeroUsize::new_unchecked(align) }
     }
 
     /// The minimum size in bytes for a memory block of this layout.
     #[inline]
-    pub fn size(&self) -> usize { self.size }
+    pub fn size(&self) -> usize { self.size_ }
 
     /// The minimum byte alignment for a memory block of this layout.
     #[inline]
-    pub fn align(&self) -> usize { self.align }
+    pub fn align(&self) -> usize { self.align_.get() }
 
     /// Constructs a `Layout` suitable for holding a value of type `T`.
+    #[inline]
     pub fn new<T>() -> Self {
         let (size, align) = size_align::<T>();
         // Note that the align is guaranteed by rustc to be a power of two and
@@ -158,6 +154,7 @@ impl Layout {
     /// Produces layout describing a record that could be used to
     /// allocate backing structure for `T` (which could be a trait
     /// or other unsized type like a slice).
+    #[inline]
     pub fn for_value<T: ?Sized>(t: &T) -> Self {
         let (size, align) = (mem::size_of_val(t), mem::align_of_val(t));
         // See rationale in `new` for why this us using an unsafe variant below
@@ -181,18 +178,19 @@ impl Layout {
     ///
     /// # Panics
     ///
-    /// Panics if the combination of `self.size` and the given `align`
-    /// violates the conditions listed in `from_size_align`.
+    /// Panics if the combination of `self.size()` and the given `align`
+    /// violates the conditions listed in
+    /// [`Layout::from_size_align`](#method.from_size_align).
     #[inline]
     pub fn align_to(&self, align: usize) -> Self {
-        Layout::from_size_align(self.size, cmp::max(self.align, align)).unwrap()
+        Layout::from_size_align(self.size(), cmp::max(self.align(), align)).unwrap()
     }
 
     /// Returns the amount of padding we must insert after `self`
     /// to ensure that the following address will satisfy `align`
     /// (measured in bytes).
     ///
-    /// E.g. if `self.size` is 9, then `self.padding_needed_for(4)`
+    /// E.g. if `self.size()` is 9, then `self.padding_needed_for(4)`
     /// returns 3, because that is the minimum number of bytes of
     /// padding required to get a 4-aligned address (assuming that the
     /// corresponding memory block starts at a 4-aligned address).
@@ -203,7 +201,7 @@ impl Layout {
     /// Note that the utility of the returned value requires `align`
     /// to be less than or equal to the alignment of the starting
     /// address for the whole allocated block of memory. One way to
-    /// satisfy this constraint is to ensure `align <= self.align`.
+    /// satisfy this constraint is to ensure `align <= self.align()`.
     #[inline]
     pub fn padding_needed_for(&self, align: usize) -> usize {
         let len = self.size();
@@ -227,7 +225,8 @@ impl Layout {
         // size and padding overflow in the above manner should cause
         // the allocator to yield an error anyway.)
 
-        let len_rounded_up = len.wrapping_add(align).wrapping_sub(1) & !align.wrapping_sub(1);
+        let len_rounded_up = len.wrapping_add(align).wrapping_sub(1)
+            & !align.wrapping_sub(1);
         return len_rounded_up.wrapping_sub(len);
     }
 
@@ -238,14 +237,19 @@ impl Layout {
     /// layout of the array and `offs` is the distance between the start
     /// of each element in the array.
     ///
-    /// On arithmetic overflow, returns `None`.
+    /// On arithmetic overflow, returns `LayoutErr`.
     #[inline]
     pub fn repeat(&self, n: usize) -> Result<(Self, usize), LayoutErr> {
-        let padded_size = self.size.checked_add(self.padding_needed_for(self.align))
+        let padded_size = self.size().checked_add(self.padding_needed_for(self.align()))
             .ok_or(LayoutErr { private: () })?;
         let alloc_size = padded_size.checked_mul(n)
             .ok_or(LayoutErr { private: () })?;
-        Ok((Layout::from_size_align(alloc_size, self.align)?, padded_size))
+
+        unsafe {
+            // self.align is already known to be valid and alloc_size has been
+            // padded already.
+            Ok((Layout::from_size_align_unchecked(alloc_size, self.align()), padded_size))
+        }
     }
 
     /// Creates a layout describing the record for `self` followed by
@@ -258,16 +262,15 @@ impl Layout {
     /// start of the `next` embedded within the concatenated record
     /// (assuming that the record itself starts at offset 0).
     ///
-    /// On arithmetic overflow, returns `None`.
+    /// On arithmetic overflow, returns `LayoutErr`.
+    #[inline]
     pub fn extend(&self, next: Self) -> Result<(Self, usize), LayoutErr> {
-        let new_align = cmp::max(self.align, next.align);
-        let realigned = Layout::from_size_align(self.size, new_align)?;
-
-        let pad = realigned.padding_needed_for(next.align);
+        let new_align = cmp::max(self.align(), next.align());
+        let pad = self.padding_needed_for(next.align());
 
-        let offset = self.size.checked_add(pad)
+        let offset = self.size().checked_add(pad)
             .ok_or(LayoutErr { private: () })?;
-        let new_size = offset.checked_add(next.size)
+        let new_size = offset.checked_add(next.size())
             .ok_or(LayoutErr { private: () })?;
 
         let layout = Layout::from_size_align(new_size, new_align)?;
@@ -285,10 +288,11 @@ impl Layout {
     /// guaranteed that all elements in the array will be properly
     /// aligned.
     ///
-    /// On arithmetic overflow, returns `None`.
+    /// On arithmetic overflow, returns `LayoutErr`.
+    #[inline]
     pub fn repeat_packed(&self, n: usize) -> Result<Self, LayoutErr> {
         let size = self.size().checked_mul(n).ok_or(LayoutErr { private: () })?;
-        Layout::from_size_align(size, self.align)
+        Layout::from_size_align(size, self.align())
     }
 
     /// Creates a layout describing the record for `self` followed by
@@ -305,17 +309,19 @@ impl Layout {
     ///  signature out of convenience in matching the signature of
     ///  `extend`.)
     ///
-    /// On arithmetic overflow, returns `None`.
+    /// On arithmetic overflow, returns `LayoutErr`.
+    #[inline]
     pub fn extend_packed(&self, next: Self) -> Result<(Self, usize), LayoutErr> {
         let new_size = self.size().checked_add(next.size())
             .ok_or(LayoutErr { private: () })?;
-        let layout = Layout::from_size_align(new_size, self.align)?;
+        let layout = Layout::from_size_align(new_size, self.align())?;
         Ok((layout, self.size()))
     }
 
     /// Creates a layout describing the record for a `[T; n]`.
     ///
-    /// On arithmetic overflow, returns `None`.
+    /// On arithmetic overflow, returns `LayoutErr`.
+    #[inline]
     pub fn array<T>(n: usize) -> Result<Self, LayoutErr> {
         Layout::new::<T>()
             .repeat(n)
@@ -842,7 +848,7 @@ pub unsafe trait Alloc {
                             layout: Layout,
                             new_size: usize) -> Result<(), CannotReallocInPlace> {
         let _ = ptr; // this default implementation doesn't care about the actual address.
-        debug_assert!(new_size >= layout.size);
+        debug_assert!(new_size >= layout.size());
         let (_l, u) = self.usable_size(&layout);
         // _l <= layout.size()                       [guaranteed by usable_size()]
         //       layout.size() <= new_layout.size()  [required by this method]
@@ -897,7 +903,7 @@ pub unsafe trait Alloc {
                               layout: Layout,
                               new_size: usize) -> Result<(), CannotReallocInPlace> {
         let _ = ptr; // this default implementation doesn't care about the actual address.
-        debug_assert!(new_size <= layout.size);
+        debug_assert!(new_size <= layout.size());
         let (l, _u) = self.usable_size(&layout);
         //                      layout.size() <= _u  [guaranteed by usable_size()]
         // new_layout.size() <= layout.size()        [required by this method]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 3169893fcde..5e1a9c25a21 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -3875,6 +3875,12 @@ impl<'a> Default for &'a str {
     fn default() -> &'a str { "" }
 }
 
+#[stable(feature = "default_mut_str", since = "1.28.0")]
+impl<'a> Default for &'a mut str {
+    /// Creates an empty mutable str
+    fn default() -> &'a mut str { unsafe { from_utf8_unchecked_mut(&mut []) } }
+}
+
 /// An iterator over the non-whitespace substrings of a string,
 /// separated by any amount of whitespace.
 ///
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index fedd0774df4..4c282f037a5 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -362,8 +362,8 @@ fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: D
         format!("#[derive] can't be used on a #[repr(packed)] struct with \
                  type parameters (error E0133)")
     } else {
-        format!("#[derive] can't be used on a non-Copy #[repr(packed)] struct \
-                 (error E0133)")
+        format!("#[derive] can't be used on a #[repr(packed)] struct that \
+                 does not derive Copy (error E0133)")
     };
     tcx.lint_node(SAFE_PACKED_BORROWS,
                   lint_node_id,
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index 6031984350b..86cd8d0fb2c 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -195,7 +195,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 let ty_string = self.ty_to_string(actual);
                 let is_method = mode == Mode::MethodCall;
                 let mut suggestion = None;
-                let type_str = if is_method {
+                let item_kind = if is_method {
                     "method"
                 } else if actual.is_enum() {
                     if let TyAdt(ref adt_def, _) = actual.sty {
@@ -235,7 +235,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                             span,
                             E0689,
                             "can't call {} `{}` on ambiguous numeric type `{}`",
-                            type_str,
+                            item_kind,
                             item_name,
                             ty_string
                         );
@@ -284,12 +284,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                             span,
                             E0599,
                             "no {} named `{}` found for type `{}` in the current scope",
-                            type_str,
+                            item_kind,
                             item_name,
                             ty_string
                         );
                         if let Some(suggestion) = suggestion {
-                            err.note(&format!("did you mean `{}::{}`?", type_str, suggestion));
+                            err.note(&format!("did you mean `{}::{}`?", ty_string, suggestion));
                         }
                         err
                     }
@@ -301,7 +301,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     if let Some(full_sp) = tcx.hir.span_if_local(def.did) {
                         let def_sp = tcx.sess.codemap().def_span(full_sp);
                         err.span_label(def_sp, format!("{} `{}` not found {}",
-                                                       type_str,
+                                                       item_kind,
                                                        item_name,
                                                        if def.is_enum() && !is_method {
                                                            "here"
@@ -355,7 +355,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         }
                     }
                 } else {
-                    err.span_label(span, format!("{} not found in `{}`", type_str, ty_string));
+                    err.span_label(span, format!("{} not found in `{}`", item_kind, ty_string));
                 }
 
                 if self.is_fn_ty(&rcvr_ty, span) {
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index 867b1e86aa2..773b8174e56 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -561,7 +561,8 @@ a {
 	content: '\2002\00a7\2002';
 }
 
-.docblock a:not(.srclink):hover, .docblock-short a:not(.srclink):hover, .stability a {
+.docblock a:not(.srclink):not(.test-arrow):hover,
+.docblock-short a:not(.srclink):not(.test-arrow):hover, .stability a {
 	text-decoration: underline;
 }
 
diff --git a/src/librustdoc/html/static/themes/dark.css b/src/librustdoc/html/static/themes/dark.css
index 765ef0cd415..f96dcd9ec1c 100644
--- a/src/librustdoc/html/static/themes/dark.css
+++ b/src/librustdoc/html/static/themes/dark.css
@@ -163,7 +163,8 @@ a {
 	color: #ddd;
 }
 
-.docblock a:not(.srclink), .docblock-short a:not(.srclink), .stability a {
+.docblock a:not(.srclink):not(.test-arrow), .docblock-short a:not(.srclink):not(.test-arrow),
+.stability a {
 	color: #D2991D;
 }
 
diff --git a/src/librustdoc/html/static/themes/light.css b/src/librustdoc/html/static/themes/light.css
index 5971dc43ded..54cf50cfffd 100644
--- a/src/librustdoc/html/static/themes/light.css
+++ b/src/librustdoc/html/static/themes/light.css
@@ -163,7 +163,8 @@ a {
 	color: #000;
 }
 
-.docblock a:not(.srclink), .docblock-short a:not(.srclink), .stability a {
+.docblock a:not(.srclink):not(.test-arrow), .docblock-short a:not(.srclink):not(.test-arrow),
+.stability a {
 	color: #3873AD;
 }
 
diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 935ea4b62b5..5cbd8891364 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -2250,6 +2250,11 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
 
     /// Gets a mutable reference to the value in the entry.
     ///
+    /// If you need a reference to the `OccupiedEntry` which may outlive the
+    /// destruction of the `Entry` value, see [`into_mut`].
+    ///
+    /// [`into_mut`]: #method.into_mut
+    ///
     /// # Examples
     ///
     /// ```
@@ -2261,10 +2266,14 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
     ///
     /// assert_eq!(map["poneyland"], 12);
     /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
-    ///      *o.get_mut() += 10;
+    ///     *o.get_mut() += 10;
+    ///     assert_eq!(*o.get(), 22);
+    ///
+    ///     // We can use the same Entry multiple times.
+    ///     *o.get_mut() += 2;
     /// }
     ///
-    /// assert_eq!(map["poneyland"], 22);
+    /// assert_eq!(map["poneyland"], 24);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut V {
@@ -2274,6 +2283,10 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
     /// Converts the OccupiedEntry into a mutable reference to the value in the entry
     /// with a lifetime bound to the map itself.
     ///
+    /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
+    ///
+    /// [`get_mut`]: #method.get_mut
+    ///
     /// # Examples
     ///
     /// ```
diff --git a/src/test/ui/deriving-with-repr-packed.rs b/src/test/ui/deriving-with-repr-packed.rs
index 0c52829799e..43375098cb5 100644
--- a/src/test/ui/deriving-with-repr-packed.rs
+++ b/src/test/ui/deriving-with-repr-packed.rs
@@ -33,7 +33,7 @@ pub struct Bar(u32, u32, u32);
 struct Y(usize);
 
 #[derive(PartialEq)]
-//~^ ERROR #[derive] can't be used on a non-Copy #[repr(packed)]
+//~^ ERROR #[derive] can't be used
 //~| hard error
 #[repr(packed)]
 struct X(Y);
diff --git a/src/test/ui/deriving-with-repr-packed.stderr b/src/test/ui/deriving-with-repr-packed.stderr
index 64aefbcd5df..a7599c1e7db 100644
--- a/src/test/ui/deriving-with-repr-packed.stderr
+++ b/src/test/ui/deriving-with-repr-packed.stderr
@@ -21,7 +21,7 @@ LL | #[derive(Copy, Clone, PartialEq, Eq)]
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #46043 <https://github.com/rust-lang/rust/issues/46043>
 
-error: #[derive] can't be used on a non-Copy #[repr(packed)] struct (error E0133)
+error: #[derive] can't be used on a #[repr(packed)] struct that does not derive Copy (error E0133)
   --> $DIR/deriving-with-repr-packed.rs:26:10
    |
 LL | #[derive(PartialEq, Eq)]
@@ -30,7 +30,7 @@ LL | #[derive(PartialEq, Eq)]
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #46043 <https://github.com/rust-lang/rust/issues/46043>
 
-error: #[derive] can't be used on a non-Copy #[repr(packed)] struct (error E0133)
+error: #[derive] can't be used on a #[repr(packed)] struct that does not derive Copy (error E0133)
   --> $DIR/deriving-with-repr-packed.rs:35:10
    |
 LL | #[derive(PartialEq)]
diff --git a/src/test/ui/issue-23217.stderr b/src/test/ui/issue-23217.stderr
index d542a10e9b6..d87f239bca6 100644
--- a/src/test/ui/issue-23217.stderr
+++ b/src/test/ui/issue-23217.stderr
@@ -6,7 +6,7 @@ LL | pub enum SomeEnum {
 LL |     B = SomeEnum::A,
    |         ^^^^^^^^^^^ variant not found in `SomeEnum`
    |
-   = note: did you mean `variant::B`?
+   = note: did you mean `SomeEnum::B`?
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issue-28971.stderr b/src/test/ui/issue-28971.stderr
index df114351ff5..c04e21f7c58 100644
--- a/src/test/ui/issue-28971.stderr
+++ b/src/test/ui/issue-28971.stderr
@@ -7,7 +7,7 @@ LL | enum Foo {
 LL |             Foo::Baz(..) => (),
    |             ^^^^^^^^^^^^ variant not found in `Foo`
    |
-   = note: did you mean `variant::Bar`?
+   = note: did you mean `Foo::Bar`?
 
 error: aborting due to previous error