Remove the private generic NonZero<T> wrapper type.

Instead, use `#[rustc_layout_scalar_valid_range_start(1)]` directly
on relevant libcore types.

src/etc/debugger_pretty_printers_common.py

@@ -342,8 +342,7 @@ def extract_length_ptr_and_cap_from_std_vec(vec_val):
 
     vec_ptr_val = buf.get_child_at_index(0)
     capacity = buf.get_child_at_index(1).as_integer()
-    unique_ptr_val = vec_ptr_val.get_child_at_index(0)
-    data_ptr = unique_ptr_val.get_child_at_index(0)
+    data_ptr = vec_ptr_val.get_child_at_index(0)
     assert data_ptr.type.get_dwarf_type_kind() == DWARF_TYPE_CODE_PTR
     return (length, data_ptr, capacity)
 
@@ -360,8 +359,7 @@ def extract_tail_head_ptr_and_cap_from_std_vecdeque(vec_val):
 
     vec_ptr_val = buf.get_child_at_index(0)
     capacity = buf.get_child_at_index(1).as_integer()
-    unique_ptr_val = vec_ptr_val.get_child_at_index(0)
-    data_ptr = unique_ptr_val.get_child_at_index(0)
+    data_ptr = vec_ptr_val.get_child_at_index(0)
     assert data_ptr.type.get_dwarf_type_kind() == DWARF_TYPE_CODE_PTR
     return (tail, head, data_ptr, capacity)
 

src/etc/gdb_rust_pretty_printing.py

@@ -322,9 +322,7 @@ def children(self):
 
 # Yield each key (and optionally value) from a BoxedNode.
 def children_of_node(boxed_node, height, want_values):
-    ptr = boxed_node['ptr']['pointer']
-    # This is written oddly because we don't want to rely on the field name being `__0`.
-    node_ptr = ptr[ptr.type.fields()[0]]
+    node_ptr = boxed_node['ptr']['pointer']
     if height > 0:
         type_name = str(node_ptr.type.target()).replace('LeafNode', 'InternalNode')
         node_type = gdb.lookup_type(type_name)

src/libcore/lib.rs

@@ -216,7 +216,6 @@ pub mod alloc;
 
 // note: does not need to be public
 mod iter_private;
-mod nonzero;
 mod tuple;
 mod unit;
 

src/libcore/num/mod.rs

@@ -6,7 +6,6 @@ use convert::TryFrom;
 use fmt;
 use intrinsics;
 use mem;
-use nonzero::NonZero;
 use ops;
 use str::FromStr;
 
@@ -48,7 +47,8 @@ assert_eq!(size_of::<Option<std::num::", stringify!($Ty), ">>(), size_of::<", st
                 #[stable(feature = "nonzero", since = "1.28.0")]
                 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
                 #[repr(transparent)]
-                pub struct $Ty(NonZero<$Int>);
+                #[rustc_layout_scalar_valid_range_start(1)]
+                pub struct $Ty($Int);
             }
 
             impl $Ty {
@@ -60,15 +60,15 @@ assert_eq!(size_of::<Option<std::num::", stringify!($Ty), ">>(), size_of::<", st
                 #[stable(feature = "nonzero", since = "1.28.0")]
                 #[inline]
                 pub const unsafe fn new_unchecked(n: $Int) -> Self {
-                    $Ty(NonZero(n))
+                    $Ty(n)
                 }
 
                 /// Create a non-zero if the given value is not zero.
                 #[stable(feature = "nonzero", since = "1.28.0")]
                 #[inline]
                 pub fn new(n: $Int) -> Option<Self> {
                     if n != 0 {
-                        Some($Ty(unsafe { NonZero(n) }))
+                        Some(unsafe { $Ty(n) })
                     } else {
                         None
                     }
@@ -78,15 +78,15 @@ assert_eq!(size_of::<Option<std::num::", stringify!($Ty), ">>(), size_of::<", st
                 #[stable(feature = "nonzero", since = "1.28.0")]
                 #[inline]
                 pub fn get(self) -> $Int {
-                    self.0 .0
+                    self.0
                 }
 
             }
 
             #[stable(feature = "from_nonzero", since = "1.31.0")]
             impl From<$Ty> for $Int {
                 fn from(nonzero: $Ty) -> Self {
-                    nonzero.0 .0
+                    nonzero.0
                 }
             }
 

src/libcore/ptr.rs

@@ -70,7 +70,6 @@ use fmt;
 use hash;
 use marker::{PhantomData, Unsize};
 use mem::{self, MaybeUninit};
-use nonzero::NonZero;
 
 use cmp::Ordering::{self, Less, Equal, Greater};
 
@@ -2718,8 +2717,9 @@ impl<T: ?Sized> PartialOrd for *mut T {
                      (if you also use #[may_dangle]), Send, and/or Sync")]
 #[doc(hidden)]
 #[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
 pub struct Unique<T: ?Sized> {
-    pointer: NonZero<*const T>,
+    pointer: *const T,
     // NOTE: this marker has no consequences for variance, but is necessary
     // for dropck to understand that we logically own a `T`.
     //
@@ -2776,21 +2776,21 @@ impl<T: ?Sized> Unique<T> {
     ///
     /// `ptr` must be non-null.
     pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
-        Unique { pointer: NonZero(ptr as _), _marker: PhantomData }
+        Unique { pointer: ptr as _, _marker: PhantomData }
     }
 
     /// Creates a new `Unique` if `ptr` is non-null.
     pub fn new(ptr: *mut T) -> Option<Self> {
         if !ptr.is_null() {
-            Some(Unique { pointer: unsafe { NonZero(ptr as _) }, _marker: PhantomData })
+            Some(unsafe { Unique { pointer: ptr as _, _marker: PhantomData } })
         } else {
             None
         }
     }
 
     /// Acquires the underlying `*mut` pointer.
     pub fn as_ptr(self) -> *mut T {
-        self.pointer.0 as *mut T
+        self.pointer as *mut T
     }
 
     /// Dereferences the content.
@@ -2838,21 +2838,21 @@ impl<T: ?Sized> fmt::Pointer for Unique<T> {
 #[unstable(feature = "ptr_internals", issue = "0")]
 impl<'a, T: ?Sized> From<&'a mut T> for Unique<T> {
     fn from(reference: &'a mut T) -> Self {
-        Unique { pointer: unsafe { NonZero(reference as *mut T) }, _marker: PhantomData }
+        unsafe { Unique { pointer: reference as *mut T, _marker: PhantomData } }
     }
 }
 
 #[unstable(feature = "ptr_internals", issue = "0")]
 impl<'a, T: ?Sized> From<&'a T> for Unique<T> {
     fn from(reference: &'a T) -> Self {
-        Unique { pointer: unsafe { NonZero(reference as *const T) }, _marker: PhantomData }
+        unsafe { Unique { pointer: reference as *const T, _marker: PhantomData } }
     }
 }
 
 #[unstable(feature = "ptr_internals", issue = "0")]
 impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
     fn from(p: NonNull<T>) -> Self {
-        Unique { pointer: p.pointer, _marker: PhantomData }
+        unsafe { Unique { pointer: p.pointer, _marker: PhantomData } }
     }
 }
 
@@ -2875,8 +2875,9 @@ impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
 /// provide a public API that follows the normal shared XOR mutable rules of Rust.
 #[stable(feature = "nonnull", since = "1.25.0")]
 #[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
 pub struct NonNull<T: ?Sized> {
-    pointer: NonZero<*const T>,
+    pointer: *const T,
 }
 
 /// `NonNull` pointers are not `Send` because the data they reference may be aliased.
@@ -2918,7 +2919,7 @@ impl<T: ?Sized> NonNull<T> {
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
     pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
-        NonNull { pointer: NonZero(ptr as _) }
+        NonNull { pointer: ptr as _ }
     }
 
     /// Creates a new `NonNull` if `ptr` is non-null.
@@ -2936,7 +2937,7 @@ impl<T: ?Sized> NonNull<T> {
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
     pub const fn as_ptr(self) -> *mut T {
-        self.pointer.0 as *mut T
+        self.pointer as *mut T
     }
 
     /// Dereferences the content.
@@ -3040,22 +3041,22 @@ impl<T: ?Sized> hash::Hash for NonNull<T> {
 impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
     #[inline]
     fn from(unique: Unique<T>) -> Self {
-        NonNull { pointer: unique.pointer }
+        unsafe { NonNull { pointer: unique.pointer } }
     }
 }
 
 #[stable(feature = "nonnull", since = "1.25.0")]
 impl<'a, T: ?Sized> From<&'a mut T> for NonNull<T> {
     #[inline]
     fn from(reference: &'a mut T) -> Self {
-        NonNull { pointer: unsafe { NonZero(reference as *mut T) } }
+        unsafe { NonNull { pointer: reference as *mut T } }
     }
 }
 
 #[stable(feature = "nonnull", since = "1.25.0")]
 impl<'a, T: ?Sized> From<&'a T> for NonNull<T> {
     #[inline]
     fn from(reference: &'a T) -> Self {
-        NonNull { pointer: unsafe { NonZero(reference as *const T) } }
+        unsafe { NonNull { pointer: reference as *const T } }
     }
 }

src/test/ui/print_type_sizes/niche-filling.stdout

@@ -36,8 +36,6 @@ print-type-size type: `MyOption<std::num::NonZeroU32>`: 4 bytes, alignment: 4 by
 print-type-size     variant `None`: 0 bytes
 print-type-size     variant `Some`: 4 bytes
 print-type-size         field `.0`: 4 bytes
-print-type-size type: `core::nonzero::NonZero<u32>`: 4 bytes, alignment: 4 bytes
-print-type-size     field `.0`: 4 bytes
 print-type-size type: `std::num::NonZeroU32`: 4 bytes, alignment: 4 bytes
 print-type-size     field `.0`: 4 bytes
 print-type-size type: `Enum4<(), (), (), MyOption<u8>>`: 2 bytes, alignment: 1 bytes