Rollup of 6 pull requests

Cargo.lock

@@ -1966,9 +1966,9 @@ dependencies = [
 
 [[package]]
 name = "measureme"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d09de7dafa3aa334bc806447c7e4de69419723312f4b88b80b561dea66601ce8"
+checksum = "cd21b0e6e1af976b269ce062038fe5e1b9ca2f817ab7a3af09ec4210aebf0d30"
 dependencies = [
  "byteorder",
  "memmap",

src/liballoc/string.rs

@@ -196,20 +196,21 @@ use crate::vec::Vec;
 ///
 /// let story = String::from("Once upon a time...");
 ///
-/// let ptr = story.as_ptr();
+// FIXME Update this when vec_into_raw_parts is stabilized
+/// // Prevent automatically dropping the String's data
+/// let mut story = mem::ManuallyDrop::new(story);
+///
+/// let ptr = story.as_mut_ptr();
 /// let len = story.len();
 /// let capacity = story.capacity();
 ///
 /// // story has nineteen bytes
 /// assert_eq!(19, len);
 ///
-/// // Now that we have our parts, we throw the story away.
-/// mem::forget(story);
-///
 /// // We can re-build a String out of ptr, len, and capacity. This is all
 /// // unsafe because we are responsible for making sure the components are
 /// // valid:
-/// let s = unsafe { String::from_raw_parts(ptr as *mut _, len, capacity) } ;
+/// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ;
 ///
 /// assert_eq!(String::from("Once upon a time..."), s);
 /// ```
@@ -647,6 +648,37 @@ impl String {
         decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect()
     }
 
+    /// Decomposes a `String` into its raw components.
+    ///
+    /// Returns the raw pointer to the underlying data, the length of
+    /// the string (in bytes), and the allocated capacity of the data
+    /// (in bytes). These are the same arguments in the same order as
+    /// the arguments to [`from_raw_parts`].
+    ///
+    /// After calling this function, the caller is responsible for the
+    /// memory previously managed by the `String`. The only way to do
+    /// this is to convert the raw pointer, length, and capacity back
+    /// into a `String` with the [`from_raw_parts`] function, allowing
+    /// the destructor to perform the cleanup.
+    ///
+    /// [`from_raw_parts`]: #method.from_raw_parts
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(vec_into_raw_parts)]
+    /// let s = String::from("hello");
+    ///
+    /// let (ptr, len, cap) = s.into_raw_parts();
+    ///
+    /// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) };
+    /// assert_eq!(rebuilt, "hello");
+    /// ```
+    #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
+    pub fn into_raw_parts(self) -> (*mut u8, usize, usize) {
+        self.vec.into_raw_parts()
+    }
+
     /// Creates a new `String` from a length, capacity, and pointer.
     ///
     /// # Safety
@@ -677,13 +709,16 @@ impl String {
     ///
     /// unsafe {
     ///     let s = String::from("hello");
-    ///     let ptr = s.as_ptr();
+    ///
+    // FIXME Update this when vec_into_raw_parts is stabilized
+    ///     // Prevent automatically dropping the String's data
+    ///     let mut s = mem::ManuallyDrop::new(s);
+    ///
+    ///     let ptr = s.as_mut_ptr();
     ///     let len = s.len();
     ///     let capacity = s.capacity();
     ///
-    ///     mem::forget(s);
-    ///
-    ///     let s = String::from_raw_parts(ptr as *mut _, len, capacity);
+    ///     let s = String::from_raw_parts(ptr, len, capacity);
     ///
     ///     assert_eq!(String::from("hello"), s);
     /// }

src/liballoc/vec.rs

@@ -358,6 +358,44 @@ impl<T> Vec<T> {
         }
     }
 
+    /// Decomposes a `Vec<T>` into its raw components.
+    ///
+    /// Returns the raw pointer to the underlying data, the length of
+    /// the vector (in elements), and the allocated capacity of the
+    /// data (in elements). These are the same arguments in the same
+    /// order as the arguments to [`from_raw_parts`].
+    ///
+    /// After calling this function, the caller is responsible for the
+    /// memory previously managed by the `Vec`. The only way to do
+    /// this is to convert the raw pointer, length, and capacity back
+    /// into a `Vec` with the [`from_raw_parts`] function, allowing
+    /// the destructor to perform the cleanup.
+    ///
+    /// [`from_raw_parts`]: #method.from_raw_parts
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(vec_into_raw_parts)]
+    /// let v: Vec<i32> = vec![-1, 0, 1];
+    ///
+    /// let (ptr, len, cap) = v.into_raw_parts();
+    ///
+    /// let rebuilt = unsafe {
+    ///     // We can now make changes to the components, such as
+    ///     // transmuting the raw pointer to a compatible type.
+    ///     let ptr = ptr as *mut u32;
+    ///
+    ///     Vec::from_raw_parts(ptr, len, cap)
+    /// };
+    /// assert_eq!(rebuilt, [4294967295, 0, 1]);
+    /// ```
+    #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
+    pub fn into_raw_parts(self) -> (*mut T, usize, usize) {
+        let mut me = mem::ManuallyDrop::new(self);
+        (me.as_mut_ptr(), me.len(), me.capacity())
+    }
+
     /// Creates a `Vec<T>` directly from the raw components of another vector.
     ///
     /// # Safety
@@ -389,18 +427,19 @@ impl<T> Vec<T> {
     /// use std::ptr;
     /// use std::mem;
     ///
-    /// let mut v = vec![1, 2, 3];
+    /// let v = vec![1, 2, 3];
+    ///
+    // FIXME Update this when vec_into_raw_parts is stabilized
+    /// // Prevent running `v`'s destructor so we are in complete control
+    /// // of the allocation.
+    /// let mut v = mem::ManuallyDrop::new(v);
     ///
     /// // Pull out the various important pieces of information about `v`
     /// let p = v.as_mut_ptr();
     /// let len = v.len();
     /// let cap = v.capacity();
     ///
     /// unsafe {
-    ///     // Cast `v` into the void: no destructor run, so we are in
-    ///     // complete control of the allocation to which `p` points.
-    ///     mem::forget(v);
-    ///
     ///     // Overwrite memory with 4, 5, 6
     ///     for i in 0..len as isize {
     ///         ptr::write(p.offset(i), 4 + i);

src/libcore/array/iter.rs

@@ -13,7 +13,7 @@ use super::LengthAtMost32;
 /// A by-value [array] iterator.
 ///
 /// [array]: ../../std/primitive.array.html
-#[unstable(feature = "array_value_iter", issue = "0")]
+#[unstable(feature = "array_value_iter", issue = "65798")]
 pub struct IntoIter<T, const N: usize>
 where
     [T; N]: LengthAtMost32,
@@ -49,7 +49,7 @@ where
     /// *Note*: this method might never get stabilized and/or removed in the
     /// future as there will likely be another, preferred way of obtaining this
     /// iterator (either via `IntoIterator` for arrays or via another way).
-    #[unstable(feature = "array_value_iter", issue = "0")]
+    #[unstable(feature = "array_value_iter", issue = "65798")]
     pub fn new(array: [T; N]) -> Self {
         // The transmute here is actually safe. The docs of `MaybeUninit`
         // promise:
@@ -95,7 +95,7 @@ where
 }
 
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T, const N: usize> Iterator for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -141,7 +141,7 @@ where
     }
 }
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T, const N: usize> DoubleEndedIterator for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -176,7 +176,7 @@ where
     }
 }
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T, const N: usize> Drop for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -189,7 +189,7 @@ where
     }
 }
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T, const N: usize> ExactSizeIterator for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -204,7 +204,7 @@ where
     }
 }
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T, const N: usize> FusedIterator for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -214,13 +214,13 @@ where
 // elements (that will still be yielded) is the length of the range `alive`.
 // This range is decremented in length in either `next` or `next_back`. It is
 // always decremented by 1 in those methods, but only if `Some(_)` is returned.
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 unsafe impl<T, const N: usize> TrustedLen for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
 {}
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T: Clone, const N: usize> Clone for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,
@@ -251,7 +251,7 @@ where
     }
 }
 
-#[stable(feature = "array_value_iter_impls", since = "1.38.0")]
+#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T: fmt::Debug, const N: usize> fmt::Debug for IntoIter<T, {N}>
 where
     [T; N]: LengthAtMost32,

src/libcore/array/mod.rs

@@ -18,7 +18,7 @@ use crate::slice::{Iter, IterMut};
 mod iter;
 
 #[cfg(not(bootstrap))]
-#[unstable(feature = "array_value_iter", issue = "0")]
+#[unstable(feature = "array_value_iter", issue = "65798")]
 pub use iter::IntoIter;
 
 /// Utility trait implemented only on arrays of fixed size

src/libcore/intrinsics.rs

@@ -874,6 +874,7 @@ extern "rust-intrinsic" {
     /// // the original inner type (`&i32`) to the converted inner type
     /// // (`Option<&i32>`), so read the nomicon pages linked above.
     /// let v_from_raw = unsafe {
+    // FIXME Update this when vec_into_raw_parts is stabilized
     ///     // Ensure the original vector is not dropped.
     ///     let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
     ///     Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,

src/libcore/slice/mod.rs

@@ -28,7 +28,7 @@ use crate::fmt;
 use crate::intrinsics::{assume, exact_div, unchecked_sub, is_aligned_and_not_null};
 use crate::isize;
 use crate::iter::*;
-use crate::ops::{FnMut, self};
+use crate::ops::{FnMut, Range, self};
 use crate::option::Option;
 use crate::option::Option::{None, Some};
 use crate::result::Result;
@@ -407,6 +407,86 @@ impl<T> [T] {
         self as *mut [T] as *mut T
     }
 
+    /// Returns the two raw pointers spanning the slice.
+    ///
+    /// The returned range is half-open, which means that the end pointer
+    /// points *one past* the last element of the slice. This way, an empty
+    /// slice is represented by two equal pointers, and the difference between
+    /// the two pointers represents the size of the size.
+    ///
+    /// See [`as_ptr`] for warnings on using these pointers. The end pointer
+    /// requires extra caution, as it does not point to a valid element in the
+    /// slice.
+    ///
+    /// This function is useful for interacting with foreign interfaces which
+    /// use two pointers to refer to a range of elements in memory, as is
+    /// common in C++.
+    ///
+    /// It can also be useful to check if a pointer to an element refers to an
+    /// element of this slice:
+    ///
+    /// ```
+    /// #![feature(slice_ptr_range)]
+    ///
+    /// let a = [1, 2, 3];
+    /// let x = &a[1] as *const _;
+    /// let y = &5 as *const _;
+    ///
+    /// assert!(a.as_ptr_range().contains(&x));
+    /// assert!(!a.as_ptr_range().contains(&y));
+    /// ```
+    ///
+    /// [`as_ptr`]: #method.as_ptr
+    #[unstable(feature = "slice_ptr_range", issue = "65807")]
+    #[inline]
+    pub fn as_ptr_range(&self) -> Range<*const T> {
+        // The `add` here is safe, because:
+        //
+        //   - Both pointers are part of the same object, as pointing directly
+        //     past the object also counts.
+        //
+        //   - The size of the slice is never larger than isize::MAX bytes, as
+        //     noted here:
+        //       - https://github.com/rust-lang/unsafe-code-guidelines/issues/102#issuecomment-473340447
+        //       - https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+        //       - https://doc.rust-lang.org/core/slice/fn.from_raw_parts.html#safety
+        //     (This doesn't seem normative yet, but the very same assumption is
+        //     made in many places, including the Index implementation of slices.)
+        //
+        //   - There is no wrapping around involved, as slices do not wrap past
+        //     the end of the address space.
+        //
+        // See the documentation of pointer::add.
+        let start = self.as_ptr();
+        let end = unsafe { start.add(self.len()) };
+        start..end
+    }
+
+    /// Returns the two unsafe mutable pointers spanning the slice.
+    ///
+    /// The returned range is half-open, which means that the end pointer
+    /// points *one past* the last element of the slice. This way, an empty
+    /// slice is represented by two equal pointers, and the difference between
+    /// the two pointers represents the size of the size.
+    ///
+    /// See [`as_mut_ptr`] for warnings on using these pointers. The end
+    /// pointer requires extra caution, as it does not point to a valid element
+    /// in the slice.
+    ///
+    /// This function is useful for interacting with foreign interfaces which
+    /// use two pointers to refer to a range of elements in memory, as is
+    /// common in C++.
+    ///
+    /// [`as_mut_ptr`]: #method.as_mut_ptr
+    #[unstable(feature = "slice_ptr_range", issue = "65807")]
+    #[inline]
+    pub fn as_mut_ptr_range(&mut self) -> Range<*mut T> {
+        // See as_ptr_range() above for why `add` here is safe.
+        let start = self.as_mut_ptr();
+        let end = unsafe { start.add(self.len()) };
+        start..end
+    }
+
     /// Swaps two elements in the slice.
     ///
     /// # Arguments

src/librustc/Cargo.toml

@@ -37,4 +37,4 @@ byteorder = { version = "1.3" }
 chalk-engine = { version = "0.9.0", default-features=false }
 rustc_fs_util = { path = "../librustc_fs_util" }
 smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
-measureme = "0.3"
+measureme = "0.4"

src/librustc/ty/context.rs

@@ -2930,14 +2930,18 @@ impl<T, R, E> InternIteratorElement<T, R> for Result<T, E> {
         // lower bounds from `size_hint` agree they are correct.
         Ok(match iter.size_hint() {
             (1, Some(1)) => {
-                f(&[iter.next().unwrap()?])
+                let t0 = iter.next().unwrap()?;
+                assert!(iter.next().is_none());
+                f(&[t0])
             }
             (2, Some(2)) => {
                 let t0 = iter.next().unwrap()?;
                 let t1 = iter.next().unwrap()?;
+                assert!(iter.next().is_none());
                 f(&[t0, t1])
             }
             (0, Some(0)) => {
+                assert!(iter.next().is_none());
                 f(&[])
             }
             _ => {