make Vec::new const :P

[rust.git] / src / liballoc / vec.rs

diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 4b883b5bce79bd48f714b5442340696024eea662..1d95f76fd7732b49acf9f55cc89795942a805318 100644 (file)
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -74,6 +74,7 @@
 use core::marker::PhantomData;
 use core::mem;
 #[cfg(not(test))]
+#[cfg(stage0)]
 use core::num::Float;
 use core::ops::Bound::{Excluded, Included, Unbounded};
 use core::ops::{Index, IndexMut, RangeBounds};
@@ -82,11 +83,11 @@
 use core::ptr::NonNull;
 use core::slice;
 
+use alloc::CollectionAllocErr;
 use borrow::ToOwned;
 use borrow::Cow;
 use boxed::Box;
 use raw_vec::RawVec;
-use super::allocator::CollectionAllocErr;
 
 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
 ///
@@ -321,9 +322,9 @@ impl<T> Vec<T> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new() -> Vec<T> {
+    pub const fn new() -> Vec<T> {
         Vec {
-            buf: RawVec::new(),
+            buf: RawVec::empty(),
             len: 0,
         }
     }
@@ -583,7 +584,9 @@ pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), CollectionA
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn shrink_to_fit(&mut self) {
-        self.buf.shrink_to_fit(self.len);
+        if self.capacity() != self.len {
+            self.buf.shrink_to_fit(self.len);
+        }
     }
 
     /// Shrinks the capacity of the vector with a lower bound.
@@ -2394,9 +2397,10 @@ fn next(&mut self) -> Option<T> {
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let exact = match self.ptr.offset_to(self.end) {
-            Some(x) => x as usize,
-            None => (self.end as usize).wrapping_sub(self.ptr as usize),
+        let exact = if mem::size_of::<T>() == 0 {
+            (self.end as usize).wrapping_sub(self.ptr as usize)
+        } else {
+            unsafe { self.end.offset_from(self.ptr) as usize }
         };
         (exact, Some(exact))
     }
@@ -2520,7 +2524,7 @@ fn next_back(&mut self) -> Option<T> {
 impl<'a, T> Drop for Drain<'a, T> {
     fn drop(&mut self) {
         // exhaust self first
-        while let Some(_) = self.next() {}
+        self.for_each(drop);
 
         if self.tail_len > 0 {
             unsafe {
@@ -2589,9 +2593,7 @@ impl<'a, I: Iterator> ExactSizeIterator for Splice<'a, I> {}
 #[stable(feature = "vec_splice", since = "1.21.0")]
 impl<'a, I: Iterator> Drop for Splice<'a, I> {
     fn drop(&mut self) {
-        // exhaust drain first
-        while let Some(_) = self.drain.next() {}
-
+        self.drain.by_ref().for_each(drop);
 
         unsafe {
             if self.drain.tail_len == 0 {
@@ -2720,8 +2722,7 @@ impl<'a, T, F> Drop for DrainFilter<'a, T, F>
     where F: FnMut(&mut T) -> bool,
 {
     fn drop(&mut self) {
-        for _ in self.by_ref() { }
-
+        self.for_each(drop);
         unsafe {
             self.vec.set_len(self.old_len - self.del);
         }