Auto merge of #23832 - petrochenkov:usize, r=aturon

These constants are small and can fit even in `u8`, but semantically they have type `usize` because they denote sizes and are almost always used in `usize` context. The change of their type to `u32` during the integer audit led only to the large amount of `as usize` noise (see the second commit, which removes this noise).

This is a minor [breaking-change] to an unstable interface.

r? @aturon 

2 files changed, 18 insertions, 18 deletions

diff --git a/src/libcollections/bit.rs b/src/libcollections/bit.rs
index 8874ac6eb87..d9255241af0 100644
--- a/src/libcollections/bit.rs
+++ b/src/libcollections/bit.rs
@@ -190,17 +190,17 @@ fn blocks_for_bits(bits: usize) -> usize {
     //
     // Note that we can technically avoid this branch with the expression
     // `(nbits + u32::BITS - 1) / 32::BITS`, but if nbits is almost usize::MAX this will overflow.
-    if bits % u32::BITS as usize == 0 {
-        bits / u32::BITS as usize
+    if bits % u32::BITS == 0 {
+        bits / u32::BITS
     } else {
-        bits / u32::BITS as usize + 1
+        bits / u32::BITS + 1
     }
 }
 
 /// Computes the bitmask for the final word of the vector
 fn mask_for_bits(bits: usize) -> u32 {
     // Note especially that a perfect multiple of u32::BITS should mask all 1s.
-    !0 >> (u32::BITS as usize - bits % u32::BITS as usize) % u32::BITS as usize
+    !0 >> (u32::BITS - bits % u32::BITS) % u32::BITS
 }
 
 impl BitVec {
@@ -238,7 +238,7 @@ impl BitVec {
     /// An operation might screw up the unused bits in the last block of the
     /// `BitVec`. As per (3), it's assumed to be all 0s. This method fixes it up.
     fn fix_last_block(&mut self) {
-        let extra_bits = self.len() % u32::BITS as usize;
+        let extra_bits = self.len() % u32::BITS;
         if extra_bits > 0 {
             let mask = (1 << extra_bits) - 1;
             let storage_len = self.storage.len();
@@ -317,7 +317,7 @@ impl BitVec {
     ///                     false, false, true, false]));
     /// ```
     pub fn from_bytes(bytes: &[u8]) -> BitVec {
-        let len = bytes.len().checked_mul(u8::BITS as usize).expect("capacity overflow");
+        let len = bytes.len().checked_mul(u8::BITS).expect("capacity overflow");
         let mut bit_vec = BitVec::with_capacity(len);
         let complete_words = bytes.len() / 4;
         let extra_bytes = bytes.len() % 4;
@@ -386,8 +386,8 @@ impl BitVec {
         if i >= self.nbits {
             return None;
         }
-        let w = i / u32::BITS as usize;
-        let b = i % u32::BITS as usize;
+        let w = i / u32::BITS;
+        let b = i % u32::BITS;
         self.storage.get(w).map(|&block|
             (block & (1 << b)) != 0
         )
@@ -414,8 +414,8 @@ impl BitVec {
                reason = "panic semantics are likely to change in the future")]
     pub fn set(&mut self, i: usize, x: bool) {
         assert!(i < self.nbits);
-        let w = i / u32::BITS as usize;
-        let b = i % u32::BITS as usize;
+        let w = i / u32::BITS;
+        let b = i % u32::BITS;
         let flag = 1 << b;
         let val = if x { self.storage[w] | flag }
                   else { self.storage[w] & !flag };
@@ -811,7 +811,7 @@ impl BitVec {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn capacity(&self) -> usize {
-        self.storage.capacity().checked_mul(u32::BITS as usize).unwrap_or(usize::MAX)
+        self.storage.capacity().checked_mul(u32::BITS).unwrap_or(usize::MAX)
     }
 
     /// Grows the `BitVec` in-place, adding `n` copies of `value` to the `BitVec`.
@@ -842,7 +842,7 @@ impl BitVec {
 
         // Correct the old tail word, setting or clearing formerly unused bits
         let num_cur_blocks = blocks_for_bits(self.nbits);
-        if self.nbits % u32::BITS as usize > 0 {
+        if self.nbits % u32::BITS > 0 {
             let mask = mask_for_bits(self.nbits);
             if value {
                 self.storage[num_cur_blocks - 1] |= !mask;
@@ -892,7 +892,7 @@ impl BitVec {
             // (3)
             self.set(i, false);
             self.nbits = i;
-            if self.nbits % u32::BITS as usize == 0 {
+            if self.nbits % u32::BITS == 0 {
                 // (2)
                 self.storage.pop();
             }
@@ -915,7 +915,7 @@ impl BitVec {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn push(&mut self, elem: bool) {
-        if self.nbits % u32::BITS as usize == 0 {
+        if self.nbits % u32::BITS == 0 {
             self.storage.push(0);
         }
         let insert_pos = self.nbits;
@@ -1433,7 +1433,7 @@ impl BitSet {
         // Truncate
         let trunc_len = cmp::max(old_len - n, 1);
         bit_vec.storage.truncate(trunc_len);
-        bit_vec.nbits = trunc_len * u32::BITS as usize;
+        bit_vec.nbits = trunc_len * u32::BITS;
     }
 
     /// Iterator over each u32 stored in the `BitSet`.
@@ -1871,13 +1871,13 @@ impl<'a> Iterator for TwoBitPositions<'a> {
     fn next(&mut self) -> Option<usize> {
         while self.next_idx < self.set.bit_vec.len() ||
               self.next_idx < self.other.bit_vec.len() {
-            let bit_idx = self.next_idx % u32::BITS as usize;
+            let bit_idx = self.next_idx % u32::BITS;
             if bit_idx == 0 {
                 let s_bit_vec = &self.set.bit_vec;
                 let o_bit_vec = &self.other.bit_vec;
                 // Merging the two words is a bit of an awkward dance since
                 // one BitVec might be longer than the other
-                let word_idx = self.next_idx / u32::BITS as usize;
+                let word_idx = self.next_idx / u32::BITS;
                 let w1 = if word_idx < s_bit_vec.storage.len() {
                              s_bit_vec.storage[word_idx]
                          } else { 0 };
diff --git a/src/libcollections/enum_set.rs b/src/libcollections/enum_set.rs
index 0b206d381dd..a3a266669b1 100644
--- a/src/libcollections/enum_set.rs
+++ b/src/libcollections/enum_set.rs
@@ -86,7 +86,7 @@ pub trait CLike {
 fn bit<E:CLike>(e: &E) -> usize {
     use core::usize;
     let value = e.to_usize();
-    assert!(value < usize::BITS as usize,
+    assert!(value < usize::BITS,
             "EnumSet only supports up to {} variants.", usize::BITS - 1);
     1 << value
 }