Remove some now-unnecessary casts of |size_t| to |usize|.

I didn't try to find every such cast. I concentrated on the files that
had now-unnecessary casts from |usize| to |size_t|.

src/liballoc_jemalloc/lib.rs

@@ -97,7 +97,7 @@ pub extern "C" fn __rust_reallocate_inplace(ptr: *mut u8,
                                             align: usize)
                                             -> usize {
     let flags = align_to_flags(align);
-    unsafe { je_xallocx(ptr as *mut c_void, size, 0, flags) as usize }
+    unsafe { je_xallocx(ptr as *mut c_void, size, 0, flags) }
 }
 
 #[no_mangle]
@@ -109,5 +109,5 @@ pub extern "C" fn __rust_deallocate(ptr: *mut u8, old_size: usize, align: usize)
 #[no_mangle]
 pub extern "C" fn __rust_usable_size(size: usize, align: usize) -> usize {
     let flags = align_to_flags(align);
-    unsafe { je_nallocx(size, flags) as usize }
+    unsafe { je_nallocx(size, flags) }
 }

src/libstd/ffi/c_str.rs

@@ -232,7 +232,7 @@ impl CString {
     #[stable(feature = "cstr_memory", since = "1.4.0")]
     pub unsafe fn from_raw(ptr: *mut libc::c_char) -> CString {
         let len = libc::strlen(ptr) + 1; // Including the NUL byte
-        let slice = slice::from_raw_parts(ptr, len as usize);
+        let slice = slice::from_raw_parts(ptr, len);
         CString { inner: mem::transmute(slice) }
     }
 
@@ -447,7 +447,7 @@ impl CStr {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub unsafe fn from_ptr<'a>(ptr: *const libc::c_char) -> &'a CStr {
         let len = libc::strlen(ptr);
-        mem::transmute(slice::from_raw_parts(ptr, len as usize + 1))
+        mem::transmute(slice::from_raw_parts(ptr, len + 1))
     }
 
     /// Returns the inner pointer to this C string.

src/libstd/fs.rs

@@ -1642,8 +1642,8 @@ mod tests {
             let stem = f.file_stem().unwrap().to_str().unwrap();
             let root = stem.as_bytes()[0] - b'0';
             let name = stem.as_bytes()[1] - b'0';
-            assert!(cur[root as usize] < name);
-            cur[root as usize] = name;
+            assert!(cur[root] < name);
+            cur[root] = name;
         }
 
         check!(fs::remove_dir_all(dir));

src/libstd/sys/unix/fs.rs

@@ -388,7 +388,7 @@ impl fmt::Debug for File {
                 return None;
             }
             let l = buf.iter().position(|&c| c == 0).unwrap();
-            buf.truncate(l as usize);
+            buf.truncate(l);
             buf.shrink_to_fit();
             Some(PathBuf::from(OsString::from_vec(buf)))
         }

src/libstd/sys/unix/os.rs

@@ -197,13 +197,13 @@ pub fn current_exe() -> io::Result<PathBuf> {
                          0 as libc::size_t);
         if err != 0 { return Err(io::Error::last_os_error()); }
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
+        let mut v: Vec<u8> = Vec::with_capacity(sz);
         let err = sysctl(mib.as_mut_ptr(), mib.len() as ::libc::c_uint,
                          v.as_mut_ptr() as *mut libc::c_void, &mut sz,
                          ptr::null_mut(), 0 as libc::size_t);
         if err != 0 { return Err(io::Error::last_os_error()); }
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        v.set_len(sz as usize - 1); // chop off trailing NUL
+        v.set_len(sz - 1); // chop off trailing NUL
         Ok(PathBuf::from(OsString::from_vec(v)))
     }
 }
@@ -252,10 +252,10 @@ pub fn current_exe() -> io::Result<PathBuf> {
         let mut sz: u32 = 0;
         _NSGetExecutablePath(ptr::null_mut(), &mut sz);
         if sz == 0 { return Err(io::Error::last_os_error()); }
-        let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
+        let mut v: Vec<u8> = Vec::with_capacity(sz);
         let err = _NSGetExecutablePath(v.as_mut_ptr() as *mut i8, &mut sz);
         if err != 0 { return Err(io::Error::last_os_error()); }
-        v.set_len(sz as usize - 1); // chop off trailing NUL
+        v.set_len(sz - 1); // chop off trailing NUL
         Ok(PathBuf::from(OsString::from_vec(v)))
     }
 }
@@ -479,7 +479,7 @@ pub fn home_dir() -> Option<PathBuf> {
                   target_os = "ios")))]
     unsafe fn fallback() -> Option<OsString> {
         let amt = match libc::sysconf(c::_SC_GETPW_R_SIZE_MAX) {
-            n if n < 0 => 512 as usize,
+            n if n < 0 => 512usize,
             n => n as usize,
         };
         let me = libc::getuid();

src/libstd/sys/unix/thread.rs

@@ -377,16 +377,16 @@ fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
     });
 
     match unsafe { __pthread_get_minstack } {
-        None => PTHREAD_STACK_MIN as usize,
-        Some(f) => unsafe { f(attr) as usize },
+        None => PTHREAD_STACK_MIN,
+        Some(f) => unsafe { f(attr) },
     }
 }
 
 // No point in looking up __pthread_get_minstack() on non-glibc
 // platforms.
 #[cfg(not(target_os = "linux"))]
 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
-    PTHREAD_STACK_MIN as usize
+    PTHREAD_STACK_MIN
 }
 
 extern {