refactor/polish ~ fix cargo clippy complaints (use b'...' notation)

src/ls/ls.rs

@@ -336,7 +336,7 @@ fn display_dir_entry_size(entry: &PathBuf, options: &getopts::Matches) -> (usize
 fn pad_left(string: String, count: usize) -> String {
     if count > string.len() {
         let pad = count - string.len();
-        let pad = String::from_utf8(vec![' ' as u8; pad]).unwrap();
+        let pad = String::from_utf8(vec![b' ' as u8; pad]).unwrap();
         format!("{}{}", pad, string)
     } else {
         string

src/mktemp/mktemp.rs

@@ -179,9 +179,9 @@ pub fn dry_exec(mut tmpdir: PathBuf, prefix: &str, rand: usize, suffix: &str) ->
         rand::thread_rng().fill(bytes);
         for byte in bytes.iter_mut() {
             *byte = match *byte % 62 {
-                v @ 0..=9 => (v + '0' as u8),
-                v @ 10..=35 => (v - 10 + 'a' as u8),
-                v @ 36..=61 => (v - 36 + 'A' as u8),
+                v @ 0..=9 => (v + b'0' as u8),
+                v @ 10..=35 => (v - 10 + b'a' as u8),
+                v @ 36..=61 => (v - 36 + b'A' as u8),
                 _ => unreachable!(),
             }
         }

src/unexpand/unexpand.rs

@@ -189,13 +189,13 @@ fn write_tabs(
                 break;
             }
 
-            safe_unwrap!(output.write_all("\t".as_bytes()));
+            safe_unwrap!(output.write_all(b"\t"));
             scol += nts;
         }
     }
 
     while col > scol {
-        safe_unwrap!(output.write_all(" ".as_bytes()));
+        safe_unwrap!(output.write_all(b" "));
         scol += 1;
     }
 }
@@ -219,7 +219,7 @@ fn unexpand(options: Options) {
     for file in options.files.into_iter() {
         let mut fh = open(file);
 
-        while match fh.read_until('\n' as u8, &mut buf) {
+        while match fh.read_until(b'\n' as u8, &mut buf) {
             Ok(s) => s > 0,
             Err(_) => !buf.is_empty(),
         } {

src/uniq/uniq.rs

@@ -99,7 +99,7 @@ impl Uniq {
         if self.zero_terminated {
             0
         } else {
-            '\n' as u8
+            b'\n' as u8
         }
     }
 

src/wc/wc.rs

@@ -121,10 +121,10 @@ pub fn uumain(args: Vec<String>) -> i32 {
     0
 }
 
-const CR: u8 = '\r' as u8;
-const LF: u8 = '\n' as u8;
-const SPACE: u8 = ' ' as u8;
-const TAB: u8 = '\t' as u8;
+const CR: u8 = b'\r';
+const LF: u8 = b'\n';
+const SPACE: u8 = b' ';
+const TAB: u8 = b'\t';
 const SYN: u8 = 0x16 as u8;
 const FF: u8 = 0x0C as u8;