clippy: simplify code according to nightly 'byte_char_slices' lint

https://rust-lang.github.io/rust-clippy/master/index.html#/byte_char_slices

src/uu/cat/src/cat.rs

@@ -623,10 +623,10 @@ fn write_nonprint_to_end<W: Write>(in_buf: &[u8], writer: &mut W, tab: &[u8]) ->
             9 => writer.write_all(tab),
             0..=8 | 10..=31 => writer.write_all(&[b'^', byte + 64]),
             32..=126 => writer.write_all(&[byte]),
-            127 => writer.write_all(&[b'^', b'?']),
+            127 => writer.write_all(b"^?"),
             128..=159 => writer.write_all(&[b'M', b'-', b'^', byte - 64]),
             160..=254 => writer.write_all(&[b'M', b'-', byte - 128]),
-            _ => writer.write_all(&[b'M', b'-', b'^', b'?']),
+            _ => writer.write_all(b"M-^?"),
         }
         .unwrap();
         count += 1;

src/uucore/src/lib/features/encoding.rs

@@ -86,7 +86,7 @@ pub fn decode(f: Format, input: &[u8]) -> DecodeResult {
         Z85 => {
             // The z85 crate implements a padded encoding by using a leading '#' which is otherwise not allowed.
             // We manually check for a leading '#' and return an error ourselves.
-            if input.starts_with(&[b'#']) {
+            if input.starts_with(b"#") {
                 return Err(z85::DecodeError::InvalidByte(0, b'#').into());
             } else {
                 z85::decode(input)?

src/uucore/src/lib/features/sum.rs

@@ -402,7 +402,7 @@ impl<'a> DigestWriter<'a> {
 
     pub fn finalize(&mut self) -> bool {
         if self.was_last_character_carriage_return {
-            self.digest.hash_update(&[b'\r']);
+            self.digest.hash_update(b"\r");
             true
         } else {
             false
@@ -433,7 +433,7 @@ impl<'a> Write for DigestWriter<'a> {
         // call to `write()`.
         let n = buf.len();
         if self.was_last_character_carriage_return && n > 0 && buf[0] != b'\n' {
-            self.digest.hash_update(&[b'\r']);
+            self.digest.hash_update(b"\r");
         }
 
         // Next, find all occurrences of "\r\n", inputting the slice
@@ -491,15 +491,15 @@ mod tests {
         // Writing "\r" in one call to `write()`, and then "\n" in another.
         let mut digest = Box::new(Md5::new()) as Box<dyn Digest>;
         let mut writer_crlf = DigestWriter::new(&mut digest, false);
-        writer_crlf.write_all(&[b'\r']).unwrap();
+        writer_crlf.write_all(b"\r").unwrap();
-        writer_crlf.write_all(&[b'\n']).unwrap();
+        writer_crlf.write_all(b"\n").unwrap();
         writer_crlf.finalize();
         let result_crlf = digest.result_str();
 
         // We expect "\r\n" to be replaced with "\n" in text mode on Windows.
         let mut digest = Box::new(Md5::new()) as Box<dyn Digest>;
         let mut writer_lf = DigestWriter::new(&mut digest, false);
-        writer_lf.write_all(&[b'\n']).unwrap();
+        writer_lf.write_all(b"\n").unwrap();
         writer_lf.finalize();
         let result_lf = digest.result_str();
 

tests/by-util/test_hashsum.rs

@@ -83,7 +83,7 @@ macro_rules! test_digest {
             // The asterisk indicates that the digest was computed in
             // binary mode.
             let n = expected.len();
-            let expected = [&expected[..n - 3], &[b' ', b'-', b'\n']].concat();
+            let expected = [&expected[..n - 3], b" -\n"].concat();
             new_ucmd!()
                 .args(&[DIGEST_ARG, BITS_ARG, "-t"])
                 .pipe_in("a\r\nb\r\nc\r\n")

tests/by-util/test_tr.rs

@@ -1434,8 +1434,8 @@ fn check_complement_set2_too_big() {
 #[test]
 #[cfg(unix)]
 fn test_truncate_non_utf8_set() {
-    let stdin = &[b'\x01', b'a', b'm', b'p', 0xfe_u8, 0xff_u8];
+    let stdin = b"\x01amp\xfe\xff";
-    let set1 = OsStr::from_bytes(&[b'a', 0xfe_u8, 0xff_u8, b'z']);
+    let set1 = OsStr::from_bytes(b"a\xfe\xffz"); // spell-checker:disable-line
     let set2 = OsStr::from_bytes(b"01234");
 
     new_ucmd!()

tests/common/util.rs

@@ -59,7 +59,7 @@ static ALREADY_RUN: &str = " you have already run this UCommand, if you want to
 static MULTIPLE_STDIN_MEANINGLESS: &str = "Ucommand is designed around a typical use case of: provide args and input stream -> spawn process -> block until completion -> return output streams. For verifying that a particular section of the input stream is what causes a particular behavior, use the Command type directly.";
 
 static NO_STDIN_MEANINGLESS: &str = "Setting this flag has no effect if there is no stdin";
-static END_OF_TRANSMISSION_SEQUENCE: &[u8] = &[b'\n', 0x04];
+static END_OF_TRANSMISSION_SEQUENCE: &[u8] = b"\n\x04";
 
 pub const TESTS_BINARY: &str = env!("CARGO_BIN_EXE_coreutils");
 pub const PATH: &str = env!("PATH");
@@ -3081,7 +3081,7 @@ mod tests {
         let result = TestScenario::new("echo").ucmd().arg("Hello world").run();
 
         result.stdout_str_check(|stdout| stdout.ends_with("world\n"));
-        result.stdout_check(|stdout| stdout.get(0..2).unwrap().eq(&[b'H', b'e']));
+        result.stdout_check(|stdout| stdout.get(0..2).unwrap().eq(b"He"));
         result.no_stderr();
     }
 
@@ -3096,7 +3096,7 @@ mod tests {
         ));
 
         result.stderr_str_check(|stderr| stderr.ends_with("world\n"));
-        result.stderr_check(|stderr| stderr.get(0..2).unwrap().eq(&[b'H', b'e']));
+        result.stderr_check(|stdout| stdout.get(0..2).unwrap().eq(b"He"));
         result.no_stdout();
     }