From cb19d68abd52c338119da83a69bead1c808dc399 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sat, 19 Sep 2020 21:17:58 +0100
Subject: [PATCH 1/9] Fixed most existing clippy lints and now `warn`ing
 against some `pedantic` clippy lints.

---
 src/ascii_char.rs   | 137 ++++++++++++++++++++++++++++++--------------
 src/ascii_str.rs    |  74 ++++++++++++++++++++----
 src/ascii_string.rs |  32 +++++++++--
 src/lib.rs          |  16 +++++-
 tests.rs            |   2 +-
 5 files changed, 198 insertions(+), 63 deletions(-)

diff --git a/src/ascii_char.rs b/src/ascii_char.rs
index c595e3a..2444b81 100644
--- a/src/ascii_char.rs
+++ b/src/ascii_char.rs
@@ -280,7 +280,7 @@ pub enum AsciiChar {
 impl AsciiChar {
     /// Constructs an ASCII character from a `u8`, `char` or other character type.
     ///
-    /// # Failure
+    /// # Errors
     /// Returns `Err(())` if the character can't be ASCII encoded.
     ///
     /// # Example
@@ -328,8 +328,13 @@ impl AsciiChar {
     ///
     /// The panic message might not be the most descriptive due to the
     /// current limitations of `const fn`.
+    #[must_use]
     pub const fn new(ch: char) -> AsciiChar {
+        // It's restricted to this function, and without it
+        // we'd need to specify `AsciiChar::` or `Self::` 128 times.
+        #[allow(clippy::enum_glob_use)]
         use AsciiChar::*;
+
         #[rustfmt::skip]
         const ALL: [AsciiChar; 128] = [
             Null, SOH, SOX, ETX, EOT, ENQ, ACK, Bell,
@@ -366,18 +371,21 @@ impl AsciiChar {
     /// might not panic, creating a buffer overflow,
     /// and `Some(AsciiChar::from_ascii_unchecked(128))` might be `None`.
     #[inline]
+    #[must_use]
     pub unsafe fn from_ascii_unchecked(ch: u8) -> Self {
         ch.to_ascii_char_unchecked()
     }
 
     /// Converts an ASCII character into a `u8`.
     #[inline]
+    #[must_use]
     pub const fn as_byte(self) -> u8 {
         self as u8
     }
 
     /// Converts an ASCII character into a `char`.
     #[inline]
+    #[must_use]
     pub const fn as_char(self) -> char {
         self as u8 as char
     }
@@ -390,12 +398,14 @@ impl AsciiChar {
     // make the compiler optimize away the indirection.
 
     /// Turns uppercase into lowercase, but also modifies '@' and '<'..='_'
+    #[must_use]
     const fn to_not_upper(self) -> u8 {
         self as u8 | 0b010_0000
     }
 
     /// Check if the character is a letter (a-z, A-Z)
     #[inline]
+    #[must_use]
     pub const fn is_alphabetic(self) -> bool {
         (self.to_not_upper() >= b'a') & (self.to_not_upper() <= b'z')
     }
@@ -404,6 +414,7 @@ impl AsciiChar {
     ///
     /// This method is identical to [`is_alphabetic()`](#method.is_alphabetic)
     #[inline]
+    #[must_use]
     pub const fn is_ascii_alphabetic(&self) -> bool {
         self.is_alphabetic()
     }
@@ -417,6 +428,7 @@ impl AsciiChar {
     /// # Panics
     ///
     /// Radixes greater than 36 are not supported and will result in a panic.
+    #[must_use]
     pub fn is_digit(self, radix: u32) -> bool {
         match (self as u8, radix) {
             (b'0'..=b'9', 0..=36) => u32::from(self as u8 - b'0') < radix,
@@ -439,12 +451,14 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('/').is_ascii_digit(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_digit(&self) -> bool {
         (*self as u8 >= b'0') & (*self as u8 <= b'9')
     }
 
     /// Check if the character is a letter or number
     #[inline]
+    #[must_use]
     pub const fn is_alphanumeric(self) -> bool {
         self.is_alphabetic() | self.is_ascii_digit()
     }
@@ -453,6 +467,7 @@ impl AsciiChar {
     ///
     /// This method is identical to [`is_alphanumeric()`](#method.is_alphanumeric)
     #[inline]
+    #[must_use]
     pub const fn is_ascii_alphanumeric(&self) -> bool {
         self.is_alphanumeric()
     }
@@ -470,6 +485,7 @@ impl AsciiChar {
     /// assert!(!AsciiChar::FF.is_ascii_blank());
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_blank(&self) -> bool {
         (*self as u8 == b' ') | (*self as u8 == b'\t')
     }
@@ -477,6 +493,7 @@ impl AsciiChar {
     /// Check if the character one of ' ', '\t', '\n', '\r',
     /// '\0xb' (vertical tab) or '\0xc' (form feed).
     #[inline]
+    #[must_use]
     pub const fn is_whitespace(self) -> bool {
         let b = self as u8;
         self.is_ascii_blank() | (b == b'\n') | (b == b'\r') | (b == 0x0b) | (b == 0x0c)
@@ -486,6 +503,7 @@ impl AsciiChar {
     ///
     /// This method is NOT identical to `is_whitespace()`.
     #[inline]
+    #[must_use]
     pub const fn is_ascii_whitespace(&self) -> bool {
         self.is_ascii_blank()
             | (*self as u8 == b'\n')
@@ -506,6 +524,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::EOT.is_ascii_control(), true);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_control(&self) -> bool {
         ((*self as u8) < b' ') | (*self as u8 == 127)
     }
@@ -520,6 +539,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('\n').is_ascii_graphic(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_graphic(&self) -> bool {
         self.as_byte().wrapping_sub(b' ' + 1) < 0x5E
     }
@@ -534,6 +554,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('\n').is_ascii_printable(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_printable(&self) -> bool {
         self.as_byte().wrapping_sub(b' ') < 0x5F
     }
@@ -548,6 +569,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('@').is_lowercase(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_lowercase(self) -> bool {
         self.as_byte().wrapping_sub(b'a') < 26
     }
@@ -556,6 +578,7 @@ impl AsciiChar {
     ///
     /// This method is identical to [`is_lowercase()`](#method.is_lowercase)
     #[inline]
+    #[must_use]
     pub const fn is_ascii_lowercase(&self) -> bool {
         self.is_lowercase()
     }
@@ -570,6 +593,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('@').is_uppercase(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_uppercase(self) -> bool {
         self.as_byte().wrapping_sub(b'A') < 26
     }
@@ -578,6 +602,7 @@ impl AsciiChar {
     ///
     /// This method is identical to [`is_uppercase()`](#method.is_uppercase)
     #[inline]
+    #[must_use]
     pub const fn is_ascii_uppercase(&self) -> bool {
         self.is_uppercase()
     }
@@ -593,6 +618,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('~').is_ascii_punctuation(), true);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_punctuation(&self) -> bool {
         self.is_ascii_graphic() & !self.is_alphanumeric()
     }
@@ -609,8 +635,9 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new(' ').is_ascii_hexdigit(), false);
     /// ```
     #[inline]
+    #[must_use]
     pub const fn is_ascii_hexdigit(&self) -> bool {
-        self.is_ascii_digit() | ((*self as u8 | 0x20u8).wrapping_sub(b'a') < 6)
+        self.is_ascii_digit() | ((*self as u8 | 0x20_u8).wrapping_sub(b'a') < 6)
     }
 
     /// Unicode has printable versions of the ASCII control codes, like '␛'.
@@ -627,6 +654,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new(' ').as_printable_char(), ' ');
     /// assert_eq!(AsciiChar::new('p').as_printable_char(), 'p');
     /// ```
+    #[must_use]
     pub fn as_printable_char(self) -> char {
         unsafe {
             match self as u8 {
@@ -659,6 +687,7 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('[').to_ascii_uppercase().as_char(), '[');
     /// ```
     #[inline]
+    #[must_use]
     pub const fn to_ascii_uppercase(&self) -> Self {
         [*self, AsciiChar::new((*self as u8 & 0b101_1111) as char)][self.is_lowercase() as usize]
     }
@@ -675,12 +704,14 @@ impl AsciiChar {
     /// assert_eq!(AsciiChar::new('\x7f').to_ascii_lowercase().as_char(), '\x7f');
     /// ```
     #[inline]
+    #[must_use]
     pub const fn to_ascii_lowercase(&self) -> Self {
         [*self, AsciiChar::new(self.to_not_upper() as char)][self.is_uppercase() as usize]
     }
 
     /// Compares two characters case-insensitively.
     #[inline]
+    #[must_use]
     pub const fn eq_ignore_ascii_case(&self, other: &Self) -> bool {
         (self.as_byte() == other.as_byte())
             | (self.is_alphabetic() & (self.to_not_upper() == other.to_not_upper()))
@@ -754,6 +785,7 @@ const ERRORMSG_CHAR: &str = "not an ASCII character";
 impl ToAsciiCharError {
     /// Returns a description for this error, like `std::error::Error::description`.
     #[inline]
+    #[must_use]
     pub const fn description(&self) -> &'static str {
         ERRORMSG_CHAR
     }
@@ -781,10 +813,14 @@ impl Error for ToAsciiCharError {
 
 /// Convert `char`, `u8` and other character types to `AsciiChar`.
 pub trait ToAsciiChar {
-    /// Convert to `AsciiChar` without checking that it is an ASCII character.
-    unsafe fn to_ascii_char_unchecked(self) -> AsciiChar;
     /// Convert to `AsciiChar`.
+    ///
+    /// # Errors
+    /// If `self` is outside the valid ascii range, this returns `Err`
     fn to_ascii_char(self) -> Result<AsciiChar, ToAsciiCharError>;
+
+    /// Convert to `AsciiChar` without checking that it is an ASCII character.
+    unsafe fn to_ascii_char_unchecked(self) -> AsciiChar;
 }
 
 impl ToAsciiChar for AsciiChar {
@@ -809,6 +845,10 @@ impl ToAsciiChar for u8 {
     }
 }
 
+// Note: Casts to `u8` here does not cause problems, as the negative
+//       range is mapped outside of ascii bounds and we don't mind losing
+//       the sign, as long as negative numbers are mapped outside ascii range.
+#[allow(clippy::cast_sign_loss)]
 impl ToAsciiChar for i8 {
     #[inline]
     fn to_ascii_char(self) -> Result<AsciiChar, ToAsciiCharError> {
@@ -842,7 +882,13 @@ impl ToAsciiChar for u32 {
     }
     #[inline]
     unsafe fn to_ascii_char_unchecked(self) -> AsciiChar {
-        (self as u8).to_ascii_char_unchecked()
+        // Note: This cast discards the top bytes, this may cause problems, see
+        //       the TODO on this method's documentation in the trait.
+        // SAFETY: Caller guarantees we're within ascii range.
+        #[allow(clippy::cast_possible_truncation)] // We want to truncate it
+        unsafe {
+            (self as u8).to_ascii_char_unchecked()
+        }
     }
 }
 
@@ -852,43 +898,48 @@ impl ToAsciiChar for u16 {
     }
     #[inline]
     unsafe fn to_ascii_char_unchecked(self) -> AsciiChar {
-        (self as u8).to_ascii_char_unchecked()
+        // Note: This cast discards the top bytes, this may cause problems, see
+        //       the TODO on this method's documentation in the trait.
+        // SAFETY: Caller guarantees we're within ascii range.
+        #[allow(clippy::cast_possible_truncation)] // We want to truncate it
+        unsafe {
+            (self as u8).to_ascii_char_unchecked()
+        }
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::{AsciiChar, ToAsciiChar, ToAsciiCharError};
-    use AsciiChar::*;
 
     #[test]
     fn to_ascii_char() {
         fn generic<C: ToAsciiChar>(ch: C) -> Result<AsciiChar, ToAsciiCharError> {
             ch.to_ascii_char()
         }
-        assert_eq!(generic(A), Ok(A));
-        assert_eq!(generic(b'A'), Ok(A));
-        assert_eq!(generic('A'), Ok(A));
-        assert!(generic(200u16).is_err());
+        assert_eq!(generic(AsciiChar::A), Ok(AsciiChar::A));
+        assert_eq!(generic(b'A'), Ok(AsciiChar::A));
+        assert_eq!(generic('A'), Ok(AsciiChar::A));
+        assert!(generic(200_u16).is_err());
         assert!(generic('λ').is_err());
     }
 
     #[test]
     fn as_byte_and_char() {
-        assert_eq!(A.as_byte(), b'A');
-        assert_eq!(A.as_char(), 'A');
+        assert_eq!(AsciiChar::A.as_byte(), b'A');
+        assert_eq!(AsciiChar::A.as_char(), 'A');
     }
 
     #[test]
     fn new_array_is_correct() {
-        for byte in 0..128u8 {
+        for byte in 0..128_u8 {
             assert_eq!(AsciiChar::new(byte as char).as_byte(), byte);
         }
     }
 
     #[test]
     fn is_all() {
-        for byte in 0..128u8 {
+        for byte in 0..128_u8 {
             let ch = byte as char;
             let ascii = AsciiChar::new(ch);
             assert_eq!(ascii.is_alphabetic(), ch.is_alphabetic());
@@ -938,49 +989,49 @@ mod tests {
     #[test]
     #[should_panic]
     fn is_digit_bad_radix() {
-        AsciiChar::_7.is_digit(37);
+        let _ = AsciiChar::_7.is_digit(37);
     }
 
     #[test]
     fn cmp_wider() {
-        assert_eq!(A, 'A');
-        assert_eq!(b'b', b);
-        assert!(a < 'z');
+        assert_eq!(AsciiChar::A, 'A');
+        assert_eq!(b'b', AsciiChar::b);
+        assert!(AsciiChar::a < 'z');
     }
 
     #[test]
     fn ascii_case() {
-        assert_eq!(At.to_ascii_lowercase(), At);
-        assert_eq!(At.to_ascii_uppercase(), At);
-        assert_eq!(A.to_ascii_lowercase(), a);
-        assert_eq!(A.to_ascii_uppercase(), A);
-        assert_eq!(a.to_ascii_lowercase(), a);
-        assert_eq!(a.to_ascii_uppercase(), A);
-
-        let mut mutable = (A, a);
+        assert_eq!(AsciiChar::At.to_ascii_lowercase(), AsciiChar::At);
+        assert_eq!(AsciiChar::At.to_ascii_uppercase(), AsciiChar::At);
+        assert_eq!(AsciiChar::A.to_ascii_lowercase(), AsciiChar::a);
+        assert_eq!(AsciiChar::A.to_ascii_uppercase(), AsciiChar::A);
+        assert_eq!(AsciiChar::a.to_ascii_lowercase(), AsciiChar::a);
+        assert_eq!(AsciiChar::a.to_ascii_uppercase(), AsciiChar::A);
+
+        let mut mutable = (AsciiChar::A, AsciiChar::a);
         mutable.0.make_ascii_lowercase();
         mutable.1.make_ascii_uppercase();
-        assert_eq!(mutable.0, a);
-        assert_eq!(mutable.1, A);
+        assert_eq!(mutable.0, AsciiChar::a);
+        assert_eq!(mutable.1, AsciiChar::A);
 
-        assert!(LineFeed.eq_ignore_ascii_case(&LineFeed));
-        assert!(!LineFeed.eq_ignore_ascii_case(&CarriageReturn));
-        assert!(z.eq_ignore_ascii_case(&Z));
-        assert!(Z.eq_ignore_ascii_case(&z));
-        assert!(A.eq_ignore_ascii_case(&a));
-        assert!(!K.eq_ignore_ascii_case(&C));
-        assert!(!Z.eq_ignore_ascii_case(&DEL));
-        assert!(!BracketOpen.eq_ignore_ascii_case(&CurlyBraceOpen));
-        assert!(!Grave.eq_ignore_ascii_case(&At));
-        assert!(!Grave.eq_ignore_ascii_case(&DEL));
+        assert!(AsciiChar::LineFeed.eq_ignore_ascii_case(&AsciiChar::LineFeed));
+        assert!(!AsciiChar::LineFeed.eq_ignore_ascii_case(&AsciiChar::CarriageReturn));
+        assert!(AsciiChar::z.eq_ignore_ascii_case(&AsciiChar::Z));
+        assert!(AsciiChar::Z.eq_ignore_ascii_case(&AsciiChar::z));
+        assert!(AsciiChar::A.eq_ignore_ascii_case(&AsciiChar::a));
+        assert!(!AsciiChar::K.eq_ignore_ascii_case(&AsciiChar::C));
+        assert!(!AsciiChar::Z.eq_ignore_ascii_case(&AsciiChar::DEL));
+        assert!(!AsciiChar::BracketOpen.eq_ignore_ascii_case(&AsciiChar::CurlyBraceOpen));
+        assert!(!AsciiChar::Grave.eq_ignore_ascii_case(&AsciiChar::At));
+        assert!(!AsciiChar::Grave.eq_ignore_ascii_case(&AsciiChar::DEL));
     }
 
     #[test]
     #[cfg(feature = "std")]
     fn fmt_ascii() {
-        assert_eq!(format!("{}", t), "t");
-        assert_eq!(format!("{:?}", t), "'t'");
-        assert_eq!(format!("{}", LineFeed), "\n");
-        assert_eq!(format!("{:?}", LineFeed), "'\\n'");
+        assert_eq!(format!("{}", AsciiChar::t), "t");
+        assert_eq!(format!("{:?}", AsciiChar::t), "'t'");
+        assert_eq!(format!("{}", AsciiChar::LineFeed), "\n");
+        assert_eq!(format!("{:?}", AsciiChar::LineFeed), "'\\n'");
     }
 }
diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index 208e9a3..36f9f31 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -11,7 +11,7 @@ use ascii_char::AsciiChar;
 #[cfg(feature = "std")]
 use ascii_string::AsciiString;
 
-/// AsciiStr represents a byte or string slice that only contains ASCII characters.
+/// [`AsciiStr`] represents a byte or string slice that only contains ASCII characters.
 ///
 /// It wraps an `[AsciiChar]` and implements many of `str`s methods and traits.
 ///
@@ -26,24 +26,28 @@ pub struct AsciiStr {
 impl AsciiStr {
     /// Converts `&self` to a `&str` slice.
     #[inline]
+    #[must_use]
     pub fn as_str(&self) -> &str {
         unsafe { &*(self as *const AsciiStr as *const str) }
     }
 
     /// Converts `&self` into a byte slice.
     #[inline]
+    #[must_use]
     pub fn as_bytes(&self) -> &[u8] {
         unsafe { &*(self as *const AsciiStr as *const [u8]) }
     }
 
     /// Returns the entire string as slice of `AsciiChar`s.
     #[inline]
+    #[must_use]
     pub const fn as_slice(&self) -> &[AsciiChar] {
         &self.slice
     }
 
     /// Returns the entire string as mutable slice of `AsciiChar`s.
     #[inline]
+    #[must_use]
     pub fn as_mut_slice(&mut self) -> &mut [AsciiChar] {
         &mut self.slice
     }
@@ -54,6 +58,7 @@ impl AsciiStr {
     /// will end up pointing to garbage. Modifying the `AsciiStr` may cause it's buffer to be
     /// reallocated, which would also make any pointers to it invalid.
     #[inline]
+    #[must_use]
     pub const fn as_ptr(&self) -> *const AsciiChar {
         self.as_slice().as_ptr()
     }
@@ -64,18 +69,23 @@ impl AsciiStr {
     /// will end up pointing to garbage. Modifying the `AsciiStr` may cause it's buffer to be
     /// reallocated, which would also make any pointers to it invalid.
     #[inline]
+    #[must_use]
     pub fn as_mut_ptr(&mut self) -> *mut AsciiChar {
         self.as_mut_slice().as_mut_ptr()
     }
 
     /// Copies the content of this `AsciiStr` into an owned `AsciiString`.
     #[cfg(feature = "std")]
+    #[must_use]
     pub fn to_ascii_string(&self) -> AsciiString {
         AsciiString::from(self.slice.to_vec())
     }
 
     /// Converts anything that can represent a byte slice into an `AsciiStr`.
     ///
+    /// # Errors
+    /// If `bytes` contains a non-ascii byte, `Err` will be returned
+    ///
     /// # Examples
     /// ```
     /// # use ascii::AsciiStr;
@@ -102,6 +112,7 @@ impl AsciiStr {
     /// assert_eq!(foo.as_str(), "foo");
     /// ```
     #[inline]
+    #[must_use]
     pub unsafe fn from_ascii_unchecked(bytes: &[u8]) -> &AsciiStr {
         bytes.as_ascii_str_unchecked()
     }
@@ -115,6 +126,7 @@ impl AsciiStr {
     /// assert_eq!(s.len(), 3);
     /// ```
     #[inline]
+    #[must_use]
     pub fn len(&self) -> usize {
         self.slice.len()
     }
@@ -130,12 +142,14 @@ impl AsciiStr {
     /// assert!(!full.is_empty());
     /// ```
     #[inline]
+    #[must_use]
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
 
     /// Returns an iterator over the characters of the `AsciiStr`.
     #[inline]
+    #[must_use]
     pub fn chars(&self) -> Chars {
         Chars(self.slice.iter())
     }
@@ -143,6 +157,7 @@ impl AsciiStr {
     /// Returns an iterator over the characters of the `AsciiStr` which allows you to modify the
     /// value of each `AsciiChar`.
     #[inline]
+    #[must_use]
     pub fn chars_mut(&mut self) -> CharsMut {
         CharsMut(self.slice.iter_mut())
     }
@@ -158,6 +173,7 @@ impl AsciiStr {
     ///     .collect::<Vec<_>>();
     /// assert_eq!(words, ["apple", "banana", "lemon"]);
     /// ```
+    #[must_use]
     pub fn split(&self, on: AsciiChar) -> impl DoubleEndedIterator<Item = &AsciiStr> {
         Split {
             on,
@@ -172,6 +188,7 @@ impl AsciiStr {
     ///
     /// The final line ending is optional.
     #[inline]
+    #[must_use]
     pub fn lines(&self) -> impl DoubleEndedIterator<Item = &AsciiStr> {
         Lines { string: self }
     }
@@ -184,6 +201,7 @@ impl AsciiStr {
     /// let example = AsciiStr::from_ascii("  \twhite \tspace  \t").unwrap();
     /// assert_eq!("white \tspace", example.trim());
     /// ```
+    #[must_use]
     pub fn trim(&self) -> &Self {
         self.trim_start().trim_end()
     }
@@ -196,8 +214,12 @@ impl AsciiStr {
     /// let example = AsciiStr::from_ascii("  \twhite \tspace  \t").unwrap();
     /// assert_eq!("white \tspace  \t", example.trim_start());
     /// ```
+    #[must_use]
     pub fn trim_start(&self) -> &Self {
-        &self[self.chars().take_while(|ch| ch.is_whitespace()).count()..]
+        &self[self
+            .chars()
+            .take_while(|ascii| ascii.is_whitespace())
+            .count()..]
     }
 
     /// Returns an ASCII string slice with trailing whitespace removed.
@@ -208,6 +230,7 @@ impl AsciiStr {
     /// let example = AsciiStr::from_ascii("  \twhite \tspace  \t").unwrap();
     /// assert_eq!("  \twhite \tspace", example.trim_end());
     /// ```
+    #[must_use]
     pub fn trim_end(&self) -> &Self {
         let trimmed = self
             .chars()
@@ -218,6 +241,7 @@ impl AsciiStr {
     }
 
     /// Compares two strings case-insensitively.
+    #[must_use]
     pub fn eq_ignore_ascii_case(&self, other: &Self) -> bool {
         self.len() == other.len()
             && self
@@ -242,6 +266,7 @@ impl AsciiStr {
 
     /// Returns a copy of this string where letters 'a' to 'z' are mapped to 'A' to 'Z'.
     #[cfg(feature = "std")]
+    #[must_use]
     pub fn to_ascii_uppercase(&self) -> AsciiString {
         let mut ascii_string = self.to_ascii_string();
         ascii_string.make_ascii_uppercase();
@@ -250,6 +275,7 @@ impl AsciiStr {
 
     /// Returns a copy of this string where letters 'A' to 'Z' are mapped to 'a' to 'z'.
     #[cfg(feature = "std")]
+    #[must_use]
     pub fn to_ascii_lowercase(&self) -> AsciiString {
         let mut ascii_string = self.to_ascii_string();
         ascii_string.make_ascii_lowercase();
@@ -258,12 +284,14 @@ impl AsciiStr {
 
     /// Returns the first character if the string is not empty.
     #[inline]
+    #[must_use]
     pub fn first(&self) -> Option<AsciiChar> {
         self.slice.first().cloned()
     }
 
     /// Returns the last character if the string is not empty.
     #[inline]
+    #[must_use]
     pub fn last(&self) -> Option<AsciiChar> {
         self.slice.last().cloned()
     }
@@ -510,6 +538,7 @@ impl<'a> IntoIterator for &'a mut AsciiStr {
 pub struct Chars<'a>(Iter<'a, AsciiChar>);
 impl<'a> Chars<'a> {
     /// Returns the ascii string slice with the remaining characters.
+    #[must_use]
     pub fn as_str(&self) -> &'a AsciiStr {
         self.0.as_slice().into()
     }
@@ -541,6 +570,7 @@ impl<'a> ExactSizeIterator for Chars<'a> {
 pub struct CharsMut<'a>(IterMut<'a, AsciiChar>);
 impl<'a> CharsMut<'a> {
     /// Returns the ascii string slice with the remaining characters.
+    #[must_use]
     pub fn into_str(self) -> &'a mut AsciiStr {
         self.0.into_slice().into()
     }
@@ -572,6 +602,7 @@ impl<'a> ExactSizeIterator for CharsMut<'a> {
 pub struct CharsRef<'a>(Iter<'a, AsciiChar>);
 impl<'a> CharsRef<'a> {
     /// Returns the ascii string slice with the remaining characters.
+    #[must_use]
     pub fn as_str(&self) -> &'a AsciiStr {
         self.0.as_slice().into()
     }
@@ -605,6 +636,7 @@ struct Split<'a> {
 impl<'a> Iterator for Split<'a> {
     type Item = &'a AsciiStr;
 
+    #[allow(clippy::option_if_let_else)] // There are side effects with `else` so we don't use iterator adaptors
     fn next(&mut self) -> Option<&'a AsciiStr> {
         if !self.ended {
             let start: &AsciiStr = self.chars.as_str();
@@ -621,6 +653,7 @@ impl<'a> Iterator for Split<'a> {
     }
 }
 impl<'a> DoubleEndedIterator for Split<'a> {
+    #[allow(clippy::option_if_let_else)] // There are side effects with `else` so we don't use iterator adaptors
     fn next_back(&mut self) -> Option<&'a AsciiStr> {
         if !self.ended {
             let start: &AsciiStr = self.chars.as_str();
@@ -702,12 +735,14 @@ impl AsAsciiStrError {
     ///
     /// It is the maximum index such that `from_ascii(input[..index])` would return `Ok(_)`.
     #[inline]
+    #[must_use]
     pub const fn valid_up_to(self) -> usize {
         self.0
     }
     #[cfg(not(feature = "std"))]
     /// Returns a description for this error, like `std::error::Error::description`.
     #[inline]
+    #[must_use]
     pub const fn description(&self) -> &'static str {
         ERRORMSG_STR
     }
@@ -725,7 +760,7 @@ impl Error for AsAsciiStrError {
     }
 }
 
-/// Convert slices of bytes or AsciiChar to `AsciiStr`.
+/// Convert slices of bytes or [`AsciiChar`] to [`AsciiStr`].
 // Could nearly replace this trait with SliceIndex, but its methods isn't even
 // on a path for stabilization.
 pub trait AsAsciiStr {
@@ -734,6 +769,7 @@ pub trait AsAsciiStr {
     type Inner;
     /// Convert a subslice to an ASCII slice.
     ///
+    /// # Errors
     /// Returns `Err` if the range is out of bounds or if not all bytes in the
     /// slice are ASCII. The value in the error will be the index of the first
     /// non-ASCII byte or the end of the slice.
@@ -752,6 +788,9 @@ pub trait AsAsciiStr {
         R: SliceIndex<[Self::Inner], Output = [Self::Inner]>;
     /// Convert to an ASCII slice.
     ///
+    /// # Errors
+    /// Returns `Err` if not all bytes are valid ascii values.
+    ///
     /// # Example
     /// ```
     /// use ascii::{AsAsciiStr, AsciiChar};
@@ -778,7 +817,7 @@ pub trait AsAsciiStr {
     fn get_ascii(&self, index: usize) -> Option<AsciiChar> {
         self.slice_ascii(index..=index)
             .ok()
-            .and_then(|str| str.first())
+            .and_then(AsciiStr::first)
     }
     /// Convert to an ASCII slice without checking for non-ASCII characters.
     ///
@@ -787,13 +826,20 @@ pub trait AsAsciiStr {
     unsafe fn as_ascii_str_unchecked(&self) -> &AsciiStr;
 }
 
-/// Convert mutable slices of bytes or AsciiChar to `AsciiStr`.
+/// Convert mutable slices of bytes or [`AsciiChar`] to [`AsciiStr`].
 pub trait AsMutAsciiStr: AsAsciiStr {
     /// Convert a subslice to an ASCII slice.
+    ///
+    /// # Errors
+    /// This function returns `Err` if range is out of bounds, or if
+    /// `self` contains non-ascii values
     fn slice_ascii_mut<R>(&mut self, range: R) -> Result<&mut AsciiStr, AsAsciiStrError>
     where
         R: SliceIndex<[Self::Inner], Output = [Self::Inner]>;
     /// Convert to a mutable ASCII slice.
+    ///
+    /// # Errors
+    /// This function returns `Err` if `self` contains non-ascii values
     fn as_mut_ascii_str(&mut self) -> Result<&mut AsciiStr, AsAsciiStrError> {
         self.slice_ascii_mut(..)
     }
@@ -928,6 +974,8 @@ impl AsMutAsciiStr for [AsciiChar] {
 
 impl AsAsciiStr for [u8] {
     type Inner = u8;
+
+    #[allow(clippy::option_if_let_else)] // `if` needs to use past results, so it's more expressive like this
     fn slice_ascii<R>(&self, range: R) -> Result<&AsciiStr, AsAsciiStrError>
     where
         R: SliceIndex<[u8], Output = [u8]>,
@@ -958,6 +1006,7 @@ impl AsAsciiStr for [u8] {
     }
 }
 impl AsMutAsciiStr for [u8] {
+    #[allow(clippy::option_if_let_else)] // `if` needs to use past results, so it's more expressive like this
     fn slice_ascii_mut<R>(&mut self, range: R) -> Result<&mut AsciiStr, AsAsciiStrError>
     where
         R: SliceIndex<[u8], Output = [u8]>,
@@ -1079,7 +1128,8 @@ mod tests {
         assert_eq!(generic(ascii_str), Ok(ascii_str));
         assert_eq!(generic(&"A"), Ok(ascii_str));
         assert_eq!(generic(&ascii_str), Ok(ascii_str));
-        assert_eq!(generic(&mut "A"), Ok(ascii_str));
+        // Note: Not sure what this is supposed to be testing, as `generic` can only accept shared references
+        //assert_eq!(generic(&mut "A"), Ok(ascii_str));
     }
 
     #[cfg(feature = "std")]
@@ -1147,11 +1197,11 @@ mod tests {
         assert_eq!(cstr.get_ascii(5), None);
         assert_eq!(cstr.get_ascii(6), Some(AsciiChar::g));
         assert_eq!(cstr.get_ascii(7), None);
-        let aslice = &[AsciiChar::X, AsciiChar::Y, AsciiChar::Z, AsciiChar::Null][..];
-        let astr: &AsciiStr = aslice.as_ref();
-        let cstr = CStr::from_bytes_with_nul(astr.as_bytes()).unwrap();
-        assert_eq!(cstr.slice_ascii(..2), Ok(&astr[..2]));
-        assert_eq!(cstr.as_ascii_str(), Ok(&astr[..3]));
+        let ascii_slice = &[AsciiChar::X, AsciiChar::Y, AsciiChar::Z, AsciiChar::Null][..];
+        let ascii_str: &AsciiStr = ascii_slice.as_ref();
+        let cstr = CStr::from_bytes_with_nul(ascii_str.as_bytes()).unwrap();
+        assert_eq!(cstr.slice_ascii(..2), Ok(&ascii_str[..2]));
+        assert_eq!(cstr.as_ascii_str(), Ok(&ascii_str[..3]));
     }
 
     #[test]
@@ -1333,7 +1383,7 @@ mod tests {
                 .as_ascii_str()
                 .unwrap()
                 .split(AsciiChar::from_ascii(needle).unwrap())
-                .map(|a| a.as_str());
+                .map(AsciiStr::as_str);
             loop {
                 assert_eq!(asciis.size_hint(), strs.size_hint());
                 let (a, s) = (asciis.next(), strs.next());
diff --git a/src/ascii_string.rs b/src/ascii_string.rs
index 5f0b644..a62abb6 100644
--- a/src/ascii_string.rs
+++ b/src/ascii_string.rs
@@ -40,6 +40,7 @@ impl AsciiString {
     /// let mut s = AsciiString::with_capacity(10);
     /// ```
     #[inline]
+    #[must_use]
     pub fn with_capacity(capacity: usize) -> Self {
         AsciiString {
             vec: Vec::with_capacity(capacity),
@@ -81,6 +82,7 @@ impl AsciiString {
     /// }
     /// ```
     #[inline]
+    #[must_use]
     pub unsafe fn from_raw_parts(buf: *mut AsciiChar, length: usize, capacity: usize) -> Self {
         AsciiString {
             vec: Vec::from_raw_parts(buf, length, capacity),
@@ -95,6 +97,7 @@ impl AsciiString {
     /// future of the `AsciiString`, as the rest of this library assumes that `AsciiString`s are
     /// ASCII encoded.
     #[inline]
+    #[must_use]
     pub unsafe fn from_ascii_unchecked<B>(bytes: B) -> Self
     where
         B: Into<Vec<u8>>,
@@ -111,7 +114,7 @@ impl AsciiString {
 
     /// Converts anything that can represent a byte buffer into an `AsciiString`.
     ///
-    /// # Failure
+    /// # Errors
     /// Returns the byte buffer if not all of the bytes are ASCII characters.
     ///
     /// # Examples
@@ -161,6 +164,7 @@ impl AsciiString {
     /// assert!(s.capacity() >= 10);
     /// ```
     #[inline]
+    #[must_use]
     pub fn capacity(&self) -> usize {
         self.vec.capacity()
     }
@@ -201,6 +205,7 @@ impl AsciiString {
     /// assert!(s.capacity() >= 10);
     /// ```
     #[inline]
+
     pub fn reserve_exact(&mut self, additional: usize) {
         self.vec.reserve_exact(additional)
     }
@@ -218,6 +223,7 @@ impl AsciiString {
     /// assert_eq!(s.capacity(), 3);
     /// ```
     #[inline]
+
     pub fn shrink_to_fit(&mut self) {
         self.vec.shrink_to_fit()
     }
@@ -234,6 +240,7 @@ impl AsciiString {
     /// assert_eq!(s, "abc123");
     /// ```
     #[inline]
+
     pub fn push(&mut self, ch: AsciiChar) {
         self.vec.push(ch)
     }
@@ -251,6 +258,7 @@ impl AsciiString {
     /// assert_eq!(s, "he");
     /// ```
     #[inline]
+
     pub fn truncate(&mut self, new_len: usize) {
         self.vec.truncate(new_len)
     }
@@ -268,6 +276,7 @@ impl AsciiString {
     /// assert_eq!(s.pop(), None);
     /// ```
     #[inline]
+    #[must_use]
     pub fn pop(&mut self) -> Option<AsciiChar> {
         self.vec.pop()
     }
@@ -289,6 +298,7 @@ impl AsciiString {
     /// assert_eq!(s.remove(0).as_char(), 'o');
     /// ```
     #[inline]
+    #[must_use]
     pub fn remove(&mut self, idx: usize) -> AsciiChar {
         self.vec.remove(idx)
     }
@@ -309,6 +319,7 @@ impl AsciiString {
     /// assert_eq!(s, "fobo");
     /// ```
     #[inline]
+
     pub fn insert(&mut self, idx: usize, ch: AsciiChar) {
         self.vec.insert(idx, ch)
     }
@@ -322,6 +333,7 @@ impl AsciiString {
     /// assert_eq!(s.len(), 3);
     /// ```
     #[inline]
+    #[must_use]
     pub fn len(&self) -> usize {
         self.vec.len()
     }
@@ -337,6 +349,7 @@ impl AsciiString {
     /// assert!(!s.is_empty());
     /// ```
     #[inline]
+    #[must_use]
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
@@ -351,6 +364,7 @@ impl AsciiString {
     /// assert!(s.is_empty());
     /// ```
     #[inline]
+
     pub fn clear(&mut self) {
         self.vec.clear()
     }
@@ -649,11 +663,13 @@ pub struct FromAsciiError<O> {
 impl<O> FromAsciiError<O> {
     /// Get the position of the first non-ASCII byte or character.
     #[inline]
+    #[must_use]
     pub fn ascii_error(&self) -> AsAsciiStrError {
         self.error
     }
     /// Get back the original, unmodified type.
     #[inline]
+    #[must_use]
     pub fn into_source(self) -> O {
         self.owner
     }
@@ -672,6 +688,7 @@ impl<O> fmt::Display for FromAsciiError<O> {
 }
 impl<O: Any> Error for FromAsciiError<O> {
     #[inline]
+    #[allow(deprecated)] // TODO: Remove deprecation once the earliest version we support deprecates this method.
     fn description(&self) -> &str {
         self.error.description()
     }
@@ -686,6 +703,9 @@ pub trait IntoAsciiString: Sized {
     /// Convert to `AsciiString` without checking for non-ASCII characters.
     unsafe fn into_ascii_string_unchecked(self) -> AsciiString;
     /// Convert to `AsciiString`.
+    ///
+    /// # Errors
+    /// If `self` contains non-ascii characters, this will return `Err`
     fn into_ascii_string(self) -> Result<AsciiString, FromAsciiError<Self>>;
 }
 
@@ -778,8 +798,8 @@ impl IntoAsciiString for CString {
                 }
             })
             .map(|mut s| {
-                let _nul = s.pop();
-                debug_assert_eq!(_nul, Some(AsciiChar::Null));
+                let nul = s.pop();
+                debug_assert_eq!(nul, Some(AsciiChar::Null));
                 s
             })
     }
@@ -799,8 +819,8 @@ impl<'a> IntoAsciiString for &'a CStr {
                 error,
             })
             .map(|mut s| {
-                let _nul = s.pop();
-                debug_assert_eq!(_nul, Some(AsciiChar::Null));
+                let nul = s.pop();
+                debug_assert_eq!(nul, Some(AsciiChar::Null));
                 s
             })
     }
@@ -879,7 +899,7 @@ mod tests {
         assert_eq!(ascii_str_unchecked.len(), 3);
         assert_eq!(ascii_str_unchecked.as_slice(), expected_chars);
 
-        let sparkle_heart_bytes = vec![240u8, 159, 146, 150];
+        let sparkle_heart_bytes = vec![240_u8, 159, 146, 150];
         let cstring = CString::new(sparkle_heart_bytes).unwrap();
         let cstr = &*cstring;
         let ascii_err = cstr.into_ascii_string().unwrap_err();
diff --git a/src/lib.rs b/src/lib.rs
index 4c77509..81eefdb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,7 +29,21 @@
 //! API changed significantly since then.
 
 #![cfg_attr(not(feature = "std"), no_std)]
-#![allow(clippy::trivially_copy_pass_by_ref)] // for compatibility with methods on char and u8
+// Clippy lints
+#![warn(clippy::pedantic)]
+// Naming conventions sometimes go against this lint
+#![allow(clippy::module_name_repetitions)]
+// We need to get literal non-asciis for tests
+#![allow(clippy::non_ascii_literal)]
+// Sometimes it looks better to invert the order, such as when the `else` block is small
+#![allow(clippy::if_not_else)]
+// Shadowing is common and doesn't affect understanding
+// TODO: Consider removing `shadow_unrelated`, as it can show some actual logic errors
+#![allow(clippy::shadow_unrelated, clippy::shadow_reuse, clippy::shadow_same)]
+// for compatibility with methods on char and u8
+#![allow(clippy::trivially_copy_pass_by_ref)]
+// In preparation for feature `unsafe_block_in_unsafe_fn` (https://github.com/rust-lang/rust/issues/71668)
+#![allow(unused_unsafe)]
 
 #[cfg(feature = "std")]
 extern crate core;
diff --git a/tests.rs b/tests.rs
index b9f3c9c..3454830 100644
--- a/tests.rs
+++ b/tests.rs
@@ -130,7 +130,7 @@ fn extend_from_iterator() {
         .unwrap()
         .split(AsciiChar::Space)
         .map(|case| {
-            if case.chars().all(|ch| ch.is_uppercase()) {
+            if case.chars().all(AsciiChar::is_uppercase) {
                 Cow::from(case)
             } else {
                 Cow::from(case.to_ascii_uppercase())

From 5fffc7e51a753147234819b3c9f8b839e06ca2cf Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sat, 19 Sep 2020 21:21:37 +0100
Subject: [PATCH 2/9] Added some clippy restriction lints. Changed most
 indexing to `get_unchecked` because of lint `clippy::indexing_slicing`. This
 should also improve performance, as the compiler doesn't need to emmit panic
 code. `clippy::option_if_let_else` is now allowed throughout the whole crate,
 as it doesn't add much.

---
 src/ascii_char.rs   |   7 ++-
 src/ascii_str.rs    | 103 ++++++++++++++++++++++++++++++--------------
 src/ascii_string.rs |   2 +
 src/lib.rs          |  11 ++++-
 4 files changed, 89 insertions(+), 34 deletions(-)

diff --git a/src/ascii_char.rs b/src/ascii_char.rs
index 2444b81..49c1b21 100644
--- a/src/ascii_char.rs
+++ b/src/ascii_char.rs
@@ -353,7 +353,10 @@ impl AsciiChar {
             h, i, j, k, l, m, n, o,
             p, q, r, s, t, u, v, w,
             x, y, z, CurlyBraceOpen, VerticalBar, CurlyBraceClose, Tilde, DEL,
-        ];
+		];
+
+        // We want to slice here and detect `const_err` from rustc if the slice is invalid
+        #[allow(clippy::indexing_slicing)]
         ALL[ch as usize]
     }
 
@@ -688,6 +691,7 @@ impl AsciiChar {
     /// ```
     #[inline]
     #[must_use]
+    #[allow(clippy::indexing_slicing)] // We're sure it'll either access one or the other, as `bool` is either `0` or `1`
     pub const fn to_ascii_uppercase(&self) -> Self {
         [*self, AsciiChar::new((*self as u8 & 0b101_1111) as char)][self.is_lowercase() as usize]
     }
@@ -705,6 +709,7 @@ impl AsciiChar {
     /// ```
     #[inline]
     #[must_use]
+    #[allow(clippy::indexing_slicing)] // We're sure it'll either access one or the other, as `bool` is either `0` or `1`
     pub const fn to_ascii_lowercase(&self) -> Self {
         [*self, AsciiChar::new(self.to_not_upper() as char)][self.is_uppercase() as usize]
     }
diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index 36f9f31..e047101 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -216,10 +216,13 @@ impl AsciiStr {
     /// ```
     #[must_use]
     pub fn trim_start(&self) -> &Self {
-        &self[self
+        let whitespace_len = self
             .chars()
-            .take_while(|ascii| ascii.is_whitespace())
-            .count()..]
+            .position(|ascii| !ascii.is_whitespace())
+            .unwrap_or_else(|| self.len());
+
+        // SAFETY: `whitespace_len` is `0..=len`, which is at most `len`, which is a valid empty slice.
+        unsafe { self.as_slice().get_unchecked(whitespace_len..).into() }
     }
 
     /// Returns an ASCII string slice with trailing whitespace removed.
@@ -232,12 +235,19 @@ impl AsciiStr {
     /// ```
     #[must_use]
     pub fn trim_end(&self) -> &Self {
-        let trimmed = self
+        // Number of whitespace characters counting from the end
+        let whitespace_len = self
             .chars()
             .rev()
-            .take_while(|ch| ch.is_whitespace())
-            .count();
-        &self[..self.len() - trimmed]
+            .position(|ascii| !ascii.is_whitespace())
+            .unwrap_or_else(|| self.len());
+
+        // SAFETY: `whitespace_len` is `0..=len`, which is at most `len`, which is a valid empty slice, and at least `0`, which is the whole slice.
+        unsafe {
+            self.as_slice()
+                .get_unchecked(..self.len() - whitespace_len)
+                .into()
+        }
     }
 
     /// Compares two strings case-insensitively.
@@ -470,6 +480,7 @@ impl fmt::Debug for AsciiStr {
 
 macro_rules! impl_index {
     ($idx:ty) => {
+        #[allow(clippy::indexing_slicing)] // In `Index`, if it's out of bounds, panic is the default
         impl Index<$idx> for AsciiStr {
             type Output = AsciiStr;
 
@@ -479,6 +490,7 @@ macro_rules! impl_index {
             }
         }
 
+        #[allow(clippy::indexing_slicing)] // In `IndexMut`, if it's out of bounds, panic is the default
         impl IndexMut<$idx> for AsciiStr {
             #[inline]
             fn index_mut(&mut self, index: $idx) -> &mut AsciiStr {
@@ -495,6 +507,7 @@ impl_index! { RangeFull }
 impl_index! { RangeInclusive<usize> }
 impl_index! { RangeToInclusive<usize> }
 
+#[allow(clippy::indexing_slicing)] // In `Index`, if it's out of bounds, panic is the default
 impl Index<usize> for AsciiStr {
     type Output = AsciiChar;
 
@@ -504,6 +517,7 @@ impl Index<usize> for AsciiStr {
     }
 }
 
+#[allow(clippy::indexing_slicing)] // In `IndexMut`, if it's out of bounds, panic is the default
 impl IndexMut<usize> for AsciiStr {
     #[inline]
     fn index_mut(&mut self, index: usize) -> &mut AsciiChar {
@@ -636,13 +650,14 @@ struct Split<'a> {
 impl<'a> Iterator for Split<'a> {
     type Item = &'a AsciiStr;
 
-    #[allow(clippy::option_if_let_else)] // There are side effects with `else` so we don't use iterator adaptors
     fn next(&mut self) -> Option<&'a AsciiStr> {
         if !self.ended {
             let start: &AsciiStr = self.chars.as_str();
             let split_on = self.on;
-            if let Some(at) = self.chars.position(|ch| ch == split_on) {
-                Some(&start[..at])
+
+            if let Some(at) = self.chars.position(|ascii| ascii == split_on) {
+                // SAFETY: `at` is guaranteed to be in bounds, as `position` returns `Ok(0..len)`.
+                Some(unsafe { start.as_slice().get_unchecked(..at).into() })
             } else {
                 self.ended = true;
                 Some(start)
@@ -653,13 +668,14 @@ impl<'a> Iterator for Split<'a> {
     }
 }
 impl<'a> DoubleEndedIterator for Split<'a> {
-    #[allow(clippy::option_if_let_else)] // There are side effects with `else` so we don't use iterator adaptors
     fn next_back(&mut self) -> Option<&'a AsciiStr> {
         if !self.ended {
             let start: &AsciiStr = self.chars.as_str();
             let split_on = self.on;
-            if let Some(at) = self.chars.rposition(|ch| ch == split_on) {
-                Some(&start[at + 1..])
+
+            if let Some(at) = self.chars.rposition(|ascii| ascii == split_on) {
+                // SAFETY: `at` is guaranteed to be in bounds, as `rposition` returns `Ok(0..len)`, and slices `1..`, `2..`, etc... until `len..` inclusive, are valid.
+                Some(unsafe { start.as_slice().get_unchecked(at + 1..).into() })
             } else {
                 self.ended = true;
                 Some(start)
@@ -684,40 +700,65 @@ impl<'a> Iterator for Lines<'a> {
             .chars()
             .position(|chr| chr == AsciiChar::LineFeed)
         {
-            let line = if idx > 0 && self.string[idx - 1] == AsciiChar::CarriageReturn {
-                &self.string[..idx - 1]
+            // SAFETY: `idx` is guaranteed to be `1..len`, as we get it from `position` as `0..len` and make sure it's not `0`.
+            let line = if idx > 0
+                && *unsafe { self.string.as_slice().get_unchecked(idx - 1) }
+                    == AsciiChar::CarriageReturn
+            {
+                // SAFETY: As per above, `idx` is guaranteed to be `1..len`
+                unsafe { self.string.as_slice().get_unchecked(..idx - 1).into() }
             } else {
-                &self.string[..idx]
+                // SAFETY: As per above, `idx` is guaranteed to be `0..len`
+                unsafe { self.string.as_slice().get_unchecked(..idx).into() }
             };
-            self.string = &self.string[idx + 1..];
+            // SAFETY: As per above, `idx` is guaranteed to be `0..len`, so at the extreme, slicing `len..` is a valid empty slice.
+            self.string = unsafe { self.string.as_slice().get_unchecked(idx + 1..).into() };
             Some(line)
         } else if self.string.is_empty() {
             None
         } else {
             let line = self.string;
-            self.string = &self.string[..0];
+            // SAFETY: Slicing `..0` is always valid and yields an empty slice
+            self.string = unsafe { self.string.as_slice().get_unchecked(..0).into() };
             Some(line)
         }
     }
 }
+
 impl<'a> DoubleEndedIterator for Lines<'a> {
     fn next_back(&mut self) -> Option<&'a AsciiStr> {
         if self.string.is_empty() {
             return None;
         }
-        let mut i = self.string.len();
-        if self.string[i - 1] == AsciiChar::LineFeed {
-            i -= 1;
-            if i > 0 && self.string[i - 1] == AsciiChar::CarriageReturn {
-                i -= 1;
-            }
-        }
-        self.string = &self.string[..i];
-        while i > 0 && self.string[i - 1] != AsciiChar::LineFeed {
-            i -= 1;
+
+        // If we end with `LF` / `CR/LF`, remove them
+        if let [slice @ .., AsciiChar::CarriageReturn, AsciiChar::LineFeed]
+        | [slice @ .., AsciiChar::LineFeed] = self.string.as_slice()
+        {
+            self.string = slice.into();
         }
-        let line = &self.string[i..];
-        self.string = &self.string[..i];
+
+        // SAFETY: This will never be `0`, as we remove any `LF` from the end, it is `1..len`
+        let lf_rev_pos = self
+            .string
+            .chars()
+            .rev()
+            .position(|ascii| ascii == AsciiChar::LineFeed)
+            .unwrap_or_else(|| self.string.len());
+
+        // SAFETY: As per above, `self.len() - lf_rev_pos` will be in range `0..len - 1`, so both indexes are correct.
+        let line = unsafe {
+            self.string
+                .as_slice()
+                .get_unchecked(self.string.len() - lf_rev_pos..)
+                .into()
+        };
+        self.string = unsafe {
+            self.string
+                .as_slice()
+                .get_unchecked(..self.string.len() - lf_rev_pos)
+                .into()
+        };
         Some(line)
     }
 }
@@ -975,7 +1016,6 @@ impl AsMutAsciiStr for [AsciiChar] {
 impl AsAsciiStr for [u8] {
     type Inner = u8;
 
-    #[allow(clippy::option_if_let_else)] // `if` needs to use past results, so it's more expressive like this
     fn slice_ascii<R>(&self, range: R) -> Result<&AsciiStr, AsAsciiStrError>
     where
         R: SliceIndex<[u8], Output = [u8]>,
@@ -1006,7 +1046,6 @@ impl AsAsciiStr for [u8] {
     }
 }
 impl AsMutAsciiStr for [u8] {
-    #[allow(clippy::option_if_let_else)] // `if` needs to use past results, so it's more expressive like this
     fn slice_ascii_mut<R>(&mut self, range: R) -> Result<&mut AsciiStr, AsAsciiStrError>
     where
         R: SliceIndex<[u8], Output = [u8]>,
diff --git a/src/ascii_string.rs b/src/ascii_string.rs
index a62abb6..fb08a21 100644
--- a/src/ascii_string.rs
+++ b/src/ascii_string.rs
@@ -619,6 +619,7 @@ impl<'a> AddAssign<&'a AsciiStr> for AsciiString {
     }
 }
 
+#[allow(clippy::indexing_slicing)] // In `Index`, if it's out of bounds, panic is the default
 impl<T> Index<T> for AsciiString
 where
     AsciiStr: Index<T>,
@@ -631,6 +632,7 @@ where
     }
 }
 
+#[allow(clippy::indexing_slicing)] // In `IndexMut`, if it's out of bounds, panic is the default
 impl<T> IndexMut<T> for AsciiString
 where
     AsciiStr: IndexMut<T>,
diff --git a/src/lib.rs b/src/lib.rs
index 81eefdb..6161c2a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -30,7 +30,12 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 // Clippy lints
-#![warn(clippy::pedantic)]
+#![warn(
+    clippy::pedantic,
+    clippy::decimal_literal_representation,
+    clippy::get_unwrap,
+    clippy::indexing_slicing
+)]
 // Naming conventions sometimes go against this lint
 #![allow(clippy::module_name_repetitions)]
 // We need to get literal non-asciis for tests
@@ -40,6 +45,10 @@
 // Shadowing is common and doesn't affect understanding
 // TODO: Consider removing `shadow_unrelated`, as it can show some actual logic errors
 #![allow(clippy::shadow_unrelated, clippy::shadow_reuse, clippy::shadow_same)]
+// A `if let` / `else` sometimes looks better than using iterator adaptors
+#![allow(clippy::option_if_let_else)]
+// In tests, we're fine with indexing, since a panic is a failure.
+#![cfg_attr(test, allow(clippy::indexing_slicing))]
 // for compatibility with methods on char and u8
 #![allow(clippy::trivially_copy_pass_by_ref)]
 // In preparation for feature `unsafe_block_in_unsafe_fn` (https://github.com/rust-lang/rust/issues/71668)

From 26b0c90db7ab9ba7d12a84f836fcd39a69d79650 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sat, 19 Sep 2020 21:26:24 +0100
Subject: [PATCH 3/9] Changed closure arguments from `|ascii| ...` to `|ch|
 ...` to match with master

---
 src/ascii_str.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index e047101..e2d1534 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -218,7 +218,7 @@ impl AsciiStr {
     pub fn trim_start(&self) -> &Self {
         let whitespace_len = self
             .chars()
-            .position(|ascii| !ascii.is_whitespace())
+            .position(|ch| !ch.is_whitespace())
             .unwrap_or_else(|| self.len());
 
         // SAFETY: `whitespace_len` is `0..=len`, which is at most `len`, which is a valid empty slice.
@@ -239,7 +239,7 @@ impl AsciiStr {
         let whitespace_len = self
             .chars()
             .rev()
-            .position(|ascii| !ascii.is_whitespace())
+            .position(|ch| !ch.is_whitespace())
             .unwrap_or_else(|| self.len());
 
         // SAFETY: `whitespace_len` is `0..=len`, which is at most `len`, which is a valid empty slice, and at least `0`, which is the whole slice.
@@ -655,7 +655,7 @@ impl<'a> Iterator for Split<'a> {
             let start: &AsciiStr = self.chars.as_str();
             let split_on = self.on;
 
-            if let Some(at) = self.chars.position(|ascii| ascii == split_on) {
+            if let Some(at) = self.chars.position(|ch| ch == split_on) {
                 // SAFETY: `at` is guaranteed to be in bounds, as `position` returns `Ok(0..len)`.
                 Some(unsafe { start.as_slice().get_unchecked(..at).into() })
             } else {
@@ -673,7 +673,7 @@ impl<'a> DoubleEndedIterator for Split<'a> {
             let start: &AsciiStr = self.chars.as_str();
             let split_on = self.on;
 
-            if let Some(at) = self.chars.rposition(|ascii| ascii == split_on) {
+            if let Some(at) = self.chars.rposition(|ch| ch == split_on) {
                 // SAFETY: `at` is guaranteed to be in bounds, as `rposition` returns `Ok(0..len)`, and slices `1..`, `2..`, etc... until `len..` inclusive, are valid.
                 Some(unsafe { start.as_slice().get_unchecked(at + 1..).into() })
             } else {
@@ -743,7 +743,7 @@ impl<'a> DoubleEndedIterator for Lines<'a> {
             .string
             .chars()
             .rev()
-            .position(|ascii| ascii == AsciiChar::LineFeed)
+            .position(|ch| ch == AsciiChar::LineFeed)
             .unwrap_or_else(|| self.string.len());
 
         // SAFETY: As per above, `self.len() - lf_rev_pos` will be in range `0..len - 1`, so both indexes are correct.

From 8d239bec453532f4ae86a957dae56036e8dc5be6 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sun, 11 Oct 2020 20:13:38 +0100
Subject: [PATCH 4/9] Fixed `ascii_str::tests::generic_as_ascii_str`'s mutable
 reference tests and added tests within it for most expected types.

---
 src/ascii_str.rs | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index e2d1534..c770e3a 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -1155,20 +1155,42 @@ mod tests {
     use super::{AsAsciiStr, AsAsciiStrError, AsMutAsciiStr, AsciiStr};
     use AsciiChar;
 
+    /// Ensures that common types, `str`, `[u8]`, `AsciiStr` and their
+    /// references, shared and mutable implement `AsAsciiStr`.
     #[test]
     fn generic_as_ascii_str() {
+        // Generic function to ensure `C` implements `AsAsciiStr`
         fn generic<C: AsAsciiStr + ?Sized>(c: &C) -> Result<&AsciiStr, AsAsciiStrError> {
             c.as_ascii_str()
         }
+
         let arr = [AsciiChar::A];
-        let ascii_str: &AsciiStr = arr.as_ref().into();
-        assert_eq!(generic("A"), Ok(ascii_str));
-        assert_eq!(generic(&b"A"[..]), Ok(ascii_str));
-        assert_eq!(generic(ascii_str), Ok(ascii_str));
-        assert_eq!(generic(&"A"), Ok(ascii_str));
-        assert_eq!(generic(&ascii_str), Ok(ascii_str));
-        // Note: Not sure what this is supposed to be testing, as `generic` can only accept shared references
-        //assert_eq!(generic(&mut "A"), Ok(ascii_str));
+        let ascii_str = arr.as_ref().into();
+        let mut mut_arr = arr; // Note: We need a second copy to prevent overlapping mutable borrows.
+        let mut_ascii_str = mut_arr.as_mut().into();
+        let mut_arr_mut_ref: &mut [AsciiChar] = &mut [AsciiChar::A];
+        let mut string = "A".to_string();
+        let mut string2 = "A".to_string();
+        let string_mut = string.as_mut();
+        let string_mut_bytes = unsafe { string2.as_bytes_mut() }; // SAFETY: We don't modify it
+
+        // Note: This is a trick because `rustfmt` doesn't support
+        //       attributes on blocks yet.
+        #[rustfmt::skip]
+        let _ = [
+            assert_eq!(generic::<str             >("A"              ), Ok(ascii_str)),
+            assert_eq!(generic::<[u8]            >(&b"A"[..]        ), Ok(ascii_str)),
+            assert_eq!(generic::<AsciiStr        >(ascii_str        ), Ok(ascii_str)),
+            assert_eq!(generic::<[AsciiChar]     >(&arr             ), Ok(ascii_str)),
+            assert_eq!(generic::<&str            >(&"A"             ), Ok(ascii_str)),
+            assert_eq!(generic::<&[u8]           >(&&b"A"[..]       ), Ok(ascii_str)),
+            assert_eq!(generic::<&AsciiStr       >(&ascii_str       ), Ok(ascii_str)),
+            assert_eq!(generic::<&[AsciiChar]    >(&&arr[..]        ), Ok(ascii_str)),
+            assert_eq!(generic::<&mut str        >(&string_mut      ), Ok(ascii_str)),
+            assert_eq!(generic::<&mut [u8]       >(&string_mut_bytes), Ok(ascii_str)),
+            assert_eq!(generic::<&mut AsciiStr   >(&mut_ascii_str   ), Ok(ascii_str)),
+            assert_eq!(generic::<&mut [AsciiChar]>(&mut_arr_mut_ref ), Ok(ascii_str)),
+        ];
     }
 
     #[cfg(feature = "std")]

From 627891cdd5df38f924f8b5534c90132defc648fb Mon Sep 17 00:00:00 2001
From: Zenithsiz <34359769+Zenithsiz@users.noreply.github.com>
Date: Sun, 11 Oct 2020 20:48:00 +0100
Subject: [PATCH 5/9] Update src/ascii_str.rs

Co-authored-by: Thomas Bahn <thomas@thomas-bahn.net>
---
 src/ascii_str.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index c770e3a..504c8a4 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -719,7 +719,7 @@ impl<'a> Iterator for Lines<'a> {
         } else {
             let line = self.string;
             // SAFETY: Slicing `..0` is always valid and yields an empty slice
-            self.string = unsafe { self.string.as_slice().get_unchecked(..0).into() };
+            self.string = unsafe { AsciiStr::from_ascii_unchecked(b"") };
             Some(line)
         }
     }

From c7e2c25a121ee2b32bd891048aaef28d19aaca73 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sun, 11 Oct 2020 21:12:33 +0100
Subject: [PATCH 6/9] Added missing `#[must_use]` to `AsciiString::new` now
 that it is a `const fn`.

---
 src/ascii_string.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/ascii_string.rs b/src/ascii_string.rs
index fb08a21..b5a66db 100644
--- a/src/ascii_string.rs
+++ b/src/ascii_string.rs
@@ -26,6 +26,7 @@ impl AsciiString {
     /// let mut s = AsciiString::new();
     /// ```
     #[inline]
+    #[must_use]
     pub const fn new() -> Self {
         AsciiString { vec: Vec::new() }
     }

From 418de0020300ea1cf84227369e3a841e77df5462 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sun, 11 Oct 2020 22:40:26 +0100
Subject: [PATCH 7/9] Fixed issue regarding usage of subslice patterns. Fixed
 usage of inexistant `AsMut<str>` impl for `String` (Only added in `1.43`).
 Extended test `ascii_str::tests::lines_iter_rev`.

---
 src/ascii_str.rs | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index 504c8a4..268e33a 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -718,7 +718,7 @@ impl<'a> Iterator for Lines<'a> {
             None
         } else {
             let line = self.string;
-            // SAFETY: Slicing `..0` is always valid and yields an empty slice
+            // SAFETY: An empty string is a valid string.
             self.string = unsafe { AsciiStr::from_ascii_unchecked(b"") };
             Some(line)
         }
@@ -732,13 +732,27 @@ impl<'a> DoubleEndedIterator for Lines<'a> {
         }
 
         // If we end with `LF` / `CR/LF`, remove them
-        if let [slice @ .., AsciiChar::CarriageReturn, AsciiChar::LineFeed]
-        | [slice @ .., AsciiChar::LineFeed] = self.string.as_slice()
-        {
-            self.string = slice.into();
+        if let Some(AsciiChar::LineFeed) = self.string.last() {
+            // SAFETY: `last()` returned `Some`, so our len is at least 1.
+            self.string = unsafe {
+                self.string
+                    .as_slice()
+                    .get_unchecked(..self.string.len() - 1)
+                    .into()
+            };
+
+            if let Some(AsciiChar::CarriageReturn) = self.string.last() {
+                // SAFETY: `last()` returned `Some`, so our len is at least 1.
+                self.string = unsafe {
+                    self.string
+                        .as_slice()
+                        .get_unchecked(..self.string.len() - 1)
+                        .into()
+                };
+            }
         }
 
-        // SAFETY: This will never be `0`, as we remove any `LF` from the end, it is `1..len`
+        // Get the position of the first `LF` from the end.
         let lf_rev_pos = self
             .string
             .chars()
@@ -746,7 +760,9 @@ impl<'a> DoubleEndedIterator for Lines<'a> {
             .position(|ch| ch == AsciiChar::LineFeed)
             .unwrap_or_else(|| self.string.len());
 
-        // SAFETY: As per above, `self.len() - lf_rev_pos` will be in range `0..len - 1`, so both indexes are correct.
+        // SAFETY: `lf_rev_pos` will be in range `0..=len`, so `len - lf_rev_pos`
+        //         will be within `0..=len`, making it correct as a start and end
+        //         point for the strings.
         let line = unsafe {
             self.string
                 .as_slice()
@@ -1171,7 +1187,7 @@ mod tests {
         let mut_arr_mut_ref: &mut [AsciiChar] = &mut [AsciiChar::A];
         let mut string = "A".to_string();
         let mut string2 = "A".to_string();
-        let string_mut = string.as_mut();
+        let string_mut = string.as_mut_str();
         let string_mut_bytes = unsafe { string2.as_bytes_mut() }; // SAFETY: We don't modify it
 
         // Note: This is a trick because `rustfmt` doesn't support
@@ -1427,6 +1443,15 @@ mod tests {
         assert_eq!(iter.next_back(), Some("baz".as_ascii_str().unwrap()));
         assert_eq!(iter.next_back(), Some("".as_ascii_str().unwrap()));
         assert_eq!(iter.next(), Some("bar".as_ascii_str().unwrap()));
+
+        let empty_lines = b"\n\r\n\n\r\n";
+        let mut iter_count = 0;
+        let ascii = AsciiStr::from_ascii(&empty_lines).unwrap();
+        for line in ascii.lines().rev() {
+            iter_count += 1;
+            assert!(line.is_empty());
+        }
+        assert_eq!(4, iter_count);
     }
 
     #[test]

From 78d9f48de3a2ad474f8fff35006f7a4d74752f21 Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sun, 11 Oct 2020 22:48:45 +0100
Subject: [PATCH 8/9] Fixed usage of `String` in a `#[no_std]` environment in
 `ascii_str::tests`.

---
 src/ascii_str.rs | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index 268e33a..5d3c690 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -1184,11 +1184,10 @@ mod tests {
         let ascii_str = arr.as_ref().into();
         let mut mut_arr = arr; // Note: We need a second copy to prevent overlapping mutable borrows.
         let mut_ascii_str = mut_arr.as_mut().into();
-        let mut_arr_mut_ref: &mut [AsciiChar] = &mut [AsciiChar::A];
-        let mut string = "A".to_string();
-        let mut string2 = "A".to_string();
-        let string_mut = string.as_mut_str();
-        let string_mut_bytes = unsafe { string2.as_bytes_mut() }; // SAFETY: We don't modify it
+		let mut_arr_mut_ref: &mut [AsciiChar] = &mut [AsciiChar::A];
+		let mut string_bytes = [b'A'];
+        let string_mut = unsafe { std::str::from_utf8_unchecked_mut(&mut string_bytes) }; // SAFETY: 'A' is a valid string.
+        let string_mut_bytes: &mut [u8] = &mut [b'A'];
 
         // Note: This is a trick because `rustfmt` doesn't support
         //       attributes on blocks yet.

From d1edb5600805af81508fea5f7bdfefc798920d6b Mon Sep 17 00:00:00 2001
From: Filipe Rodrigues <filipejacintorodrigues1@gmail.com>
Date: Sun, 11 Oct 2020 22:51:58 +0100
Subject: [PATCH 9/9] Fixed usage of `std` instead of `core` in a
 `ascii_str::tests::generic_as_ascii_str`.

---
 src/ascii_str.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index 5d3c690..2d1fbbd 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -1186,7 +1186,7 @@ mod tests {
         let mut_ascii_str = mut_arr.as_mut().into();
 		let mut_arr_mut_ref: &mut [AsciiChar] = &mut [AsciiChar::A];
 		let mut string_bytes = [b'A'];
-        let string_mut = unsafe { std::str::from_utf8_unchecked_mut(&mut string_bytes) }; // SAFETY: 'A' is a valid string.
+        let string_mut = unsafe { core::str::from_utf8_unchecked_mut(&mut string_bytes) }; // SAFETY: 'A' is a valid string.
         let string_mut_bytes: &mut [u8] = &mut [b'A'];
 
         // Note: This is a trick because `rustfmt` doesn't support