]> git.lizzy.rs Git - rust.git/blobdiff - src/comment.rs
Use correct span for match arms with the leading pipe and attributes (#3975)
[rust.git] / src / comment.rs
index 213879e50a1948a0fef958fa194c9aafa8581920..1da62d176817171b46b433b06978f6c6fc2fcd74 100644 (file)
@@ -1,26 +1,18 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
 // Formatting and tools for comments.
 
 use std::{self, borrow::Cow, iter};
 
 use itertools::{multipeek, MultiPeek};
-use syntax::source_map::Span;
+use rustc_span::Span;
 
-use config::Config;
-use rewrite::RewriteContext;
-use shape::{Indent, Shape};
-use string::{rewrite_string, StringFormat};
-use utils::{count_newlines, first_line_width, last_line_width};
-use {ErrorKind, FormattingError};
+use crate::config::Config;
+use crate::rewrite::RewriteContext;
+use crate::shape::{Indent, Shape};
+use crate::string::{rewrite_string, StringFormat};
+use crate::utils::{
+    count_newlines, first_line_width, last_line_width, trim_left_preserve_layout, unicode_str_width,
+};
+use crate::{ErrorKind, FormattingError};
 
 fn is_custom_comment(comment: &str) -> bool {
     if !comment.starts_with("//") {
@@ -33,7 +25,7 @@ fn is_custom_comment(comment: &str) -> bool {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq)]
-pub enum CommentStyle<'a> {
+pub(crate) enum CommentStyle<'a> {
     DoubleSlash,
     TripleSlash,
     Doc,
@@ -52,8 +44,8 @@ fn custom_opener(s: &str) -> &str {
 }
 
 impl<'a> CommentStyle<'a> {
-    /// Returns true if the commenting style covers a line only.
-    pub fn is_line_comment(&self) -> bool {
+    /// Returns `true` if the commenting style covers a line only.
+    pub(crate) fn is_line_comment(&self) -> bool {
         match *self {
             CommentStyle::DoubleSlash
             | CommentStyle::TripleSlash
@@ -63,8 +55,8 @@ pub fn is_line_comment(&self) -> bool {
         }
     }
 
-    /// Returns true if the commenting style can span over multiple lines.
-    pub fn is_block_comment(&self) -> bool {
+    /// Returns `true` if the commenting style can span over multiple lines.
+    pub(crate) fn is_block_comment(&self) -> bool {
         match *self {
             CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
                 true
@@ -73,15 +65,15 @@ pub fn is_block_comment(&self) -> bool {
         }
     }
 
-    /// Returns true if the commenting style is for documentation.
-    pub fn is_doc_comment(&self) -> bool {
+    /// Returns `true` if the commenting style is for documentation.
+    pub(crate) fn is_doc_comment(&self) -> bool {
         match *self {
             CommentStyle::TripleSlash | CommentStyle::Doc => true,
             _ => false,
         }
     }
 
-    pub fn opener(&self) -> &'a str {
+    pub(crate) fn opener(&self) -> &'a str {
         match *self {
             CommentStyle::DoubleSlash => "// ",
             CommentStyle::TripleSlash => "/// ",
@@ -93,34 +85,36 @@ pub fn opener(&self) -> &'a str {
         }
     }
 
-    pub fn closer(&self) -> &'a str {
+    pub(crate) fn closer(&self) -> &'a str {
         match *self {
             CommentStyle::DoubleSlash
             | CommentStyle::TripleSlash
             | CommentStyle::Custom(..)
             | CommentStyle::Doc => "",
-            CommentStyle::DoubleBullet => " **/",
-            CommentStyle::SingleBullet | CommentStyle::Exclamation => " */",
+            CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
+                " */"
+            }
         }
     }
 
-    pub fn line_start(&self) -> &'a str {
+    pub(crate) fn line_start(&self) -> &'a str {
         match *self {
             CommentStyle::DoubleSlash => "// ",
             CommentStyle::TripleSlash => "/// ",
             CommentStyle::Doc => "//! ",
-            CommentStyle::SingleBullet | CommentStyle::Exclamation => " * ",
-            CommentStyle::DoubleBullet => " ** ",
+            CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
+                " * "
+            }
             CommentStyle::Custom(opener) => opener,
         }
     }
 
-    pub fn to_str_tuplet(&self) -> (&'a str, &'a str, &'a str) {
+    pub(crate) fn to_str_tuplet(&self) -> (&'a str, &'a str, &'a str) {
         (self.opener(), self.closer(), self.line_start())
     }
 }
 
-fn comment_style(orig: &str, normalize_comments: bool) -> CommentStyle {
+pub(crate) fn comment_style(orig: &str, normalize_comments: bool) -> CommentStyle<'_> {
     if !normalize_comments {
         if orig.starts_with("/**") && !orig.starts_with("/**/") {
             CommentStyle::DoubleBullet
@@ -150,19 +144,32 @@ fn comment_style(orig: &str, normalize_comments: bool) -> CommentStyle {
     }
 }
 
+/// Returns true if the last line of the passed string finishes with a block-comment.
+pub(crate) fn is_last_comment_block(s: &str) -> bool {
+    s.trim_end().ends_with("*/")
+}
+
 /// Combine `prev_str` and `next_str` into a single `String`. `span` may contain
 /// comments between two strings. If there are such comments, then that will be
 /// recovered. If `allow_extend` is true and there is no comment between the two
 /// strings, then they will be put on a single line as long as doing so does not
 /// exceed max width.
-pub fn combine_strs_with_missing_comments(
-    context: &RewriteContext,
+pub(crate) fn combine_strs_with_missing_comments(
+    context: &RewriteContext<'_>,
     prev_str: &str,
     next_str: &str,
     span: Span,
     shape: Shape,
     allow_extend: bool,
 ) -> Option<String> {
+    trace!(
+        "combine_strs_with_missing_comments `{}` `{}` {:?} {:?}",
+        prev_str,
+        next_str,
+        span,
+        shape
+    );
+
     let mut result =
         String::with_capacity(prev_str.len() + next_str.len() + shape.indent.width() + 128);
     result.push_str(prev_str);
@@ -234,11 +241,11 @@ pub fn combine_strs_with_missing_comments(
     Some(result)
 }
 
-pub fn rewrite_doc_comment(orig: &str, shape: Shape, config: &Config) -> Option<String> {
+pub(crate) fn rewrite_doc_comment(orig: &str, shape: Shape, config: &Config) -> Option<String> {
     identify_comment(orig, false, shape, config, true)
 }
 
-pub fn rewrite_comment(
+pub(crate) fn rewrite_comment(
     orig: &str,
     block_style: bool,
     shape: Shape,
@@ -256,7 +263,8 @@ fn identify_comment(
 ) -> Option<String> {
     let style = comment_style(orig, false);
 
-    // Computes the len of line taking into account a newline if the line is part of a paragraph.
+    // Computes the byte length of line taking into account a newline if the line is part of a
+    // paragraph.
     fn compute_len(orig: &str, line: &str) -> usize {
         if orig.len() > line.len() {
             if orig.as_bytes()[line.len()] == b'\r' {
@@ -275,7 +283,7 @@ fn compute_len(orig: &str, line: &str) -> usize {
     // - a boolean indicating if there is a blank line
     // - a number indicating the size of the first group of comments
     fn consume_same_line_comments(
-        style: CommentStyle,
+        style: CommentStyle<'_>,
         orig: &str,
         line_start: &str,
     ) -> (bool, usize) {
@@ -283,7 +291,7 @@ fn consume_same_line_comments(
         let mut hbl = false;
 
         for line in orig.lines() {
-            let trimmed_line = line.trim_left();
+            let trimmed_line = line.trim_start();
             if trimmed_line.is_empty() {
                 hbl = true;
                 break;
@@ -300,29 +308,41 @@ fn consume_same_line_comments(
 
     let (has_bare_lines, first_group_ending) = match style {
         CommentStyle::DoubleSlash | CommentStyle::TripleSlash | CommentStyle::Doc => {
-            let line_start = style.line_start().trim_left();
+            let line_start = style.line_start().trim_start();
             consume_same_line_comments(style, orig, line_start)
         }
         CommentStyle::Custom(opener) => {
-            let trimmed_opener = opener.trim_right();
+            let trimmed_opener = opener.trim_end();
             consume_same_line_comments(style, orig, trimmed_opener)
         }
         // for a block comment, search for the closing symbol
         CommentStyle::DoubleBullet | CommentStyle::SingleBullet | CommentStyle::Exclamation => {
-            let closer = style.closer().trim_left();
+            let closer = style.closer().trim_start();
+            let mut count = orig.matches(closer).count();
             let mut closing_symbol_offset = 0;
             let mut hbl = false;
+            let mut first = true;
             for line in orig.lines() {
                 closing_symbol_offset += compute_len(&orig[closing_symbol_offset..], line);
-                let trimmed_line = line.trim_left();
+                let mut trimmed_line = line.trim_start();
                 if !trimmed_line.starts_with('*')
                     && !trimmed_line.starts_with("//")
                     && !trimmed_line.starts_with("/*")
                 {
                     hbl = true;
                 }
+
+                // Remove opener from consideration when searching for closer
+                if first {
+                    let opener = style.opener().trim_end();
+                    trimmed_line = &trimmed_line[opener.len()..];
+                    first = false;
+                }
                 if trimmed_line.ends_with(closer) {
-                    break;
+                    count -= 1;
+                    if count == 0 {
+                        break;
+                    }
                 }
             }
             (hbl, closing_symbol_offset)
@@ -332,12 +352,12 @@ fn consume_same_line_comments(
     let (first_group, rest) = orig.split_at(first_group_ending);
     let rewritten_first_group =
         if !config.normalize_comments() && has_bare_lines && style.is_block_comment() {
-            light_rewrite_block_comment_with_bare_lines(first_group, shape, config)?
+            trim_left_preserve_layout(first_group, shape.indent, config)?
         } else if !config.normalize_comments()
             && !config.wrap_comments()
-            && !config.format_doc_comments()
+            && !config.format_code_in_doc_comments()
         {
-            light_rewrite_comment(first_group, shape.indent, config, is_doc_comment)?
+            light_rewrite_comment(first_group, shape.indent, config, is_doc_comment)
         } else {
             rewrite_comment_inner(
                 first_group,
@@ -351,64 +371,28 @@ fn consume_same_line_comments(
     if rest.is_empty() {
         Some(rewritten_first_group)
     } else {
-        identify_comment(rest.trim_left(), block_style, shape, config, is_doc_comment).map(
-            |rest_str| {
-                format!(
-                    "{}\n{}{}{}",
-                    rewritten_first_group,
-                    // insert back the blank line
-                    if has_bare_lines && style.is_line_comment() {
-                        "\n"
-                    } else {
-                        ""
-                    },
-                    shape.indent.to_string(config),
-                    rest_str
-                )
-            },
+        identify_comment(
+            rest.trim_start(),
+            block_style,
+            shape,
+            config,
+            is_doc_comment,
         )
-    }
-}
-
-/// Trims a minimum of leading whitespaces so that the content layout is kept and aligns to indent.
-fn light_rewrite_block_comment_with_bare_lines(
-    orig: &str,
-    shape: Shape,
-    config: &Config,
-) -> Option<String> {
-    let prefix_whitespace_min = orig
-        .lines()
-        // skip the line with the starting sigil since the leading whitespace is removed
-        // otherwise, the minimum would always be zero
-        .skip(1)
-        .filter(|line| !line.is_empty())
-        .map(|line| {
-            let mut width = 0;
-            for c in line.chars() {
-                match c {
-                    ' ' => width += 1,
-                    '\t' => width += config.tab_spaces(),
-                    _ => break,
-                }
-            }
-            width
-        })
-        .min()?;
-
-    let indent_str = shape.indent.to_string(config);
-    let mut lines = orig.lines();
-    let first_line = lines.next()?;
-    let rest = lines
-        .map(|line| {
-            if line.is_empty() {
-                line
-            } else {
-                &line[prefix_whitespace_min..]
-            }
+        .map(|rest_str| {
+            format!(
+                "{}\n{}{}{}",
+                rewritten_first_group,
+                // insert back the blank line
+                if has_bare_lines && style.is_line_comment() {
+                    "\n"
+                } else {
+                    ""
+                },
+                shape.indent.to_string(config),
+                rest_str
+            )
         })
-        .collect::<Vec<&str>>()
-        .join(&format!("\n{}", indent_str));
-    Some(format!("{}\n{}{}", first_line, indent_str, rest))
+    }
 }
 
 /// Attributes for code blocks in rustdoc.
@@ -439,8 +423,10 @@ fn new(attribute: &str) -> CodeBlockAttribute {
 /// Block that is formatted as an item.
 ///
 /// An item starts with either a star `*` or a dash `-`. Different level of indentation are
-/// handled.
+/// handled by shrinking the shape accordingly.
 struct ItemizedBlock {
+    /// the lines that are identified as part of an itemized block
+    lines: Vec<String>,
     /// the number of whitespaces up to the item sigil
     indent: usize,
     /// the string that marks the start of an item
@@ -450,9 +436,9 @@ struct ItemizedBlock {
 }
 
 impl ItemizedBlock {
-    /// Returns true if the line is formatted as an item
+    /// Returns `true` if the line is formatted as an item
     fn is_itemized_line(line: &str) -> bool {
-        let trimmed = line.trim_left();
+        let trimmed = line.trim_start();
         trimmed.starts_with("* ") || trimmed.starts_with("- ")
     }
 
@@ -462,14 +448,15 @@ fn new(line: &str) -> ItemizedBlock {
         let space_to_sigil = line.chars().take_while(|c| c.is_whitespace()).count();
         let indent = space_to_sigil + 2;
         ItemizedBlock {
+            lines: vec![line[indent..].to_string()],
             indent,
             opener: line[..indent].to_string(),
             line_start: " ".repeat(indent),
         }
     }
 
-    /// Returns a `StringFormat` used for formatting the content of an item
-    fn create_string_format<'a>(&'a self, fmt: &'a StringFormat) -> StringFormat<'a> {
+    /// Returns a `StringFormat` used for formatting the content of an item.
+    fn create_string_format<'a>(&'a self, fmt: &'a StringFormat<'_>) -> StringFormat<'a> {
         StringFormat {
             opener: "",
             closer: "",
@@ -481,266 +468,364 @@ fn create_string_format<'a>(&'a self, fmt: &'a StringFormat) -> StringFormat<'a>
         }
     }
 
-    /// Returns true if the line is part of the current itemized block
-    fn in_block(&self, line: &str) -> bool {
-        !ItemizedBlock::is_itemized_line(line)
+    /// Returns `true` if the line is part of the current itemized block.
+    /// If it is, then it is added to the internal lines list.
+    fn add_line(&mut self, line: &str) -> bool {
+        if !ItemizedBlock::is_itemized_line(line)
             && self.indent <= line.chars().take_while(|c| c.is_whitespace()).count()
+        {
+            self.lines.push(line.to_string());
+            return true;
+        }
+        false
+    }
+
+    /// Returns the block as a string, with each line trimmed at the start.
+    fn trimmed_block_as_string(&self) -> String {
+        self.lines
+            .iter()
+            .map(|line| format!("{} ", line.trim_start()))
+            .collect::<String>()
+    }
+
+    /// Returns the block as a string under its original form.
+    fn original_block_as_string(&self) -> String {
+        self.lines.join("\n")
     }
 }
 
-fn rewrite_comment_inner(
-    orig: &str,
-    block_style: bool,
-    style: CommentStyle,
-    shape: Shape,
-    config: &Config,
-    is_doc_comment: bool,
-) -> Option<String> {
-    let (opener, closer, line_start) = if block_style {
-        CommentStyle::SingleBullet.to_str_tuplet()
-    } else {
-        comment_style(orig, config.normalize_comments()).to_str_tuplet()
-    };
+struct CommentRewrite<'a> {
+    result: String,
+    code_block_buffer: String,
+    is_prev_line_multi_line: bool,
+    code_block_attr: Option<CodeBlockAttribute>,
+    item_block: Option<ItemizedBlock>,
+    comment_line_separator: String,
+    indent_str: String,
+    max_width: usize,
+    fmt_indent: Indent,
+    fmt: StringFormat<'a>,
 
-    let max_chars = shape
-        .width
-        .checked_sub(closer.len() + opener.len())
-        .unwrap_or(1);
-    let indent_str = shape.indent.to_string_with_newline(config);
-    let fmt_indent = shape.indent + (opener.len() - line_start.len());
-    let mut fmt = StringFormat {
-        opener: "",
-        closer: "",
-        line_start,
-        line_end: "",
-        shape: Shape::legacy(max_chars, fmt_indent),
-        trim_end: true,
-        config,
-    };
+    opener: String,
+    closer: String,
+    line_start: String,
+}
 
-    let line_breaks = count_newlines(orig.trim_right());
-    let lines = orig
-        .lines()
-        .enumerate()
-        .map(|(i, mut line)| {
-            line = trim_right_unless_two_whitespaces(line.trim_left(), is_doc_comment);
-            // Drop old closer.
-            if i == line_breaks && line.ends_with("*/") && !line.starts_with("//") {
-                line = line[..(line.len() - 2)].trim_right();
-            }
+impl<'a> CommentRewrite<'a> {
+    fn new(
+        orig: &'a str,
+        block_style: bool,
+        shape: Shape,
+        config: &'a Config,
+    ) -> CommentRewrite<'a> {
+        let (opener, closer, line_start) = if block_style {
+            CommentStyle::SingleBullet.to_str_tuplet()
+        } else {
+            comment_style(orig, config.normalize_comments()).to_str_tuplet()
+        };
 
-            line
-        })
-        .map(|s| left_trim_comment_line(s, &style))
-        .map(|(line, has_leading_whitespace)| {
-            if orig.starts_with("/*") && line_breaks == 0 {
-                (
-                    line.trim_left(),
-                    has_leading_whitespace || config.normalize_comments(),
-                )
-            } else {
-                (line, has_leading_whitespace || config.normalize_comments())
-            }
-        });
+        let max_width = shape
+            .width
+            .checked_sub(closer.len() + opener.len())
+            .unwrap_or(1);
+        let indent_str = shape.indent.to_string_with_newline(config).to_string();
+
+        let mut cr = CommentRewrite {
+            result: String::with_capacity(orig.len() * 2),
+            code_block_buffer: String::with_capacity(128),
+            is_prev_line_multi_line: false,
+            code_block_attr: None,
+            item_block: None,
+            comment_line_separator: format!("{}{}", indent_str, line_start),
+            max_width,
+            indent_str,
+            fmt_indent: shape.indent,
+
+            fmt: StringFormat {
+                opener: "",
+                closer: "",
+                line_start,
+                line_end: "",
+                shape: Shape::legacy(max_width, shape.indent),
+                trim_end: true,
+                config,
+            },
+
+            opener: opener.to_owned(),
+            closer: closer.to_owned(),
+            line_start: line_start.to_owned(),
+        };
+        cr.result.push_str(opener);
+        cr
+    }
 
-    let mut result = String::with_capacity(orig.len() * 2);
-    result.push_str(opener);
-    let mut code_block_buffer = String::with_capacity(128);
-    let mut is_prev_line_multi_line = false;
-    let mut code_block_attr = None;
-    let mut item_block_buffer = String::with_capacity(128);
-    let mut item_block: Option<ItemizedBlock> = None;
-    let comment_line_separator = format!("{}{}", indent_str, line_start);
-    let join_block = |s: &str, sep: &str| {
+    fn join_block(s: &str, sep: &str) -> String {
         let mut result = String::with_capacity(s.len() + 128);
         let mut iter = s.lines().peekable();
         while let Some(line) = iter.next() {
             result.push_str(line);
             result.push_str(match iter.peek() {
-                Some(next_line) if next_line.is_empty() => sep.trim_right(),
+                Some(next_line) if next_line.is_empty() => sep.trim_end(),
                 Some(..) => &sep,
                 None => "",
             });
         }
         result
-    };
+    }
 
-    for (i, (line, has_leading_whitespace)) in lines.enumerate() {
+    fn finish(mut self) -> String {
+        if !self.code_block_buffer.is_empty() {
+            // There is a code block that is not properly enclosed by backticks.
+            // We will leave them untouched.
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&Self::join_block(
+                &trim_custom_comment_prefix(&self.code_block_buffer),
+                &self.comment_line_separator,
+            ));
+        }
+
+        if let Some(ref ib) = self.item_block {
+            // the last few lines are part of an itemized block
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            let item_fmt = ib.create_string_format(&self.fmt);
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&ib.opener);
+            match rewrite_string(
+                &ib.trimmed_block_as_string(),
+                &item_fmt,
+                self.max_width.saturating_sub(ib.indent),
+            ) {
+                Some(s) => self.result.push_str(&Self::join_block(
+                    &s,
+                    &format!("{}{}", self.comment_line_separator, ib.line_start),
+                )),
+                None => self.result.push_str(&Self::join_block(
+                    &ib.original_block_as_string(),
+                    &self.comment_line_separator,
+                )),
+            };
+        }
+
+        self.result.push_str(&self.closer);
+        if self.result.ends_with(&self.opener) && self.opener.ends_with(' ') {
+            // Trailing space.
+            self.result.pop();
+        }
+
+        self.result
+    }
+
+    fn handle_line(
+        &mut self,
+        orig: &'a str,
+        i: usize,
+        line: &'a str,
+        has_leading_whitespace: bool,
+    ) -> bool {
         let is_last = i == count_newlines(orig);
 
-        if let Some(ref ib) = item_block {
-            if ib.in_block(&line) {
-                item_block_buffer.push_str(&line);
-                item_block_buffer.push('\n');
-                continue;
+        if let Some(ref mut ib) = self.item_block {
+            if ib.add_line(&line) {
+                return false;
             }
-            is_prev_line_multi_line = false;
-            fmt.shape = Shape::legacy(max_chars, fmt_indent);
-            let item_fmt = ib.create_string_format(&fmt);
-            result.push_str(&comment_line_separator);
-            result.push_str(&ib.opener);
-            match rewrite_string(&item_block_buffer.replace("\n", " "), &item_fmt) {
-                Some(s) => result.push_str(&join_block(
+            self.is_prev_line_multi_line = false;
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            let item_fmt = ib.create_string_format(&self.fmt);
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&ib.opener);
+            match rewrite_string(
+                &ib.trimmed_block_as_string(),
+                &item_fmt,
+                self.max_width.saturating_sub(ib.indent),
+            ) {
+                Some(s) => self.result.push_str(&Self::join_block(
                     &s,
-                    &format!("{}{}", &comment_line_separator, ib.line_start),
+                    &format!("{}{}", self.comment_line_separator, ib.line_start),
+                )),
+                None => self.result.push_str(&Self::join_block(
+                    &ib.original_block_as_string(),
+                    &self.comment_line_separator,
                 )),
-                None => result.push_str(&join_block(&item_block_buffer, &comment_line_separator)),
             };
-            item_block_buffer.clear();
-        } else if let Some(ref attr) = code_block_attr {
+        } else if self.code_block_attr.is_some() {
             if line.starts_with("```") {
-                let code_block = match attr {
+                let code_block = match self.code_block_attr.as_ref().unwrap() {
                     CodeBlockAttribute::Ignore | CodeBlockAttribute::Text => {
-                        trim_custom_comment_prefix(&code_block_buffer)
+                        trim_custom_comment_prefix(&self.code_block_buffer)
                     }
-                    _ if code_block_buffer.is_empty() => String::new(),
+                    _ if self.code_block_buffer.is_empty() => String::new(),
                     _ => {
-                        let mut config = config.clone();
-                        config.set().format_doc_comments(false);
-                        match ::format_code_block(&code_block_buffer, &config) {
-                            Some(ref s) => trim_custom_comment_prefix(s),
-                            None => trim_custom_comment_prefix(&code_block_buffer),
+                        let mut config = self.fmt.config.clone();
+                        config.set().wrap_comments(false);
+                        if config.format_code_in_doc_comments() {
+                            if let Some(s) =
+                                crate::format_code_block(&self.code_block_buffer, &config)
+                            {
+                                trim_custom_comment_prefix(&s.snippet)
+                            } else {
+                                trim_custom_comment_prefix(&self.code_block_buffer)
+                            }
+                        } else {
+                            trim_custom_comment_prefix(&self.code_block_buffer)
                         }
                     }
                 };
                 if !code_block.is_empty() {
-                    result.push_str(&comment_line_separator);
-                    result.push_str(&join_block(&code_block, &comment_line_separator));
+                    self.result.push_str(&self.comment_line_separator);
+                    self.result
+                        .push_str(&Self::join_block(&code_block, &self.comment_line_separator));
                 }
-                code_block_buffer.clear();
-                result.push_str(&comment_line_separator);
-                result.push_str(line);
-                code_block_attr = None;
+                self.code_block_buffer.clear();
+                self.result.push_str(&self.comment_line_separator);
+                self.result.push_str(line);
+                self.code_block_attr = None;
             } else {
-                code_block_buffer.push_str(&hide_sharp_behind_comment(line));
-                code_block_buffer.push('\n');
+                self.code_block_buffer
+                    .push_str(&hide_sharp_behind_comment(line));
+                self.code_block_buffer.push('\n');
             }
-            continue;
+            return false;
         }
 
-        code_block_attr = None;
-        item_block = None;
+        self.code_block_attr = None;
+        self.item_block = None;
         if line.starts_with("```") {
-            code_block_attr = Some(CodeBlockAttribute::new(&line[3..]))
-        } else if config.wrap_comments() && ItemizedBlock::is_itemized_line(&line) {
+            self.code_block_attr = Some(CodeBlockAttribute::new(&line[3..]))
+        } else if self.fmt.config.wrap_comments() && ItemizedBlock::is_itemized_line(&line) {
             let ib = ItemizedBlock::new(&line);
-            item_block_buffer.push_str(&line[ib.indent..]);
-            item_block_buffer.push('\n');
-            item_block = Some(ib);
-            continue;
+            self.item_block = Some(ib);
+            return false;
         }
 
-        if result == opener {
-            let force_leading_whitespace = opener == "/* " && count_newlines(orig) == 0;
-            if !has_leading_whitespace && !force_leading_whitespace && result.ends_with(' ') {
-                result.pop();
+        if self.result == self.opener {
+            let force_leading_whitespace = &self.opener == "/* " && count_newlines(orig) == 0;
+            if !has_leading_whitespace && !force_leading_whitespace && self.result.ends_with(' ') {
+                self.result.pop();
             }
             if line.is_empty() {
-                continue;
+                return false;
             }
-        } else if is_prev_line_multi_line && !line.is_empty() {
-            result.push(' ')
+        } else if self.is_prev_line_multi_line && !line.is_empty() {
+            self.result.push(' ')
         } else if is_last && line.is_empty() {
             // trailing blank lines are unwanted
-            if !closer.is_empty() {
-                result.push_str(&indent_str);
+            if !self.closer.is_empty() {
+                self.result.push_str(&self.indent_str);
             }
-            break;
+            return true;
         } else {
-            result.push_str(&comment_line_separator);
-            if !has_leading_whitespace && result.ends_with(' ') {
-                result.pop();
+            self.result.push_str(&self.comment_line_separator);
+            if !has_leading_whitespace && self.result.ends_with(' ') {
+                self.result.pop();
             }
         }
 
-        if config.wrap_comments() && line.len() > fmt.shape.width && !has_url(line) {
-            match rewrite_string(line, &fmt) {
+        if self.fmt.config.wrap_comments()
+            && unicode_str_width(line) > self.fmt.shape.width
+            && !has_url(line)
+        {
+            match rewrite_string(line, &self.fmt, self.max_width) {
                 Some(ref s) => {
-                    is_prev_line_multi_line = s.contains('\n');
-                    result.push_str(s);
+                    self.is_prev_line_multi_line = s.contains('\n');
+                    self.result.push_str(s);
                 }
-                None if is_prev_line_multi_line => {
+                None if self.is_prev_line_multi_line => {
                     // We failed to put the current `line` next to the previous `line`.
                     // Remove the trailing space, then start rewrite on the next line.
-                    result.pop();
-                    result.push_str(&comment_line_separator);
-                    fmt.shape = Shape::legacy(max_chars, fmt_indent);
-                    match rewrite_string(line, &fmt) {
+                    self.result.pop();
+                    self.result.push_str(&self.comment_line_separator);
+                    self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+                    match rewrite_string(line, &self.fmt, self.max_width) {
                         Some(ref s) => {
-                            is_prev_line_multi_line = s.contains('\n');
-                            result.push_str(s);
+                            self.is_prev_line_multi_line = s.contains('\n');
+                            self.result.push_str(s);
                         }
                         None => {
-                            is_prev_line_multi_line = false;
-                            result.push_str(line);
+                            self.is_prev_line_multi_line = false;
+                            self.result.push_str(line);
                         }
                     }
                 }
                 None => {
-                    is_prev_line_multi_line = false;
-                    result.push_str(line);
+                    self.is_prev_line_multi_line = false;
+                    self.result.push_str(line);
                 }
             }
 
-            fmt.shape = if is_prev_line_multi_line {
+            self.fmt.shape = if self.is_prev_line_multi_line {
                 // 1 = " "
-                let offset = 1 + last_line_width(&result) - line_start.len();
+                let offset = 1 + last_line_width(&self.result) - self.line_start.len();
                 Shape {
-                    width: max_chars.saturating_sub(offset),
-                    indent: fmt_indent,
-                    offset: fmt.shape.offset + offset,
+                    width: self.max_width.saturating_sub(offset),
+                    indent: self.fmt_indent,
+                    offset: self.fmt.shape.offset + offset,
                 }
             } else {
-                Shape::legacy(max_chars, fmt_indent)
+                Shape::legacy(self.max_width, self.fmt_indent)
             };
         } else {
-            if line.is_empty() && result.ends_with(' ') && !is_last {
+            if line.is_empty() && self.result.ends_with(' ') && !is_last {
                 // Remove space if this is an empty comment or a doc comment.
-                result.pop();
+                self.result.pop();
             }
-            result.push_str(line);
-            fmt.shape = Shape::legacy(max_chars, fmt_indent);
-            is_prev_line_multi_line = false;
+            self.result.push_str(line);
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            self.is_prev_line_multi_line = false;
         }
+
+        false
     }
-    if !code_block_buffer.is_empty() {
-        // There is a code block that is not properly enclosed by backticks.
-        // We will leave them untouched.
-        result.push_str(&comment_line_separator);
-        result.push_str(&join_block(
-            &trim_custom_comment_prefix(&code_block_buffer),
-            &comment_line_separator,
-        ));
-    }
-    if !item_block_buffer.is_empty() {
-        // the last few lines are part of an itemized block
-        let ib = item_block.unwrap();
-        fmt.shape = Shape::legacy(max_chars, fmt_indent);
-        let item_fmt = ib.create_string_format(&fmt);
-        result.push_str(&comment_line_separator);
-        result.push_str(&ib.opener);
-        match rewrite_string(&item_block_buffer.replace("\n", " "), &item_fmt) {
-            Some(s) => result.push_str(&join_block(
-                &s,
-                &format!("{}{}", &comment_line_separator, ib.line_start),
-            )),
-            None => result.push_str(&join_block(&item_block_buffer, &comment_line_separator)),
-        };
-    }
+}
+
+fn rewrite_comment_inner(
+    orig: &str,
+    block_style: bool,
+    style: CommentStyle<'_>,
+    shape: Shape,
+    config: &Config,
+    is_doc_comment: bool,
+) -> Option<String> {
+    let mut rewriter = CommentRewrite::new(orig, block_style, shape, config);
+
+    let line_breaks = count_newlines(orig.trim_end());
+    let lines = orig
+        .lines()
+        .enumerate()
+        .map(|(i, mut line)| {
+            line = trim_end_unless_two_whitespaces(line.trim_start(), is_doc_comment);
+            // Drop old closer.
+            if i == line_breaks && line.ends_with("*/") && !line.starts_with("//") {
+                line = line[..(line.len() - 2)].trim_end();
+            }
 
-    result.push_str(closer);
-    if result.ends_with(opener) && opener.ends_with(' ') {
-        // Trailing space.
-        result.pop();
+            line
+        })
+        .map(|s| left_trim_comment_line(s, &style))
+        .map(|(line, has_leading_whitespace)| {
+            if orig.starts_with("/*") && line_breaks == 0 {
+                (
+                    line.trim_start(),
+                    has_leading_whitespace || config.normalize_comments(),
+                )
+            } else {
+                (line, has_leading_whitespace || config.normalize_comments())
+            }
+        });
+
+    for (i, (line, has_leading_whitespace)) in lines.enumerate() {
+        if rewriter.handle_line(orig, i, line, has_leading_whitespace) {
+            break;
+        }
     }
 
-    Some(result)
+    Some(rewriter.finish())
 }
 
 const RUSTFMT_CUSTOM_COMMENT_PREFIX: &str = "//#### ";
 
-fn hide_sharp_behind_comment(s: &str) -> Cow<str> {
-    if s.trim_left().starts_with("# ") {
+fn hide_sharp_behind_comment(s: &str) -> Cow<'_, str> {
+    let s_trimmed = s.trim();
+    if s_trimmed.starts_with("# ") || s_trimmed == "#" {
         Cow::from(format!("{}{}", RUSTFMT_CUSTOM_COMMENT_PREFIX, s))
     } else {
         Cow::from(s)
@@ -750,9 +835,9 @@ fn hide_sharp_behind_comment(s: &str) -> Cow<str> {
 fn trim_custom_comment_prefix(s: &str) -> String {
     s.lines()
         .map(|line| {
-            let left_trimmed = line.trim_left();
+            let left_trimmed = line.trim_start();
             if left_trimmed.starts_with(RUSTFMT_CUSTOM_COMMENT_PREFIX) {
-                left_trimmed.trim_left_matches(RUSTFMT_CUSTOM_COMMENT_PREFIX)
+                left_trimmed.trim_start_matches(RUSTFMT_CUSTOM_COMMENT_PREFIX)
             } else {
                 line
             }
@@ -761,7 +846,7 @@ fn trim_custom_comment_prefix(s: &str) -> String {
         .join("\n")
 }
 
-/// Returns true if the given string MAY include URLs or alike.
+/// Returns `true` if the given string MAY include URLs or alike.
 fn has_url(s: &str) -> bool {
     // This function may return false positive, but should get its job done in most cases.
     s.contains("https://") || s.contains("http://") || s.contains("ftp://") || s.contains("file://")
@@ -769,14 +854,16 @@ fn has_url(s: &str) -> bool {
 
 /// Given the span, rewrite the missing comment inside it if available.
 /// Note that the given span must only include comments (or leading/trailing whitespaces).
-pub fn rewrite_missing_comment(
+pub(crate) fn rewrite_missing_comment(
     span: Span,
     shape: Shape,
-    context: &RewriteContext,
+    context: &RewriteContext<'_>,
 ) -> Option<String> {
     let missing_snippet = context.snippet(span);
     let trimmed_snippet = missing_snippet.trim();
-    if !trimmed_snippet.is_empty() {
+    // check the span starts with a comment
+    let pos = trimmed_snippet.find('/');
+    if !trimmed_snippet.is_empty() && pos.is_some() {
         rewrite_comment(trimmed_snippet, false, shape, context.config)
     } else {
         Some(String::new())
@@ -786,10 +873,10 @@ pub fn rewrite_missing_comment(
 /// Recover the missing comments in the specified span, if available.
 /// The layout of the comments will be preserved as long as it does not break the code
 /// and its total width does not exceed the max width.
-pub fn recover_missing_comment_in_span(
+pub(crate) fn recover_missing_comment_in_span(
     span: Span,
     shape: Shape,
-    context: &RewriteContext,
+    context: &RewriteContext<'_>,
     used_width: usize,
 ) -> Option<String> {
     let missing_comment = rewrite_missing_comment(span, shape, context)?;
@@ -797,7 +884,7 @@ pub fn recover_missing_comment_in_span(
         Some(String::new())
     } else {
         let missing_snippet = context.snippet(span);
-        let pos = missing_snippet.find('/').unwrap_or(0);
+        let pos = missing_snippet.find('/')?;
         // 1 = ` `
         let total_width = missing_comment.len() + used_width + 1;
         let force_new_line_before_comment =
@@ -812,11 +899,11 @@ pub fn recover_missing_comment_in_span(
 }
 
 /// Trim trailing whitespaces unless they consist of two or more whitespaces.
-fn trim_right_unless_two_whitespaces(s: &str, is_doc_comment: bool) -> &str {
+fn trim_end_unless_two_whitespaces(s: &str, is_doc_comment: bool) -> &str {
     if is_doc_comment && s.ends_with("  ") {
         s
     } else {
-        s.trim_right()
+        s.trim_end()
     }
 }
 
@@ -826,7 +913,7 @@ fn light_rewrite_comment(
     offset: Indent,
     config: &Config,
     is_doc_comment: bool,
-) -> Option<String> {
+) -> String {
     let lines: Vec<&str> = orig
         .lines()
         .map(|l| {
@@ -844,16 +931,16 @@ fn light_rewrite_comment(
                 ""
             };
             // Preserve markdown's double-space line break syntax in doc comment.
-            trim_right_unless_two_whitespaces(left_trimmed, is_doc_comment)
+            trim_end_unless_two_whitespaces(left_trimmed, is_doc_comment)
         })
         .collect();
-    Some(lines.join(&format!("\n{}", offset.to_string(config))))
+    lines.join(&format!("\n{}", offset.to_string(config)))
 }
 
 /// Trims comment characters and possibly a single space from the left of a string.
 /// Does not trim all whitespace. If a single space is trimmed from the left of the string,
 /// this function returns true.
-fn left_trim_comment_line<'a>(line: &'a str, style: &CommentStyle) -> (&'a str, bool) {
+fn left_trim_comment_line<'a>(line: &'a str, style: &CommentStyle<'_>) -> (&'a str, bool) {
     if line.starts_with("//! ")
         || line.starts_with("/// ")
         || line.starts_with("/*! ")
@@ -864,7 +951,7 @@ fn left_trim_comment_line<'a>(line: &'a str, style: &CommentStyle) -> (&'a str,
         if line.starts_with(opener) {
             (&line[opener.len()..], true)
         } else {
-            (&line[opener.trim_right().len()..], false)
+            (&line[opener.trim_end().len()..], false)
         }
     } else if line.starts_with("/* ")
         || line.starts_with("// ")
@@ -888,7 +975,7 @@ fn left_trim_comment_line<'a>(line: &'a str, style: &CommentStyle) -> (&'a str,
     }
 }
 
-pub trait FindUncommented {
+pub(crate) trait FindUncommented {
     fn find_uncommented(&self, pat: &str) -> Option<usize>;
 }
 
@@ -919,9 +1006,9 @@ fn find_uncommented(&self, pat: &str) -> Option<usize> {
 
 // Returns the first byte position after the first comment. The given string
 // is expected to be prefixed by a comment, including delimiters.
-// Good: "/* /* inner */ outer */ code();"
-// Bad:  "code(); // hello\n world!"
-pub fn find_comment_end(s: &str) -> Option<usize> {
+// Good: `/* /* inner */ outer */ code();`
+// Bad:  `code(); // hello\n world!`
+pub(crate) fn find_comment_end(s: &str) -> Option<usize> {
     let mut iter = CharClasses::new(s.char_indices());
     for (kind, (i, _c)) in &mut iter {
         if kind == FullCodeCharKind::Normal || kind == FullCodeCharKind::InString {
@@ -929,7 +1016,7 @@ pub fn find_comment_end(s: &str) -> Option<usize> {
         }
     }
 
-    // Handle case where the comment ends at the end of s.
+    // Handle case where the comment ends at the end of `s`.
     if iter.status == CharClassesStatus::Normal {
         Some(s.len())
     } else {
@@ -937,41 +1024,12 @@ pub fn find_comment_end(s: &str) -> Option<usize> {
     }
 }
 
-/// Returns true if text contains any comment.
-pub fn contains_comment(text: &str) -> bool {
+/// Returns `true` if text contains any comment.
+pub(crate) fn contains_comment(text: &str) -> bool {
     CharClasses::new(text.chars()).any(|(kind, _)| kind.is_comment())
 }
 
-/// Remove trailing spaces from the specified snippet. We do not remove spaces
-/// inside strings or comments.
-pub fn remove_trailing_white_spaces(text: &str) -> String {
-    let mut buffer = String::with_capacity(text.len());
-    let mut space_buffer = String::with_capacity(128);
-    for (char_kind, c) in CharClasses::new(text.chars()) {
-        match c {
-            '\n' => {
-                if char_kind == FullCodeCharKind::InString {
-                    buffer.push_str(&space_buffer);
-                }
-                space_buffer.clear();
-                buffer.push('\n');
-            }
-            _ if c.is_whitespace() => {
-                space_buffer.push(c);
-            }
-            _ => {
-                if !space_buffer.is_empty() {
-                    buffer.push_str(&space_buffer);
-                    space_buffer.clear();
-                }
-                buffer.push(c);
-            }
-        }
-    }
-    buffer
-}
-
-pub struct CharClasses<T>
+pub(crate) struct CharClasses<T>
 where
     T: Iterator,
     T::Item: RichChar,
@@ -980,7 +1038,7 @@ pub struct CharClasses<T>
     status: CharClassesStatus,
 }
 
-pub trait RichChar {
+pub(crate) trait RichChar {
     fn get_char(&self) -> char;
 }
 
@@ -999,27 +1057,34 @@ fn get_char(&self) -> char {
 #[derive(PartialEq, Eq, Debug, Clone, Copy)]
 enum CharClassesStatus {
     Normal,
+    /// Character is within a string
     LitString,
     LitStringEscape,
+    /// Character is within a raw string
     LitRawString(u32),
     RawStringPrefix(u32),
     RawStringSuffix(u32),
     LitChar,
     LitCharEscape,
-    // The u32 is the nesting deepness of the comment
+    /// Character inside a block comment, with the integer indicating the nesting deepness of the
+    /// comment
     BlockComment(u32),
-    // Status when the '/' has been consumed, but not yet the '*', deepness is
-    // the new deepness (after the comment opening).
+    /// Character inside a block-commented string, with the integer indicating the nesting deepness
+    /// of the comment
+    StringInBlockComment(u32),
+    /// Status when the '/' has been consumed, but not yet the '*', deepness is
+    /// the new deepness (after the comment opening).
     BlockCommentOpening(u32),
-    // Status when the '*' has been consumed, but not yet the '/', deepness is
-    // the new deepness (after the comment closing).
+    /// Status when the '*' has been consumed, but not yet the '/', deepness is
+    /// the new deepness (after the comment closing).
     BlockCommentClosing(u32),
+    /// Character is within a line comment
     LineComment,
 }
 
 /// Distinguish between functional part of code and comments
 #[derive(PartialEq, Eq, Debug, Clone, Copy)]
-pub enum CodeCharKind {
+pub(crate) enum CodeCharKind {
     Normal,
     Comment,
 }
@@ -1028,7 +1093,7 @@ pub enum CodeCharKind {
 /// describing opening and closing of comments for ease when chunking
 /// code from tagged characters
 #[derive(PartialEq, Eq, Debug, Clone, Copy)]
-pub enum FullCodeCharKind {
+pub(crate) enum FullCodeCharKind {
     Normal,
     /// The first character of a comment, there is only one for a comment (always '/')
     StartComment,
@@ -1037,6 +1102,12 @@ pub enum FullCodeCharKind {
     InComment,
     /// Last character of a comment, '\n' for a line comment, '/' for a block comment.
     EndComment,
+    /// Start of a mutlitine string inside a comment
+    StartStringCommented,
+    /// End of a mutlitine string inside a comment
+    EndStringCommented,
+    /// Inside a commented string
+    InStringCommented,
     /// Start of a mutlitine string
     StartString,
     /// End of a mutlitine string
@@ -1046,19 +1117,39 @@ pub enum FullCodeCharKind {
 }
 
 impl FullCodeCharKind {
-    pub fn is_comment(self) -> bool {
+    pub(crate) fn is_comment(self) -> bool {
         match self {
             FullCodeCharKind::StartComment
             | FullCodeCharKind::InComment
-            | FullCodeCharKind::EndComment => true,
+            | FullCodeCharKind::EndComment
+            | FullCodeCharKind::StartStringCommented
+            | FullCodeCharKind::InStringCommented
+            | FullCodeCharKind::EndStringCommented => true,
             _ => false,
         }
     }
 
-    pub fn is_string(self) -> bool {
+    /// Returns true if the character is inside a comment
+    pub(crate) fn inside_comment(self) -> bool {
+        match self {
+            FullCodeCharKind::InComment
+            | FullCodeCharKind::StartStringCommented
+            | FullCodeCharKind::InStringCommented
+            | FullCodeCharKind::EndStringCommented => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn is_string(self) -> bool {
         self == FullCodeCharKind::InString || self == FullCodeCharKind::StartString
     }
 
+    /// Returns true if the character is within a commented string
+    pub(crate) fn is_commented_string(self) -> bool {
+        self == FullCodeCharKind::InStringCommented
+            || self == FullCodeCharKind::StartStringCommented
+    }
+
     fn to_codecharkind(self) -> CodeCharKind {
         if self.is_comment() {
             CodeCharKind::Comment
@@ -1073,7 +1164,7 @@ impl<T> CharClasses<T>
     T: Iterator,
     T::Item: RichChar,
 {
-    pub fn new(base: T) -> CharClasses<T> {
+    pub(crate) fn new(base: T) -> CharClasses<T> {
         CharClasses {
             base: multipeek(base),
             status: CharClassesStatus::Normal,
@@ -1163,7 +1254,7 @@ fn next(&mut self) -> Option<(FullCodeCharKind, T::Item)> {
             },
             CharClassesStatus::LitCharEscape => CharClassesStatus::LitChar,
             CharClassesStatus::Normal => match chr {
-                'r' => match self.base.peek().map(|c| c.get_char()) {
+                'r' => match self.base.peek().map(RichChar::get_char) {
                     Some('#') | Some('"') => {
                         char_kind = FullCodeCharKind::InString;
                         CharClassesStatus::RawStringPrefix(0)
@@ -1202,18 +1293,27 @@ fn next(&mut self) -> Option<(FullCodeCharKind, T::Item)> {
                 },
                 _ => CharClassesStatus::Normal,
             },
+            CharClassesStatus::StringInBlockComment(deepness) => {
+                char_kind = FullCodeCharKind::InStringCommented;
+                if chr == '"' {
+                    CharClassesStatus::BlockComment(deepness)
+                } else {
+                    CharClassesStatus::StringInBlockComment(deepness)
+                }
+            }
             CharClassesStatus::BlockComment(deepness) => {
                 assert_ne!(deepness, 0);
-                self.status = match self.base.peek() {
+                char_kind = FullCodeCharKind::InComment;
+                match self.base.peek() {
                     Some(next) if next.get_char() == '/' && chr == '*' => {
                         CharClassesStatus::BlockCommentClosing(deepness - 1)
                     }
                     Some(next) if next.get_char() == '*' && chr == '/' => {
                         CharClassesStatus::BlockCommentOpening(deepness + 1)
                     }
-                    _ => CharClassesStatus::BlockComment(deepness),
-                };
-                return Some((FullCodeCharKind::InComment, item));
+                    _ if chr == '"' => CharClassesStatus::StringInBlockComment(deepness),
+                    _ => self.status,
+                }
             }
             CharClassesStatus::BlockCommentOpening(deepness) => {
                 assert_eq!(chr, '*');
@@ -1247,13 +1347,13 @@ fn next(&mut self) -> Option<(FullCodeCharKind, T::Item)> {
 
 /// An iterator over the lines of a string, paired with the char kind at the
 /// end of the line.
-pub struct LineClasses<'a> {
+pub(crate) struct LineClasses<'a> {
     base: iter::Peekable<CharClasses<std::str::Chars<'a>>>,
     kind: FullCodeCharKind,
 }
 
 impl<'a> LineClasses<'a> {
-    pub fn new(s: &'a str) -> Self {
+    pub(crate) fn new(s: &'a str) -> Self {
         LineClasses {
             base: CharClasses::new(s.chars()).peekable(),
             kind: FullCodeCharKind::Normal,
@@ -1269,26 +1369,38 @@ fn next(&mut self) -> Option<Self::Item> {
 
         let mut line = String::new();
 
-        let start_class = match self.base.peek() {
+        let start_kind = match self.base.peek() {
             Some((kind, _)) => *kind,
-            None => FullCodeCharKind::Normal,
+            None => unreachable!(),
         };
 
         while let Some((kind, c)) = self.base.next() {
+            // needed to set the kind of the ending character on the last line
+            self.kind = kind;
             if c == '\n' {
-                self.kind = match (start_class, kind) {
+                self.kind = match (start_kind, kind) {
                     (FullCodeCharKind::Normal, FullCodeCharKind::InString) => {
                         FullCodeCharKind::StartString
                     }
                     (FullCodeCharKind::InString, FullCodeCharKind::Normal) => {
                         FullCodeCharKind::EndString
                     }
+                    (FullCodeCharKind::InComment, FullCodeCharKind::InStringCommented) => {
+                        FullCodeCharKind::StartStringCommented
+                    }
+                    (FullCodeCharKind::InStringCommented, FullCodeCharKind::InComment) => {
+                        FullCodeCharKind::EndStringCommented
+                    }
                     _ => kind,
                 };
                 break;
-            } else {
-                line.push(c);
             }
+            line.push(c);
+        }
+
+        // Workaround for CRLF newline.
+        if line.ends_with('\r') {
+            line.pop();
         }
 
         Some((self.kind, line))
@@ -1329,7 +1441,12 @@ fn next(&mut self) -> Option<Self::Item> {
             }
             FullCodeCharKind::StartComment => {
                 // Consume the whole comment
-                while let Some((FullCodeCharKind::InComment, (_, _))) = self.iter.next() {}
+                loop {
+                    match self.iter.next() {
+                        Some((kind, ..)) if kind.inside_comment() => continue,
+                        _ => break,
+                    }
+                }
             }
             _ => panic!(),
         }
@@ -1352,14 +1469,14 @@ fn next(&mut self) -> Option<Self::Item> {
 /// Iterator over an alternating sequence of functional and commented parts of
 /// a string. The first item is always a, possibly zero length, subslice of
 /// functional text. Line style comments contain their ending newlines.
-pub struct CommentCodeSlices<'a> {
+pub(crate) struct CommentCodeSlices<'a> {
     slice: &'a str,
     last_slice_kind: CodeCharKind,
     last_slice_end: usize,
 }
 
 impl<'a> CommentCodeSlices<'a> {
-    pub fn new(slice: &'a str) -> CommentCodeSlices<'a> {
+    pub(crate) fn new(slice: &'a str) -> CommentCodeSlices<'a> {
         CommentCodeSlices {
             slice,
             last_slice_kind: CodeCharKind::Comment,
@@ -1429,21 +1546,21 @@ fn next(&mut self) -> Option<Self::Item> {
 }
 
 /// Checks is `new` didn't miss any comment from `span`, if it removed any, return previous text
-/// (if it fits in the width/offset, else return None), else return `new`
-pub fn recover_comment_removed(
+/// (if it fits in the width/offset, else return `None`), else return `new`
+pub(crate) fn recover_comment_removed(
     new: String,
     span: Span,
-    context: &RewriteContext,
+    context: &RewriteContext<'_>,
 ) -> Option<String> {
     let snippet = context.snippet(span);
     if snippet != new && changed_comment_content(snippet, &new) {
         // We missed some comments. Warn and keep the original text.
         if context.config.error_on_unformatted() {
             context.report.append(
-                context.source_map.span_to_filename(span).into(),
+                context.parse_sess.span_to_filename(span),
                 vec![FormattingError::from_span(
                     span,
-                    &context.source_map,
+                    &context.parse_sess,
                     ErrorKind::LostComment,
                 )],
             );
@@ -1454,7 +1571,7 @@ pub fn recover_comment_removed(
     }
 }
 
-pub fn filter_normal_code(code: &str) -> String {
+pub(crate) fn filter_normal_code(code: &str) -> String {
     let mut buffer = String::with_capacity(code.len());
     LineClasses::new(code).for_each(|(kind, line)| match kind {
         FullCodeCharKind::Normal
@@ -1472,14 +1589,14 @@ pub fn filter_normal_code(code: &str) -> String {
     buffer
 }
 
-/// Return true if the two strings of code have the same payload of comments.
+/// Returns `true` if the two strings of code have the same payload of comments.
 /// The payload of comments is everything in the string except:
-///     - actual code (not comments)
-///     - comment start/end marks
-///     - whitespace
-///     - '*' at the beginning of lines in block comments
+/// - actual code (not comments),
+/// - comment start/end marks,
+/// - whitespace,
+/// - '*' at the beginning of lines in block comments.
 fn changed_comment_content(orig: &str, new: &str) -> bool {
-    // Cannot write this as a fn since we cannot return types containing closures
+    // Cannot write this as a fn since we cannot return types containing closures.
     let code_comment_content = |code| {
         let slices = UngroupedCommentCodeSlices::new(code);
         slices
@@ -1514,7 +1631,8 @@ fn new(comment: &'a str) -> CommentReducer<'a> {
         let comment = remove_comment_header(comment);
         CommentReducer {
             is_block,
-            at_start_line: false, // There are no supplementary '*' on the first line
+            // There are no supplementary '*' on the first line.
+            at_start_line: false,
             iter: comment.chars(),
         }
     }
@@ -1530,7 +1648,7 @@ fn next(&mut self) -> Option<Self::Item> {
                 while c.is_whitespace() {
                     c = self.iter.next()?;
                 }
-                // Ignore leading '*'
+                // Ignore leading '*'.
                 if c == '*' {
                     c = self.iter.next()?;
                 }
@@ -1565,7 +1683,7 @@ fn remove_comment_header(comment: &str) -> &str {
 #[cfg(test)]
 mod test {
     use super::*;
-    use shape::{Indent, Shape};
+    use crate::shape::{Indent, Shape};
 
     #[test]
     fn char_classes() {
@@ -1626,11 +1744,11 @@ fn comment_code_slices_three() {
     #[test]
     #[rustfmt::skip]
     fn format_doc_comments() {
-        let mut wrap_normalize_config: ::config::Config = Default::default();
+        let mut wrap_normalize_config: crate::config::Config = Default::default();
         wrap_normalize_config.set().wrap_comments(true);
         wrap_normalize_config.set().normalize_comments(true);
 
-        let mut wrap_config: ::config::Config = Default::default();
+        let mut wrap_config: crate::config::Config = Default::default();
         wrap_config.set().wrap_comments(true);
 
         let comment = rewrite_comment(" //test",
@@ -1666,7 +1784,7 @@ fn format_doc_comments() {
                                       &wrap_normalize_config).unwrap();
         assert_eq!("/* trimmed */", comment);
 
-        // check that different comment style are properly recognised
+        // Check that different comment style are properly recognised.
         let comment = rewrite_comment(r#"/// test1
                                          /// test2
                                          /*
@@ -1677,7 +1795,7 @@ fn format_doc_comments() {
                                       &wrap_normalize_config).unwrap();
         assert_eq!("/// test1\n/// test2\n// test3", comment);
 
-        // check that the blank line marks the end of a commented paragraph
+        // Check that the blank line marks the end of a commented paragraph.
         let comment = rewrite_comment(r#"// test1
 
                                          // test2"#,
@@ -1686,7 +1804,7 @@ fn format_doc_comments() {
                                       &wrap_normalize_config).unwrap();
         assert_eq!("// test1\n\n// test2", comment);
 
-        // check that the blank line marks the end of a custom-commented paragraph
+        // Check that the blank line marks the end of a custom-commented paragraph.
         let comment = rewrite_comment(r#"//@ test1
 
                                          //@ test2"#,
@@ -1695,7 +1813,7 @@ fn format_doc_comments() {
                                       &wrap_normalize_config).unwrap();
         assert_eq!("//@ test1\n\n//@ test2", comment);
 
-        // check that bare lines are just indented but left unchanged otherwise
+        // Check that bare lines are just indented but otherwise left unchanged.
         let comment = rewrite_comment(r#"// test1
                                          /*
                                            a bare line!
@@ -1708,8 +1826,8 @@ fn format_doc_comments() {
         assert_eq!("// test1\n/*\n a bare line!\n\n      another bare line!\n*/", comment);
     }
 
-    // This is probably intended to be a non-test fn, but it is not used. I'm
-    // keeping it around unless it helps us test stuff.
+    // This is probably intended to be a non-test fn, but it is not used.
+    // We should keep this around unless it helps us test stuff to remove it.
     fn uncommented(text: &str) -> String {
         CharClasses::new(text.chars())
             .filter_map(|(s, c)| match s {
@@ -1765,12 +1883,6 @@ fn check(haystack: &str, needle: &str, expected: Option<usize>) {
         check("\"/* abc", "abc", Some(4));
     }
 
-    #[test]
-    fn test_remove_trailing_white_spaces() {
-        let s = "    r#\"\n        test\n    \"#";
-        assert_eq!(remove_trailing_white_spaces(&s), s);
-    }
-
     #[test]
     fn test_filter_normal_code() {
         let s = r#"