feat: add fork of prettyplease for autoformatting

Cargo.toml

@@ -67,6 +67,7 @@ members = [
     "packages/fermi",
     "packages/tui",
     "packages/liveview",
+    "packages/autofmt",
     "packages/rsx",
     "packages/rsx_interpreter",
     "packages/native-core",

packages/autofmt/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "dioxus-autofmt"
+version = "0.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+proc-macro2 = { version = "1.0.6", features = ["span-locations"] }
+quote = "1.0"
+syn = { version = "1.0.11", features = ["full", "extra-traits"] }
+dioxus-rsx = { path = "../rsx" }
+triple_accel = "0.4.0"
+serde = { version = "1.0.136", features = ["derive"] }

packages/autofmt/README.md

@@ -0,0 +1,5 @@
+# This crate autofmts blocks of rsx!
+
+This crate formats rsx! by parsing call bodies and pretty-printing them back out.
+
+It also incorporates a fork of prettyplease to allow formatting arbitrary rust code too. Prettyplease rejected a suggestion to allow arbitrary expression formatting - something our fork lets us do.

packages/autofmt/src/lib.rs

@@ -0,0 +1,413 @@
+//! pretty printer for rsx!
+use dioxus_rsx::*;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::ToTokens;
+use std::{
+    fmt::{self, Write},
+    ptr::NonNull,
+};
+use syn::{
+    buffer::TokenBuffer,
+    parse::{ParseBuffer, ParseStream},
+};
+use triple_accel::{levenshtein_search, Match};
+
+mod prettyplease;
+
+#[derive(serde::Deserialize, serde::Serialize, Clone, Debug, PartialEq, Hash)]
+pub struct FormattedBlock {
+    pub formatted: String,
+    pub start: usize,
+    pub end: usize,
+}
+
+/*
+
+
+*/
+pub fn get_format_blocks(contents: &str) -> Vec<FormattedBlock> {
+    let mut matches = levenshtein_search(b"rsx! {", contents.as_bytes()).peekable();
+
+    let mut cur_match: Option<Match> = None;
+
+    let mut formatted_blocks = Vec::new();
+
+    let mut last_bracket_end = 0;
+
+    for item in matches {
+        let Match { start, end, k } = item;
+
+        if start < last_bracket_end {
+            continue;
+        }
+
+        let remaining = &contents[end - 1..];
+
+        if let Some(bracket_end) = find_bracket_end(remaining) {
+            let sub_string = &contents[end..bracket_end + end - 1];
+
+            last_bracket_end = bracket_end + end - 1;
+
+            // with the edge brackets
+            // println!("{}", &contents[end - 1..bracket_end + end]);
+
+            if let Some(new) = fmt_block(sub_string) {
+                if !new.is_empty() {
+                    println!("{}", &contents[end + 1..bracket_end + end - 1]);
+                    println!("{}", new);
+
+                    let stripped = &contents[end + 1..bracket_end + end - 1];
+                    if stripped == new {
+                        println!("no changes necessary");
+                    }
+
+                    // if we have code to push, we want the code to end up on the right lines with the right indentation
+
+                    let mut output = String::new();
+                    writeln!(output).unwrap();
+
+                    for line in new.lines() {
+                        writeln!(output, "        {}", line).ok();
+                    }
+
+                    formatted_blocks.push(FormattedBlock {
+                        formatted: output,
+                        start: end,
+                        end: end + bracket_end - 1,
+                    });
+                }
+            } else {
+                panic!("failed to format block: {}", sub_string);
+            }
+        } else {
+            panic!("failed to find end of block: {}", remaining);
+        }
+    }
+
+    formatted_blocks
+}
+
+pub fn fmt_block(block: &str) -> Option<String> {
+    let mut raw_lines = block.split('\n').collect::<Vec<_>>();
+
+    let parsed: CallBody = syn::parse_str(block).ok()?;
+
+    let mut buf = String::new();
+
+    for node in parsed.roots.iter() {
+        write_ident(&mut buf, &raw_lines, node, 0).ok()?;
+    }
+
+    Some(buf)
+}
+
+pub fn write_ident(
+    buf: &mut String,
+    lines: &[&str],
+    node: &BodyNode,
+    indent: usize,
+) -> fmt::Result {
+    match node {
+        BodyNode::Element(el) => {
+            let Element {
+                name,
+                key,
+                attributes,
+                children,
+                _is_static,
+            } = el;
+
+            write_tabs(buf, indent)?;
+            write!(buf, "{name} {{")?;
+
+            let total_attr_len = attributes
+                .iter()
+                .map(|attr| match &attr.attr {
+                    ElementAttr::AttrText { name, value } => value.value().len(),
+                    ElementAttr::AttrExpression { name, value } => 10,
+                    ElementAttr::CustomAttrText { name, value } => value.value().len(),
+                    ElementAttr::CustomAttrExpression { name, value } => 10,
+                    ElementAttr::EventTokens { name, tokens } => 1000000,
+                    ElementAttr::Meta(_) => todo!(),
+                })
+                .sum::<usize>();
+
+            let is_long_attr_list = total_attr_len > 80;
+
+            if let Some(key) = key {
+                let key = key.value();
+                if is_long_attr_list {
+                    write_tabs(buf, indent + 1)?;
+                } else {
+                    write!(buf, " ")?;
+                }
+                write!(buf, "key: \"{key}\"")?;
+
+                if !attributes.is_empty() {
+                    writeln!(buf, ",")?;
+                }
+            }
+
+            let mut attr_iter = attributes.iter().peekable();
+            while let Some(attr) = attr_iter.next() {
+                if is_long_attr_list {
+                    writeln!(buf)?;
+                    write_tabs(buf, indent + 1)?;
+                } else {
+                    write!(buf, " ")?;
+                }
+
+                match &attr.attr {
+                    ElementAttr::AttrText { name, value } => {
+                        write!(buf, "{name}: \"{value}\"", value = value.value())?;
+                    }
+                    ElementAttr::AttrExpression { name, value } => {
+                        let out = prettyplease::unparse_expr(value);
+                        write!(buf, "{}: {}", name, out)?;
+                    }
+
+                    ElementAttr::CustomAttrText { name, value } => {
+                        write!(
+                            buf,
+                            "\"{name}\": \"{value}\"",
+                            name = name.value(),
+                            value = value.value()
+                        )?;
+                    }
+
+                    ElementAttr::CustomAttrExpression { name, value } => {
+                        let out = prettyplease::unparse_expr(value);
+                        write!(buf, "\"{}\": {}", name.value(), out)?;
+                    }
+
+                    ElementAttr::EventTokens { name, tokens } => {
+                        let out = prettyplease::unparse_expr(tokens);
+
+                        dbg!(&out);
+
+                        let mut lines = out.split('\n').peekable();
+                        let first = lines.next().unwrap();
+
+                        // a one-liner for whatever reason
+                        // Does not need a new line
+                        if lines.peek().is_none() {
+                            write!(buf, "{}: {}", name, first)?;
+                        } else {
+                            writeln!(buf, "{}: {}", name, first)?;
+
+                            while let Some(line) = lines.next() {
+                                write_tabs(buf, indent + 1)?;
+                                write!(buf, "{}", line)?;
+                                if lines.peek().is_none() {
+                                    write!(buf, "")?;
+                                } else {
+                                    writeln!(buf)?;
+                                }
+                            }
+                        }
+                    }
+                    ElementAttr::Meta(_) => {}
+                }
+
+                if attr_iter.peek().is_some() || !children.is_empty() {
+                    write!(buf, ",")?;
+                }
+            }
+
+            if children.len() == 1 && children[0].is_litstr() && !is_long_attr_list {
+                if let BodyNode::Text(text) = &children[0] {
+                    let text_val = text.value();
+                    if total_attr_len + text_val.len() > 80 {
+                        writeln!(buf)?;
+                        write_tabs(buf, indent + 1)?;
+                        writeln!(buf, "\"{}\"", text.value())?;
+                        write_tabs(buf, indent)?;
+                    } else {
+                        write!(buf, " \"{}\" ", text.value())?;
+                    }
+                }
+            } else {
+                if is_long_attr_list || !children.is_empty() {
+                    writeln!(buf)?;
+                }
+
+                for child in children {
+                    write_ident(buf, lines, child, indent + 1)?;
+                }
+
+                if is_long_attr_list || !children.is_empty() {
+                    write_tabs(buf, indent)?;
+                } else {
+                    write!(buf, " ")?;
+                }
+            }
+
+            writeln!(buf, "}}")?;
+        }
+        BodyNode::Component(component) => {
+            let Component {
+                name,
+                body,
+                children,
+                manual_props,
+            } = component;
+
+            let mut name = name.to_token_stream().to_string();
+            name.retain(|c| !c.is_whitespace());
+
+            write_tabs(buf, indent)?;
+            write!(buf, "{name} {{")?;
+
+            if !body.is_empty() || !children.is_empty() {
+                writeln!(buf)?;
+            }
+
+            for field in body {
+                write_tabs(buf, indent + 1)?;
+                let name = &field.name;
+                match &field.content {
+                    ContentField::ManExpr(exp) => {
+                        let out = prettyplease::unparse_expr(exp);
+                        writeln!(buf, "{}: {},", name, out)?;
+                    }
+                    ContentField::Formatted(s) => {
+                        writeln!(buf, "{}: \"{}\",", name, s.value())?;
+                    }
+                    ContentField::OnHandlerRaw(exp) => {
+                        let out = prettyplease::unparse_expr(exp);
+                        let mut lines = out.split('\n').peekable();
+                        let first = lines.next().unwrap();
+                        write!(buf, "{}: {}", name, first)?;
+                        for line in lines {
+                            writeln!(buf)?;
+                            write_tabs(buf, indent + 1)?;
+                            write!(buf, "{}", line)?;
+                        }
+                        writeln!(buf, ",")?;
+                    }
+                }
+            }
+
+            if let Some(exp) = manual_props {
+                write_tabs(buf, indent + 1)?;
+                let out = prettyplease::unparse_expr(exp);
+                let mut lines = out.split('\n').peekable();
+                let first = lines.next().unwrap();
+                write!(buf, "..{}", first)?;
+                for line in lines {
+                    writeln!(buf)?;
+                    write_tabs(buf, indent + 1)?;
+                    write!(buf, "{}", line)?;
+                }
+                writeln!(buf)?;
+            }
+
+            for child in children {
+                write_ident(buf, lines, child, indent + 1)?;
+            }
+
+            if !body.is_empty() || !children.is_empty() {
+                write_tabs(buf, indent)?;
+            }
+
+            writeln!(buf, "}}")?;
+
+            //
+            // write!(buf, "{}", " ".repeat(ident))
+        }
+        BodyNode::Text(t) => {
+            //
+            // write!(buf, "{}", " ".repeat(ident))
+            write_tabs(buf, indent)?;
+            writeln!(buf, "\"{}\"", t.value())?;
+        }
+        BodyNode::RawExpr(exp) => {
+            use syn::spanned::Spanned;
+
+            let placement = exp.span();
+
+            let start = placement.start();
+            let end = placement.end();
+
+            let num_spaces_desired = (indent * 4) as isize;
+            let first = lines[start.line - 1];
+            let num_spaces_real = first.chars().take_while(|c| c.is_whitespace()).count() as isize;
+            let offset = num_spaces_real - num_spaces_desired;
+
+            for line_id in start.line - 1..end.line {
+                let line = lines[line_id];
+
+                // trim the leading whitespace
+
+                if offset < 0 {
+                    for _ in 0..-offset {
+                        write!(buf, " ")?;
+                    }
+
+                    writeln!(buf, "{}", line)?;
+                } else {
+                    let offset = offset as usize;
+
+                    let right = &line[offset..];
+                    writeln!(buf, "{}", right)?;
+                }
+            }
+
+            // let toks = exp.to_token_stream();
+
+            // let out = prettyplease::unparse_expr(exp);
+            // let mut lines = out.split('\n').peekable();
+            // for line in lines {
+            //     write_tabs(buf, indent)?;
+            //     writeln!(buf, "{}", line)?;
+            //     // writeln!(buf)?;
+            // }
+            // write_tabs(buf, indent)?;
+            // let first = lines.next().unwrap();
+            // write!(buf, "{}", name, first)?;
+            // writeln!(buf)?;
+
+            //
+            // write!(buf, "{}", " ".repeat(ident))
+        }
+        BodyNode::Meta(att) => {
+            //
+            // if att.path.segments.last().unwrap().ident == "doc" {
+            let val = att.to_string();
+            write_tabs(buf, indent)?;
+            writeln!(buf, "{}", val)?;
+            // }
+            // match att {}
+        }
+    }
+
+    Ok(())
+}
+
+pub fn write_tabs(f: &mut dyn Write, num: usize) -> std::fmt::Result {
+    for _ in 0..num {
+        write!(f, "    ")?
+    }
+    Ok(())
+}
+
+fn find_bracket_end(contents: &str) -> Option<usize> {
+    let mut depth = 0;
+    let mut i = 0;
+
+    for c in contents.chars() {
+        if c == '{' {
+            depth += 1;
+        } else if c == '}' {
+            depth -= 1;
+        }
+
+        if depth == 0 {
+            return Some(i);
+        }
+
+        i += 1;
+    }
+
+    None
+}

packages/autofmt/src/prettyplease/algorithm.rs

@@ -0,0 +1,376 @@
+// Adapted from https://github.com/rust-lang/rust/blob/1.57.0/compiler/rustc_ast_pretty/src/pp.rs.
+// See "Algorithm notes" in the crate-level rustdoc.
+
+use super::ring::RingBuffer;
+use super::{MARGIN, MIN_SPACE};
+use std::borrow::Cow;
+use std::cmp;
+use std::collections::VecDeque;
+use std::iter;
+
+#[derive(Clone, Copy, PartialEq)]
+pub enum Breaks {
+    Consistent,
+    Inconsistent,
+}
+
+#[derive(Clone, Copy, Default)]
+pub struct BreakToken {
+    pub offset: isize,
+    pub blank_space: usize,
+    pub pre_break: Option<char>,
+    pub post_break: Option<char>,
+    pub no_break: Option<char>,
+    pub if_nonempty: bool,
+    pub never_break: bool,
+}
+
+#[derive(Clone, Copy)]
+pub struct BeginToken {
+    pub offset: isize,
+    pub breaks: Breaks,
+}
+
+#[derive(Clone)]
+pub enum Token {
+    String(Cow<'static, str>),
+    Break(BreakToken),
+    Begin(BeginToken),
+    End,
+}
+
+#[derive(Copy, Clone)]
+enum PrintFrame {
+    Fits(Breaks),
+    Broken(usize, Breaks),
+}
+
+pub const SIZE_INFINITY: isize = 0xffff;
+
+pub struct Printer {
+    out: String,
+    // Number of spaces left on line
+    space: isize,
+    // Ring-buffer of tokens and calculated sizes
+    buf: RingBuffer<BufEntry>,
+    // Total size of tokens already printed
+    left_total: isize,
+    // Total size of tokens enqueued, including printed and not yet printed
+    right_total: isize,
+    // Holds the ring-buffer index of the Begin that started the current block,
+    // possibly with the most recent Break after that Begin (if there is any) on
+    // top of it. Values are pushed and popped on the back of the queue using it
+    // like stack, and elsewhere old values are popped from the front of the
+    // queue as they become irrelevant due to the primary ring-buffer advancing.
+    scan_stack: VecDeque<usize>,
+    // Stack of blocks-in-progress being flushed by print
+    print_stack: Vec<PrintFrame>,
+    // Level of indentation of current line
+    indent: usize,
+    // Buffered indentation to avoid writing trailing whitespace
+    pending_indentation: usize,
+}
+
+#[derive(Clone)]
+struct BufEntry {
+    token: Token,
+    size: isize,
+}
+
+impl Printer {
+    pub fn new() -> Self {
+        Printer {
+            out: String::new(),
+            space: MARGIN,
+            buf: RingBuffer::new(),
+            left_total: 0,
+            right_total: 0,
+            scan_stack: VecDeque::new(),
+            print_stack: Vec::new(),
+            indent: 0,
+            pending_indentation: 0,
+        }
+    }
+
+    pub fn eof(mut self) -> String {
+        if !self.scan_stack.is_empty() {
+            self.check_stack(0);
+            self.advance_left();
+        }
+        self.out
+    }
+
+    pub fn scan_begin(&mut self, token: BeginToken) {
+        if self.scan_stack.is_empty() {
+            self.left_total = 1;
+            self.right_total = 1;
+            self.buf.clear();
+        }
+        let right = self.buf.push(BufEntry {
+            token: Token::Begin(token),
+            size: -self.right_total,
+        });
+        self.scan_stack.push_back(right);
+    }
+
+    pub fn scan_end(&mut self) {
+        if self.scan_stack.is_empty() {
+            self.print_end();
+        } else {
+            if !self.buf.is_empty() {
+                if let Token::Break(break_token) = self.buf.last().token {
+                    if self.buf.len() >= 2 {
+                        if let Token::Begin(_) = self.buf.second_last().token {
+                            self.buf.pop_last();
+                            self.buf.pop_last();
+                            self.scan_stack.pop_back();
+                            self.scan_stack.pop_back();
+                            self.right_total -= break_token.blank_space as isize;
+                            return;
+                        }
+                    }
+                    if break_token.if_nonempty {
+                        self.buf.pop_last();
+                        self.scan_stack.pop_back();
+                        self.right_total -= break_token.blank_space as isize;
+                    }
+                }
+            }
+            let right = self.buf.push(BufEntry {
+                token: Token::End,
+                size: -1,
+            });
+            self.scan_stack.push_back(right);
+        }
+    }
+
+    pub fn scan_break(&mut self, token: BreakToken) {
+        if self.scan_stack.is_empty() {
+            self.left_total = 1;
+            self.right_total = 1;
+            self.buf.clear();
+        } else {
+            self.check_stack(0);
+        }
+        let right = self.buf.push(BufEntry {
+            token: Token::Break(token),
+            size: -self.right_total,
+        });
+        self.scan_stack.push_back(right);
+        self.right_total += token.blank_space as isize;
+    }
+
+    pub fn scan_string(&mut self, string: Cow<'static, str>) {
+        if self.scan_stack.is_empty() {
+            self.print_string(string);
+        } else {
+            let len = string.len() as isize;
+            self.buf.push(BufEntry {
+                token: Token::String(string),
+                size: len,
+            });
+            self.right_total += len;
+            self.check_stream();
+        }
+    }
+
+    pub fn offset(&mut self, offset: isize) {
+        match &mut self.buf.last_mut().token {
+            Token::Break(token) => token.offset += offset,
+            Token::Begin(_) => {}
+            Token::String(_) | Token::End => unreachable!(),
+        }
+    }
+
+    pub fn end_with_max_width(&mut self, max: isize) {
+        let mut depth = 1;
+        for &index in self.scan_stack.iter().rev() {
+            let entry = &self.buf[index];
+            match entry.token {
+                Token::Begin(_) => {
+                    depth -= 1;
+                    if depth == 0 {
+                        if entry.size < 0 {
+                            let actual_width = entry.size + self.right_total;
+                            if actual_width > max {
+                                self.buf.push(BufEntry {
+                                    token: Token::String(Cow::Borrowed("")),
+                                    size: SIZE_INFINITY,
+                                });
+                                self.right_total += SIZE_INFINITY;
+                            }
+                        }
+                        break;
+                    }
+                }
+                Token::End => depth += 1,
+                Token::Break(_) => {}
+                Token::String(_) => unreachable!(),
+            }
+        }
+        self.scan_end();
+    }
+
+    fn check_stream(&mut self) {
+        while self.right_total - self.left_total > self.space {
+            if *self.scan_stack.front().unwrap() == self.buf.index_of_first() {
+                self.scan_stack.pop_front().unwrap();
+                self.buf.first_mut().size = SIZE_INFINITY;
+            }
+
+            self.advance_left();
+
+            if self.buf.is_empty() {
+                break;
+            }
+        }
+    }
+
+    fn advance_left(&mut self) {
+        while self.buf.first().size >= 0 {
+            let left = self.buf.pop_first();
+
+            match left.token {
+                Token::String(string) => {
+                    self.left_total += left.size;
+                    self.print_string(string);
+                }
+                Token::Break(token) => {
+                    self.left_total += token.blank_space as isize;
+                    self.print_break(token, left.size);
+                }
+                Token::Begin(token) => self.print_begin(token, left.size),
+                Token::End => self.print_end(),
+            }
+
+            if self.buf.is_empty() {
+                break;
+            }
+        }
+    }
+
+    fn check_stack(&mut self, mut depth: usize) {
+        while let Some(&index) = self.scan_stack.back() {
+            let mut entry = &mut self.buf[index];
+            match entry.token {
+                Token::Begin(_) => {
+                    if depth == 0 {
+                        break;
+                    }
+                    self.scan_stack.pop_back().unwrap();
+                    entry.size += self.right_total;
+                    depth -= 1;
+                }
+                Token::End => {
+                    self.scan_stack.pop_back().unwrap();
+                    entry.size = 1;
+                    depth += 1;
+                }
+                Token::Break(_) => {
+                    self.scan_stack.pop_back().unwrap();
+                    entry.size += self.right_total;
+                    if depth == 0 {
+                        break;
+                    }
+                }
+                Token::String(_) => unreachable!(),
+            }
+        }
+    }
+
+    fn get_top(&self) -> PrintFrame {
+        const OUTER: PrintFrame = PrintFrame::Broken(0, Breaks::Inconsistent);
+        self.print_stack.last().map_or(OUTER, PrintFrame::clone)
+    }
+
+    fn print_begin(&mut self, token: BeginToken, size: isize) {
+        if cfg!(prettyplease_debug) {
+            self.out.push(match token.breaks {
+                Breaks::Consistent => '«',
+                Breaks::Inconsistent => '‹',
+            });
+            if cfg!(prettyplease_debug_indent) {
+                self.out
+                    .extend(token.offset.to_string().chars().map(|ch| match ch {
+                        '0'..='9' => ['₀', '₁', '₂', '₃', '₄', '₅', '₆', '₇', '₈', '₉']
+                            [(ch as u8 - b'0') as usize]
+                            as char,
+                        '-' => '₋',
+                        _ => unreachable!(),
+                    }));
+            }
+        }
+        if size > self.space {
+            self.print_stack
+                .push(PrintFrame::Broken(self.indent, token.breaks));
+            self.indent = usize::try_from(self.indent as isize + token.offset).unwrap();
+        } else {
+            self.print_stack.push(PrintFrame::Fits(token.breaks));
+        }
+    }
+
+    fn print_end(&mut self) {
+        let breaks = match self.print_stack.pop().unwrap() {
+            PrintFrame::Broken(indent, breaks) => {
+                self.indent = indent;
+                breaks
+            }
+            PrintFrame::Fits(breaks) => breaks,
+        };
+        if cfg!(prettyplease_debug) {
+            self.out.push(match breaks {
+                Breaks::Consistent => '»',
+                Breaks::Inconsistent => '›',
+            });
+        }
+    }
+
+    fn print_break(&mut self, token: BreakToken, size: isize) {
+        let fits = token.never_break
+            || match self.get_top() {
+                PrintFrame::Fits(..) => true,
+                PrintFrame::Broken(.., Breaks::Consistent) => false,
+                PrintFrame::Broken(.., Breaks::Inconsistent) => size <= self.space,
+            };
+        if fits {
+            self.pending_indentation += token.blank_space;
+            self.space -= token.blank_space as isize;
+            if let Some(no_break) = token.no_break {
+                self.out.push(no_break);
+                self.space -= no_break.len_utf8() as isize;
+            }
+            if cfg!(prettyplease_debug) {
+                self.out.push('·');
+            }
+        } else {
+            if let Some(pre_break) = token.pre_break {
+                self.out.push(pre_break);
+            }
+            if cfg!(prettyplease_debug) {
+                self.out.push('·');
+            }
+            self.out.push('\n');
+            let indent = self.indent as isize + token.offset;
+            self.pending_indentation = usize::try_from(indent).unwrap();
+            self.space = cmp::max(MARGIN - indent, MIN_SPACE);
+            if let Some(post_break) = token.post_break {
+                self.print_indent();
+                self.out.push(post_break);
+                self.space -= post_break.len_utf8() as isize;
+            }
+        }
+    }
+
+    fn print_string(&mut self, string: Cow<'static, str>) {
+        self.print_indent();
+        self.out.push_str(&string);
+        self.space -= string.len() as isize;
+    }
+
+    fn print_indent(&mut self) {
+        self.out.reserve(self.pending_indentation);
+        self.out
+            .extend(iter::repeat(' ').take(self.pending_indentation));
+        self.pending_indentation = 0;
+    }
+}

packages/autofmt/src/prettyplease/attr.rs

@@ -0,0 +1,208 @@
+use super::algorithm::Printer;
+use super::INDENT;
+use proc_macro2::{Delimiter, TokenStream, TokenTree};
+use syn::{AttrStyle, Attribute, Lit, PathArguments};
+
+impl Printer {
+    pub fn outer_attrs(&mut self, attrs: &[Attribute]) {
+        for attr in attrs {
+            if let AttrStyle::Outer = attr.style {
+                self.attr(attr);
+            }
+        }
+    }
+
+    pub fn inner_attrs(&mut self, attrs: &[Attribute]) {
+        for attr in attrs {
+            if let AttrStyle::Inner(_) = attr.style {
+                self.attr(attr);
+            }
+        }
+    }
+
+    fn attr(&mut self, attr: &Attribute) {
+        if let Some(doc) = value_of_attribute("doc", attr) {
+            if doc.contains('\n') {
+                self.word(match attr.style {
+                    AttrStyle::Outer => "/**",
+                    AttrStyle::Inner(_) => "/*!",
+                });
+                self.word(doc);
+                self.word("*/");
+            } else {
+                self.word(match attr.style {
+                    AttrStyle::Outer => "///",
+                    AttrStyle::Inner(_) => "//!",
+                });
+                self.word(doc);
+            }
+            self.hardbreak();
+        } else if let Some(comment) = value_of_attribute("comment", attr) {
+            if comment.contains('\n') {
+                self.word("/*");
+                self.word(comment);
+                self.word("*/");
+            } else {
+                self.word("//");
+                self.word(comment);
+            }
+            self.hardbreak();
+        } else {
+            self.word(match attr.style {
+                AttrStyle::Outer => "#",
+                AttrStyle::Inner(_) => "#!",
+            });
+            self.word("[");
+            self.path(&attr.path);
+            self.attr_tokens(attr.tokens.clone());
+            self.word("]");
+            self.space();
+        }
+    }
+
+    fn attr_tokens(&mut self, tokens: TokenStream) {
+        let mut stack = Vec::new();
+        stack.push((tokens.into_iter().peekable(), Delimiter::None));
+        let mut space = Self::nbsp as fn(&mut Self);
+
+        #[derive(PartialEq)]
+        enum State {
+            Word,
+            Punct,
+            TrailingComma,
+        }
+
+        use State::*;
+        let mut state = Word;
+
+        while let Some((tokens, delimiter)) = stack.last_mut() {
+            match tokens.next() {
+                Some(TokenTree::Ident(ident)) => {
+                    if let Word = state {
+                        space(self);
+                    }
+                    self.ident(&ident);
+                    state = Word;
+                }
+                Some(TokenTree::Punct(punct)) => {
+                    let ch = punct.as_char();
+                    if let (Word, '=') = (state, ch) {
+                        self.nbsp();
+                    }
+                    if ch == ',' && tokens.peek().is_none() {
+                        self.trailing_comma(true);
+                        state = TrailingComma;
+                    } else {
+                        self.token_punct(ch);
+                        if ch == '=' {
+                            self.nbsp();
+                        } else if ch == ',' {
+                            space(self);
+                        }
+                        state = Punct;
+                    }
+                }
+                Some(TokenTree::Literal(literal)) => {
+                    if let Word = state {
+                        space(self);
+                    }
+                    self.token_literal(&literal);
+                    state = Word;
+                }
+                Some(TokenTree::Group(group)) => {
+                    let delimiter = group.delimiter();
+                    let stream = group.stream();
+                    match delimiter {
+                        Delimiter::Parenthesis => {
+                            self.word("(");
+                            self.cbox(INDENT);
+                            self.zerobreak();
+                            state = Punct;
+                        }
+                        Delimiter::Brace => {
+                            self.word("{");
+                            state = Punct;
+                        }
+                        Delimiter::Bracket => {
+                            self.word("[");
+                            state = Punct;
+                        }
+                        Delimiter::None => {}
+                    }
+                    stack.push((stream.into_iter().peekable(), delimiter));
+                    space = Self::space;
+                }
+                None => {
+                    match delimiter {
+                        Delimiter::Parenthesis => {
+                            if state != TrailingComma {
+                                self.zerobreak();
+                            }
+                            self.offset(-INDENT);
+                            self.end();
+                            self.word(")");
+                            state = Punct;
+                        }
+                        Delimiter::Brace => {
+                            self.word("}");
+                            state = Punct;
+                        }
+                        Delimiter::Bracket => {
+                            self.word("]");
+                            state = Punct;
+                        }
+                        Delimiter::None => {}
+                    }
+                    stack.pop();
+                    if stack.is_empty() {
+                        space = Self::nbsp;
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn value_of_attribute(requested: &str, attr: &Attribute) -> Option<String> {
+    let is_doc = attr.path.leading_colon.is_none()
+        && attr.path.segments.len() == 1
+        && matches!(attr.path.segments[0].arguments, PathArguments::None)
+        && attr.path.segments[0].ident == requested;
+    if !is_doc {
+        return None;
+    }
+    let mut tokens = attr.tokens.clone().into_iter();
+    match tokens.next() {
+        Some(TokenTree::Punct(punct)) if punct.as_char() == '=' => {}
+        _ => return None,
+    }
+    let literal = match tokens.next() {
+        Some(TokenTree::Literal(literal)) => literal,
+        _ => return None,
+    };
+    if tokens.next().is_some() {
+        return None;
+    }
+    match Lit::new(literal) {
+        Lit::Str(string) => Some(string.value()),
+        _ => None,
+    }
+}
+
+pub fn has_outer(attrs: &[Attribute]) -> bool {
+    for attr in attrs {
+        if let AttrStyle::Outer = attr.style {
+            return true;
+        }
+    }
+    false
+}
+
+pub fn has_inner(attrs: &[Attribute]) -> bool {
+    for attr in attrs {
+        if let AttrStyle::Inner(_) = attr.style {
+            return true;
+        }
+    }
+    false
+}

packages/autofmt/src/prettyplease/convenience.rs

@@ -0,0 +1,98 @@
+use super::algorithm::{self, BeginToken, BreakToken, Breaks, Printer};
+use std::borrow::Cow;
+
+impl Printer {
+    pub fn ibox(&mut self, indent: isize) {
+        self.scan_begin(BeginToken {
+            offset: indent,
+            breaks: Breaks::Inconsistent,
+        });
+    }
+
+    pub fn cbox(&mut self, indent: isize) {
+        self.scan_begin(BeginToken {
+            offset: indent,
+            breaks: Breaks::Consistent,
+        });
+    }
+
+    pub fn end(&mut self) {
+        self.scan_end();
+    }
+
+    pub fn word<S: Into<Cow<'static, str>>>(&mut self, wrd: S) {
+        let s = wrd.into();
+        self.scan_string(s);
+    }
+
+    fn spaces(&mut self, n: usize) {
+        self.scan_break(BreakToken {
+            blank_space: n,
+            ..BreakToken::default()
+        });
+    }
+
+    pub fn zerobreak(&mut self) {
+        self.spaces(0);
+    }
+
+    pub fn space(&mut self) {
+        self.spaces(1);
+    }
+
+    pub fn nbsp(&mut self) {
+        self.word(" ");
+    }
+
+    pub fn hardbreak(&mut self) {
+        self.spaces(algorithm::SIZE_INFINITY as usize);
+    }
+
+    pub fn space_if_nonempty(&mut self) {
+        self.scan_break(BreakToken {
+            blank_space: 1,
+            if_nonempty: true,
+            ..BreakToken::default()
+        });
+    }
+
+    pub fn hardbreak_if_nonempty(&mut self) {
+        self.scan_break(BreakToken {
+            blank_space: algorithm::SIZE_INFINITY as usize,
+            if_nonempty: true,
+            ..BreakToken::default()
+        });
+    }
+
+    pub fn trailing_comma(&mut self, is_last: bool) {
+        if is_last {
+            self.scan_break(BreakToken {
+                pre_break: Some(','),
+                ..BreakToken::default()
+            });
+        } else {
+            self.word(",");
+            self.space();
+        }
+    }
+
+    pub fn trailing_comma_or_space(&mut self, is_last: bool) {
+        if is_last {
+            self.scan_break(BreakToken {
+                blank_space: 1,
+                pre_break: Some(','),
+                ..BreakToken::default()
+            });
+        } else {
+            self.word(",");
+            self.space();
+        }
+    }
+
+    pub fn neverbreak(&mut self) {
+        self.scan_break(BreakToken {
+            never_break: true,
+            ..BreakToken::default()
+        });
+    }
+}

packages/autofmt/src/prettyplease/data.rs

@@ -0,0 +1,95 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use syn::{
+    Field, Fields, FieldsUnnamed, PathArguments, Variant, VisCrate, VisPublic, VisRestricted,
+    Visibility,
+};
+
+impl Printer {
+    pub fn variant(&mut self, variant: &Variant) {
+        self.outer_attrs(&variant.attrs);
+        self.ident(&variant.ident);
+        match &variant.fields {
+            Fields::Named(fields) => {
+                self.nbsp();
+                self.word("{");
+                self.cbox(INDENT);
+                self.space();
+                for field in fields.named.iter().delimited() {
+                    self.field(&field);
+                    self.trailing_comma_or_space(field.is_last);
+                }
+                self.offset(-INDENT);
+                self.end();
+                self.word("}");
+            }
+            Fields::Unnamed(fields) => {
+                self.cbox(INDENT);
+                self.fields_unnamed(fields);
+                self.end();
+            }
+            Fields::Unit => {}
+        }
+        if let Some((_eq_token, discriminant)) = &variant.discriminant {
+            self.word(" = ");
+            self.expr(discriminant);
+        }
+    }
+
+    pub fn fields_unnamed(&mut self, fields: &FieldsUnnamed) {
+        self.word("(");
+        self.zerobreak();
+        for field in fields.unnamed.iter().delimited() {
+            self.field(&field);
+            self.trailing_comma(field.is_last);
+        }
+        self.offset(-INDENT);
+        self.word(")");
+    }
+
+    pub fn field(&mut self, field: &Field) {
+        self.outer_attrs(&field.attrs);
+        self.visibility(&field.vis);
+        if let Some(ident) = &field.ident {
+            self.ident(ident);
+            self.word(": ");
+        }
+        self.ty(&field.ty);
+    }
+
+    pub fn visibility(&mut self, vis: &Visibility) {
+        match vis {
+            Visibility::Public(vis) => self.vis_public(vis),
+            Visibility::Crate(vis) => self.vis_crate(vis),
+            Visibility::Restricted(vis) => self.vis_restricted(vis),
+            Visibility::Inherited => {}
+        }
+    }
+
+    fn vis_public(&mut self, vis: &VisPublic) {
+        let _ = vis;
+        self.word("pub ");
+    }
+
+    fn vis_crate(&mut self, vis: &VisCrate) {
+        let _ = vis;
+        self.word("crate ");
+    }
+
+    fn vis_restricted(&mut self, vis: &VisRestricted) {
+        self.word("pub(");
+        let omit_in = vis.path.leading_colon.is_none()
+            && vis.path.segments.len() == 1
+            && matches!(vis.path.segments[0].arguments, PathArguments::None)
+            && matches!(
+                vis.path.segments[0].ident.to_string().as_str(),
+                "self" | "super" | "crate",
+            );
+        if !omit_in {
+            self.word("in ");
+        }
+        self.path(&vis.path);
+        self.word(") ");
+    }
+}

packages/autofmt/src/prettyplease/file.rs

@@ -0,0 +1,17 @@
+use super::algorithm::Printer;
+use syn::File;
+
+impl Printer {
+    pub fn file(&mut self, file: &File) {
+        self.cbox(0);
+        if let Some(shebang) = &file.shebang {
+            self.word(shebang.clone());
+            self.hardbreak();
+        }
+        self.inner_attrs(&file.attrs);
+        for item in &file.items {
+            self.item(item);
+        }
+        self.end();
+    }
+}

packages/autofmt/src/prettyplease/generics.rs

@@ -0,0 +1,280 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use syn::{
+    BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeDef, PredicateEq,
+    PredicateLifetime, PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound,
+    WhereClause, WherePredicate,
+};
+
+impl Printer {
+    pub fn generics(&mut self, generics: &Generics) {
+        if generics.params.is_empty() {
+            return;
+        }
+
+        self.word("<");
+        self.cbox(0);
+        self.zerobreak();
+
+        // Print lifetimes before types and consts, regardless of their
+        // order in self.params.
+        //
+        // TODO: ordering rules for const parameters vs type parameters have
+        // not been settled yet. https://github.com/rust-lang/rust/issues/44580
+        for param in generics.params.iter().delimited() {
+            if let GenericParam::Lifetime(_) = *param {
+                self.generic_param(&param);
+                self.trailing_comma(param.is_last);
+            }
+        }
+        for param in generics.params.iter().delimited() {
+            match *param {
+                GenericParam::Type(_) | GenericParam::Const(_) => {
+                    self.generic_param(&param);
+                    self.trailing_comma(param.is_last);
+                }
+                GenericParam::Lifetime(_) => {}
+            }
+        }
+
+        self.offset(-INDENT);
+        self.end();
+        self.word(">");
+    }
+
+    fn generic_param(&mut self, generic_param: &GenericParam) {
+        match generic_param {
+            GenericParam::Type(type_param) => self.type_param(type_param),
+            GenericParam::Lifetime(lifetime_def) => self.lifetime_def(lifetime_def),
+            GenericParam::Const(const_param) => self.const_param(const_param),
+        }
+    }
+
+    pub fn bound_lifetimes(&mut self, bound_lifetimes: &BoundLifetimes) {
+        self.word("for<");
+        for lifetime_def in bound_lifetimes.lifetimes.iter().delimited() {
+            self.lifetime_def(&lifetime_def);
+            if !lifetime_def.is_last {
+                self.word(", ");
+            }
+        }
+        self.word("> ");
+    }
+
+    fn lifetime_def(&mut self, lifetime_def: &LifetimeDef) {
+        self.outer_attrs(&lifetime_def.attrs);
+        self.lifetime(&lifetime_def.lifetime);
+        for lifetime in lifetime_def.bounds.iter().delimited() {
+            if lifetime.is_first {
+                self.word(": ");
+            } else {
+                self.word(" + ");
+            }
+            self.lifetime(&lifetime);
+        }
+    }
+
+    fn type_param(&mut self, type_param: &TypeParam) {
+        self.outer_attrs(&type_param.attrs);
+        self.ident(&type_param.ident);
+        self.ibox(INDENT);
+        for type_param_bound in type_param.bounds.iter().delimited() {
+            if type_param_bound.is_first {
+                self.word(": ");
+            } else {
+                self.space();
+                self.word("+ ");
+            }
+            self.type_param_bound(&type_param_bound);
+        }
+        if let Some(default) = &type_param.default {
+            self.space();
+            self.word("= ");
+            self.ty(default);
+        }
+        self.end();
+    }
+
+    pub fn type_param_bound(&mut self, type_param_bound: &TypeParamBound) {
+        match type_param_bound {
+            TypeParamBound::Trait(trait_bound) => self.trait_bound(trait_bound),
+            TypeParamBound::Lifetime(lifetime) => self.lifetime(lifetime),
+        }
+    }
+
+    fn trait_bound(&mut self, trait_bound: &TraitBound) {
+        if trait_bound.paren_token.is_some() {
+            self.word("(");
+        }
+        let skip = match trait_bound.path.segments.first() {
+            Some(segment) if segment.ident == "const" => {
+                self.word("~const ");
+                1
+            }
+            _ => 0,
+        };
+        self.trait_bound_modifier(&trait_bound.modifier);
+        if let Some(bound_lifetimes) = &trait_bound.lifetimes {
+            self.bound_lifetimes(bound_lifetimes);
+        }
+        for segment in trait_bound.path.segments.iter().skip(skip).delimited() {
+            if !segment.is_first || trait_bound.path.leading_colon.is_some() {
+                self.word("::");
+            }
+            self.path_segment(&segment);
+        }
+        if trait_bound.paren_token.is_some() {
+            self.word(")");
+        }
+    }
+
+    fn trait_bound_modifier(&mut self, trait_bound_modifier: &TraitBoundModifier) {
+        match trait_bound_modifier {
+            TraitBoundModifier::None => {}
+            TraitBoundModifier::Maybe(_question_mark) => self.word("?"),
+        }
+    }
+
+    fn const_param(&mut self, const_param: &ConstParam) {
+        self.outer_attrs(&const_param.attrs);
+        self.word("const ");
+        self.ident(&const_param.ident);
+        self.word(": ");
+        self.ty(&const_param.ty);
+        if let Some(default) = &const_param.default {
+            self.word(" = ");
+            self.expr(default);
+        }
+    }
+
+    pub fn where_clause_for_body(&mut self, where_clause: &Option<WhereClause>) {
+        let hardbreaks = true;
+        let semi = false;
+        self.where_clause_impl(where_clause, hardbreaks, semi);
+    }
+
+    pub fn where_clause_semi(&mut self, where_clause: &Option<WhereClause>) {
+        let hardbreaks = true;
+        let semi = true;
+        self.where_clause_impl(where_clause, hardbreaks, semi);
+    }
+
+    pub fn where_clause_oneline(&mut self, where_clause: &Option<WhereClause>) {
+        let hardbreaks = false;
+        let semi = false;
+        self.where_clause_impl(where_clause, hardbreaks, semi);
+    }
+
+    pub fn where_clause_oneline_semi(&mut self, where_clause: &Option<WhereClause>) {
+        let hardbreaks = false;
+        let semi = true;
+        self.where_clause_impl(where_clause, hardbreaks, semi);
+    }
+
+    fn where_clause_impl(
+        &mut self,
+        where_clause: &Option<WhereClause>,
+        hardbreaks: bool,
+        semi: bool,
+    ) {
+        let where_clause = match where_clause {
+            Some(where_clause) if !where_clause.predicates.is_empty() => where_clause,
+            _ => {
+                if semi {
+                    self.word(";");
+                } else {
+                    self.nbsp();
+                }
+                return;
+            }
+        };
+        if hardbreaks {
+            self.hardbreak();
+            self.offset(-INDENT);
+            self.word("where");
+            self.hardbreak();
+            for predicate in where_clause.predicates.iter().delimited() {
+                self.where_predicate(&predicate);
+                if predicate.is_last && semi {
+                    self.word(";");
+                } else {
+                    self.word(",");
+                    self.hardbreak();
+                }
+            }
+            if !semi {
+                self.offset(-INDENT);
+            }
+        } else {
+            self.space();
+            self.offset(-INDENT);
+            self.word("where");
+            self.space();
+            for predicate in where_clause.predicates.iter().delimited() {
+                self.where_predicate(&predicate);
+                if predicate.is_last && semi {
+                    self.word(";");
+                } else {
+                    self.trailing_comma_or_space(predicate.is_last);
+                }
+            }
+            if !semi {
+                self.offset(-INDENT);
+            }
+        }
+    }
+
+    fn where_predicate(&mut self, predicate: &WherePredicate) {
+        match predicate {
+            WherePredicate::Type(predicate) => self.predicate_type(predicate),
+            WherePredicate::Lifetime(predicate) => self.predicate_lifetime(predicate),
+            WherePredicate::Eq(predicate) => self.predicate_eq(predicate),
+        }
+    }
+
+    fn predicate_type(&mut self, predicate: &PredicateType) {
+        if let Some(bound_lifetimes) = &predicate.lifetimes {
+            self.bound_lifetimes(bound_lifetimes);
+        }
+        self.ty(&predicate.bounded_ty);
+        self.word(":");
+        if predicate.bounds.len() == 1 {
+            self.ibox(0);
+        } else {
+            self.ibox(INDENT);
+        }
+        for type_param_bound in predicate.bounds.iter().delimited() {
+            if type_param_bound.is_first {
+                self.nbsp();
+            } else {
+                self.space();
+                self.word("+ ");
+            }
+            self.type_param_bound(&type_param_bound);
+        }
+        self.end();
+    }
+
+    fn predicate_lifetime(&mut self, predicate: &PredicateLifetime) {
+        self.lifetime(&predicate.lifetime);
+        self.word(":");
+        self.ibox(INDENT);
+        for lifetime in predicate.bounds.iter().delimited() {
+            if lifetime.is_first {
+                self.nbsp();
+            } else {
+                self.space();
+                self.word("+ ");
+            }
+            self.lifetime(&lifetime);
+        }
+        self.end();
+    }
+
+    fn predicate_eq(&mut self, predicate: &PredicateEq) {
+        self.ty(&predicate.lhs_ty);
+        self.word(" = ");
+        self.ty(&predicate.rhs_ty);
+    }
+}

packages/autofmt/src/prettyplease/item.rs

@@ -0,0 +1,757 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use proc_macro2::TokenStream;
+use syn::{
+    Fields, FnArg, ForeignItem, ForeignItemFn, ForeignItemMacro, ForeignItemStatic,
+    ForeignItemType, ImplItem, ImplItemConst, ImplItemMacro, ImplItemMethod, ImplItemType, Item,
+    ItemConst, ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMacro2,
+    ItemMod, ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, ItemType, ItemUnion, ItemUse, Pat,
+    Receiver, Signature, Stmt, TraitItem, TraitItemConst, TraitItemMacro, TraitItemMethod,
+    TraitItemType, Type, UseGlob, UseGroup, UseName, UsePath, UseRename, UseTree,
+};
+
+impl Printer {
+    pub fn item(&mut self, item: &Item) {
+        match item {
+            Item::Const(item) => self.item_const(item),
+            Item::Enum(item) => self.item_enum(item),
+            Item::ExternCrate(item) => self.item_extern_crate(item),
+            Item::Fn(item) => self.item_fn(item),
+            Item::ForeignMod(item) => self.item_foreign_mod(item),
+            Item::Impl(item) => self.item_impl(item),
+            Item::Macro(item) => self.item_macro(item),
+            Item::Macro2(item) => self.item_macro2(item),
+            Item::Mod(item) => self.item_mod(item),
+            Item::Static(item) => self.item_static(item),
+            Item::Struct(item) => self.item_struct(item),
+            Item::Trait(item) => self.item_trait(item),
+            Item::TraitAlias(item) => self.item_trait_alias(item),
+            Item::Type(item) => self.item_type(item),
+            Item::Union(item) => self.item_union(item),
+            Item::Use(item) => self.item_use(item),
+            Item::Verbatim(item) => self.item_verbatim(item),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown Item"),
+        }
+    }
+
+    fn item_const(&mut self, item: &ItemConst) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(0);
+        self.visibility(&item.vis);
+        self.word("const ");
+        self.ident(&item.ident);
+        self.word(": ");
+        self.ty(&item.ty);
+        self.word(" = ");
+        self.neverbreak();
+        self.expr(&item.expr);
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn item_enum(&mut self, item: &ItemEnum) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("enum ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        self.where_clause_for_body(&item.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        for variant in &item.variants {
+            self.variant(variant);
+            self.word(",");
+            self.hardbreak();
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_extern_crate(&mut self, item: &ItemExternCrate) {
+        self.outer_attrs(&item.attrs);
+        self.visibility(&item.vis);
+        self.word("extern crate ");
+        self.ident(&item.ident);
+        if let Some((_as_token, rename)) = &item.rename {
+            self.word(" as ");
+            self.ident(rename);
+        }
+        self.word(";");
+        self.hardbreak();
+    }
+
+    fn item_fn(&mut self, item: &ItemFn) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.signature(&item.sig);
+        self.where_clause_for_body(&item.sig.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        self.inner_attrs(&item.attrs);
+        for stmt in &item.block.stmts {
+            self.stmt(stmt);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_foreign_mod(&mut self, item: &ItemForeignMod) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.abi(&item.abi);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        self.inner_attrs(&item.attrs);
+        for foreign_item in &item.items {
+            self.foreign_item(foreign_item);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_impl(&mut self, item: &ItemImpl) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.ibox(-INDENT);
+        self.cbox(INDENT);
+        if item.defaultness.is_some() {
+            self.word("default ");
+        }
+        if item.unsafety.is_some() {
+            self.word("unsafe ");
+        }
+        self.word("impl");
+        self.generics(&item.generics);
+        self.end();
+        self.nbsp();
+        if let Some((negative_polarity, path, _for_token)) = &item.trait_ {
+            if negative_polarity.is_some() {
+                self.word("!");
+            }
+            self.path(path);
+            self.space();
+            self.word("for ");
+        }
+        self.ty(&item.self_ty);
+        self.end();
+        self.where_clause_for_body(&item.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        self.inner_attrs(&item.attrs);
+        for impl_item in &item.items {
+            self.impl_item(impl_item);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_macro(&mut self, item: &ItemMacro) {
+        self.outer_attrs(&item.attrs);
+        self.mac(&item.mac, item.ident.as_ref());
+        self.mac_semi_if_needed(&item.mac.delimiter);
+        self.hardbreak();
+    }
+
+    fn item_macro2(&mut self, item: &ItemMacro2) {
+        unimplemented!("Item::Macro2 `macro {} {}`", item.ident, item.rules);
+    }
+
+    fn item_mod(&mut self, item: &ItemMod) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("mod ");
+        self.ident(&item.ident);
+        if let Some((_brace, items)) = &item.content {
+            self.word(" {");
+            self.hardbreak_if_nonempty();
+            self.inner_attrs(&item.attrs);
+            for item in items {
+                self.item(item);
+            }
+            self.offset(-INDENT);
+            self.end();
+            self.word("}");
+        } else {
+            self.word(";");
+            self.end();
+        }
+        self.hardbreak();
+    }
+
+    fn item_static(&mut self, item: &ItemStatic) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(0);
+        self.visibility(&item.vis);
+        self.word("static ");
+        if item.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.ident(&item.ident);
+        self.word(": ");
+        self.ty(&item.ty);
+        self.word(" = ");
+        self.neverbreak();
+        self.expr(&item.expr);
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn item_struct(&mut self, item: &ItemStruct) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("struct ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        match &item.fields {
+            Fields::Named(fields) => {
+                self.where_clause_for_body(&item.generics.where_clause);
+                self.word("{");
+                self.hardbreak_if_nonempty();
+                for field in &fields.named {
+                    self.field(field);
+                    self.word(",");
+                    self.hardbreak();
+                }
+                self.offset(-INDENT);
+                self.end();
+                self.word("}");
+            }
+            Fields::Unnamed(fields) => {
+                self.fields_unnamed(fields);
+                self.where_clause_semi(&item.generics.where_clause);
+                self.end();
+            }
+            Fields::Unit => {
+                self.where_clause_semi(&item.generics.where_clause);
+                self.end();
+            }
+        }
+        self.hardbreak();
+    }
+
+    fn item_trait(&mut self, item: &ItemTrait) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        if item.unsafety.is_some() {
+            self.word("unsafe ");
+        }
+        if item.auto_token.is_some() {
+            self.word("auto ");
+        }
+        self.word("trait ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        for supertrait in item.supertraits.iter().delimited() {
+            if supertrait.is_first {
+                self.word(": ");
+            } else {
+                self.word(" + ");
+            }
+            self.type_param_bound(&supertrait);
+        }
+        self.where_clause_for_body(&item.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        self.inner_attrs(&item.attrs);
+        for trait_item in &item.items {
+            self.trait_item(trait_item);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_trait_alias(&mut self, item: &ItemTraitAlias) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("trait ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        self.word(" = ");
+        self.neverbreak();
+        for bound in item.bounds.iter().delimited() {
+            if !bound.is_first {
+                self.space();
+                self.word("+ ");
+            }
+            self.type_param_bound(&bound);
+        }
+        self.where_clause_semi(&item.generics.where_clause);
+        self.end();
+        self.hardbreak();
+    }
+
+    fn item_type(&mut self, item: &ItemType) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("type ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        self.where_clause_oneline(&item.generics.where_clause);
+        self.word("= ");
+        self.neverbreak();
+        self.ibox(-INDENT);
+        self.ty(&item.ty);
+        self.end();
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn item_union(&mut self, item: &ItemUnion) {
+        self.outer_attrs(&item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&item.vis);
+        self.word("union ");
+        self.ident(&item.ident);
+        self.generics(&item.generics);
+        self.where_clause_for_body(&item.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        for field in &item.fields.named {
+            self.field(field);
+            self.word(",");
+            self.hardbreak();
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn item_use(&mut self, item: &ItemUse) {
+        self.outer_attrs(&item.attrs);
+        self.visibility(&item.vis);
+        self.word("use ");
+        if item.leading_colon.is_some() {
+            self.word("::");
+        }
+        self.use_tree(&item.tree);
+        self.word(";");
+        self.hardbreak();
+    }
+
+    fn item_verbatim(&mut self, item: &TokenStream) {
+        if !item.is_empty() {
+            unimplemented!("Item::Verbatim `{}`", item);
+        }
+        self.hardbreak();
+    }
+
+    fn use_tree(&mut self, use_tree: &UseTree) {
+        match use_tree {
+            UseTree::Path(use_path) => self.use_path(use_path),
+            UseTree::Name(use_name) => self.use_name(use_name),
+            UseTree::Rename(use_rename) => self.use_rename(use_rename),
+            UseTree::Glob(use_glob) => self.use_glob(use_glob),
+            UseTree::Group(use_group) => self.use_group(use_group),
+        }
+    }
+
+    fn use_path(&mut self, use_path: &UsePath) {
+        self.ident(&use_path.ident);
+        self.word("::");
+        self.use_tree(&use_path.tree);
+    }
+
+    fn use_name(&mut self, use_name: &UseName) {
+        self.ident(&use_name.ident);
+    }
+
+    fn use_rename(&mut self, use_rename: &UseRename) {
+        self.ident(&use_rename.ident);
+        self.word(" as ");
+        self.ident(&use_rename.rename);
+    }
+
+    fn use_glob(&mut self, use_glob: &UseGlob) {
+        let _ = use_glob;
+        self.word("*");
+    }
+
+    fn use_group(&mut self, use_group: &UseGroup) {
+        if use_group.items.is_empty() {
+            self.word("{}");
+        } else if use_group.items.len() == 1 {
+            self.use_tree(&use_group.items[0]);
+        } else {
+            self.cbox(INDENT);
+            self.word("{");
+            self.zerobreak();
+            self.ibox(0);
+            for use_tree in use_group.items.iter().delimited() {
+                self.use_tree(&use_tree);
+                if !use_tree.is_last {
+                    self.word(",");
+                    let mut use_tree = *use_tree;
+                    while let UseTree::Path(use_path) = use_tree {
+                        use_tree = &use_path.tree;
+                    }
+                    if let UseTree::Group(_) = use_tree {
+                        self.hardbreak();
+                    } else {
+                        self.space();
+                    }
+                }
+            }
+            self.end();
+            self.trailing_comma(true);
+            self.offset(-INDENT);
+            self.word("}");
+            self.end();
+        }
+    }
+
+    fn foreign_item(&mut self, foreign_item: &ForeignItem) {
+        match foreign_item {
+            ForeignItem::Fn(item) => self.foreign_item_fn(item),
+            ForeignItem::Static(item) => self.foreign_item_static(item),
+            ForeignItem::Type(item) => self.foreign_item_type(item),
+            ForeignItem::Macro(item) => self.foreign_item_macro(item),
+            ForeignItem::Verbatim(item) => self.foreign_item_verbatim(item),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown ForeignItem"),
+        }
+    }
+
+    fn foreign_item_fn(&mut self, foreign_item: &ForeignItemFn) {
+        self.outer_attrs(&foreign_item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&foreign_item.vis);
+        self.signature(&foreign_item.sig);
+        self.where_clause_semi(&foreign_item.sig.generics.where_clause);
+        self.end();
+        self.hardbreak();
+    }
+
+    fn foreign_item_static(&mut self, foreign_item: &ForeignItemStatic) {
+        self.outer_attrs(&foreign_item.attrs);
+        self.cbox(0);
+        self.visibility(&foreign_item.vis);
+        self.word("static ");
+        if foreign_item.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.ident(&foreign_item.ident);
+        self.word(": ");
+        self.ty(&foreign_item.ty);
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn foreign_item_type(&mut self, foreign_item: &ForeignItemType) {
+        self.outer_attrs(&foreign_item.attrs);
+        self.cbox(0);
+        self.visibility(&foreign_item.vis);
+        self.word("type ");
+        self.ident(&foreign_item.ident);
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn foreign_item_macro(&mut self, foreign_item: &ForeignItemMacro) {
+        self.outer_attrs(&foreign_item.attrs);
+        self.mac(&foreign_item.mac, None);
+        self.mac_semi_if_needed(&foreign_item.mac.delimiter);
+        self.hardbreak();
+    }
+
+    fn foreign_item_verbatim(&mut self, foreign_item: &TokenStream) {
+        if !foreign_item.is_empty() {
+            unimplemented!("ForeignItem::Verbatim `{}`", foreign_item);
+        }
+        self.hardbreak();
+    }
+
+    fn trait_item(&mut self, trait_item: &TraitItem) {
+        match trait_item {
+            TraitItem::Const(item) => self.trait_item_const(item),
+            TraitItem::Method(item) => self.trait_item_method(item),
+            TraitItem::Type(item) => self.trait_item_type(item),
+            TraitItem::Macro(item) => self.trait_item_macro(item),
+            TraitItem::Verbatim(item) => self.trait_item_verbatim(item),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown TraitItem"),
+        }
+    }
+
+    fn trait_item_const(&mut self, trait_item: &TraitItemConst) {
+        self.outer_attrs(&trait_item.attrs);
+        self.cbox(0);
+        self.word("const ");
+        self.ident(&trait_item.ident);
+        self.word(": ");
+        self.ty(&trait_item.ty);
+        if let Some((_eq_token, default)) = &trait_item.default {
+            self.word(" = ");
+            self.neverbreak();
+            self.expr(default);
+        }
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn trait_item_method(&mut self, trait_item: &TraitItemMethod) {
+        self.outer_attrs(&trait_item.attrs);
+        self.cbox(INDENT);
+        self.signature(&trait_item.sig);
+        if let Some(block) = &trait_item.default {
+            self.where_clause_for_body(&trait_item.sig.generics.where_clause);
+            self.word("{");
+            self.hardbreak_if_nonempty();
+            self.inner_attrs(&trait_item.attrs);
+            for stmt in &block.stmts {
+                self.stmt(stmt);
+            }
+            self.offset(-INDENT);
+            self.end();
+            self.word("}");
+        } else {
+            self.where_clause_semi(&trait_item.sig.generics.where_clause);
+            self.end();
+        }
+        self.hardbreak();
+    }
+
+    fn trait_item_type(&mut self, trait_item: &TraitItemType) {
+        self.outer_attrs(&trait_item.attrs);
+        self.cbox(INDENT);
+        self.word("type ");
+        self.ident(&trait_item.ident);
+        self.generics(&trait_item.generics);
+        for bound in trait_item.bounds.iter().delimited() {
+            if bound.is_first {
+                self.word(": ");
+            } else {
+                self.space();
+                self.word("+ ");
+            }
+            self.type_param_bound(&bound);
+        }
+        if let Some((_eq_token, default)) = &trait_item.default {
+            self.where_clause_oneline(&trait_item.generics.where_clause);
+            self.word("= ");
+            self.neverbreak();
+            self.ty(default);
+        } else {
+            self.where_clause_oneline_semi(&trait_item.generics.where_clause);
+        }
+        self.end();
+        self.hardbreak();
+    }
+
+    fn trait_item_macro(&mut self, trait_item: &TraitItemMacro) {
+        self.outer_attrs(&trait_item.attrs);
+        self.mac(&trait_item.mac, None);
+        self.mac_semi_if_needed(&trait_item.mac.delimiter);
+        self.hardbreak();
+    }
+
+    fn trait_item_verbatim(&mut self, trait_item: &TokenStream) {
+        if !trait_item.is_empty() {
+            unimplemented!("TraitItem::Verbatim `{}`", trait_item);
+        }
+        self.hardbreak();
+    }
+
+    fn impl_item(&mut self, impl_item: &ImplItem) {
+        match impl_item {
+            ImplItem::Const(item) => self.impl_item_const(item),
+            ImplItem::Method(item) => self.impl_item_method(item),
+            ImplItem::Type(item) => self.impl_item_type(item),
+            ImplItem::Macro(item) => self.impl_item_macro(item),
+            ImplItem::Verbatim(item) => self.impl_item_verbatim(item),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown ImplItem"),
+        }
+    }
+
+    fn impl_item_const(&mut self, impl_item: &ImplItemConst) {
+        self.outer_attrs(&impl_item.attrs);
+        self.cbox(0);
+        self.visibility(&impl_item.vis);
+        if impl_item.defaultness.is_some() {
+            self.word("default ");
+        }
+        self.word("const ");
+        self.ident(&impl_item.ident);
+        self.word(": ");
+        self.ty(&impl_item.ty);
+        self.word(" = ");
+        self.neverbreak();
+        self.expr(&impl_item.expr);
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn impl_item_method(&mut self, impl_item: &ImplItemMethod) {
+        self.outer_attrs(&impl_item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&impl_item.vis);
+        if impl_item.defaultness.is_some() {
+            self.word("default ");
+        }
+        self.signature(&impl_item.sig);
+        if impl_item.block.stmts.len() == 1 {
+            if let Stmt::Item(Item::Verbatim(verbatim)) = &impl_item.block.stmts[0] {
+                if verbatim.to_string() == ";" {
+                    self.where_clause_semi(&impl_item.sig.generics.where_clause);
+                    self.end();
+                    self.hardbreak();
+                    return;
+                }
+            }
+        }
+        self.where_clause_for_body(&impl_item.sig.generics.where_clause);
+        self.word("{");
+        self.hardbreak_if_nonempty();
+        self.inner_attrs(&impl_item.attrs);
+        for stmt in &impl_item.block.stmts {
+            self.stmt(stmt);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+        self.hardbreak();
+    }
+
+    fn impl_item_type(&mut self, impl_item: &ImplItemType) {
+        self.outer_attrs(&impl_item.attrs);
+        self.cbox(INDENT);
+        self.visibility(&impl_item.vis);
+        if impl_item.defaultness.is_some() {
+            self.word("default ");
+        }
+        self.word("type ");
+        self.ident(&impl_item.ident);
+        self.generics(&impl_item.generics);
+        self.where_clause_oneline(&impl_item.generics.where_clause);
+        self.word("= ");
+        self.neverbreak();
+        self.ibox(-INDENT);
+        self.ty(&impl_item.ty);
+        self.end();
+        self.word(";");
+        self.end();
+        self.hardbreak();
+    }
+
+    fn impl_item_macro(&mut self, impl_item: &ImplItemMacro) {
+        self.outer_attrs(&impl_item.attrs);
+        self.mac(&impl_item.mac, None);
+        self.mac_semi_if_needed(&impl_item.mac.delimiter);
+        self.hardbreak();
+    }
+
+    fn impl_item_verbatim(&mut self, impl_item: &TokenStream) {
+        if !impl_item.is_empty() {
+            unimplemented!("ImplItem::Verbatim `{}`", impl_item);
+        }
+        self.hardbreak();
+    }
+
+    fn maybe_variadic(&mut self, arg: &FnArg) -> bool {
+        let pat_type = match arg {
+            FnArg::Typed(pat_type) => pat_type,
+            FnArg::Receiver(receiver) => {
+                self.receiver(receiver);
+                return false;
+            }
+        };
+
+        match pat_type.ty.as_ref() {
+            Type::Verbatim(ty) if ty.to_string() == "..." => {
+                match pat_type.pat.as_ref() {
+                    Pat::Verbatim(pat) if pat.to_string() == "..." => {
+                        self.outer_attrs(&pat_type.attrs);
+                        self.word("...");
+                    }
+                    _ => self.pat_type(pat_type),
+                }
+                true
+            }
+            _ => {
+                self.pat_type(pat_type);
+                false
+            }
+        }
+    }
+
+    fn signature(&mut self, signature: &Signature) {
+        if signature.constness.is_some() {
+            self.word("const ");
+        }
+        if signature.asyncness.is_some() {
+            self.word("async ");
+        }
+        if signature.unsafety.is_some() {
+            self.word("unsafe ");
+        }
+        if let Some(abi) = &signature.abi {
+            self.abi(abi);
+        }
+        self.word("fn ");
+        self.ident(&signature.ident);
+        self.generics(&signature.generics);
+        self.word("(");
+        self.neverbreak();
+        self.cbox(0);
+        self.zerobreak();
+        let mut last_is_variadic = false;
+        for input in signature.inputs.iter().delimited() {
+            last_is_variadic = self.maybe_variadic(&input);
+            if last_is_variadic {
+                self.zerobreak();
+            } else {
+                self.trailing_comma(input.is_last);
+            }
+        }
+        if signature.variadic.is_some() && !last_is_variadic {
+            self.word("...");
+            self.zerobreak();
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word(")");
+        self.return_type(&signature.output);
+    }
+
+    fn receiver(&mut self, receiver: &Receiver) {
+        self.outer_attrs(&receiver.attrs);
+        if let Some((_ampersand, lifetime)) = &receiver.reference {
+            self.word("&");
+            if let Some(lifetime) = lifetime {
+                self.lifetime(lifetime);
+                self.nbsp();
+            }
+        }
+        if receiver.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.word("self");
+    }
+}

packages/autofmt/src/prettyplease/iter.rs

@@ -0,0 +1,46 @@
+use std::iter::Peekable;
+use std::ops::Deref;
+
+pub struct Delimited<I: Iterator> {
+    is_first: bool,
+    iter: Peekable<I>,
+}
+
+pub trait IterDelimited: Iterator + Sized {
+    fn delimited(self) -> Delimited<Self> {
+        Delimited {
+            is_first: true,
+            iter: self.peekable(),
+        }
+    }
+}
+
+impl<I: Iterator> IterDelimited for I {}
+
+pub struct IteratorItem<T> {
+    value: T,
+    pub is_first: bool,
+    pub is_last: bool,
+}
+
+impl<I: Iterator> Iterator for Delimited<I> {
+    type Item = IteratorItem<I::Item>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let item = IteratorItem {
+            value: self.iter.next()?,
+            is_first: self.is_first,
+            is_last: self.iter.peek().is_none(),
+        };
+        self.is_first = false;
+        Some(item)
+    }
+}
+
+impl<T> Deref for IteratorItem<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}

packages/autofmt/src/prettyplease/lifetime.rs

@@ -0,0 +1,9 @@
+use super::algorithm::Printer;
+use syn::Lifetime;
+
+impl Printer {
+    pub fn lifetime(&mut self, lifetime: &Lifetime) {
+        self.word("'");
+        self.ident(&lifetime.ident);
+    }
+}

packages/autofmt/src/prettyplease/lit.rs

@@ -0,0 +1,50 @@
+use super::algorithm::Printer;
+use proc_macro2::Literal;
+use syn::{Lit, LitBool, LitByte, LitByteStr, LitChar, LitFloat, LitInt, LitStr};
+
+impl Printer {
+    pub fn lit(&mut self, lit: &Lit) {
+        match lit {
+            Lit::Str(lit) => self.lit_str(lit),
+            Lit::ByteStr(lit) => self.lit_byte_str(lit),
+            Lit::Byte(lit) => self.lit_byte(lit),
+            Lit::Char(lit) => self.lit_char(lit),
+            Lit::Int(lit) => self.lit_int(lit),
+            Lit::Float(lit) => self.lit_float(lit),
+            Lit::Bool(lit) => self.lit_bool(lit),
+            Lit::Verbatim(lit) => self.lit_verbatim(lit),
+        }
+    }
+
+    pub fn lit_str(&mut self, lit: &LitStr) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_byte_str(&mut self, lit: &LitByteStr) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_byte(&mut self, lit: &LitByte) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_char(&mut self, lit: &LitChar) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_int(&mut self, lit: &LitInt) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_float(&mut self, lit: &LitFloat) {
+        self.word(lit.token().to_string());
+    }
+
+    fn lit_bool(&mut self, lit: &LitBool) {
+        self.word(if lit.value { "true" } else { "false" });
+    }
+
+    fn lit_verbatim(&mut self, token: &Literal) {
+        self.word(token.to_string());
+    }
+}

packages/autofmt/src/prettyplease/mac.rs

@@ -0,0 +1,220 @@
+use super::algorithm::Printer;
+use super::token::Token;
+use super::INDENT;
+use proc_macro2::{Delimiter, Spacing, TokenStream};
+use syn::{Ident, Macro, MacroDelimiter, PathArguments};
+
+impl Printer {
+    pub fn mac(&mut self, mac: &Macro, ident: Option<&Ident>) {
+        let is_macro_rules = mac.path.leading_colon.is_none()
+            && mac.path.segments.len() == 1
+            && matches!(mac.path.segments[0].arguments, PathArguments::None)
+            && mac.path.segments[0].ident == "macro_rules";
+        if is_macro_rules {
+            if let Some(ident) = ident {
+                self.macro_rules(ident, &mac.tokens);
+                return;
+            }
+        }
+        self.path(&mac.path);
+        self.word("!");
+        if let Some(ident) = ident {
+            self.nbsp();
+            self.ident(ident);
+        }
+        let (open, close, delimiter_break) = match mac.delimiter {
+            MacroDelimiter::Paren(_) => ("(", ")", Self::zerobreak as fn(&mut Self)),
+            MacroDelimiter::Brace(_) => (" {", "}", Self::hardbreak as fn(&mut Self)),
+            MacroDelimiter::Bracket(_) => ("[", "]", Self::zerobreak as fn(&mut Self)),
+        };
+        self.word(open);
+        self.cbox(INDENT);
+        delimiter_break(self);
+        self.ibox(0);
+        self.macro_rules_tokens(mac.tokens.clone(), false);
+        self.end();
+        delimiter_break(self);
+        self.offset(-INDENT);
+        self.end();
+        self.word(close);
+    }
+
+    pub fn mac_semi_if_needed(&mut self, delimiter: &MacroDelimiter) {
+        match delimiter {
+            MacroDelimiter::Paren(_) | MacroDelimiter::Bracket(_) => self.word(";"),
+            MacroDelimiter::Brace(_) => {}
+        }
+    }
+
+    fn macro_rules(&mut self, name: &Ident, rules: &TokenStream) {
+        enum State {
+            Start,
+            Matcher,
+            Equal,
+            Greater,
+            Expander,
+        }
+
+        use State::*;
+
+        self.word("macro_rules! ");
+        self.ident(name);
+        self.word(" {");
+        self.cbox(INDENT);
+        self.hardbreak_if_nonempty();
+        let mut state = State::Start;
+        for tt in rules.clone() {
+            let token = Token::from(tt);
+            match (state, token) {
+                (Start, Token::Group(delimiter, stream)) => {
+                    self.delimiter_open(delimiter);
+                    if !stream.is_empty() {
+                        self.cbox(INDENT);
+                        self.zerobreak();
+                        self.ibox(0);
+                        self.macro_rules_tokens(stream, true);
+                        self.end();
+                        self.zerobreak();
+                        self.offset(-INDENT);
+                        self.end();
+                    }
+                    self.delimiter_close(delimiter);
+                    state = Matcher;
+                }
+                (Matcher, Token::Punct('=', Spacing::Joint)) => {
+                    self.word(" =");
+                    state = Equal;
+                }
+                (Equal, Token::Punct('>', Spacing::Alone)) => {
+                    self.word(">");
+                    state = Greater;
+                }
+                (Greater, Token::Group(_delimiter, stream)) => {
+                    self.word(" {");
+                    self.neverbreak();
+                    if !stream.is_empty() {
+                        self.cbox(INDENT);
+                        self.hardbreak();
+                        self.ibox(0);
+                        self.macro_rules_tokens(stream, false);
+                        self.end();
+                        self.hardbreak();
+                        self.offset(-INDENT);
+                        self.end();
+                    }
+                    self.word("}");
+                    state = Expander;
+                }
+                (Expander, Token::Punct(';', Spacing::Alone)) => {
+                    self.word(";");
+                    self.hardbreak();
+                    state = Start;
+                }
+                _ => unimplemented!("bad macro_rules syntax"),
+            }
+        }
+        match state {
+            Start => {}
+            Expander => {
+                self.word(";");
+                self.hardbreak();
+            }
+            _ => self.hardbreak(),
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+    }
+
+    fn macro_rules_tokens(&mut self, stream: TokenStream, matcher: bool) {
+        #[derive(PartialEq)]
+        enum State {
+            Start,
+            Dollar,
+            DollarIdent,
+            DollarIdentColon,
+            DollarParen,
+            DollarParenSep,
+            Pound,
+            PoundBang,
+            Dot,
+            Colon,
+            Colon2,
+            Ident,
+            IdentBang,
+            Delim,
+            Other,
+        }
+
+        use State::*;
+
+        let mut state = Start;
+        let mut previous_is_joint = true;
+        for tt in stream {
+            let token = Token::from(tt);
+            let (needs_space, next_state) = match (&state, &token) {
+                (Dollar, Token::Ident(_)) => (false, if matcher { DollarIdent } else { Other }),
+                (DollarIdent, Token::Punct(':', Spacing::Alone)) => (false, DollarIdentColon),
+                (DollarIdentColon, Token::Ident(_)) => (false, Other),
+                (DollarParen, Token::Punct('+' | '*' | '?', Spacing::Alone)) => (false, Other),
+                (DollarParen, Token::Ident(_) | Token::Literal(_)) => (false, DollarParenSep),
+                (DollarParen, Token::Punct(_, Spacing::Joint)) => (false, DollarParen),
+                (DollarParen, Token::Punct(_, Spacing::Alone)) => (false, DollarParenSep),
+                (DollarParenSep, Token::Punct('+' | '*', _)) => (false, Other),
+                (Pound, Token::Punct('!', _)) => (false, PoundBang),
+                (Dollar, Token::Group(Delimiter::Parenthesis, _)) => (false, DollarParen),
+                (Pound | PoundBang, Token::Group(Delimiter::Bracket, _)) => (false, Other),
+                (Ident, Token::Group(Delimiter::Parenthesis | Delimiter::Bracket, _)) => {
+                    (false, Delim)
+                }
+                (Ident, Token::Punct('!', Spacing::Alone)) => (false, IdentBang),
+                (IdentBang, Token::Group(Delimiter::Parenthesis | Delimiter::Bracket, _)) => {
+                    (false, Other)
+                }
+                (Colon, Token::Punct(':', _)) => (false, Colon2),
+                (_, Token::Group(Delimiter::Parenthesis | Delimiter::Bracket, _)) => (true, Delim),
+                (_, Token::Group(Delimiter::Brace | Delimiter::None, _)) => (true, Other),
+                (_, Token::Ident(ident)) if !is_keyword(ident) => {
+                    (state != Dot && state != Colon2, Ident)
+                }
+                (_, Token::Literal(_)) => (state != Dot, Ident),
+                (_, Token::Punct(',' | ';', _)) => (false, Other),
+                (_, Token::Punct('.', _)) if !matcher => (state != Ident && state != Delim, Dot),
+                (_, Token::Punct(':', Spacing::Joint)) => (state != Ident, Colon),
+                (_, Token::Punct('$', _)) => (true, Dollar),
+                (_, Token::Punct('#', _)) => (true, Pound),
+                (_, _) => (true, Other),
+            };
+            if !previous_is_joint {
+                if needs_space {
+                    self.space();
+                } else if let Token::Punct('.', _) = token {
+                    self.zerobreak();
+                }
+            }
+            previous_is_joint = match token {
+                Token::Punct(_, Spacing::Joint) | Token::Punct('$', _) => true,
+                _ => false,
+            };
+            self.single_token(
+                token,
+                if matcher {
+                    |printer, stream| printer.macro_rules_tokens(stream, true)
+                } else {
+                    |printer, stream| printer.macro_rules_tokens(stream, false)
+                },
+            );
+            state = next_state;
+        }
+    }
+}
+
+fn is_keyword(ident: &Ident) -> bool {
+    match ident.to_string().as_str() {
+        "as" | "box" | "break" | "const" | "continue" | "crate" | "else" | "enum" | "extern"
+        | "fn" | "for" | "if" | "impl" | "in" | "let" | "loop" | "macro" | "match" | "mod"
+        | "move" | "mut" | "pub" | "ref" | "return" | "static" | "struct" | "trait" | "type"
+        | "unsafe" | "use" | "where" | "while" | "yield" => true,
+        _ => false,
+    }
+}

packages/autofmt/src/prettyplease/mod.rs

@@ -0,0 +1,381 @@
+//! [![github]](https://github.com/dtolnay/prettyplease) [![crates-io]](https://crates.io/crates/prettyplease) [![docs-rs]](https://docs.rs/prettyplease)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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
+//!
+//! <br>
+//!
+//! **prettyplease::unparse** &mdash; a minimal `syn` syntax tree pretty-printer
+//!
+//! <br>
+//!
+//! # Overview
+//!
+//! This is a pretty-printer to turn a `syn` syntax tree into a `String` of
+//! well-formatted source code. In contrast to rustfmt, this library is intended
+//! to be suitable for arbitrary generated code.
+//!
+//! Rustfmt prioritizes high-quality output that is impeccable enough that you'd
+//! be comfortable spending your career staring at its output &mdash; but that
+//! means some heavyweight algorithms, and it has a tendency to bail out on code
+//! that is hard to format (for example [rustfmt#3697], and there are dozens
+//! more issues like it). That's not necessarily a big deal for human-generated
+//! code because when code gets highly nested, the human will naturally be
+//! inclined to refactor into more easily formattable code. But for generated
+//! code, having the formatter just give up leaves it totally unreadable.
+//!
+//! [rustfmt#3697]: https://github.com/rust-lang/rustfmt/issues/3697
+//!
+//! This library is designed using the simplest possible algorithm and data
+//! structures that can deliver about 95% of the quality of rustfmt-formatted
+//! output. In my experience testing real-world code, approximately 97-98% of
+//! output lines come out identical between rustfmt's formatting and this
+//! crate's. The rest have slightly different linebreak decisions, but still
+//! clearly follow the dominant modern Rust style.
+//!
+//! The tradeoffs made by this crate are a good fit for generated code that you
+//! will *not* spend your career staring at. For example, the output of
+//! `bindgen`, or the output of `cargo-expand`. In those cases it's more
+//! important that the whole thing be formattable without the formatter giving
+//! up, than that it be flawless.
+//!
+//! <br>
+//!
+//! # Feature matrix
+//!
+//! Here are a few superficial comparisons of this crate against the AST
+//! pretty-printer built into rustc, and rustfmt. The sections below go into
+//! more detail comparing the output of each of these libraries.
+//!
+//! | | prettyplease | rustc | rustfmt |
+//! | --- | --- | --- | --- |
+//! | non-pathological behavior on big or generated code | ✅ | ❌ | ❌ |
+//! | idiomatic modern formatting ("locally indistinguishable from rustfmt") | ✅ | ❌ | ✅ |
+//! | throughput | 60 MB/s | 39 MB/s | 2.8 MB/s |
+//! | number of dependencies | 3 | 72 | 66 |
+//! | compile time including dependencies | 2.4 sec | 23.1 sec | 29.8 sec |
+//! | buildable using a stable Rust compiler | ✅ | ❌ | ❌ |
+//! | published to crates.io | ✅ | ❌ | ❌ |
+//! | extensively configurable output | ❌ | ❌ | ✅ |
+//! | intended to accommodate hand-maintained source code | ❌ | ❌ | ✅ |
+//!
+//! <br>
+//!
+//! # Comparison to rustfmt
+//!
+//! - [input.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/input.rs)
+//! - [output.prettyplease.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/output.prettyplease.rs)
+//! - [output.rustfmt.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/output.rustfmt.rs)
+//!
+//! If you weren't told which output file is which, it would be practically
+//! impossible to tell &mdash; **except** for line 435 in the rustfmt output,
+//! which is more than 1000 characters long because rustfmt just gave up
+//! formatting that part of the file:
+//!
+//! ```
+//! # const _: &str = stringify! {{{
+//!             match segments[5] {
+//!                 0 => write!(f, "::{}", ipv4),
+//!                 0xffff => write!(f, "::ffff:{}", ipv4),
+//!                 _ => unreachable!(),
+//!             }
+//!         } else { # [derive (Copy , Clone , Default)] struct Span { start : usize , len : usize , } let zeroes = { let mut longest = Span :: default () ; let mut current = Span :: default () ; for (i , & segment) in segments . iter () . enumerate () { if segment == 0 { if current . len == 0 { current . start = i ; } current . len += 1 ; if current . len > longest . len { longest = current ; } } else { current = Span :: default () ; } } longest } ; # [doc = " Write a colon-separated part of the address"] # [inline] fn fmt_subslice (f : & mut fmt :: Formatter < '_ > , chunk : & [u16]) -> fmt :: Result { if let Some ((first , tail)) = chunk . split_first () { write ! (f , "{:x}" , first) ? ; for segment in tail { f . write_char (':') ? ; write ! (f , "{:x}" , segment) ? ; } } Ok (()) } if zeroes . len > 1 { fmt_subslice (f , & segments [.. zeroes . start]) ? ; f . write_str ("::") ? ; fmt_subslice (f , & segments [zeroes . start + zeroes . len ..]) } else { fmt_subslice (f , & segments) } }
+//!     } else {
+//!         const IPV6_BUF_LEN: usize = (4 * 8) + 7;
+//!         let mut buf = [0u8; IPV6_BUF_LEN];
+//!         let mut buf_slice = &mut buf[..];
+//! # }};
+//! ```
+//!
+//! This is a pretty typical manifestation of rustfmt bailing out in generated
+//! code &mdash; a chunk of the input ends up on one line. The other
+//! manifestation is that you're working on some code, running rustfmt on save
+//! like a conscientious developer, but after a while notice it isn't doing
+//! anything. You introduce an intentional formatting issue, like a stray indent
+//! or semicolon, and run rustfmt to check your suspicion. Nope, it doesn't get
+//! cleaned up &mdash; rustfmt is just not formatting the part of the file you
+//! are working on.
+//!
+//! The prettyplease library is designed to have no pathological cases that
+//! force a bail out; the entire input you give it will get formatted in some
+//! "good enough" form.
+//!
+//! Separately, rustfmt can be problematic to integrate into projects. It's
+//! written using rustc's internal syntax tree, so it can't be built by a stable
+//! compiler. Its releases are not regularly published to crates.io, so in Cargo
+//! builds you'd need to depend on it as a git dependency, which precludes
+//! publishing your crate to crates.io also. You can shell out to a `rustfmt`
+//! binary, but that'll be whatever rustfmt version is installed on each
+//! developer's system (if any), which can lead to spurious diffs in checked-in
+//! generated code formatted by different versions. In contrast prettyplease is
+//! designed to be easy to pull in as a library, and compiles fast.
+//!
+//! <br>
+//!
+//! # Comparison to rustc_ast_pretty
+//!
+//! - [input.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/input.rs)
+//! - [output.prettyplease.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/output.prettyplease.rs)
+//! - [output.rustc.rs](https://github.com/dtolnay/prettyplease/blob/0.1.0/examples/output.rustc.rs)
+//!
+//! This is the pretty-printer that gets used when rustc prints source code,
+//! such as `rustc -Zunpretty=expanded`. It's used also by the standard
+//! library's `stringify!` when stringifying an interpolated macro_rules AST
+//! fragment, like an $:expr, and transitively by `dbg!` and many macros in the
+//! ecosystem.
+//!
+//! Rustc's formatting is mostly okay, but does not hew closely to the dominant
+//! contemporary style of Rust formatting. Some things wouldn't ever be written
+//! on one line, like this `match` expression, and certainly not with a comma in
+//! front of the closing brace:
+//!
+//! ```
+//! # const _: &str = stringify! {
+//! fn eq(&self, other: &IpAddr) -> bool {
+//!     match other { IpAddr::V4(v4) => self == v4, IpAddr::V6(_) => false, }
+//! }
+//! # };
+//! ```
+//!
+//! Some places use non-multiple-of-4 indentation, which is definitely not the
+//! norm:
+//!
+//! ```
+//! # const _: &str = stringify! {
+//! pub const fn to_ipv6_mapped(&self) -> Ipv6Addr {
+//!     let [a, b, c, d] = self.octets();
+//!     Ipv6Addr{inner:
+//!                  c::in6_addr{s6_addr:
+//!                                  [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF,
+//!                                   0xFF, a, b, c, d],},}
+//! }
+//! # };
+//! ```
+//!
+//! And although there isn't an egregious example of it in the link because the
+//! input code is pretty tame, in general rustc_ast_pretty has pathological
+//! behavior on generated code. It has a tendency to use excessive horizontal
+//! indentation and rapidly run out of width:
+//!
+//! ```
+//! # const _: &str = stringify! {
+//! ::std::io::_print(::core::fmt::Arguments::new_v1(&[""],
+//!                                                  &match (&msg,) {
+//!                                                       _args =>
+//!                                                       [::core::fmt::ArgumentV1::new(_args.0,
+//!                                                                                     ::core::fmt::Display::fmt)],
+//!                                                   }));
+//! # };
+//! ```
+//!
+//! The snippets above are clearly different from modern rustfmt style. In
+//! contrast, prettyplease is designed to have output that is practically
+//! indistinguishable from rustfmt-formatted code.
+//!
+//! <br>
+//!
+//! # Example
+//!
+//! ```
+//! // [dependencies]
+//! // prettyplease = "0.1"
+//! // syn = { version = "1", default-features = false, features = ["full", "parsing"] }
+//!
+//! const INPUT: &str = stringify! {
+//!     use super::{
+//!           lazy::{Lazy, SyncLazy, SyncOnceCell}, panic,
+//!         sync::{ atomic::{AtomicUsize, Ordering::SeqCst},
+//!             mpsc::channel, Mutex, },
+//!       thread,
+//!     };
+//!     impl<T, U> Into<U> for T where U: From<T> {
+//!         fn into(self) -> U { U::from(self) }
+//!     }
+//! };
+//!
+//! fn main() {
+//!     let syntax_tree = syn::parse_file(INPUT).unwrap();
+//!     let formatted = prettyplease::unparse(&syntax_tree);
+//!     print!("{}", formatted);
+//! }
+//! ```
+//!
+//! <br>
+//!
+//! # Algorithm notes
+//!
+//! The approach and terminology used in the implementation are derived from
+//! [*Derek C. Oppen, "Pretty Printing" (1979)*][paper], on which
+//! rustc_ast_pretty is also based, and from rustc_ast_pretty's implementation
+//! written by Graydon Hoare in 2011 (and modernized over the years by dozens of
+//! volunteer maintainers).
+//!
+//! [paper]: http://i.stanford.edu/pub/cstr/reports/cs/tr/79/770/CS-TR-79-770.pdf
+//!
+//! The paper describes two language-agnostic interacting procedures `Scan()`
+//! and `Print()`. Language-specific code decomposes an input data structure
+//! into a stream of `string` and `break` tokens, and `begin` and `end` tokens
+//! for grouping. Each `begin`&ndash;`end` range may be identified as either
+//! "consistent breaking" or "inconsistent breaking". If a group is consistently
+//! breaking, then if the whole contents do not fit on the line, *every* `break`
+//! token in the group will receive a linebreak. This is appropriate, for
+//! example, for Rust struct literals, or arguments of a function call. If a
+//! group is inconsistently breaking, then the `string` tokens in the group are
+//! greedily placed on the line until out of space, and linebroken only at those
+//! `break` tokens for which the next string would not fit. For example, this is
+//! appropriate for the contents of a braced `use` statement in Rust.
+//!
+//! Scan's job is to efficiently accumulate sizing information about groups and
+//! breaks. For every `begin` token we compute the distance to the matched `end`
+//! token, and for every `break` we compute the distance to the next `break`.
+//! The algorithm uses a ringbuffer to hold tokens whose size is not yet
+//! ascertained. The maximum size of the ringbuffer is bounded by the target
+//! line length and does not grow indefinitely, regardless of deep nesting in
+//! the input stream. That's because once a group is sufficiently big, the
+//! precise size can no longer make a difference to linebreak decisions and we
+//! can effectively treat it as "infinity".
+//!
+//! Print's job is to use the sizing information to efficiently assign a
+//! "broken" or "not broken" status to every `begin` token. At that point the
+//! output is easily constructed by concatenating `string` tokens and breaking
+//! at `break` tokens contained within a broken group.
+//!
+//! Leveraging these primitives (i.e. cleverly placing the all-or-nothing
+//! consistent breaks and greedy inconsistent breaks) to yield
+//! rustfmt-compatible formatting for all of Rust's syntax tree nodes is a fun
+//! challenge.
+//!
+//! Here is a visualization of some Rust tokens fed into the pretty printing
+//! algorithm. Consistently breaking `begin`&mdash;`end` pairs are represented
+//! by `«`&#8288;`»`, inconsistently breaking by `‹`&#8288;`›`, `break` by `·`,
+//! and the rest of the non-whitespace are `string`.
+//!
+//! ```text
+//! use super::«{·
+//! ‹    lazy::«{·‹Lazy,· SyncLazy,· SyncOnceCell›·}»,·
+//!     panic,·
+//!     sync::«{·
+//! ‹        atomic::«{·‹AtomicUsize,· Ordering::SeqCst›·}»,·
+//!         mpsc::channel,· Mutex›,·
+//!     }»,·
+//!     thread›,·
+//! }»;·
+//! «‹«impl<«·T‹›,· U‹›·»>» Into<«·U·»>· for T›·
+//! where·
+//!     U:‹ From<«·T·»>›,·
+//! {·
+//! «    fn into(·«·self·») -> U {·
+//! ‹        U::from(«·self·»)›·
+//! »    }·
+//! »}·
+//! ```
+//!
+//! The algorithm described in the paper is not quite sufficient for producing
+//! well-formatted Rust code that is locally indistinguishable from rustfmt's
+//! style. The reason is that in the paper, the complete non-whitespace contents
+//! are assumed to be independent of linebreak decisions, with Scan and Print
+//! being only in control of the whitespace (spaces and line breaks). In Rust as
+//! idiomatically formattted by rustfmt, that is not the case. Trailing commas
+//! are one example; the punctuation is only known *after* the broken vs
+//! non-broken status of the surrounding group is known:
+//!
+//! ```
+//! # struct Struct { x: u64, y: bool }
+//! # let xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx = 0;
+//! # let yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy = true;
+//! #
+//! let _ = Struct { x: 0, y: true };
+//!
+//! let _ = Struct {
+//!     x: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+//!     y: yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,   //<- trailing comma if the expression wrapped
+//! };
+//! ```
+//!
+//! The formatting of `match` expressions is another case; we want small arms on
+//! the same line as the pattern, and big arms wrapped in a brace. The presence
+//! of the brace punctuation, comma, and semicolon are all dependent on whether
+//! the arm fits on the line:
+//!
+//! ```
+//! # struct Entry { nanos: u32 }
+//! # let total_nanos = 0u64;
+//! # let mut total_secs = 0u64;
+//! # let tmp;
+//! # let entry = Entry { nanos: 0 };
+//! # const NANOS_PER_SEC: u32 = 1_000_000_000;
+//! #
+//! match total_nanos.checked_add(entry.nanos as u64) {
+//!     Some(n) => tmp = n,   //<- small arm, inline with comma
+//!     None => {
+//!         total_secs = total_secs
+//!             .checked_add(total_nanos / NANOS_PER_SEC as u64)
+//!             .expect("overflow in iter::sum over durations");
+//!     }   //<- big arm, needs brace added, and also semicolon^
+//! }
+//! ```
+//!
+//! The printing algorithm implementation in this crate accommodates all of
+//! these situations with conditional punctuation tokens whose selection can be
+//! deferred and populated after it's known that the group is or is not broken.
+
+#![allow(
+    clippy::cast_possible_wrap,
+    clippy::cast_sign_loss,
+    clippy::doc_markdown,
+    clippy::enum_glob_use,
+    clippy::items_after_statements,
+    clippy::match_like_matches_macro,
+    clippy::match_same_arms,
+    clippy::module_name_repetitions,
+    clippy::must_use_candidate,
+    clippy::needless_pass_by_value,
+    clippy::similar_names,
+    clippy::unused_self,
+    clippy::vec_init_then_push
+)]
+#![cfg_attr(all(test, exhaustive), feature(non_exhaustive_omitted_patterns_lint))]
+
+mod algorithm;
+mod attr;
+mod convenience;
+mod data;
+mod expr;
+mod file;
+mod generics;
+mod item;
+mod iter;
+mod lifetime;
+mod lit;
+mod mac;
+mod pat;
+mod path;
+mod ring;
+mod stmt;
+mod token;
+mod ty;
+
+use algorithm::Printer;
+use syn::{Expr, File};
+
+// Target line width.
+const MARGIN: isize = 89;
+
+// Number of spaces increment at each level of block indentation.
+const INDENT: isize = 4;
+
+// Every line is allowed at least this much space, even if highly indented.
+const MIN_SPACE: isize = 60;
+
+pub fn unparse(file: &File) -> String {
+    let mut p = Printer::new();
+    p.file(file);
+    p.eof()
+}
+
+pub fn unparse_expr(file: &Expr) -> String {
+    let mut p = Printer::new();
+    p.expr(file);
+    p.eof()
+}

packages/autofmt/src/prettyplease/pat.rs

@@ -0,0 +1,210 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use proc_macro2::TokenStream;
+use syn::{
+    FieldPat, Pat, PatBox, PatIdent, PatLit, PatMacro, PatOr, PatPath, PatRange, PatReference,
+    PatRest, PatSlice, PatStruct, PatTuple, PatTupleStruct, PatType, PatWild, RangeLimits,
+};
+
+impl Printer {
+    pub fn pat(&mut self, pat: &Pat) {
+        match pat {
+            Pat::Box(pat) => self.pat_box(pat),
+            Pat::Ident(pat) => self.pat_ident(pat),
+            Pat::Lit(pat) => self.pat_lit(pat),
+            Pat::Macro(pat) => self.pat_macro(pat),
+            Pat::Or(pat) => self.pat_or(pat),
+            Pat::Path(pat) => self.pat_path(pat),
+            Pat::Range(pat) => self.pat_range(pat),
+            Pat::Reference(pat) => self.pat_reference(pat),
+            Pat::Rest(pat) => self.pat_rest(pat),
+            Pat::Slice(pat) => self.pat_slice(pat),
+            Pat::Struct(pat) => self.pat_struct(pat),
+            Pat::Tuple(pat) => self.pat_tuple(pat),
+            Pat::TupleStruct(pat) => self.pat_tuple_struct(pat),
+            Pat::Type(pat) => self.pat_type(pat),
+            Pat::Verbatim(pat) => self.pat_verbatim(pat),
+            Pat::Wild(pat) => self.pat_wild(pat),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown Pat"),
+        }
+    }
+
+    fn pat_box(&mut self, pat: &PatBox) {
+        self.outer_attrs(&pat.attrs);
+        self.word("box ");
+        self.pat(&pat.pat);
+    }
+
+    fn pat_ident(&mut self, pat: &PatIdent) {
+        self.outer_attrs(&pat.attrs);
+        if pat.by_ref.is_some() {
+            self.word("ref ");
+        }
+        if pat.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.ident(&pat.ident);
+        if let Some((_at_token, subpat)) = &pat.subpat {
+            self.word(" @ ");
+            self.pat(subpat);
+        }
+    }
+
+    fn pat_lit(&mut self, pat: &PatLit) {
+        self.outer_attrs(&pat.attrs);
+        self.expr(&pat.expr);
+    }
+
+    fn pat_macro(&mut self, pat: &PatMacro) {
+        self.outer_attrs(&pat.attrs);
+        self.mac(&pat.mac, None);
+    }
+
+    fn pat_or(&mut self, pat: &PatOr) {
+        self.outer_attrs(&pat.attrs);
+        let mut consistent_break = false;
+        for case in &pat.cases {
+            match case {
+                Pat::Lit(_) | Pat::Wild(_) => {}
+                _ => {
+                    consistent_break = true;
+                    break;
+                }
+            }
+        }
+        if consistent_break {
+            self.cbox(0);
+        } else {
+            self.ibox(0);
+        }
+        for case in pat.cases.iter().delimited() {
+            if !case.is_first {
+                self.space();
+                self.word("| ");
+            }
+            self.pat(&case);
+        }
+        self.end();
+    }
+
+    fn pat_path(&mut self, pat: &PatPath) {
+        self.outer_attrs(&pat.attrs);
+        self.qpath(&pat.qself, &pat.path);
+    }
+
+    fn pat_range(&mut self, pat: &PatRange) {
+        self.outer_attrs(&pat.attrs);
+        self.expr(&pat.lo);
+        match &pat.limits {
+            RangeLimits::HalfOpen(_) => self.word(".."),
+            RangeLimits::Closed(_) => self.word("..="),
+        }
+        self.expr(&pat.hi);
+    }
+
+    fn pat_reference(&mut self, pat: &PatReference) {
+        self.outer_attrs(&pat.attrs);
+        self.word("&");
+        if pat.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.pat(&pat.pat);
+    }
+
+    fn pat_rest(&mut self, pat: &PatRest) {
+        self.outer_attrs(&pat.attrs);
+        self.word("..");
+    }
+
+    fn pat_slice(&mut self, pat: &PatSlice) {
+        self.outer_attrs(&pat.attrs);
+        self.word("[");
+        for elem in pat.elems.iter().delimited() {
+            self.pat(&elem);
+            self.trailing_comma(elem.is_last);
+        }
+        self.word("]");
+    }
+
+    fn pat_struct(&mut self, pat: &PatStruct) {
+        self.outer_attrs(&pat.attrs);
+        self.cbox(INDENT);
+        self.path(&pat.path);
+        self.word(" {");
+        self.space_if_nonempty();
+        for field in pat.fields.iter().delimited() {
+            self.field_pat(&field);
+            self.trailing_comma_or_space(field.is_last && pat.dot2_token.is_none());
+        }
+        if pat.dot2_token.is_some() {
+            self.word("..");
+            self.space();
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word("}");
+    }
+
+    fn pat_tuple(&mut self, pat: &PatTuple) {
+        self.outer_attrs(&pat.attrs);
+        self.word("(");
+        self.cbox(INDENT);
+        self.zerobreak();
+        for elem in pat.elems.iter().delimited() {
+            self.pat(&elem);
+            if pat.elems.len() == 1 {
+                if pat.elems.trailing_punct() {
+                    self.word(",");
+                }
+                self.zerobreak();
+            } else {
+                self.trailing_comma(elem.is_last);
+            }
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word(")");
+    }
+
+    fn pat_tuple_struct(&mut self, pat: &PatTupleStruct) {
+        self.outer_attrs(&pat.attrs);
+        self.path(&pat.path);
+        self.word("(");
+        self.cbox(INDENT);
+        self.zerobreak();
+        for elem in pat.pat.elems.iter().delimited() {
+            self.pat(&elem);
+            self.trailing_comma(elem.is_last);
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word(")");
+    }
+
+    pub fn pat_type(&mut self, pat: &PatType) {
+        self.outer_attrs(&pat.attrs);
+        self.pat(&pat.pat);
+        self.word(": ");
+        self.ty(&pat.ty);
+    }
+
+    fn pat_verbatim(&mut self, pat: &TokenStream) {
+        unimplemented!("Pat::Verbatim `{}`", pat);
+    }
+
+    fn pat_wild(&mut self, pat: &PatWild) {
+        self.outer_attrs(&pat.attrs);
+        self.word("_");
+    }
+
+    fn field_pat(&mut self, field_pat: &FieldPat) {
+        self.outer_attrs(&field_pat.attrs);
+        if field_pat.colon_token.is_some() {
+            self.member(&field_pat.member);
+            self.word(": ");
+        }
+        self.pat(&field_pat.pat);
+    }
+}

packages/autofmt/src/prettyplease/path.rs

@@ -0,0 +1,181 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use syn::{
+    AngleBracketedGenericArguments, Binding, Constraint, Expr, GenericArgument,
+    ParenthesizedGenericArguments, Path, PathArguments, PathSegment, QSelf,
+};
+
+impl Printer {
+    pub fn path(&mut self, path: &Path) {
+        assert!(!path.segments.is_empty());
+        for segment in path.segments.iter().delimited() {
+            if !segment.is_first || path.leading_colon.is_some() {
+                self.word("::");
+            }
+            self.path_segment(&segment);
+        }
+    }
+
+    pub fn path_segment(&mut self, segment: &PathSegment) {
+        self.ident(&segment.ident);
+        self.path_arguments(&segment.arguments);
+    }
+
+    fn path_arguments(&mut self, arguments: &PathArguments) {
+        match arguments {
+            PathArguments::None => {}
+            PathArguments::AngleBracketed(arguments) => {
+                self.angle_bracketed_generic_arguments(arguments);
+            }
+            PathArguments::Parenthesized(arguments) => {
+                self.parenthesized_generic_arguments(arguments);
+            }
+        }
+    }
+
+    fn generic_argument(&mut self, arg: &GenericArgument) {
+        match arg {
+            GenericArgument::Lifetime(lifetime) => self.lifetime(lifetime),
+            GenericArgument::Type(ty) => self.ty(ty),
+            GenericArgument::Binding(binding) => self.binding(binding),
+            GenericArgument::Constraint(constraint) => self.constraint(constraint),
+            GenericArgument::Const(expr) => {
+                match expr {
+                    Expr::Lit(expr) => self.expr_lit(expr),
+                    Expr::Block(expr) => self.expr_block(expr),
+                    // ERROR CORRECTION: Add braces to make sure that the
+                    // generated code is valid.
+                    _ => {
+                        self.word("{");
+                        self.expr(expr);
+                        self.word("}");
+                    }
+                }
+            }
+        }
+    }
+
+    fn angle_bracketed_generic_arguments(&mut self, generic: &AngleBracketedGenericArguments) {
+        if generic.colon2_token.is_some() {
+            self.word("::");
+        }
+        self.word("<");
+        self.cbox(INDENT);
+        self.zerobreak();
+
+        // Print lifetimes before types and consts, all before bindings,
+        // regardless of their order in self.args.
+        //
+        // TODO: ordering rules for const arguments vs type arguments have
+        // not been settled yet. https://github.com/rust-lang/rust/issues/44580
+        for arg in generic.args.iter().delimited() {
+            match *arg {
+                GenericArgument::Lifetime(_) => {
+                    self.generic_argument(&arg);
+                    self.trailing_comma(arg.is_last);
+                }
+                GenericArgument::Type(_)
+                | GenericArgument::Binding(_)
+                | GenericArgument::Constraint(_)
+                | GenericArgument::Const(_) => {}
+            }
+        }
+        for arg in generic.args.iter().delimited() {
+            match *arg {
+                GenericArgument::Type(_) | GenericArgument::Const(_) => {
+                    self.generic_argument(&arg);
+                    self.trailing_comma(arg.is_last);
+                }
+                GenericArgument::Lifetime(_)
+                | GenericArgument::Binding(_)
+                | GenericArgument::Constraint(_) => {}
+            }
+        }
+        for arg in generic.args.iter().delimited() {
+            match *arg {
+                GenericArgument::Binding(_) | GenericArgument::Constraint(_) => {
+                    self.generic_argument(&arg);
+                    self.trailing_comma(arg.is_last);
+                }
+                GenericArgument::Lifetime(_)
+                | GenericArgument::Type(_)
+                | GenericArgument::Const(_) => {}
+            }
+        }
+
+        self.offset(-INDENT);
+        self.end();
+        self.word(">");
+    }
+
+    fn binding(&mut self, binding: &Binding) {
+        self.ident(&binding.ident);
+        self.word(" = ");
+        self.ty(&binding.ty);
+    }
+
+    fn constraint(&mut self, constraint: &Constraint) {
+        self.ident(&constraint.ident);
+        self.ibox(INDENT);
+        for bound in constraint.bounds.iter().delimited() {
+            if bound.is_first {
+                self.word(": ");
+            } else {
+                self.space();
+                self.word("+ ");
+            }
+            self.type_param_bound(&bound);
+        }
+        self.end();
+    }
+
+    fn parenthesized_generic_arguments(&mut self, arguments: &ParenthesizedGenericArguments) {
+        self.cbox(INDENT);
+        self.word("(");
+        self.zerobreak();
+        for ty in arguments.inputs.iter().delimited() {
+            self.ty(&ty);
+            self.trailing_comma(ty.is_last);
+        }
+        self.offset(-INDENT);
+        self.word(")");
+        self.return_type(&arguments.output);
+        self.end();
+    }
+
+    pub fn qpath(&mut self, qself: &Option<QSelf>, path: &Path) {
+        let qself = match qself {
+            Some(qself) => qself,
+            None => {
+                self.path(path);
+                return;
+            }
+        };
+
+        assert!(qself.position < path.segments.len());
+
+        self.word("<");
+        self.ty(&qself.ty);
+
+        let mut segments = path.segments.iter();
+        if qself.position > 0 {
+            self.word(" as ");
+            for segment in segments.by_ref().take(qself.position).delimited() {
+                if !segment.is_first || path.leading_colon.is_some() {
+                    self.word("::");
+                }
+                self.path_segment(&segment);
+                if segment.is_last {
+                    self.word(">");
+                }
+            }
+        } else {
+            self.word(">");
+        }
+        for segment in segments {
+            self.word("::");
+            self.path_segment(segment);
+        }
+    }
+}

packages/autofmt/src/prettyplease/ring.rs

@@ -0,0 +1,81 @@
+use std::collections::VecDeque;
+use std::ops::{Index, IndexMut};
+
+pub struct RingBuffer<T> {
+    data: VecDeque<T>,
+    // Abstract index of data[0] in infinitely sized queue
+    offset: usize,
+}
+
+impl<T> RingBuffer<T> {
+    pub fn new() -> Self {
+        RingBuffer {
+            data: VecDeque::new(),
+            offset: 0,
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.data.is_empty()
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn push(&mut self, value: T) -> usize {
+        let index = self.offset + self.data.len();
+        self.data.push_back(value);
+        index
+    }
+
+    pub fn clear(&mut self) {
+        self.data.clear();
+    }
+
+    pub fn index_of_first(&self) -> usize {
+        self.offset
+    }
+
+    pub fn first(&self) -> &T {
+        &self.data[0]
+    }
+
+    pub fn first_mut(&mut self) -> &mut T {
+        &mut self.data[0]
+    }
+
+    pub fn pop_first(&mut self) -> T {
+        self.offset += 1;
+        self.data.pop_front().unwrap()
+    }
+
+    pub fn last(&self) -> &T {
+        self.data.back().unwrap()
+    }
+
+    pub fn last_mut(&mut self) -> &mut T {
+        self.data.back_mut().unwrap()
+    }
+
+    pub fn second_last(&self) -> &T {
+        &self.data[self.data.len() - 2]
+    }
+
+    pub fn pop_last(&mut self) {
+        self.data.pop_back().unwrap();
+    }
+}
+
+impl<T> Index<usize> for RingBuffer<T> {
+    type Output = T;
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.data[index.checked_sub(self.offset).unwrap()]
+    }
+}
+
+impl<T> IndexMut<usize> for RingBuffer<T> {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.data[index.checked_sub(self.offset).unwrap()]
+    }
+}

packages/autofmt/src/prettyplease/stmt.rs

@@ -0,0 +1,85 @@
+use super::algorithm::Printer;
+use syn::{Expr, Stmt};
+
+impl Printer {
+    pub fn stmt(&mut self, stmt: &Stmt) {
+        match stmt {
+            Stmt::Local(local) => {
+                self.outer_attrs(&local.attrs);
+                self.ibox(0);
+                self.word("let ");
+                self.pat(&local.pat);
+                if let Some((_eq, init)) = &local.init {
+                    self.word(" = ");
+                    self.neverbreak();
+                    self.expr(init);
+                }
+                self.word(";");
+                self.end();
+                self.hardbreak();
+            }
+            Stmt::Item(item) => self.item(item),
+            Stmt::Expr(expr) => {
+                if break_after(expr) {
+                    self.ibox(0);
+                    self.expr_beginning_of_line(expr, true);
+                    if add_semi(expr) {
+                        self.word(";");
+                    }
+                    self.end();
+                    self.hardbreak();
+                } else {
+                    self.expr_beginning_of_line(expr, true);
+                }
+            }
+            Stmt::Semi(expr, _semi) => {
+                if let Expr::Verbatim(tokens) = expr {
+                    if tokens.is_empty() {
+                        return;
+                    }
+                }
+                self.ibox(0);
+                self.expr_beginning_of_line(expr, true);
+                if !remove_semi(expr) {
+                    self.word(";");
+                }
+                self.end();
+                self.hardbreak();
+            }
+        }
+    }
+}
+
+pub fn add_semi(expr: &Expr) -> bool {
+    match expr {
+        Expr::Assign(_)
+        | Expr::AssignOp(_)
+        | Expr::Break(_)
+        | Expr::Continue(_)
+        | Expr::Return(_)
+        | Expr::Yield(_) => true,
+        Expr::Group(group) => add_semi(&group.expr),
+        _ => false,
+    }
+}
+
+pub fn break_after(expr: &Expr) -> bool {
+    if let Expr::Group(group) = expr {
+        if let Expr::Verbatim(verbatim) = group.expr.as_ref() {
+            return !verbatim.is_empty();
+        }
+    }
+    true
+}
+
+fn remove_semi(expr: &Expr) -> bool {
+    match expr {
+        Expr::ForLoop(_) | Expr::While(_) => true,
+        Expr::Group(group) => remove_semi(&group.expr),
+        Expr::If(expr) => match &expr.else_branch {
+            Some((_else_token, else_branch)) => remove_semi(else_branch),
+            None => true,
+        },
+        _ => false,
+    }
+}

packages/autofmt/src/prettyplease/token.rs

@@ -0,0 +1,80 @@
+use super::algorithm::Printer;
+use proc_macro2::{Delimiter, Ident, Literal, Spacing, TokenStream, TokenTree};
+
+impl Printer {
+    pub fn single_token(&mut self, token: Token, group_contents: fn(&mut Self, TokenStream)) {
+        match token {
+            Token::Group(delimiter, stream) => self.token_group(delimiter, stream, group_contents),
+            Token::Ident(ident) => self.ident(&ident),
+            Token::Punct(ch, _spacing) => self.token_punct(ch),
+            Token::Literal(literal) => self.token_literal(&literal),
+        }
+    }
+
+    fn token_group(
+        &mut self,
+        delimiter: Delimiter,
+        stream: TokenStream,
+        group_contents: fn(&mut Self, TokenStream),
+    ) {
+        self.delimiter_open(delimiter);
+        if !stream.is_empty() {
+            if delimiter == Delimiter::Brace {
+                self.space();
+            }
+            group_contents(self, stream);
+            if delimiter == Delimiter::Brace {
+                self.space();
+            }
+        }
+        self.delimiter_close(delimiter);
+    }
+
+    pub fn ident(&mut self, ident: &Ident) {
+        self.word(ident.to_string());
+    }
+
+    pub fn token_punct(&mut self, ch: char) {
+        self.word(ch.to_string());
+    }
+
+    pub fn token_literal(&mut self, literal: &Literal) {
+        self.word(literal.to_string());
+    }
+
+    pub fn delimiter_open(&mut self, delimiter: Delimiter) {
+        self.word(match delimiter {
+            Delimiter::Parenthesis => "(",
+            Delimiter::Brace => "{",
+            Delimiter::Bracket => "[",
+            Delimiter::None => return,
+        });
+    }
+
+    pub fn delimiter_close(&mut self, delimiter: Delimiter) {
+        self.word(match delimiter {
+            Delimiter::Parenthesis => ")",
+            Delimiter::Brace => "}",
+            Delimiter::Bracket => "]",
+            Delimiter::None => return,
+        });
+    }
+}
+
+pub enum Token {
+    Group(Delimiter, TokenStream),
+    Ident(Ident),
+    Punct(char, Spacing),
+    Literal(Literal),
+}
+
+impl From<TokenTree> for Token {
+    fn from(tt: TokenTree) -> Self {
+        match tt {
+            TokenTree::Group(group) => Token::Group(group.delimiter(), group.stream()),
+            TokenTree::Ident(ident) => Token::Ident(ident),
+            TokenTree::Punct(punct) => Token::Punct(punct.as_char(), punct.spacing()),
+            TokenTree::Literal(literal) => Token::Literal(literal),
+        }
+    }
+}

packages/autofmt/src/prettyplease/ty.rs

@@ -0,0 +1,202 @@
+use super::algorithm::Printer;
+use super::iter::IterDelimited;
+use super::INDENT;
+use proc_macro2::TokenStream;
+use syn::{
+    Abi, BareFnArg, ReturnType, Type, TypeArray, TypeBareFn, TypeGroup, TypeImplTrait, TypeInfer,
+    TypeMacro, TypeNever, TypeParen, TypePath, TypePtr, TypeReference, TypeSlice, TypeTraitObject,
+    TypeTuple, Variadic,
+};
+
+impl Printer {
+    pub fn ty(&mut self, ty: &Type) {
+        match ty {
+            Type::Array(ty) => self.type_array(ty),
+            Type::BareFn(ty) => self.type_bare_fn(ty),
+            Type::Group(ty) => self.type_group(ty),
+            Type::ImplTrait(ty) => self.type_impl_trait(ty),
+            Type::Infer(ty) => self.type_infer(ty),
+            Type::Macro(ty) => self.type_macro(ty),
+            Type::Never(ty) => self.type_never(ty),
+            Type::Paren(ty) => self.type_paren(ty),
+            Type::Path(ty) => self.type_path(ty),
+            Type::Ptr(ty) => self.type_ptr(ty),
+            Type::Reference(ty) => self.type_reference(ty),
+            Type::Slice(ty) => self.type_slice(ty),
+            Type::TraitObject(ty) => self.type_trait_object(ty),
+            Type::Tuple(ty) => self.type_tuple(ty),
+            Type::Verbatim(ty) => self.type_verbatim(ty),
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
+            _ => unimplemented!("unknown Type"),
+        }
+    }
+
+    fn type_array(&mut self, ty: &TypeArray) {
+        self.word("[");
+        self.ty(&ty.elem);
+        self.word("; ");
+        self.expr(&ty.len);
+        self.word("]");
+    }
+
+    fn type_bare_fn(&mut self, ty: &TypeBareFn) {
+        if let Some(bound_lifetimes) = &ty.lifetimes {
+            self.bound_lifetimes(bound_lifetimes);
+        }
+        if ty.unsafety.is_some() {
+            self.word("unsafe ");
+        }
+        if let Some(abi) = &ty.abi {
+            self.abi(abi);
+        }
+        self.word("fn(");
+        self.cbox(INDENT);
+        self.zerobreak();
+        for bare_fn_arg in ty.inputs.iter().delimited() {
+            self.bare_fn_arg(&bare_fn_arg);
+            self.trailing_comma(bare_fn_arg.is_last && ty.variadic.is_none());
+        }
+        if let Some(variadic) = &ty.variadic {
+            self.variadic(variadic);
+            self.zerobreak();
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word(")");
+        self.return_type(&ty.output);
+    }
+
+    fn type_group(&mut self, ty: &TypeGroup) {
+        self.ty(&ty.elem);
+    }
+
+    fn type_impl_trait(&mut self, ty: &TypeImplTrait) {
+        self.word("impl ");
+        for type_param_bound in ty.bounds.iter().delimited() {
+            if !type_param_bound.is_first {
+                self.word(" + ");
+            }
+            self.type_param_bound(&type_param_bound);
+        }
+    }
+
+    fn type_infer(&mut self, ty: &TypeInfer) {
+        let _ = ty;
+        self.word("_");
+    }
+
+    fn type_macro(&mut self, ty: &TypeMacro) {
+        self.mac(&ty.mac, None);
+    }
+
+    fn type_never(&mut self, ty: &TypeNever) {
+        let _ = ty;
+        self.word("!");
+    }
+
+    fn type_paren(&mut self, ty: &TypeParen) {
+        self.word("(");
+        self.ty(&ty.elem);
+        self.word(")");
+    }
+
+    fn type_path(&mut self, ty: &TypePath) {
+        self.qpath(&ty.qself, &ty.path);
+    }
+
+    fn type_ptr(&mut self, ty: &TypePtr) {
+        self.word("*");
+        if ty.mutability.is_some() {
+            self.word("mut ");
+        } else {
+            self.word("const ");
+        }
+        self.ty(&ty.elem);
+    }
+
+    fn type_reference(&mut self, ty: &TypeReference) {
+        self.word("&");
+        if let Some(lifetime) = &ty.lifetime {
+            self.lifetime(lifetime);
+            self.nbsp();
+        }
+        if ty.mutability.is_some() {
+            self.word("mut ");
+        }
+        self.ty(&ty.elem);
+    }
+
+    fn type_slice(&mut self, ty: &TypeSlice) {
+        self.word("[");
+        self.ty(&ty.elem);
+        self.word("]");
+    }
+
+    fn type_trait_object(&mut self, ty: &TypeTraitObject) {
+        self.word("dyn ");
+        for type_param_bound in ty.bounds.iter().delimited() {
+            if !type_param_bound.is_first {
+                self.word(" + ");
+            }
+            self.type_param_bound(&type_param_bound);
+        }
+    }
+
+    fn type_tuple(&mut self, ty: &TypeTuple) {
+        self.word("(");
+        self.cbox(INDENT);
+        self.zerobreak();
+        for elem in ty.elems.iter().delimited() {
+            self.ty(&elem);
+            if ty.elems.len() == 1 {
+                self.word(",");
+                self.zerobreak();
+            } else {
+                self.trailing_comma(elem.is_last);
+            }
+        }
+        self.offset(-INDENT);
+        self.end();
+        self.word(")");
+    }
+
+    fn type_verbatim(&mut self, ty: &TokenStream) {
+        if ty.to_string() == "..." {
+            self.word("...");
+        } else {
+            unimplemented!("Type::Verbatim `{}`", ty);
+        }
+    }
+
+    pub fn return_type(&mut self, ty: &ReturnType) {
+        match ty {
+            ReturnType::Default => {}
+            ReturnType::Type(_arrow, ty) => {
+                self.word(" -> ");
+                self.ty(ty);
+            }
+        }
+    }
+
+    fn bare_fn_arg(&mut self, bare_fn_arg: &BareFnArg) {
+        self.outer_attrs(&bare_fn_arg.attrs);
+        if let Some((name, _colon)) = &bare_fn_arg.name {
+            self.ident(name);
+            self.word(": ");
+        }
+        self.ty(&bare_fn_arg.ty);
+    }
+
+    fn variadic(&mut self, variadic: &Variadic) {
+        self.outer_attrs(&variadic.attrs);
+        self.word("...");
+    }
+
+    pub fn abi(&mut self, abi: &Abi) {
+        self.word("extern ");
+        if let Some(name) = &abi.name {
+            self.lit_str(name);
+            self.nbsp();
+        }
+    }
+}

packages/autofmt/tests/sink.rs

@@ -0,0 +1,471 @@
+use dioxus_autofmt::*;
+use proc_macro2::TokenStream as TokenStream2;
+use syn::{Attribute, Meta};
+
+#[test]
+fn formats_block() {
+    let block = r#"
+        div {
+                                    div {
+                                    class: "asd",
+                                    class: "asd",class: "asd",class: "asd",class: "asd",class: "asd",
+                                    key: "ddd",
+                                    onclick: move |_| {
+                                        let blah = 120;
+                                                    true
+                                    },
+                                    blah: 123,
+                                    onclick: move |_| {
+                                        let blah = 120;
+                                                    true
+                                    },
+                                    onclick: move |_| {
+                                        let blah = 120;
+                                                    true
+                                    },
+                                    onclick: move |_| {
+                                        let blah = 120;
+                                                    true
+                                    },
+
+                                    div {
+                                        div {
+                                            "hi"
+                                        }
+                                        h2 {
+                            class: "asd",
+                                        }
+                                    }
+            }
+        }
+    "#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn parse_comment() {
+    let block = r#"
+    div {
+        adsasd: "asd", // this is a comment
+    }
+        "#;
+
+    let parsed: TokenStream2 = syn::parse_str(block).unwrap();
+
+    dbg!(parsed);
+}
+
+#[test]
+fn formats_component() {
+    let block = r#"
+    Component {
+        adsasd: "asd", // this is a comment
+        onclick: move |_| {
+            let blah = 120;
+            let blah = 120;
+        },
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_element() {
+    let block = r#"
+    div {
+        a: "1234567891012345678910123456789101234567891012345678910123456789101234567891012345678910123456789101234567891012345678910",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_element_short() {
+    let block = r#"
+    div {
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+        a: "123",
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_element_nested() {
+    let block = r#"
+    h3 {
+        class: "mb-2 text-xl font-bold",
+        "Invite Member"
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_element_nested_no_trailing_tabs() {
+    let block = r#"
+    img { class: "mb-6 mx-auto h-24", src: "artemis-assets/images/friends.png", alt: "",                }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_element_with_correct_indent() {
+    let block = r###"
+    div {
+
+                        a { class: "py-2 px-3 bg-indigo-500 hover:bg-indigo-600 rounded text-xs text-white", href: "#",
+                            "Send invitation"
+          }
+    }
+
+"###;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn small_elements_and_text_are_small() {
+    let block = r###"
+                        a { class: " text-white",
+                            "Send invitation"
+          }
+"###;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_component_man_props() {
+    let block = r#"
+    Component {
+        ..MyProps {
+            val: 123
+        },
+        adsasd: "asd", // this is a comment
+        onclick: move |_| {
+            let blah = 120;
+        },
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_component_tiny() {
+    let block = r#"
+    Component { a: 123
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_exprs() {
+    let block = r#"
+    ul {
+        (0..10).map(|f| rsx!{
+            li {
+                "hi"
+            }
+        })
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_exprs_neg_indent() {
+    let block = r#"
+            ul {
+        (0..10).map(|f| rsx!{
+            li {
+                "hi"
+            }
+        })
+    }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_exprs_handlers() {
+    let block = r#"
+            button {
+                class: "flex items-center pl-3 py-3 pr-2 text-gray-500 hover:bg-indigo-50 rounded",
+                onclick: move |evt| {
+                    show_user_menu.set(!show_user_menu.get());            evt.cancel_bubble();        },
+
+                onclick: move |evt|
+
+                show_user_menu.set(!show_user_menu.get()),
+                span { class: "inline-block mr-4",
+                    icons::icon_14 {}
+                }
+                span { "Settings" }
+            }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_complex() {
+    let block = r#"
+        li {
+            Link {
+                class: "flex items-center pl-3 py-3 pr-4 {active_class} rounded",
+                to: "{to}",
+                span { class: "inline-block mr-3",
+                    icons::icon_0 {}
+                }
+                span { "{name}" }
+                children.is_some().then(|| rsx!{
+                    span {
+                        class: "inline-block ml-auto hover:bg-gray-500",
+                        onclick: move |evt| {
+                            // open.set(!open.get());
+                            evt.cancel_bubble();
+                        },
+                        icons::icon_8 {}
+                    }
+                })
+            }
+            div {
+                class: "px-4",
+                is_current.then(|| rsx!{ children })
+                // open.then(|| rsx!{ children })
+            }
+        }
+"#;
+
+    let formatted = fmt_block(block).unwrap();
+
+    print!("{formatted}");
+}
+
+#[test]
+fn formats_document() {
+    let block = r#"
+rsx!{
+    Component {
+        adsasd: "asd", // this is a comment
+        onclick: move |_| {
+            let blah = 120;
+        },
+    }
+}
+
+
+"#;
+
+    let formatted = get_format_blocks(block);
+
+    print!("{formatted:?}");
+}
+
+#[test]
+fn component_path_mod_style() {
+    let block = r#"
+rsx!{
+    my::thing::Component {
+        adsasd: "asd", // this is a comment
+        onclick: move |_| {
+            let blah = 120;
+        },
+    }
+}
+"#;
+
+    let formatted = get_format_blocks(block);
+
+    print!("{formatted:?}");
+}
+
+#[test]
+fn formats_valid_rust_src() {
+    let src = r#"
+//
+rsx! {
+    div {}
+    div {
+        h3 {"asd"
+        }
+    }
+}
+"#;
+
+    let formatted = get_format_blocks(src);
+
+    println!("{formatted:?}");
+}
+
+#[test]
+fn formats_valid_rust_src_with_indents() {
+    let mut src = r#"
+#[inline_props]
+fn NavItem<'a>(cx: Scope, to: &'static str, children: Element<'a>, icon: Shape) -> Element {
+    const ICON_SIZE: u32 = 36;
+
+    rsx! {
+        div {
+
+            h1 {"thing"}
+
+
+        }
+
+
+
+
+    }
+}
+"#
+    .to_string();
+
+    let formatted = get_format_blocks(&src);
+
+    let block = formatted.into_iter().next().unwrap();
+
+    src.replace_range(
+        block.start - 1..block.end + 1,
+        &format!("{{ {}    }}", &block.formatted),
+    );
+}
+
+#[test]
+fn formats_multiple_blocks() {
+    let mut src = r#"
+#[inline_props]
+fn NavItem<'a>(cx: Scope, to: &'static str, children: Element<'a>, icon: Shape) -> Element {
+    const ICON_SIZE: u32 = 36;
+
+    rsx! {
+        div {
+
+            h1 {"thing"}
+
+
+        }
+
+
+    }
+
+    rsx! {
+        div {
+
+            Ball {
+                a: rsx!{
+                    "asdasd"
+                }
+            }
+        }
+    }
+}
+#[inline_props]
+fn NavItem<'a>(cx: Scope, to: &'static str, children: Element<'a>, icon: Shape) -> Element {
+    const ICON_SIZE: u32 = 36;
+
+    rsx! {
+        div {
+
+            h1 {"thing"}
+
+
+        }
+
+
+    }
+
+    rsx! {
+        div {
+
+            Ball {
+                a: rsx!{
+                    "asdasd"
+                }
+            }
+        }
+    }
+}
+"#
+    .to_string();
+
+    let formatted = get_format_blocks(&src);
+
+    dbg!(&formatted);
+
+    let block = formatted.into_iter().next().unwrap();
+
+    src.replace_range(
+        block.start - 1..block.end + 1,
+        &format!("{{ {}    }}", &block.formatted),
+    );
+}
+
+#[test]
+fn empty_blocks() {
+    let mut src = r###"
+pub fn Alert(cx: Scope) -> Element {
+    cx.render(rsx! {
+        div { }
+    })
+}
+"###
+    .to_string();
+
+    let formatted = get_format_blocks(&src);
+
+    dbg!(&formatted);
+}