Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

12 files changed, 3978 insertions, 0 deletions

diff --git a/compiler/rustc_ast_pretty/Cargo.toml b/compiler/rustc_ast_pretty/Cargo.toml
new file mode 100644
index 000000000..5ad8714e9
--- /dev/null
+++ b/compiler/rustc_ast_pretty/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rustc_ast_pretty"
+version = "0.0.0"
+edition = "2021"
+
+[lib]
+doctest = false
+
+[dependencies]
+rustc_span = { path = "../rustc_span" }
+rustc_ast = { path = "../rustc_ast" }
diff --git a/compiler/rustc_ast_pretty/src/helpers.rs b/compiler/rustc_ast_pretty/src/helpers.rs
new file mode 100644
index 000000000..5ec71cddf
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/helpers.rs
@@ -0,0 +1,48 @@
+use crate::pp::Printer;
+use std::borrow::Cow;
+
+impl Printer {
+    pub fn word_space<W: Into<Cow<'static, str>>>(&mut self, w: W) {
+        self.word(w);
+        self.space();
+    }
+
+    pub fn popen(&mut self) {
+        self.word("(");
+    }
+
+    pub fn pclose(&mut self) {
+        self.word(")");
+    }
+
+    pub fn hardbreak_if_not_bol(&mut self) {
+        if !self.is_beginning_of_line() {
+            self.hardbreak()
+        }
+    }
+
+    pub fn space_if_not_bol(&mut self) {
+        if !self.is_beginning_of_line() {
+            self.space();
+        }
+    }
+
+    pub fn nbsp(&mut self) {
+        self.word(" ")
+    }
+
+    pub fn word_nbsp<S: Into<Cow<'static, str>>>(&mut self, w: S) {
+        self.word(w);
+        self.nbsp()
+    }
+
+    // Synthesizes a comment that was not textually present in the original
+    // source file.
+    pub fn synth_comment(&mut self, text: impl Into<Cow<'static, str>>) {
+        self.word("/*");
+        self.space();
+        self.word(text);
+        self.space();
+        self.word("*/")
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/lib.rs b/compiler/rustc_ast_pretty/src/lib.rs
new file mode 100644
index 000000000..79178830b
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/lib.rs
@@ -0,0 +1,8 @@
+#![feature(associated_type_bounds)]
+#![feature(box_patterns)]
+#![feature(with_negative_coherence)]
+#![recursion_limit = "256"]
+
+mod helpers;
+pub mod pp;
+pub mod pprust;
diff --git a/compiler/rustc_ast_pretty/src/pp.rs b/compiler/rustc_ast_pretty/src/pp.rs
new file mode 100644
index 000000000..c93022308
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pp.rs
@@ -0,0 +1,451 @@
+//! This pretty-printer is a direct reimplementation of Philip Karlton's
+//! Mesa pretty-printer, as described in the appendix to
+//! Derek C. Oppen, "Pretty Printing" (1979),
+//! Stanford Computer Science Department STAN-CS-79-770,
+//! <http://i.stanford.edu/pub/cstr/reports/cs/tr/79/770/CS-TR-79-770.pdf>.
+//!
+//! The algorithm's aim is to break a stream into as few lines as possible
+//! while respecting the indentation-consistency requirements of the enclosing
+//! block, and avoiding breaking at silly places on block boundaries, for
+//! example, between "x" and ")" in "x)".
+//!
+//! I am implementing this algorithm because it comes with 20 pages of
+//! documentation explaining its theory, and because it addresses the set of
+//! concerns I've seen other pretty-printers fall down on. Weirdly. Even though
+//! it's 32 years old. What can I say?
+//!
+//! Despite some redundancies and quirks in the way it's implemented in that
+//! paper, I've opted to keep the implementation here as similar as I can,
+//! changing only what was blatantly wrong, a typo, or sufficiently
+//! non-idiomatic rust that it really stuck out.
+//!
+//! In particular you'll see a certain amount of churn related to INTEGER vs.
+//! CARDINAL in the Mesa implementation. Mesa apparently interconverts the two
+//! somewhat readily? In any case, I've used usize for indices-in-buffers and
+//! ints for character-sizes-and-indentation-offsets. This respects the need
+//! for ints to "go negative" while carrying a pending-calculation balance, and
+//! helps differentiate all the numbers flying around internally (slightly).
+//!
+//! I also inverted the indentation arithmetic used in the print stack, since
+//! the Mesa implementation (somewhat randomly) stores the offset on the print
+//! stack in terms of margin-col rather than col itself. I store col.
+//!
+//! I also implemented a small change in the String token, in that I store an
+//! explicit length for the string. For most tokens this is just the length of
+//! the accompanying string. But it's necessary to permit it to differ, for
+//! encoding things that are supposed to "go on their own line" -- certain
+//! classes of comment and blank-line -- where relying on adjacent
+//! hardbreak-like Break tokens with long blankness indication doesn't actually
+//! work. To see why, consider when there is a "thing that should be on its own
+//! line" between two long blocks, say functions. If you put a hardbreak after
+//! each function (or before each) and the breaking algorithm decides to break
+//! there anyways (because the functions themselves are long) you wind up with
+//! extra blank lines. If you don't put hardbreaks you can wind up with the
+//! "thing which should be on its own line" not getting its own line in the
+//! rare case of "really small functions" or such. This re-occurs with comments
+//! and explicit blank lines. So in those cases we use a string with a payload
+//! we want isolated to a line and an explicit length that's huge, surrounded
+//! by two zero-length breaks. The algorithm will try its best to fit it on a
+//! line (which it can't) and so naturally place the content on its own line to
+//! avoid combining it with other lines and making matters even worse.
+//!
+//! # Explanation
+//!
+//! In case you do not have the paper, here is an explanation of what's going
+//! on.
+//!
+//! There is a stream of input tokens flowing through this printer.
+//!
+//! The printer buffers up to 3N tokens inside itself, where N is linewidth.
+//! Yes, linewidth is chars and tokens are multi-char, but in the worst
+//! case every token worth buffering is 1 char long, so it's ok.
+//!
+//! Tokens are String, Break, and Begin/End to delimit blocks.
+//!
+//! Begin tokens can carry an offset, saying "how far to indent when you break
+//! inside here", as well as a flag indicating "consistent" or "inconsistent"
+//! breaking. Consistent breaking means that after the first break, no attempt
+//! will be made to flow subsequent breaks together onto lines. Inconsistent
+//! is the opposite. Inconsistent breaking example would be, say:
+//!
+//! ```ignore (illustrative)
+//! foo(hello, there, good, friends)
+//! ```
+//!
+//! breaking inconsistently to become
+//!
+//! ```ignore (illustrative)
+//! foo(hello, there,
+//!     good, friends);
+//! ```
+//!
+//! whereas a consistent breaking would yield:
+//!
+//! ```ignore (illustrative)
+//! foo(hello,
+//!     there,
+//!     good,
+//!     friends);
+//! ```
+//!
+//! That is, in the consistent-break blocks we value vertical alignment
+//! more than the ability to cram stuff onto a line. But in all cases if it
+//! can make a block a one-liner, it'll do so.
+//!
+//! Carrying on with high-level logic:
+//!
+//! The buffered tokens go through a ring-buffer, 'tokens'. The 'left' and
+//! 'right' indices denote the active portion of the ring buffer as well as
+//! describing hypothetical points-in-the-infinite-stream at most 3N tokens
+//! apart (i.e., "not wrapped to ring-buffer boundaries"). The paper will switch
+//! between using 'left' and 'right' terms to denote the wrapped-to-ring-buffer
+//! and point-in-infinite-stream senses freely.
+//!
+//! There is a parallel ring buffer, `size`, that holds the calculated size of
+//! each token. Why calculated? Because for Begin/End pairs, the "size"
+//! includes everything between the pair. That is, the "size" of Begin is
+//! actually the sum of the sizes of everything between Begin and the paired
+//! End that follows. Since that is arbitrarily far in the future, `size` is
+//! being rewritten regularly while the printer runs; in fact most of the
+//! machinery is here to work out `size` entries on the fly (and give up when
+//! they're so obviously over-long that "infinity" is a good enough
+//! approximation for purposes of line breaking).
+//!
+//! The "input side" of the printer is managed as an abstract process called
+//! SCAN, which uses `scan_stack`, to manage calculating `size`. SCAN is, in
+//! other words, the process of calculating 'size' entries.
+//!
+//! The "output side" of the printer is managed by an abstract process called
+//! PRINT, which uses `print_stack`, `margin` and `space` to figure out what to
+//! do with each token/size pair it consumes as it goes. It's trying to consume
+//! the entire buffered window, but can't output anything until the size is >=
+//! 0 (sizes are set to negative while they're pending calculation).
+//!
+//! So SCAN takes input and buffers tokens and pending calculations, while
+//! PRINT gobbles up completed calculations and tokens from the buffer. The
+//! theory is that the two can never get more than 3N tokens apart, because
+//! once there's "obviously" too much data to fit on a line, in a size
+//! calculation, SCAN will write "infinity" to the size and let PRINT consume
+//! it.
+//!
+//! In this implementation (following the paper, again) the SCAN process is the
+//! methods called `Printer::scan_*`, and the 'PRINT' process is the
+//! method called `Printer::print`.
+
+mod convenience;
+mod ring;
+
+use ring::RingBuffer;
+use std::borrow::Cow;
+use std::cmp;
+use std::collections::VecDeque;
+use std::iter;
+
+/// How to break. Described in more detail in the module docs.
+#[derive(Clone, Copy, PartialEq)]
+pub enum Breaks {
+    Consistent,
+    Inconsistent,
+}
+
+#[derive(Clone, Copy, PartialEq)]
+enum IndentStyle {
+    /// Vertically aligned under whatever column this block begins at.
+    ///
+    ///     fn demo(arg1: usize,
+    ///             arg2: usize) {}
+    Visual,
+    /// Indented relative to the indentation level of the previous line.
+    ///
+    ///     fn demo(
+    ///         arg1: usize,
+    ///         arg2: usize,
+    ///     ) {}
+    Block { offset: isize },
+}
+
+#[derive(Clone, Copy, Default, PartialEq)]
+pub struct BreakToken {
+    offset: isize,
+    blank_space: isize,
+    pre_break: Option<char>,
+}
+
+#[derive(Clone, Copy, PartialEq)]
+pub struct BeginToken {
+    indent: IndentStyle,
+    breaks: Breaks,
+}
+
+#[derive(Clone, PartialEq)]
+pub enum Token {
+    // In practice a string token contains either a `&'static str` or a
+    // `String`. `Cow` is overkill for this because we never modify the data,
+    // but it's more convenient than rolling our own more specialized type.
+    String(Cow<'static, str>),
+    Break(BreakToken),
+    Begin(BeginToken),
+    End,
+}
+
+#[derive(Copy, Clone)]
+enum PrintFrame {
+    Fits,
+    Broken { indent: usize, breaks: Breaks },
+}
+
+const SIZE_INFINITY: isize = 0xffff;
+
+/// Target line width.
+const MARGIN: isize = 78;
+/// Every line is allowed at least this much space, even if highly indented.
+const MIN_SPACE: isize = 60;
+
+pub struct Printer {
+    out: String,
+    /// Number of spaces left on line
+    space: isize,
+    /// Ring-buffer of tokens and calculated sizes
+    buf: RingBuffer<BufEntry>,
+    /// Running size of stream "...left"
+    left_total: isize,
+    /// Running size of stream "...right"
+    right_total: isize,
+    /// Pseudo-stack, really a ring too. Holds the
+    /// primary-ring-buffers 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. Stuff is flushed off the
+    /// bottom as it becomes 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: isize,
+    /// The token most recently popped from the left boundary of the
+    /// ring-buffer for printing
+    last_printed: Option<Token>,
+}
+
+#[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,
+            last_printed: None,
+        }
+    }
+
+    pub fn last_token(&self) -> Option<&Token> {
+        self.last_token_still_buffered().or_else(|| self.last_printed.as_ref())
+    }
+
+    pub fn last_token_still_buffered(&self) -> Option<&Token> {
+        self.buf.last().map(|last| &last.token)
+    }
+
+    /// Be very careful with this!
+    pub fn replace_last_token_still_buffered(&mut self, token: Token) {
+        self.buf.last_mut().unwrap().token = token;
+    }
+
+    fn scan_eof(&mut self) {
+        if !self.scan_stack.is_empty() {
+            self.check_stack(0);
+            self.advance_left();
+        }
+    }
+
+    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);
+    }
+
+    fn scan_end(&mut self) {
+        if self.scan_stack.is_empty() {
+            self.print_end();
+        } else {
+            let right = self.buf.push(BufEntry { token: Token::End, size: -1 });
+            self.scan_stack.push_back(right);
+        }
+    }
+
+    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;
+    }
+
+    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) {
+        if let Some(BufEntry { token: Token::Break(token), .. }) = &mut self.buf.last_mut() {
+            token.offset += offset;
+        }
+    }
+
+    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().unwrap().size = SIZE_INFINITY;
+            }
+            self.advance_left();
+            if self.buf.is_empty() {
+                break;
+            }
+        }
+    }
+
+    fn advance_left(&mut self) {
+        while self.buf.first().unwrap().size >= 0 {
+            let left = self.buf.pop_first().unwrap();
+
+            match &left.token {
+                Token::String(string) => {
+                    self.left_total += string.len() as isize;
+                    self.print_string(string);
+                }
+                Token::Break(token) => {
+                    self.left_total += token.blank_space;
+                    self.print_break(*token, left.size);
+                }
+                Token::Begin(token) => self.print_begin(*token, left.size),
+                Token::End => self.print_end(),
+            }
+
+            self.last_printed = Some(left.token);
+
+            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 => {
+                    // paper says + not =, but that makes no sense.
+                    self.scan_stack.pop_back().unwrap();
+                    entry.size = 1;
+                    depth += 1;
+                }
+                _ => {
+                    self.scan_stack.pop_back().unwrap();
+                    entry.size += self.right_total;
+                    if depth == 0 {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    fn get_top(&self) -> PrintFrame {
+        *self
+            .print_stack
+            .last()
+            .unwrap_or(&PrintFrame::Broken { indent: 0, breaks: Breaks::Inconsistent })
+    }
+
+    fn print_begin(&mut self, token: BeginToken, size: isize) {
+        if size > self.space {
+            self.print_stack.push(PrintFrame::Broken { indent: self.indent, breaks: token.breaks });
+            self.indent = match token.indent {
+                IndentStyle::Block { offset } => {
+                    usize::try_from(self.indent as isize + offset).unwrap()
+                }
+                IndentStyle::Visual => (MARGIN - self.space) as usize,
+            };
+        } else {
+            self.print_stack.push(PrintFrame::Fits);
+        }
+    }
+
+    fn print_end(&mut self) {
+        if let PrintFrame::Broken { indent, .. } = self.print_stack.pop().unwrap() {
+            self.indent = indent;
+        }
+    }
+
+    fn print_break(&mut self, token: BreakToken, size: isize) {
+        let fits = match self.get_top() {
+            PrintFrame::Fits => true,
+            PrintFrame::Broken { breaks: Breaks::Consistent, .. } => false,
+            PrintFrame::Broken { breaks: Breaks::Inconsistent, .. } => size <= self.space,
+        };
+        if fits {
+            self.pending_indentation += token.blank_space;
+            self.space -= token.blank_space;
+        } else {
+            if let Some(pre_break) = token.pre_break {
+                self.out.push(pre_break);
+            }
+            self.out.push('\n');
+            let indent = self.indent as isize + token.offset;
+            self.pending_indentation = indent;
+            self.space = cmp::max(MARGIN - indent, MIN_SPACE);
+        }
+    }
+
+    fn print_string(&mut self, string: &str) {
+        // Write the pending indent. A more concise way of doing this would be:
+        //
+        //   write!(self.out, "{: >n$}", "", n = self.pending_indentation as usize)?;
+        //
+        // But that is significantly slower. This code is sufficiently hot, and indents can get
+        // sufficiently large, that the difference is significant on some workloads.
+        self.out.reserve(self.pending_indentation as usize);
+        self.out.extend(iter::repeat(' ').take(self.pending_indentation as usize));
+        self.pending_indentation = 0;
+
+        self.out.push_str(string);
+        self.space -= string.len() as isize;
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pp/convenience.rs b/compiler/rustc_ast_pretty/src/pp/convenience.rs
new file mode 100644
index 000000000..93310dd45
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pp/convenience.rs
@@ -0,0 +1,94 @@
+use crate::pp::{BeginToken, BreakToken, Breaks, IndentStyle, Printer, Token, SIZE_INFINITY};
+use std::borrow::Cow;
+
+impl Printer {
+    /// "raw box"
+    pub fn rbox(&mut self, indent: isize, breaks: Breaks) {
+        self.scan_begin(BeginToken { indent: IndentStyle::Block { offset: indent }, breaks })
+    }
+
+    /// Inconsistent breaking box
+    pub fn ibox(&mut self, indent: isize) {
+        self.rbox(indent, Breaks::Inconsistent)
+    }
+
+    /// Consistent breaking box
+    pub fn cbox(&mut self, indent: isize) {
+        self.rbox(indent, Breaks::Consistent)
+    }
+
+    pub fn visual_align(&mut self) {
+        self.scan_begin(BeginToken { indent: IndentStyle::Visual, breaks: Breaks::Consistent });
+    }
+
+    pub fn break_offset(&mut self, n: usize, off: isize) {
+        self.scan_break(BreakToken {
+            offset: off,
+            blank_space: n as isize,
+            ..BreakToken::default()
+        });
+    }
+
+    pub fn end(&mut self) {
+        self.scan_end()
+    }
+
+    pub fn eof(mut self) -> String {
+        self.scan_eof();
+        self.out
+    }
+
+    pub fn word<S: Into<Cow<'static, str>>>(&mut self, wrd: S) {
+        let string = wrd.into();
+        self.scan_string(string)
+    }
+
+    fn spaces(&mut self, n: usize) {
+        self.break_offset(n, 0)
+    }
+
+    pub fn zerobreak(&mut self) {
+        self.spaces(0)
+    }
+
+    pub fn space(&mut self) {
+        self.spaces(1)
+    }
+
+    pub fn hardbreak(&mut self) {
+        self.spaces(SIZE_INFINITY as usize)
+    }
+
+    pub fn is_beginning_of_line(&self) -> bool {
+        match self.last_token() {
+            Some(last_token) => last_token.is_hardbreak_tok(),
+            None => true,
+        }
+    }
+
+    pub fn hardbreak_tok_offset(off: isize) -> Token {
+        Token::Break(BreakToken {
+            offset: off,
+            blank_space: SIZE_INFINITY,
+            ..BreakToken::default()
+        })
+    }
+
+    pub fn trailing_comma(&mut self) {
+        self.scan_break(BreakToken { pre_break: Some(','), ..BreakToken::default() });
+    }
+
+    pub fn trailing_comma_or_space(&mut self) {
+        self.scan_break(BreakToken {
+            blank_space: 1,
+            pre_break: Some(','),
+            ..BreakToken::default()
+        });
+    }
+}
+
+impl Token {
+    pub fn is_hardbreak_tok(&self) -> bool {
+        *self == Printer::hardbreak_tok_offset(0)
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pp/ring.rs b/compiler/rustc_ast_pretty/src/pp/ring.rs
new file mode 100644
index 000000000..8187394fe
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pp/ring.rs
@@ -0,0 +1,77 @@
+use std::collections::VecDeque;
+use std::ops::{Index, IndexMut};
+
+/// A view onto a finite range of an infinitely long sequence of T.
+///
+/// The Ts are indexed 0..infinity. A RingBuffer begins as a view of elements
+/// 0..0 (i.e. nothing). The user of the RingBuffer advances its left and right
+/// position independently, although only in the positive direction, and only
+/// with left <= right at all times.
+///
+/// Holding a RingBuffer whose view is elements left..right gives the ability to
+/// use Index and IndexMut to access elements i in the infinitely long queue for
+/// which left <= i < right.
+pub struct RingBuffer<T> {
+    data: VecDeque<T>,
+    // Abstract index of data[0] in the 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 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) -> Option<&T> {
+        self.data.front()
+    }
+
+    pub fn first_mut(&mut self) -> Option<&mut T> {
+        self.data.front_mut()
+    }
+
+    pub fn pop_first(&mut self) -> Option<T> {
+        let first = self.data.pop_front()?;
+        self.offset += 1;
+        Some(first)
+    }
+
+    pub fn last(&self) -> Option<&T> {
+        self.data.back()
+    }
+
+    pub fn last_mut(&mut self) -> Option<&mut T> {
+        self.data.back_mut()
+    }
+}
+
+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()]
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/mod.rs b/compiler/rustc_ast_pretty/src/pprust/mod.rs
new file mode 100644
index 000000000..ac9e7d06c
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/mod.rs
@@ -0,0 +1,86 @@
+#[cfg(test)]
+mod tests;
+
+pub mod state;
+pub use state::{print_crate, AnnNode, Comments, PpAnn, PrintState, State};
+
+use rustc_ast as ast;
+use rustc_ast::token::{Nonterminal, Token, TokenKind};
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
+
+use std::borrow::Cow;
+
+pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
+    State::new().nonterminal_to_string(nt)
+}
+
+/// Print the token kind precisely, without converting `$crate` into its respective crate name.
+pub fn token_kind_to_string(tok: &TokenKind) -> Cow<'static, str> {
+    State::new().token_kind_to_string(tok)
+}
+
+/// Print the token precisely, without converting `$crate` into its respective crate name.
+pub fn token_to_string(token: &Token) -> Cow<'static, str> {
+    State::new().token_to_string(token)
+}
+
+pub fn ty_to_string(ty: &ast::Ty) -> String {
+    State::new().ty_to_string(ty)
+}
+
+pub fn bounds_to_string(bounds: &[ast::GenericBound]) -> String {
+    State::new().bounds_to_string(bounds)
+}
+
+pub fn pat_to_string(pat: &ast::Pat) -> String {
+    State::new().pat_to_string(pat)
+}
+
+pub fn expr_to_string(e: &ast::Expr) -> String {
+    State::new().expr_to_string(e)
+}
+
+pub fn tt_to_string(tt: &TokenTree) -> String {
+    State::new().tt_to_string(tt)
+}
+
+pub fn tts_to_string(tokens: &TokenStream) -> String {
+    State::new().tts_to_string(tokens)
+}
+
+pub fn item_to_string(i: &ast::Item) -> String {
+    State::new().item_to_string(i)
+}
+
+pub fn path_to_string(p: &ast::Path) -> String {
+    State::new().path_to_string(p)
+}
+
+pub fn path_segment_to_string(p: &ast::PathSegment) -> String {
+    State::new().path_segment_to_string(p)
+}
+
+pub fn vis_to_string(v: &ast::Visibility) -> String {
+    State::new().vis_to_string(v)
+}
+
+pub fn meta_list_item_to_string(li: &ast::NestedMetaItem) -> String {
+    State::new().meta_list_item_to_string(li)
+}
+
+pub fn attribute_to_string(attr: &ast::Attribute) -> String {
+    State::new().attribute_to_string(attr)
+}
+
+pub fn to_string(f: impl FnOnce(&mut State<'_>)) -> String {
+    State::to_string(f)
+}
+
+pub fn crate_to_string_for_macros(krate: &ast::Crate) -> String {
+    State::to_string(|s| {
+        s.print_inner_attributes(&krate.attrs);
+        for item in &krate.items {
+            s.print_item(item);
+        }
+    })
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
new file mode 100644
index 000000000..5eb7bf634
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -0,0 +1,1770 @@
+mod delimited;
+mod expr;
+mod item;
+
+use crate::pp::Breaks::{Consistent, Inconsistent};
+use crate::pp::{self, Breaks};
+
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, BinOpToken, CommentKind, Delimiter, Nonterminal, Token, TokenKind};
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast::util::classify;
+use rustc_ast::util::comments::{gather_comments, Comment, CommentStyle};
+use rustc_ast::util::parser;
+use rustc_ast::{self as ast, BlockCheckMode, PatKind, RangeEnd, RangeSyntax};
+use rustc_ast::{attr, Term};
+use rustc_ast::{GenericArg, MacArgs, MacArgsEq};
+use rustc_ast::{GenericBound, SelfKind, TraitBoundModifier};
+use rustc_ast::{InlineAsmOperand, InlineAsmRegOrRegClass};
+use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_span::edition::Edition;
+use rustc_span::source_map::{SourceMap, Spanned};
+use rustc_span::symbol::{kw, sym, Ident, IdentPrinter, Symbol};
+use rustc_span::{BytePos, FileName, Span};
+
+use std::borrow::Cow;
+
+pub use self::delimited::IterDelimited;
+
+pub enum MacHeader<'a> {
+    Path(&'a ast::Path),
+    Keyword(&'static str),
+}
+
+pub enum AnnNode<'a> {
+    Ident(&'a Ident),
+    Name(&'a Symbol),
+    Block(&'a ast::Block),
+    Item(&'a ast::Item),
+    SubItem(ast::NodeId),
+    Expr(&'a ast::Expr),
+    Pat(&'a ast::Pat),
+    Crate(&'a ast::Crate),
+}
+
+pub trait PpAnn {
+    fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
+    fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
+}
+
+#[derive(Copy, Clone)]
+pub struct NoAnn;
+
+impl PpAnn for NoAnn {}
+
+pub struct Comments<'a> {
+    sm: &'a SourceMap,
+    comments: Vec<Comment>,
+    current: usize,
+}
+
+impl<'a> Comments<'a> {
+    pub fn new(sm: &'a SourceMap, filename: FileName, input: String) -> Comments<'a> {
+        let comments = gather_comments(sm, filename, input);
+        Comments { sm, comments, current: 0 }
+    }
+
+    pub fn next(&self) -> Option<Comment> {
+        self.comments.get(self.current).cloned()
+    }
+
+    pub fn trailing_comment(
+        &self,
+        span: rustc_span::Span,
+        next_pos: Option<BytePos>,
+    ) -> Option<Comment> {
+        if let Some(cmnt) = self.next() {
+            if cmnt.style != CommentStyle::Trailing {
+                return None;
+            }
+            let span_line = self.sm.lookup_char_pos(span.hi());
+            let comment_line = self.sm.lookup_char_pos(cmnt.pos);
+            let next = next_pos.unwrap_or_else(|| cmnt.pos + BytePos(1));
+            if span.hi() < cmnt.pos && cmnt.pos < next && span_line.line == comment_line.line {
+                return Some(cmnt);
+            }
+        }
+
+        None
+    }
+}
+
+pub struct State<'a> {
+    pub s: pp::Printer,
+    comments: Option<Comments<'a>>,
+    ann: &'a (dyn PpAnn + 'a),
+}
+
+pub(crate) const INDENT_UNIT: isize = 4;
+
+/// Requires you to pass an input filename and reader so that
+/// it can scan the input text for comments to copy forward.
+pub fn print_crate<'a>(
+    sm: &'a SourceMap,
+    krate: &ast::Crate,
+    filename: FileName,
+    input: String,
+    ann: &'a dyn PpAnn,
+    is_expanded: bool,
+    edition: Edition,
+) -> String {
+    let mut s =
+        State { s: pp::Printer::new(), comments: Some(Comments::new(sm, filename, input)), ann };
+
+    if is_expanded && !krate.attrs.iter().any(|attr| attr.has_name(sym::no_core)) {
+        // We need to print `#![no_std]` (and its feature gate) so that
+        // compiling pretty-printed source won't inject libstd again.
+        // However, we don't want these attributes in the AST because
+        // of the feature gate, so we fake them up here.
+
+        // `#![feature(prelude_import)]`
+        let pi_nested = attr::mk_nested_word_item(Ident::with_dummy_span(sym::prelude_import));
+        let list = attr::mk_list_item(Ident::with_dummy_span(sym::feature), vec![pi_nested]);
+        let fake_attr = attr::mk_attr_inner(list);
+        s.print_attribute(&fake_attr);
+
+        // Currently, in Rust 2018 we don't have `extern crate std;` at the crate
+        // root, so this is not needed, and actually breaks things.
+        if edition == Edition::Edition2015 {
+            // `#![no_std]`
+            let no_std_meta = attr::mk_word_item(Ident::with_dummy_span(sym::no_std));
+            let fake_attr = attr::mk_attr_inner(no_std_meta);
+            s.print_attribute(&fake_attr);
+        }
+    }
+
+    s.print_inner_attributes(&krate.attrs);
+    for item in &krate.items {
+        s.print_item(item);
+    }
+    s.print_remaining_comments();
+    s.ann.post(&mut s, AnnNode::Crate(krate));
+    s.s.eof()
+}
+
+/// This makes printed token streams look slightly nicer,
+/// and also addresses some specific regressions described in #63896 and #73345.
+fn tt_prepend_space(tt: &TokenTree, prev: &TokenTree) -> bool {
+    if let TokenTree::Token(token, _) = prev {
+        if matches!(token.kind, token::Dot | token::Dollar) {
+            return false;
+        }
+        if let token::DocComment(comment_kind, ..) = token.kind {
+            return comment_kind != CommentKind::Line;
+        }
+    }
+    match tt {
+        TokenTree::Token(token, _) => !matches!(token.kind, token::Comma | token::Not | token::Dot),
+        TokenTree::Delimited(_, Delimiter::Parenthesis, _) => {
+            !matches!(prev, TokenTree::Token(Token { kind: token::Ident(..), .. }, _))
+        }
+        TokenTree::Delimited(_, Delimiter::Bracket, _) => {
+            !matches!(prev, TokenTree::Token(Token { kind: token::Pound, .. }, _))
+        }
+        TokenTree::Delimited(..) => true,
+    }
+}
+
+fn binop_to_string(op: BinOpToken) -> &'static str {
+    match op {
+        token::Plus => "+",
+        token::Minus => "-",
+        token::Star => "*",
+        token::Slash => "/",
+        token::Percent => "%",
+        token::Caret => "^",
+        token::And => "&",
+        token::Or => "|",
+        token::Shl => "<<",
+        token::Shr => ">>",
+    }
+}
+
+fn doc_comment_to_string(
+    comment_kind: CommentKind,
+    attr_style: ast::AttrStyle,
+    data: Symbol,
+) -> String {
+    match (comment_kind, attr_style) {
+        (CommentKind::Line, ast::AttrStyle::Outer) => format!("///{}", data),
+        (CommentKind::Line, ast::AttrStyle::Inner) => format!("//!{}", data),
+        (CommentKind::Block, ast::AttrStyle::Outer) => format!("/**{}*/", data),
+        (CommentKind::Block, ast::AttrStyle::Inner) => format!("/*!{}*/", data),
+    }
+}
+
+pub fn literal_to_string(lit: token::Lit) -> String {
+    let token::Lit { kind, symbol, suffix } = lit;
+    let mut out = match kind {
+        token::Byte => format!("b'{}'", symbol),
+        token::Char => format!("'{}'", symbol),
+        token::Str => format!("\"{}\"", symbol),
+        token::StrRaw(n) => {
+            format!("r{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = symbol)
+        }
+        token::ByteStr => format!("b\"{}\"", symbol),
+        token::ByteStrRaw(n) => {
+            format!("br{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = symbol)
+        }
+        token::Integer | token::Float | token::Bool | token::Err => symbol.to_string(),
+    };
+
+    if let Some(suffix) = suffix {
+        out.push_str(suffix.as_str())
+    }
+
+    out
+}
+
+impl std::ops::Deref for State<'_> {
+    type Target = pp::Printer;
+    fn deref(&self) -> &Self::Target {
+        &self.s
+    }
+}
+
+impl std::ops::DerefMut for State<'_> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.s
+    }
+}
+
+pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::DerefMut {
+    fn comments(&mut self) -> &mut Option<Comments<'a>>;
+    fn print_ident(&mut self, ident: Ident);
+    fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool);
+
+    fn strsep<T, F>(
+        &mut self,
+        sep: &'static str,
+        space_before: bool,
+        b: Breaks,
+        elts: &[T],
+        mut op: F,
+    ) where
+        F: FnMut(&mut Self, &T),
+    {
+        self.rbox(0, b);
+        if let Some((first, rest)) = elts.split_first() {
+            op(self, first);
+            for elt in rest {
+                if space_before {
+                    self.space();
+                }
+                self.word_space(sep);
+                op(self, elt);
+            }
+        }
+        self.end();
+    }
+
+    fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], op: F)
+    where
+        F: FnMut(&mut Self, &T),
+    {
+        self.strsep(",", false, b, elts, op)
+    }
+
+    fn maybe_print_comment(&mut self, pos: BytePos) -> bool {
+        let mut has_comment = false;
+        while let Some(ref cmnt) = self.next_comment() {
+            if cmnt.pos < pos {
+                has_comment = true;
+                self.print_comment(cmnt);
+            } else {
+                break;
+            }
+        }
+        has_comment
+    }
+
+    fn print_comment(&mut self, cmnt: &Comment) {
+        match cmnt.style {
+            CommentStyle::Mixed => {
+                if !self.is_beginning_of_line() {
+                    self.zerobreak();
+                }
+                if let Some((last, lines)) = cmnt.lines.split_last() {
+                    self.ibox(0);
+
+                    for line in lines {
+                        self.word(line.clone());
+                        self.hardbreak()
+                    }
+
+                    self.word(last.clone());
+                    self.space();
+
+                    self.end();
+                }
+                self.zerobreak()
+            }
+            CommentStyle::Isolated => {
+                self.hardbreak_if_not_bol();
+                for line in &cmnt.lines {
+                    // Don't print empty lines because they will end up as trailing
+                    // whitespace.
+                    if !line.is_empty() {
+                        self.word(line.clone());
+                    }
+                    self.hardbreak();
+                }
+            }
+            CommentStyle::Trailing => {
+                if !self.is_beginning_of_line() {
+                    self.word(" ");
+                }
+                if cmnt.lines.len() == 1 {
+                    self.word(cmnt.lines[0].clone());
+                    self.hardbreak()
+                } else {
+                    self.visual_align();
+                    for line in &cmnt.lines {
+                        if !line.is_empty() {
+                            self.word(line.clone());
+                        }
+                        self.hardbreak();
+                    }
+                    self.end();
+                }
+            }
+            CommentStyle::BlankLine => {
+                // We need to do at least one, possibly two hardbreaks.
+                let twice = match self.last_token() {
+                    Some(pp::Token::String(s)) => ";" == s,
+                    Some(pp::Token::Begin(_)) => true,
+                    Some(pp::Token::End) => true,
+                    _ => false,
+                };
+                if twice {
+                    self.hardbreak();
+                }
+                self.hardbreak();
+            }
+        }
+        if let Some(cmnts) = self.comments() {
+            cmnts.current += 1;
+        }
+    }
+
+    fn next_comment(&mut self) -> Option<Comment> {
+        self.comments().as_mut().and_then(|c| c.next())
+    }
+
+    fn maybe_print_trailing_comment(&mut self, span: rustc_span::Span, next_pos: Option<BytePos>) {
+        if let Some(cmnts) = self.comments() {
+            if let Some(cmnt) = cmnts.trailing_comment(span, next_pos) {
+                self.print_comment(&cmnt);
+            }
+        }
+    }
+
+    fn print_remaining_comments(&mut self) {
+        // If there aren't any remaining comments, then we need to manually
+        // make sure there is a line break at the end.
+        if self.next_comment().is_none() {
+            self.hardbreak();
+        }
+        while let Some(ref cmnt) = self.next_comment() {
+            self.print_comment(cmnt)
+        }
+    }
+
+    fn print_literal(&mut self, lit: &ast::Lit) {
+        self.maybe_print_comment(lit.span.lo());
+        self.word(lit.token.to_string())
+    }
+
+    fn print_string(&mut self, st: &str, style: ast::StrStyle) {
+        let st = match style {
+            ast::StrStyle::Cooked => format!("\"{}\"", st.escape_debug()),
+            ast::StrStyle::Raw(n) => {
+                format!("r{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = st)
+            }
+        };
+        self.word(st)
+    }
+
+    fn print_symbol(&mut self, sym: Symbol, style: ast::StrStyle) {
+        self.print_string(sym.as_str(), style);
+    }
+
+    fn print_inner_attributes(&mut self, attrs: &[ast::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, true)
+    }
+
+    fn print_inner_attributes_no_trailing_hardbreak(&mut self, attrs: &[ast::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, false)
+    }
+
+    fn print_outer_attributes(&mut self, attrs: &[ast::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Outer, false, true)
+    }
+
+    fn print_inner_attributes_inline(&mut self, attrs: &[ast::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Inner, true, true)
+    }
+
+    fn print_outer_attributes_inline(&mut self, attrs: &[ast::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Outer, true, true)
+    }
+
+    fn print_either_attributes(
+        &mut self,
+        attrs: &[ast::Attribute],
+        kind: ast::AttrStyle,
+        is_inline: bool,
+        trailing_hardbreak: bool,
+    ) -> bool {
+        let mut printed = false;
+        for attr in attrs {
+            if attr.style == kind {
+                self.print_attribute_inline(attr, is_inline);
+                if is_inline {
+                    self.nbsp();
+                }
+                printed = true;
+            }
+        }
+        if printed && trailing_hardbreak && !is_inline {
+            self.hardbreak_if_not_bol();
+        }
+        printed
+    }
+
+    fn print_attribute(&mut self, attr: &ast::Attribute) {
+        self.print_attribute_inline(attr, false)
+    }
+
+    fn print_attribute_inline(&mut self, attr: &ast::Attribute, is_inline: bool) {
+        if !is_inline {
+            self.hardbreak_if_not_bol();
+        }
+        self.maybe_print_comment(attr.span.lo());
+        match attr.kind {
+            ast::AttrKind::Normal(ref item, _) => {
+                match attr.style {
+                    ast::AttrStyle::Inner => self.word("#!["),
+                    ast::AttrStyle::Outer => self.word("#["),
+                }
+                self.print_attr_item(&item, attr.span);
+                self.word("]");
+            }
+            ast::AttrKind::DocComment(comment_kind, data) => {
+                self.word(doc_comment_to_string(comment_kind, attr.style, data));
+                self.hardbreak()
+            }
+        }
+    }
+
+    fn print_attr_item(&mut self, item: &ast::AttrItem, span: Span) {
+        self.ibox(0);
+        match &item.args {
+            MacArgs::Delimited(_, delim, tokens) => self.print_mac_common(
+                Some(MacHeader::Path(&item.path)),
+                false,
+                None,
+                Some(delim.to_token()),
+                tokens,
+                true,
+                span,
+            ),
+            MacArgs::Empty => {
+                self.print_path(&item.path, false, 0);
+            }
+            MacArgs::Eq(_, MacArgsEq::Ast(expr)) => {
+                self.print_path(&item.path, false, 0);
+                self.space();
+                self.word_space("=");
+                let token_str = self.expr_to_string(expr);
+                self.word(token_str);
+            }
+            MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+                self.print_path(&item.path, false, 0);
+                self.space();
+                self.word_space("=");
+                let token_str = self.literal_to_string(lit);
+                self.word(token_str);
+            }
+        }
+        self.end();
+    }
+
+    fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) {
+        match item {
+            ast::NestedMetaItem::MetaItem(ref mi) => self.print_meta_item(mi),
+            ast::NestedMetaItem::Literal(ref lit) => self.print_literal(lit),
+        }
+    }
+
+    fn print_meta_item(&mut self, item: &ast::MetaItem) {
+        self.ibox(INDENT_UNIT);
+        match item.kind {
+            ast::MetaItemKind::Word => self.print_path(&item.path, false, 0),
+            ast::MetaItemKind::NameValue(ref value) => {
+                self.print_path(&item.path, false, 0);
+                self.space();
+                self.word_space("=");
+                self.print_literal(value);
+            }
+            ast::MetaItemKind::List(ref items) => {
+                self.print_path(&item.path, false, 0);
+                self.popen();
+                self.commasep(Consistent, &items, |s, i| s.print_meta_list_item(i));
+                self.pclose();
+            }
+        }
+        self.end();
+    }
+
+    /// This doesn't deserve to be called "pretty" printing, but it should be
+    /// meaning-preserving. A quick hack that might help would be to look at the
+    /// spans embedded in the TTs to decide where to put spaces and newlines.
+    /// But it'd be better to parse these according to the grammar of the
+    /// appropriate macro, transcribe back into the grammar we just parsed from,
+    /// and then pretty-print the resulting AST nodes (so, e.g., we print
+    /// expression arguments as expressions). It can be done! I think.
+    fn print_tt(&mut self, tt: &TokenTree, convert_dollar_crate: bool) {
+        match tt {
+            TokenTree::Token(token, _) => {
+                let token_str = self.token_to_string_ext(&token, convert_dollar_crate);
+                self.word(token_str);
+                if let token::DocComment(..) = token.kind {
+                    self.hardbreak()
+                }
+            }
+            TokenTree::Delimited(dspan, delim, tts) => {
+                self.print_mac_common(
+                    None,
+                    false,
+                    None,
+                    Some(*delim),
+                    tts,
+                    convert_dollar_crate,
+                    dspan.entire(),
+                );
+            }
+        }
+    }
+
+    fn print_tts(&mut self, tts: &TokenStream, convert_dollar_crate: bool) {
+        let mut iter = tts.trees().peekable();
+        while let Some(tt) = iter.next() {
+            self.print_tt(tt, convert_dollar_crate);
+            if let Some(next) = iter.peek() {
+                if tt_prepend_space(next, tt) {
+                    self.space();
+                }
+            }
+        }
+    }
+
+    fn print_mac_common(
+        &mut self,
+        header: Option<MacHeader<'_>>,
+        has_bang: bool,
+        ident: Option<Ident>,
+        delim: Option<Delimiter>,
+        tts: &TokenStream,
+        convert_dollar_crate: bool,
+        span: Span,
+    ) {
+        if delim == Some(Delimiter::Brace) {
+            self.cbox(INDENT_UNIT);
+        }
+        match header {
+            Some(MacHeader::Path(path)) => self.print_path(path, false, 0),
+            Some(MacHeader::Keyword(kw)) => self.word(kw),
+            None => {}
+        }
+        if has_bang {
+            self.word("!");
+        }
+        if let Some(ident) = ident {
+            self.nbsp();
+            self.print_ident(ident);
+        }
+        match delim {
+            Some(Delimiter::Brace) => {
+                if header.is_some() || has_bang || ident.is_some() {
+                    self.nbsp();
+                }
+                self.word("{");
+                if !tts.is_empty() {
+                    self.space();
+                }
+                self.ibox(0);
+                self.print_tts(tts, convert_dollar_crate);
+                self.end();
+                let empty = tts.is_empty();
+                self.bclose(span, empty);
+            }
+            Some(delim) => {
+                let token_str = self.token_kind_to_string(&token::OpenDelim(delim));
+                self.word(token_str);
+                self.ibox(0);
+                self.print_tts(tts, convert_dollar_crate);
+                self.end();
+                let token_str = self.token_kind_to_string(&token::CloseDelim(delim));
+                self.word(token_str);
+            }
+            None => {
+                self.ibox(0);
+                self.print_tts(tts, convert_dollar_crate);
+                self.end();
+            }
+        }
+    }
+
+    fn print_mac_def(
+        &mut self,
+        macro_def: &ast::MacroDef,
+        ident: &Ident,
+        sp: Span,
+        print_visibility: impl FnOnce(&mut Self),
+    ) {
+        let (kw, has_bang) = if macro_def.macro_rules {
+            ("macro_rules", true)
+        } else {
+            print_visibility(self);
+            ("macro", false)
+        };
+        self.print_mac_common(
+            Some(MacHeader::Keyword(kw)),
+            has_bang,
+            Some(*ident),
+            macro_def.body.delim(),
+            &macro_def.body.inner_tokens(),
+            true,
+            sp,
+        );
+        if macro_def.body.need_semicolon() {
+            self.word(";");
+        }
+    }
+
+    fn print_path(&mut self, path: &ast::Path, colons_before_params: bool, depth: usize) {
+        self.maybe_print_comment(path.span.lo());
+
+        for (i, segment) in path.segments[..path.segments.len() - depth].iter().enumerate() {
+            if i > 0 {
+                self.word("::")
+            }
+            self.print_path_segment(segment, colons_before_params);
+        }
+    }
+
+    fn print_path_segment(&mut self, segment: &ast::PathSegment, colons_before_params: bool) {
+        if segment.ident.name != kw::PathRoot {
+            self.print_ident(segment.ident);
+            if let Some(ref args) = segment.args {
+                self.print_generic_args(args, colons_before_params);
+            }
+        }
+    }
+
+    fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) {
+        let w = w.into();
+        // Outer-box is consistent.
+        self.cbox(INDENT_UNIT);
+        // Head-box is inconsistent.
+        self.ibox(0);
+        // Keyword that starts the head.
+        if !w.is_empty() {
+            self.word_nbsp(w);
+        }
+    }
+
+    fn bopen(&mut self) {
+        self.word("{");
+        self.end(); // Close the head-box.
+    }
+
+    fn bclose_maybe_open(&mut self, span: rustc_span::Span, empty: bool, close_box: bool) {
+        let has_comment = self.maybe_print_comment(span.hi());
+        if !empty || has_comment {
+            self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
+        }
+        self.word("}");
+        if close_box {
+            self.end(); // Close the outer-box.
+        }
+    }
+
+    fn bclose(&mut self, span: rustc_span::Span, empty: bool) {
+        let close_box = true;
+        self.bclose_maybe_open(span, empty, close_box)
+    }
+
+    fn break_offset_if_not_bol(&mut self, n: usize, off: isize) {
+        if !self.is_beginning_of_line() {
+            self.break_offset(n, off)
+        } else if off != 0 {
+            if let Some(last_token) = self.last_token_still_buffered() {
+                if last_token.is_hardbreak_tok() {
+                    // We do something pretty sketchy here: tuck the nonzero
+                    // offset-adjustment we were going to deposit along with the
+                    // break into the previous hardbreak.
+                    self.replace_last_token_still_buffered(pp::Printer::hardbreak_tok_offset(off));
+                }
+            }
+        }
+    }
+
+    fn nonterminal_to_string(&self, nt: &Nonterminal) -> String {
+        match *nt {
+            token::NtExpr(ref e) => self.expr_to_string(e),
+            token::NtMeta(ref e) => self.attr_item_to_string(e),
+            token::NtTy(ref e) => self.ty_to_string(e),
+            token::NtPath(ref e) => self.path_to_string(e),
+            token::NtItem(ref e) => self.item_to_string(e),
+            token::NtBlock(ref e) => self.block_to_string(e),
+            token::NtStmt(ref e) => self.stmt_to_string(e),
+            token::NtPat(ref e) => self.pat_to_string(e),
+            token::NtIdent(e, is_raw) => IdentPrinter::for_ast_ident(e, is_raw).to_string(),
+            token::NtLifetime(e) => e.to_string(),
+            token::NtLiteral(ref e) => self.expr_to_string(e),
+            token::NtVis(ref e) => self.vis_to_string(e),
+        }
+    }
+
+    /// Print the token kind precisely, without converting `$crate` into its respective crate name.
+    fn token_kind_to_string(&self, tok: &TokenKind) -> Cow<'static, str> {
+        self.token_kind_to_string_ext(tok, None)
+    }
+
+    fn token_kind_to_string_ext(
+        &self,
+        tok: &TokenKind,
+        convert_dollar_crate: Option<Span>,
+    ) -> Cow<'static, str> {
+        match *tok {
+            token::Eq => "=".into(),
+            token::Lt => "<".into(),
+            token::Le => "<=".into(),
+            token::EqEq => "==".into(),
+            token::Ne => "!=".into(),
+            token::Ge => ">=".into(),
+            token::Gt => ">".into(),
+            token::Not => "!".into(),
+            token::Tilde => "~".into(),
+            token::OrOr => "||".into(),
+            token::AndAnd => "&&".into(),
+            token::BinOp(op) => binop_to_string(op).into(),
+            token::BinOpEq(op) => format!("{}=", binop_to_string(op)).into(),
+
+            /* Structural symbols */
+            token::At => "@".into(),
+            token::Dot => ".".into(),
+            token::DotDot => "..".into(),
+            token::DotDotDot => "...".into(),
+            token::DotDotEq => "..=".into(),
+            token::Comma => ",".into(),
+            token::Semi => ";".into(),
+            token::Colon => ":".into(),
+            token::ModSep => "::".into(),
+            token::RArrow => "->".into(),
+            token::LArrow => "<-".into(),
+            token::FatArrow => "=>".into(),
+            token::OpenDelim(Delimiter::Parenthesis) => "(".into(),
+            token::CloseDelim(Delimiter::Parenthesis) => ")".into(),
+            token::OpenDelim(Delimiter::Bracket) => "[".into(),
+            token::CloseDelim(Delimiter::Bracket) => "]".into(),
+            token::OpenDelim(Delimiter::Brace) => "{".into(),
+            token::CloseDelim(Delimiter::Brace) => "}".into(),
+            token::OpenDelim(Delimiter::Invisible) | token::CloseDelim(Delimiter::Invisible) => {
+                "".into()
+            }
+            token::Pound => "#".into(),
+            token::Dollar => "$".into(),
+            token::Question => "?".into(),
+            token::SingleQuote => "'".into(),
+
+            /* Literals */
+            token::Literal(lit) => literal_to_string(lit).into(),
+
+            /* Name components */
+            token::Ident(s, is_raw) => {
+                IdentPrinter::new(s, is_raw, convert_dollar_crate).to_string().into()
+            }
+            token::Lifetime(s) => s.to_string().into(),
+
+            /* Other */
+            token::DocComment(comment_kind, attr_style, data) => {
+                doc_comment_to_string(comment_kind, attr_style, data).into()
+            }
+            token::Eof => "<eof>".into(),
+
+            token::Interpolated(ref nt) => self.nonterminal_to_string(nt).into(),
+        }
+    }
+
+    /// Print the token precisely, without converting `$crate` into its respective crate name.
+    fn token_to_string(&self, token: &Token) -> Cow<'static, str> {
+        self.token_to_string_ext(token, false)
+    }
+
+    fn token_to_string_ext(&self, token: &Token, convert_dollar_crate: bool) -> Cow<'static, str> {
+        let convert_dollar_crate = convert_dollar_crate.then_some(token.span);
+        self.token_kind_to_string_ext(&token.kind, convert_dollar_crate)
+    }
+
+    fn ty_to_string(&self, ty: &ast::Ty) -> String {
+        Self::to_string(|s| s.print_type(ty))
+    }
+
+    fn bounds_to_string(&self, bounds: &[ast::GenericBound]) -> String {
+        Self::to_string(|s| s.print_type_bounds(bounds))
+    }
+
+    fn pat_to_string(&self, pat: &ast::Pat) -> String {
+        Self::to_string(|s| s.print_pat(pat))
+    }
+
+    fn expr_to_string(&self, e: &ast::Expr) -> String {
+        Self::to_string(|s| s.print_expr(e))
+    }
+
+    fn literal_to_string(&self, lit: &ast::Lit) -> String {
+        Self::to_string(|s| s.print_literal(lit))
+    }
+
+    fn tt_to_string(&self, tt: &TokenTree) -> String {
+        Self::to_string(|s| s.print_tt(tt, false))
+    }
+
+    fn tts_to_string(&self, tokens: &TokenStream) -> String {
+        Self::to_string(|s| s.print_tts(tokens, false))
+    }
+
+    fn stmt_to_string(&self, stmt: &ast::Stmt) -> String {
+        Self::to_string(|s| s.print_stmt(stmt))
+    }
+
+    fn item_to_string(&self, i: &ast::Item) -> String {
+        Self::to_string(|s| s.print_item(i))
+    }
+
+    fn assoc_item_to_string(&self, i: &ast::AssocItem) -> String {
+        Self::to_string(|s| s.print_assoc_item(i))
+    }
+
+    fn foreign_item_to_string(&self, i: &ast::ForeignItem) -> String {
+        Self::to_string(|s| s.print_foreign_item(i))
+    }
+
+    fn generic_params_to_string(&self, generic_params: &[ast::GenericParam]) -> String {
+        Self::to_string(|s| s.print_generic_params(generic_params))
+    }
+
+    fn path_to_string(&self, p: &ast::Path) -> String {
+        Self::to_string(|s| s.print_path(p, false, 0))
+    }
+
+    fn path_segment_to_string(&self, p: &ast::PathSegment) -> String {
+        Self::to_string(|s| s.print_path_segment(p, false))
+    }
+
+    fn vis_to_string(&self, v: &ast::Visibility) -> String {
+        Self::to_string(|s| s.print_visibility(v))
+    }
+
+    fn block_to_string(&self, blk: &ast::Block) -> String {
+        Self::to_string(|s| {
+            // Containing cbox, will be closed by `print_block` at `}`.
+            s.cbox(INDENT_UNIT);
+            // Head-ibox, will be closed by `print_block` after `{`.
+            s.ibox(0);
+            s.print_block(blk)
+        })
+    }
+
+    fn meta_list_item_to_string(&self, li: &ast::NestedMetaItem) -> String {
+        Self::to_string(|s| s.print_meta_list_item(li))
+    }
+
+    fn attr_item_to_string(&self, ai: &ast::AttrItem) -> String {
+        Self::to_string(|s| s.print_attr_item(ai, ai.path.span))
+    }
+
+    fn attribute_to_string(&self, attr: &ast::Attribute) -> String {
+        Self::to_string(|s| s.print_attribute(attr))
+    }
+
+    fn param_to_string(&self, arg: &ast::Param) -> String {
+        Self::to_string(|s| s.print_param(arg, false))
+    }
+
+    fn to_string(f: impl FnOnce(&mut State<'_>)) -> String {
+        let mut printer = State::new();
+        f(&mut printer);
+        printer.s.eof()
+    }
+}
+
+impl<'a> PrintState<'a> for State<'a> {
+    fn comments(&mut self) -> &mut Option<Comments<'a>> {
+        &mut self.comments
+    }
+
+    fn print_ident(&mut self, ident: Ident) {
+        self.word(IdentPrinter::for_ast_ident(ident, ident.is_raw_guess()).to_string());
+        self.ann.post(self, AnnNode::Ident(&ident))
+    }
+
+    fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool) {
+        if colons_before_params {
+            self.word("::")
+        }
+
+        match *args {
+            ast::GenericArgs::AngleBracketed(ref data) => {
+                self.word("<");
+                self.commasep(Inconsistent, &data.args, |s, arg| match arg {
+                    ast::AngleBracketedArg::Arg(a) => s.print_generic_arg(a),
+                    ast::AngleBracketedArg::Constraint(c) => s.print_assoc_constraint(c),
+                });
+                self.word(">")
+            }
+
+            ast::GenericArgs::Parenthesized(ref data) => {
+                self.word("(");
+                self.commasep(Inconsistent, &data.inputs, |s, ty| s.print_type(ty));
+                self.word(")");
+                self.print_fn_ret_ty(&data.output);
+            }
+        }
+    }
+}
+
+impl<'a> State<'a> {
+    pub fn new() -> State<'a> {
+        State { s: pp::Printer::new(), comments: None, ann: &NoAnn }
+    }
+
+    pub(crate) fn commasep_cmnt<T, F, G>(
+        &mut self,
+        b: Breaks,
+        elts: &[T],
+        mut op: F,
+        mut get_span: G,
+    ) where
+        F: FnMut(&mut State<'_>, &T),
+        G: FnMut(&T) -> rustc_span::Span,
+    {
+        self.rbox(0, b);
+        let len = elts.len();
+        let mut i = 0;
+        for elt in elts {
+            self.maybe_print_comment(get_span(elt).hi());
+            op(self, elt);
+            i += 1;
+            if i < len {
+                self.word(",");
+                self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()));
+                self.space_if_not_bol();
+            }
+        }
+        self.end();
+    }
+
+    pub(crate) fn commasep_exprs(&mut self, b: Breaks, exprs: &[P<ast::Expr>]) {
+        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
+    }
+
+    pub fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
+        if let Some(lt) = *lifetime {
+            self.print_lifetime(lt);
+            self.nbsp();
+        }
+    }
+
+    pub fn print_assoc_constraint(&mut self, constraint: &ast::AssocConstraint) {
+        self.print_ident(constraint.ident);
+        constraint.gen_args.as_ref().map(|args| self.print_generic_args(args, false));
+        self.space();
+        match &constraint.kind {
+            ast::AssocConstraintKind::Equality { term } => {
+                self.word_space("=");
+                match term {
+                    Term::Ty(ty) => self.print_type(ty),
+                    Term::Const(c) => self.print_expr_anon_const(c, &[]),
+                }
+            }
+            ast::AssocConstraintKind::Bound { bounds } => {
+                if !bounds.is_empty() {
+                    self.word_nbsp(":");
+                    self.print_type_bounds(&bounds);
+                }
+            }
+        }
+    }
+
+    pub fn print_generic_arg(&mut self, generic_arg: &GenericArg) {
+        match generic_arg {
+            GenericArg::Lifetime(lt) => self.print_lifetime(*lt),
+            GenericArg::Type(ty) => self.print_type(ty),
+            GenericArg::Const(ct) => self.print_expr(&ct.value),
+        }
+    }
+
+    pub fn print_type(&mut self, ty: &ast::Ty) {
+        self.maybe_print_comment(ty.span.lo());
+        self.ibox(0);
+        match ty.kind {
+            ast::TyKind::Slice(ref ty) => {
+                self.word("[");
+                self.print_type(ty);
+                self.word("]");
+            }
+            ast::TyKind::Ptr(ref mt) => {
+                self.word("*");
+                self.print_mt(mt, true);
+            }
+            ast::TyKind::Rptr(ref lifetime, ref mt) => {
+                self.word("&");
+                self.print_opt_lifetime(lifetime);
+                self.print_mt(mt, false);
+            }
+            ast::TyKind::Never => {
+                self.word("!");
+            }
+            ast::TyKind::Tup(ref elts) => {
+                self.popen();
+                self.commasep(Inconsistent, &elts, |s, ty| s.print_type(ty));
+                if elts.len() == 1 {
+                    self.word(",");
+                }
+                self.pclose();
+            }
+            ast::TyKind::Paren(ref typ) => {
+                self.popen();
+                self.print_type(typ);
+                self.pclose();
+            }
+            ast::TyKind::BareFn(ref f) => {
+                self.print_ty_fn(f.ext, f.unsafety, &f.decl, None, &f.generic_params);
+            }
+            ast::TyKind::Path(None, ref path) => {
+                self.print_path(path, false, 0);
+            }
+            ast::TyKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, false),
+            ast::TyKind::TraitObject(ref bounds, syntax) => {
+                if syntax == ast::TraitObjectSyntax::Dyn {
+                    self.word_nbsp("dyn");
+                }
+                self.print_type_bounds(bounds);
+            }
+            ast::TyKind::ImplTrait(_, ref bounds) => {
+                self.word_nbsp("impl");
+                self.print_type_bounds(bounds);
+            }
+            ast::TyKind::Array(ref ty, ref length) => {
+                self.word("[");
+                self.print_type(ty);
+                self.word("; ");
+                self.print_expr(&length.value);
+                self.word("]");
+            }
+            ast::TyKind::Typeof(ref e) => {
+                self.word("typeof(");
+                self.print_expr(&e.value);
+                self.word(")");
+            }
+            ast::TyKind::Infer => {
+                self.word("_");
+            }
+            ast::TyKind::Err => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
+            ast::TyKind::ImplicitSelf => {
+                self.word("Self");
+            }
+            ast::TyKind::MacCall(ref m) => {
+                self.print_mac(m);
+            }
+            ast::TyKind::CVarArgs => {
+                self.word("...");
+            }
+        }
+        self.end();
+    }
+
+    fn print_trait_ref(&mut self, t: &ast::TraitRef) {
+        self.print_path(&t.path, false, 0)
+    }
+
+    fn print_formal_generic_params(&mut self, generic_params: &[ast::GenericParam]) {
+        if !generic_params.is_empty() {
+            self.word("for");
+            self.print_generic_params(generic_params);
+            self.nbsp();
+        }
+    }
+
+    fn print_poly_trait_ref(&mut self, t: &ast::PolyTraitRef) {
+        self.print_formal_generic_params(&t.bound_generic_params);
+        self.print_trait_ref(&t.trait_ref)
+    }
+
+    pub(crate) fn print_stmt(&mut self, st: &ast::Stmt) {
+        self.maybe_print_comment(st.span.lo());
+        match st.kind {
+            ast::StmtKind::Local(ref loc) => {
+                self.print_outer_attributes(&loc.attrs);
+                self.space_if_not_bol();
+                self.ibox(INDENT_UNIT);
+                self.word_nbsp("let");
+
+                self.ibox(INDENT_UNIT);
+                self.print_local_decl(loc);
+                self.end();
+                if let Some((init, els)) = loc.kind.init_else_opt() {
+                    self.nbsp();
+                    self.word_space("=");
+                    self.print_expr(init);
+                    if let Some(els) = els {
+                        self.cbox(INDENT_UNIT);
+                        self.ibox(INDENT_UNIT);
+                        self.word(" else ");
+                        self.print_block(els);
+                    }
+                }
+                self.word(";");
+                self.end(); // `let` ibox
+            }
+            ast::StmtKind::Item(ref item) => self.print_item(item),
+            ast::StmtKind::Expr(ref expr) => {
+                self.space_if_not_bol();
+                self.print_expr_outer_attr_style(expr, false);
+                if classify::expr_requires_semi_to_be_stmt(expr) {
+                    self.word(";");
+                }
+            }
+            ast::StmtKind::Semi(ref expr) => {
+                self.space_if_not_bol();
+                self.print_expr_outer_attr_style(expr, false);
+                self.word(";");
+            }
+            ast::StmtKind::Empty => {
+                self.space_if_not_bol();
+                self.word(";");
+            }
+            ast::StmtKind::MacCall(ref mac) => {
+                self.space_if_not_bol();
+                self.print_outer_attributes(&mac.attrs);
+                self.print_mac(&mac.mac);
+                if mac.style == ast::MacStmtStyle::Semicolon {
+                    self.word(";");
+                }
+            }
+        }
+        self.maybe_print_trailing_comment(st.span, None)
+    }
+
+    pub(crate) fn print_block(&mut self, blk: &ast::Block) {
+        self.print_block_with_attrs(blk, &[])
+    }
+
+    pub(crate) fn print_block_unclosed_indent(&mut self, blk: &ast::Block) {
+        self.print_block_maybe_unclosed(blk, &[], false)
+    }
+
+    pub(crate) fn print_block_with_attrs(&mut self, blk: &ast::Block, attrs: &[ast::Attribute]) {
+        self.print_block_maybe_unclosed(blk, attrs, true)
+    }
+
+    pub(crate) fn print_block_maybe_unclosed(
+        &mut self,
+        blk: &ast::Block,
+        attrs: &[ast::Attribute],
+        close_box: bool,
+    ) {
+        match blk.rules {
+            BlockCheckMode::Unsafe(..) => self.word_space("unsafe"),
+            BlockCheckMode::Default => (),
+        }
+        self.maybe_print_comment(blk.span.lo());
+        self.ann.pre(self, AnnNode::Block(blk));
+        self.bopen();
+
+        let has_attrs = self.print_inner_attributes(attrs);
+
+        for (i, st) in blk.stmts.iter().enumerate() {
+            match st.kind {
+                ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
+                    self.maybe_print_comment(st.span.lo());
+                    self.space_if_not_bol();
+                    self.print_expr_outer_attr_style(expr, false);
+                    self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
+                }
+                _ => self.print_stmt(st),
+            }
+        }
+
+        let empty = !has_attrs && blk.stmts.is_empty();
+        self.bclose_maybe_open(blk.span, empty, close_box);
+        self.ann.post(self, AnnNode::Block(blk))
+    }
+
+    /// Print a `let pat = expr` expression.
+    pub(crate) fn print_let(&mut self, pat: &ast::Pat, expr: &ast::Expr) {
+        self.word("let ");
+        self.print_pat(pat);
+        self.space();
+        self.word_space("=");
+        let npals = || parser::needs_par_as_let_scrutinee(expr.precedence().order());
+        self.print_expr_cond_paren(expr, Self::cond_needs_par(expr) || npals())
+    }
+
+    pub(crate) fn print_mac(&mut self, m: &ast::MacCall) {
+        self.print_mac_common(
+            Some(MacHeader::Path(&m.path)),
+            true,
+            None,
+            m.args.delim(),
+            &m.args.inner_tokens(),
+            true,
+            m.span(),
+        );
+    }
+
+    fn print_inline_asm(&mut self, asm: &ast::InlineAsm) {
+        enum AsmArg<'a> {
+            Template(String),
+            Operand(&'a InlineAsmOperand),
+            ClobberAbi(Symbol),
+            Options(InlineAsmOptions),
+        }
+
+        let mut args = vec![AsmArg::Template(InlineAsmTemplatePiece::to_string(&asm.template))];
+        args.extend(asm.operands.iter().map(|(o, _)| AsmArg::Operand(o)));
+        for (abi, _) in &asm.clobber_abis {
+            args.push(AsmArg::ClobberAbi(*abi));
+        }
+        if !asm.options.is_empty() {
+            args.push(AsmArg::Options(asm.options));
+        }
+
+        self.popen();
+        self.commasep(Consistent, &args, |s, arg| match arg {
+            AsmArg::Template(template) => s.print_string(&template, ast::StrStyle::Cooked),
+            AsmArg::Operand(op) => {
+                let print_reg_or_class = |s: &mut Self, r: &InlineAsmRegOrRegClass| match r {
+                    InlineAsmRegOrRegClass::Reg(r) => s.print_symbol(*r, ast::StrStyle::Cooked),
+                    InlineAsmRegOrRegClass::RegClass(r) => s.word(r.to_string()),
+                };
+                match op {
+                    InlineAsmOperand::In { reg, expr } => {
+                        s.word("in");
+                        s.popen();
+                        print_reg_or_class(s, reg);
+                        s.pclose();
+                        s.space();
+                        s.print_expr(expr);
+                    }
+                    InlineAsmOperand::Out { reg, late, expr } => {
+                        s.word(if *late { "lateout" } else { "out" });
+                        s.popen();
+                        print_reg_or_class(s, reg);
+                        s.pclose();
+                        s.space();
+                        match expr {
+                            Some(expr) => s.print_expr(expr),
+                            None => s.word("_"),
+                        }
+                    }
+                    InlineAsmOperand::InOut { reg, late, expr } => {
+                        s.word(if *late { "inlateout" } else { "inout" });
+                        s.popen();
+                        print_reg_or_class(s, reg);
+                        s.pclose();
+                        s.space();
+                        s.print_expr(expr);
+                    }
+                    InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
+                        s.word(if *late { "inlateout" } else { "inout" });
+                        s.popen();
+                        print_reg_or_class(s, reg);
+                        s.pclose();
+                        s.space();
+                        s.print_expr(in_expr);
+                        s.space();
+                        s.word_space("=>");
+                        match out_expr {
+                            Some(out_expr) => s.print_expr(out_expr),
+                            None => s.word("_"),
+                        }
+                    }
+                    InlineAsmOperand::Const { anon_const } => {
+                        s.word("const");
+                        s.space();
+                        s.print_expr(&anon_const.value);
+                    }
+                    InlineAsmOperand::Sym { sym } => {
+                        s.word("sym");
+                        s.space();
+                        if let Some(qself) = &sym.qself {
+                            s.print_qpath(&sym.path, qself, true);
+                        } else {
+                            s.print_path(&sym.path, true, 0);
+                        }
+                    }
+                }
+            }
+            AsmArg::ClobberAbi(abi) => {
+                s.word("clobber_abi");
+                s.popen();
+                s.print_symbol(*abi, ast::StrStyle::Cooked);
+                s.pclose();
+            }
+            AsmArg::Options(opts) => {
+                s.word("options");
+                s.popen();
+                let mut options = vec![];
+                if opts.contains(InlineAsmOptions::PURE) {
+                    options.push("pure");
+                }
+                if opts.contains(InlineAsmOptions::NOMEM) {
+                    options.push("nomem");
+                }
+                if opts.contains(InlineAsmOptions::READONLY) {
+                    options.push("readonly");
+                }
+                if opts.contains(InlineAsmOptions::PRESERVES_FLAGS) {
+                    options.push("preserves_flags");
+                }
+                if opts.contains(InlineAsmOptions::NORETURN) {
+                    options.push("noreturn");
+                }
+                if opts.contains(InlineAsmOptions::NOSTACK) {
+                    options.push("nostack");
+                }
+                if opts.contains(InlineAsmOptions::ATT_SYNTAX) {
+                    options.push("att_syntax");
+                }
+                if opts.contains(InlineAsmOptions::RAW) {
+                    options.push("raw");
+                }
+                if opts.contains(InlineAsmOptions::MAY_UNWIND) {
+                    options.push("may_unwind");
+                }
+                s.commasep(Inconsistent, &options, |s, &opt| {
+                    s.word(opt);
+                });
+                s.pclose();
+            }
+        });
+        self.pclose();
+    }
+
+    pub(crate) fn print_local_decl(&mut self, loc: &ast::Local) {
+        self.print_pat(&loc.pat);
+        if let Some(ref ty) = loc.ty {
+            self.word_space(":");
+            self.print_type(ty);
+        }
+    }
+
+    pub(crate) fn print_name(&mut self, name: Symbol) {
+        self.word(name.to_string());
+        self.ann.post(self, AnnNode::Name(&name))
+    }
+
+    fn print_qpath(&mut self, path: &ast::Path, qself: &ast::QSelf, colons_before_params: bool) {
+        self.word("<");
+        self.print_type(&qself.ty);
+        if qself.position > 0 {
+            self.space();
+            self.word_space("as");
+            let depth = path.segments.len() - qself.position;
+            self.print_path(path, false, depth);
+        }
+        self.word(">");
+        for item_segment in &path.segments[qself.position..] {
+            self.word("::");
+            self.print_ident(item_segment.ident);
+            if let Some(ref args) = item_segment.args {
+                self.print_generic_args(args, colons_before_params)
+            }
+        }
+    }
+
+    pub(crate) fn print_pat(&mut self, pat: &ast::Pat) {
+        self.maybe_print_comment(pat.span.lo());
+        self.ann.pre(self, AnnNode::Pat(pat));
+        /* Pat isn't normalized, but the beauty of it
+        is that it doesn't matter */
+        match pat.kind {
+            PatKind::Wild => self.word("_"),
+            PatKind::Ident(binding_mode, ident, ref sub) => {
+                match binding_mode {
+                    ast::BindingMode::ByRef(mutbl) => {
+                        self.word_nbsp("ref");
+                        self.print_mutability(mutbl, false);
+                    }
+                    ast::BindingMode::ByValue(ast::Mutability::Not) => {}
+                    ast::BindingMode::ByValue(ast::Mutability::Mut) => {
+                        self.word_nbsp("mut");
+                    }
+                }
+                self.print_ident(ident);
+                if let Some(ref p) = *sub {
+                    self.space();
+                    self.word_space("@");
+                    self.print_pat(p);
+                }
+            }
+            PatKind::TupleStruct(ref qself, ref path, ref elts) => {
+                if let Some(qself) = qself {
+                    self.print_qpath(path, qself, true);
+                } else {
+                    self.print_path(path, true, 0);
+                }
+                self.popen();
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                self.pclose();
+            }
+            PatKind::Or(ref pats) => {
+                self.strsep("|", true, Inconsistent, &pats, |s, p| s.print_pat(p));
+            }
+            PatKind::Path(None, ref path) => {
+                self.print_path(path, true, 0);
+            }
+            PatKind::Path(Some(ref qself), ref path) => {
+                self.print_qpath(path, qself, false);
+            }
+            PatKind::Struct(ref qself, ref path, ref fields, etc) => {
+                if let Some(qself) = qself {
+                    self.print_qpath(path, qself, true);
+                } else {
+                    self.print_path(path, true, 0);
+                }
+                self.nbsp();
+                self.word("{");
+                let empty = fields.is_empty() && !etc;
+                if !empty {
+                    self.space();
+                }
+                self.commasep_cmnt(
+                    Consistent,
+                    &fields,
+                    |s, f| {
+                        s.cbox(INDENT_UNIT);
+                        if !f.is_shorthand {
+                            s.print_ident(f.ident);
+                            s.word_nbsp(":");
+                        }
+                        s.print_pat(&f.pat);
+                        s.end();
+                    },
+                    |f| f.pat.span,
+                );
+                if etc {
+                    if !fields.is_empty() {
+                        self.word_space(",");
+                    }
+                    self.word("..");
+                }
+                if !empty {
+                    self.space();
+                }
+                self.word("}");
+            }
+            PatKind::Tuple(ref elts) => {
+                self.popen();
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                if elts.len() == 1 {
+                    self.word(",");
+                }
+                self.pclose();
+            }
+            PatKind::Box(ref inner) => {
+                self.word("box ");
+                self.print_pat(inner);
+            }
+            PatKind::Ref(ref inner, mutbl) => {
+                self.word("&");
+                if mutbl == ast::Mutability::Mut {
+                    self.word("mut ");
+                }
+                if let PatKind::Ident(ast::BindingMode::ByValue(ast::Mutability::Mut), ..) =
+                    inner.kind
+                {
+                    self.popen();
+                    self.print_pat(inner);
+                    self.pclose();
+                } else {
+                    self.print_pat(inner);
+                }
+            }
+            PatKind::Lit(ref e) => self.print_expr(&**e),
+            PatKind::Range(ref begin, ref end, Spanned { node: ref end_kind, .. }) => {
+                if let Some(e) = begin {
+                    self.print_expr(e);
+                }
+                match *end_kind {
+                    RangeEnd::Included(RangeSyntax::DotDotDot) => self.word("..."),
+                    RangeEnd::Included(RangeSyntax::DotDotEq) => self.word("..="),
+                    RangeEnd::Excluded => self.word(".."),
+                }
+                if let Some(e) = end {
+                    self.print_expr(e);
+                }
+            }
+            PatKind::Slice(ref elts) => {
+                self.word("[");
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                self.word("]");
+            }
+            PatKind::Rest => self.word(".."),
+            PatKind::Paren(ref inner) => {
+                self.popen();
+                self.print_pat(inner);
+                self.pclose();
+            }
+            PatKind::MacCall(ref m) => self.print_mac(m),
+        }
+        self.ann.post(self, AnnNode::Pat(pat))
+    }
+
+    fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
+        match explicit_self.node {
+            SelfKind::Value(m) => {
+                self.print_mutability(m, false);
+                self.word("self")
+            }
+            SelfKind::Region(ref lt, m) => {
+                self.word("&");
+                self.print_opt_lifetime(lt);
+                self.print_mutability(m, false);
+                self.word("self")
+            }
+            SelfKind::Explicit(ref typ, m) => {
+                self.print_mutability(m, false);
+                self.word("self");
+                self.word_space(":");
+                self.print_type(typ)
+            }
+        }
+    }
+
+    pub(crate) fn print_asyncness(&mut self, asyncness: ast::Async) {
+        if asyncness.is_async() {
+            self.word_nbsp("async");
+        }
+    }
+
+    pub fn print_type_bounds(&mut self, bounds: &[ast::GenericBound]) {
+        let mut first = true;
+        for bound in bounds {
+            if first {
+                first = false;
+            } else {
+                self.nbsp();
+                self.word_space("+");
+            }
+
+            match bound {
+                GenericBound::Trait(tref, modifier) => {
+                    if modifier == &TraitBoundModifier::Maybe {
+                        self.word("?");
+                    }
+                    self.print_poly_trait_ref(tref);
+                }
+                GenericBound::Outlives(lt) => self.print_lifetime(*lt),
+            }
+        }
+    }
+
+    pub(crate) fn print_lifetime(&mut self, lifetime: ast::Lifetime) {
+        self.print_name(lifetime.ident.name)
+    }
+
+    pub(crate) fn print_lifetime_bounds(&mut self, bounds: &ast::GenericBounds) {
+        for (i, bound) in bounds.iter().enumerate() {
+            if i != 0 {
+                self.word(" + ");
+            }
+            match bound {
+                ast::GenericBound::Outlives(lt) => self.print_lifetime(*lt),
+                _ => panic!(),
+            }
+        }
+    }
+
+    pub(crate) fn print_generic_params(&mut self, generic_params: &[ast::GenericParam]) {
+        if generic_params.is_empty() {
+            return;
+        }
+
+        self.word("<");
+
+        self.commasep(Inconsistent, &generic_params, |s, param| {
+            s.print_outer_attributes_inline(&param.attrs);
+
+            match param.kind {
+                ast::GenericParamKind::Lifetime => {
+                    let lt = ast::Lifetime { id: param.id, ident: param.ident };
+                    s.print_lifetime(lt);
+                    if !param.bounds.is_empty() {
+                        s.word_nbsp(":");
+                        s.print_lifetime_bounds(&param.bounds)
+                    }
+                }
+                ast::GenericParamKind::Type { ref default } => {
+                    s.print_ident(param.ident);
+                    if !param.bounds.is_empty() {
+                        s.word_nbsp(":");
+                        s.print_type_bounds(&param.bounds);
+                    }
+                    if let Some(ref default) = default {
+                        s.space();
+                        s.word_space("=");
+                        s.print_type(default)
+                    }
+                }
+                ast::GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
+                    s.word_space("const");
+                    s.print_ident(param.ident);
+                    s.space();
+                    s.word_space(":");
+                    s.print_type(ty);
+                    if !param.bounds.is_empty() {
+                        s.word_nbsp(":");
+                        s.print_type_bounds(&param.bounds);
+                    }
+                    if let Some(ref default) = default {
+                        s.space();
+                        s.word_space("=");
+                        s.print_expr(&default.value);
+                    }
+                }
+            }
+        });
+
+        self.word(">");
+    }
+
+    pub fn print_mutability(&mut self, mutbl: ast::Mutability, print_const: bool) {
+        match mutbl {
+            ast::Mutability::Mut => self.word_nbsp("mut"),
+            ast::Mutability::Not => {
+                if print_const {
+                    self.word_nbsp("const");
+                }
+            }
+        }
+    }
+
+    pub(crate) fn print_mt(&mut self, mt: &ast::MutTy, print_const: bool) {
+        self.print_mutability(mt.mutbl, print_const);
+        self.print_type(&mt.ty)
+    }
+
+    pub(crate) fn print_param(&mut self, input: &ast::Param, is_closure: bool) {
+        self.ibox(INDENT_UNIT);
+
+        self.print_outer_attributes_inline(&input.attrs);
+
+        match input.ty.kind {
+            ast::TyKind::Infer if is_closure => self.print_pat(&input.pat),
+            _ => {
+                if let Some(eself) = input.to_self() {
+                    self.print_explicit_self(&eself);
+                } else {
+                    let invalid = if let PatKind::Ident(_, ident, _) = input.pat.kind {
+                        ident.name == kw::Empty
+                    } else {
+                        false
+                    };
+                    if !invalid {
+                        self.print_pat(&input.pat);
+                        self.word(":");
+                        self.space();
+                    }
+                    self.print_type(&input.ty);
+                }
+            }
+        }
+        self.end();
+    }
+
+    pub(crate) fn print_fn_ret_ty(&mut self, fn_ret_ty: &ast::FnRetTy) {
+        if let ast::FnRetTy::Ty(ty) = fn_ret_ty {
+            self.space_if_not_bol();
+            self.ibox(INDENT_UNIT);
+            self.word_space("->");
+            self.print_type(ty);
+            self.end();
+            self.maybe_print_comment(ty.span.lo());
+        }
+    }
+
+    pub(crate) fn print_ty_fn(
+        &mut self,
+        ext: ast::Extern,
+        unsafety: ast::Unsafe,
+        decl: &ast::FnDecl,
+        name: Option<Ident>,
+        generic_params: &[ast::GenericParam],
+    ) {
+        self.ibox(INDENT_UNIT);
+        self.print_formal_generic_params(generic_params);
+        let generics = ast::Generics {
+            params: Vec::new(),
+            where_clause: ast::WhereClause {
+                has_where_token: false,
+                predicates: Vec::new(),
+                span: rustc_span::DUMMY_SP,
+            },
+            span: rustc_span::DUMMY_SP,
+        };
+        let header = ast::FnHeader { unsafety, ext, ..ast::FnHeader::default() };
+        self.print_fn(decl, header, name, &generics);
+        self.end();
+    }
+
+    pub(crate) fn print_fn_header_info(&mut self, header: ast::FnHeader) {
+        self.print_constness(header.constness);
+        self.print_asyncness(header.asyncness);
+        self.print_unsafety(header.unsafety);
+
+        match header.ext {
+            ast::Extern::None => {}
+            ast::Extern::Implicit(_) => {
+                self.word_nbsp("extern");
+            }
+            ast::Extern::Explicit(abi, _) => {
+                self.word_nbsp("extern");
+                self.print_literal(&abi.as_lit());
+                self.nbsp();
+            }
+        }
+
+        self.word("fn")
+    }
+
+    pub(crate) fn print_unsafety(&mut self, s: ast::Unsafe) {
+        match s {
+            ast::Unsafe::No => {}
+            ast::Unsafe::Yes(_) => self.word_nbsp("unsafe"),
+        }
+    }
+
+    pub(crate) fn print_constness(&mut self, s: ast::Const) {
+        match s {
+            ast::Const::No => {}
+            ast::Const::Yes(_) => self.word_nbsp("const"),
+        }
+    }
+
+    pub(crate) fn print_is_auto(&mut self, s: ast::IsAuto) {
+        match s {
+            ast::IsAuto::Yes => self.word_nbsp("auto"),
+            ast::IsAuto::No => {}
+        }
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs b/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs
new file mode 100644
index 000000000..fe0640baa
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs
@@ -0,0 +1,41 @@
+use std::iter::Peekable;
+use std::mem;
+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 value = self.iter.next()?;
+        let is_first = mem::replace(&mut self.is_first, false);
+        let is_last = self.iter.peek().is_none();
+        Some(IteratorItem { value, is_first, is_last })
+    }
+}
+
+impl<T> Deref for IteratorItem<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
new file mode 100644
index 000000000..ead38caee
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -0,0 +1,621 @@
+use crate::pp::Breaks::Inconsistent;
+use crate::pprust::state::{AnnNode, IterDelimited, PrintState, State, INDENT_UNIT};
+
+use rustc_ast::ptr::P;
+use rustc_ast::util::parser::{self, AssocOp, Fixity};
+use rustc_ast::{self as ast, BlockCheckMode};
+
+impl<'a> State<'a> {
+    fn print_else(&mut self, els: Option<&ast::Expr>) {
+        if let Some(_else) = els {
+            match _else.kind {
+                // Another `else if` block.
+                ast::ExprKind::If(ref i, ref then, ref e) => {
+                    self.cbox(INDENT_UNIT - 1);
+                    self.ibox(0);
+                    self.word(" else if ");
+                    self.print_expr_as_cond(i);
+                    self.space();
+                    self.print_block(then);
+                    self.print_else(e.as_deref())
+                }
+                // Final `else` block.
+                ast::ExprKind::Block(ref b, _) => {
+                    self.cbox(INDENT_UNIT - 1);
+                    self.ibox(0);
+                    self.word(" else ");
+                    self.print_block(b)
+                }
+                // Constraints would be great here!
+                _ => {
+                    panic!("print_if saw if with weird alternative");
+                }
+            }
+        }
+    }
+
+    fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block, elseopt: Option<&ast::Expr>) {
+        self.head("if");
+        self.print_expr_as_cond(test);
+        self.space();
+        self.print_block(blk);
+        self.print_else(elseopt)
+    }
+
+    fn print_call_post(&mut self, args: &[P<ast::Expr>]) {
+        self.popen();
+        self.commasep_exprs(Inconsistent, args);
+        self.pclose()
+    }
+
+    fn print_expr_maybe_paren(&mut self, expr: &ast::Expr, prec: i8) {
+        self.print_expr_cond_paren(expr, expr.precedence().order() < prec)
+    }
+
+    /// Prints an expr using syntax that's acceptable in a condition position, such as the `cond` in
+    /// `if cond { ... }`.
+    fn print_expr_as_cond(&mut self, expr: &ast::Expr) {
+        self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
+    }
+
+    // Does `expr` need parentheses when printed in a condition position?
+    //
+    // These cases need parens due to the parse error observed in #26461: `if return {}`
+    // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
+    pub(super) fn cond_needs_par(expr: &ast::Expr) -> bool {
+        match expr.kind {
+            ast::ExprKind::Break(..)
+            | ast::ExprKind::Closure(..)
+            | ast::ExprKind::Ret(..)
+            | ast::ExprKind::Yeet(..) => true,
+            _ => parser::contains_exterior_struct_lit(expr),
+        }
+    }
+
+    /// Prints `expr` or `(expr)` when `needs_par` holds.
+    pub(super) fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) {
+        if needs_par {
+            self.popen();
+        }
+        self.print_expr(expr);
+        if needs_par {
+            self.pclose();
+        }
+    }
+
+    fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>]) {
+        self.ibox(INDENT_UNIT);
+        self.word("[");
+        self.commasep_exprs(Inconsistent, exprs);
+        self.word("]");
+        self.end();
+    }
+
+    pub(super) fn print_expr_anon_const(
+        &mut self,
+        expr: &ast::AnonConst,
+        attrs: &[ast::Attribute],
+    ) {
+        self.ibox(INDENT_UNIT);
+        self.word("const");
+        self.nbsp();
+        if let ast::ExprKind::Block(block, None) = &expr.value.kind {
+            self.cbox(0);
+            self.ibox(0);
+            self.print_block_with_attrs(block, attrs);
+        } else {
+            self.print_expr(&expr.value);
+        }
+        self.end();
+    }
+
+    fn print_expr_repeat(&mut self, element: &ast::Expr, count: &ast::AnonConst) {
+        self.ibox(INDENT_UNIT);
+        self.word("[");
+        self.print_expr(element);
+        self.word_space(";");
+        self.print_expr(&count.value);
+        self.word("]");
+        self.end();
+    }
+
+    fn print_expr_struct(
+        &mut self,
+        qself: &Option<ast::QSelf>,
+        path: &ast::Path,
+        fields: &[ast::ExprField],
+        rest: &ast::StructRest,
+    ) {
+        if let Some(qself) = qself {
+            self.print_qpath(path, qself, true);
+        } else {
+            self.print_path(path, true, 0);
+        }
+        self.nbsp();
+        self.word("{");
+        let has_rest = match rest {
+            ast::StructRest::Base(_) | ast::StructRest::Rest(_) => true,
+            ast::StructRest::None => false,
+        };
+        if fields.is_empty() && !has_rest {
+            self.word("}");
+            return;
+        }
+        self.cbox(0);
+        for field in fields.iter().delimited() {
+            self.maybe_print_comment(field.span.hi());
+            self.print_outer_attributes(&field.attrs);
+            if field.is_first {
+                self.space_if_not_bol();
+            }
+            if !field.is_shorthand {
+                self.print_ident(field.ident);
+                self.word_nbsp(":");
+            }
+            self.print_expr(&field.expr);
+            if !field.is_last || has_rest {
+                self.word_space(",");
+            } else {
+                self.trailing_comma_or_space();
+            }
+        }
+        if has_rest {
+            if fields.is_empty() {
+                self.space();
+            }
+            self.word("..");
+            if let ast::StructRest::Base(expr) = rest {
+                self.print_expr(expr);
+            }
+            self.space();
+        }
+        self.offset(-INDENT_UNIT);
+        self.end();
+        self.word("}");
+    }
+
+    fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>]) {
+        self.popen();
+        self.commasep_exprs(Inconsistent, exprs);
+        if exprs.len() == 1 {
+            self.word(",");
+        }
+        self.pclose()
+    }
+
+    fn print_expr_call(&mut self, func: &ast::Expr, args: &[P<ast::Expr>]) {
+        let prec = match func.kind {
+            ast::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
+            _ => parser::PREC_POSTFIX,
+        };
+
+        self.print_expr_maybe_paren(func, prec);
+        self.print_call_post(args)
+    }
+
+    fn print_expr_method_call(&mut self, segment: &ast::PathSegment, args: &[P<ast::Expr>]) {
+        let base_args = &args[1..];
+        self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX);
+        self.word(".");
+        self.print_ident(segment.ident);
+        if let Some(ref args) = segment.args {
+            self.print_generic_args(args, true);
+        }
+        self.print_call_post(base_args)
+    }
+
+    fn print_expr_binary(&mut self, op: ast::BinOp, lhs: &ast::Expr, rhs: &ast::Expr) {
+        let assoc_op = AssocOp::from_ast_binop(op.node);
+        let prec = assoc_op.precedence() as i8;
+        let fixity = assoc_op.fixity();
+
+        let (left_prec, right_prec) = match fixity {
+            Fixity::Left => (prec, prec + 1),
+            Fixity::Right => (prec + 1, prec),
+            Fixity::None => (prec + 1, prec + 1),
+        };
+
+        let left_prec = match (&lhs.kind, op.node) {
+            // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
+            // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
+            // of `(x as i32) < ...`. We need to convince it _not_ to do that.
+            (&ast::ExprKind::Cast { .. }, ast::BinOpKind::Lt | ast::BinOpKind::Shl) => {
+                parser::PREC_FORCE_PAREN
+            }
+            // We are given `(let _ = a) OP b`.
+            //
+            // - When `OP <= LAnd` we should print `let _ = a OP b` to avoid redundant parens
+            //   as the parser will interpret this as `(let _ = a) OP b`.
+            //
+            // - Otherwise, e.g. when we have `(let a = b) < c` in AST,
+            //   parens are required since the parser would interpret `let a = b < c` as
+            //   `let a = (b < c)`. To achieve this, we force parens.
+            (&ast::ExprKind::Let { .. }, _) if !parser::needs_par_as_let_scrutinee(prec) => {
+                parser::PREC_FORCE_PAREN
+            }
+            _ => left_prec,
+        };
+
+        self.print_expr_maybe_paren(lhs, left_prec);
+        self.space();
+        self.word_space(op.node.to_string());
+        self.print_expr_maybe_paren(rhs, right_prec)
+    }
+
+    fn print_expr_unary(&mut self, op: ast::UnOp, expr: &ast::Expr) {
+        self.word(ast::UnOp::to_string(op));
+        self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
+    }
+
+    fn print_expr_addr_of(
+        &mut self,
+        kind: ast::BorrowKind,
+        mutability: ast::Mutability,
+        expr: &ast::Expr,
+    ) {
+        self.word("&");
+        match kind {
+            ast::BorrowKind::Ref => self.print_mutability(mutability, false),
+            ast::BorrowKind::Raw => {
+                self.word_nbsp("raw");
+                self.print_mutability(mutability, true);
+            }
+        }
+        self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
+    }
+
+    pub fn print_expr(&mut self, expr: &ast::Expr) {
+        self.print_expr_outer_attr_style(expr, true)
+    }
+
+    pub(super) fn print_expr_outer_attr_style(&mut self, expr: &ast::Expr, is_inline: bool) {
+        self.maybe_print_comment(expr.span.lo());
+
+        let attrs = &expr.attrs;
+        if is_inline {
+            self.print_outer_attributes_inline(attrs);
+        } else {
+            self.print_outer_attributes(attrs);
+        }
+
+        self.ibox(INDENT_UNIT);
+        self.ann.pre(self, AnnNode::Expr(expr));
+        match expr.kind {
+            ast::ExprKind::Box(ref expr) => {
+                self.word_space("box");
+                self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
+            }
+            ast::ExprKind::Array(ref exprs) => {
+                self.print_expr_vec(exprs);
+            }
+            ast::ExprKind::ConstBlock(ref anon_const) => {
+                self.print_expr_anon_const(anon_const, attrs);
+            }
+            ast::ExprKind::Repeat(ref element, ref count) => {
+                self.print_expr_repeat(element, count);
+            }
+            ast::ExprKind::Struct(ref se) => {
+                self.print_expr_struct(&se.qself, &se.path, &se.fields, &se.rest);
+            }
+            ast::ExprKind::Tup(ref exprs) => {
+                self.print_expr_tup(exprs);
+            }
+            ast::ExprKind::Call(ref func, ref args) => {
+                self.print_expr_call(func, &args);
+            }
+            ast::ExprKind::MethodCall(ref segment, ref args, _) => {
+                self.print_expr_method_call(segment, &args);
+            }
+            ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
+                self.print_expr_binary(op, lhs, rhs);
+            }
+            ast::ExprKind::Unary(op, ref expr) => {
+                self.print_expr_unary(op, expr);
+            }
+            ast::ExprKind::AddrOf(k, m, ref expr) => {
+                self.print_expr_addr_of(k, m, expr);
+            }
+            ast::ExprKind::Lit(ref lit) => {
+                self.print_literal(lit);
+            }
+            ast::ExprKind::Cast(ref expr, ref ty) => {
+                let prec = AssocOp::As.precedence() as i8;
+                self.print_expr_maybe_paren(expr, prec);
+                self.space();
+                self.word_space("as");
+                self.print_type(ty);
+            }
+            ast::ExprKind::Type(ref expr, ref ty) => {
+                let prec = AssocOp::Colon.precedence() as i8;
+                self.print_expr_maybe_paren(expr, prec);
+                self.word_space(":");
+                self.print_type(ty);
+            }
+            ast::ExprKind::Let(ref pat, ref scrutinee, _) => {
+                self.print_let(pat, scrutinee);
+            }
+            ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
+                self.print_if(test, blk, elseopt.as_deref())
+            }
+            ast::ExprKind::While(ref test, ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+                self.cbox(0);
+                self.ibox(0);
+                self.word_nbsp("while");
+                self.print_expr_as_cond(test);
+                self.space();
+                self.print_block_with_attrs(blk, attrs);
+            }
+            ast::ExprKind::ForLoop(ref pat, ref iter, ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+                self.cbox(0);
+                self.ibox(0);
+                self.word_nbsp("for");
+                self.print_pat(pat);
+                self.space();
+                self.word_space("in");
+                self.print_expr_as_cond(iter);
+                self.space();
+                self.print_block_with_attrs(blk, attrs);
+            }
+            ast::ExprKind::Loop(ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+                self.cbox(0);
+                self.ibox(0);
+                self.word_nbsp("loop");
+                self.print_block_with_attrs(blk, attrs);
+            }
+            ast::ExprKind::Match(ref expr, ref arms) => {
+                self.cbox(0);
+                self.ibox(0);
+                self.word_nbsp("match");
+                self.print_expr_as_cond(expr);
+                self.space();
+                self.bopen();
+                self.print_inner_attributes_no_trailing_hardbreak(attrs);
+                for arm in arms {
+                    self.print_arm(arm);
+                }
+                let empty = attrs.is_empty() && arms.is_empty();
+                self.bclose(expr.span, empty);
+            }
+            ast::ExprKind::Closure(
+                ref binder,
+                capture_clause,
+                asyncness,
+                movability,
+                ref decl,
+                ref body,
+                _,
+            ) => {
+                self.print_closure_binder(binder);
+                self.print_movability(movability);
+                self.print_asyncness(asyncness);
+                self.print_capture_clause(capture_clause);
+
+                self.print_fn_params_and_ret(decl, true);
+                self.space();
+                self.print_expr(body);
+                self.end(); // need to close a box
+
+                // a box will be closed by print_expr, but we didn't want an overall
+                // wrapper so we closed the corresponding opening. so create an
+                // empty box to satisfy the close.
+                self.ibox(0);
+            }
+            ast::ExprKind::Block(ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+                // containing cbox, will be closed by print-block at }
+                self.cbox(0);
+                // head-box, will be closed by print-block after {
+                self.ibox(0);
+                self.print_block_with_attrs(blk, attrs);
+            }
+            ast::ExprKind::Async(capture_clause, _, ref blk) => {
+                self.word_nbsp("async");
+                self.print_capture_clause(capture_clause);
+                // cbox/ibox in analogy to the `ExprKind::Block` arm above
+                self.cbox(0);
+                self.ibox(0);
+                self.print_block_with_attrs(blk, attrs);
+            }
+            ast::ExprKind::Await(ref expr) => {
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.word(".await");
+            }
+            ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
+                let prec = AssocOp::Assign.precedence() as i8;
+                self.print_expr_maybe_paren(lhs, prec + 1);
+                self.space();
+                self.word_space("=");
+                self.print_expr_maybe_paren(rhs, prec);
+            }
+            ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
+                let prec = AssocOp::Assign.precedence() as i8;
+                self.print_expr_maybe_paren(lhs, prec + 1);
+                self.space();
+                self.word(op.node.to_string());
+                self.word_space("=");
+                self.print_expr_maybe_paren(rhs, prec);
+            }
+            ast::ExprKind::Field(ref expr, ident) => {
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.word(".");
+                self.print_ident(ident);
+            }
+            ast::ExprKind::Index(ref expr, ref index) => {
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.word("[");
+                self.print_expr(index);
+                self.word("]");
+            }
+            ast::ExprKind::Range(ref start, ref end, limits) => {
+                // Special case for `Range`.  `AssocOp` claims that `Range` has higher precedence
+                // than `Assign`, but `x .. x = x` gives a parse error instead of `x .. (x = x)`.
+                // Here we use a fake precedence value so that any child with lower precedence than
+                // a "normal" binop gets parenthesized.  (`LOr` is the lowest-precedence binop.)
+                let fake_prec = AssocOp::LOr.precedence() as i8;
+                if let Some(ref e) = *start {
+                    self.print_expr_maybe_paren(e, fake_prec);
+                }
+                if limits == ast::RangeLimits::HalfOpen {
+                    self.word("..");
+                } else {
+                    self.word("..=");
+                }
+                if let Some(ref e) = *end {
+                    self.print_expr_maybe_paren(e, fake_prec);
+                }
+            }
+            ast::ExprKind::Underscore => self.word("_"),
+            ast::ExprKind::Path(None, ref path) => self.print_path(path, true, 0),
+            ast::ExprKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, true),
+            ast::ExprKind::Break(opt_label, ref opt_expr) => {
+                self.word("break");
+                if let Some(label) = opt_label {
+                    self.space();
+                    self.print_ident(label.ident);
+                }
+                if let Some(ref expr) = *opt_expr {
+                    self.space();
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            ast::ExprKind::Continue(opt_label) => {
+                self.word("continue");
+                if let Some(label) = opt_label {
+                    self.space();
+                    self.print_ident(label.ident);
+                }
+            }
+            ast::ExprKind::Ret(ref result) => {
+                self.word("return");
+                if let Some(ref expr) = *result {
+                    self.word(" ");
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            ast::ExprKind::Yeet(ref result) => {
+                self.word("do");
+                self.word(" ");
+                self.word("yeet");
+                if let Some(ref expr) = *result {
+                    self.word(" ");
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            ast::ExprKind::InlineAsm(ref a) => {
+                self.word("asm!");
+                self.print_inline_asm(a);
+            }
+            ast::ExprKind::MacCall(ref m) => self.print_mac(m),
+            ast::ExprKind::Paren(ref e) => {
+                self.popen();
+                self.print_expr(e);
+                self.pclose();
+            }
+            ast::ExprKind::Yield(ref e) => {
+                self.word("yield");
+
+                if let Some(ref expr) = *e {
+                    self.space();
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            ast::ExprKind::Try(ref e) => {
+                self.print_expr_maybe_paren(e, parser::PREC_POSTFIX);
+                self.word("?")
+            }
+            ast::ExprKind::TryBlock(ref blk) => {
+                self.cbox(0);
+                self.ibox(0);
+                self.word_nbsp("try");
+                self.print_block_with_attrs(blk, attrs)
+            }
+            ast::ExprKind::Err => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose()
+            }
+        }
+        self.ann.post(self, AnnNode::Expr(expr));
+        self.end();
+    }
+
+    fn print_arm(&mut self, arm: &ast::Arm) {
+        // Note, I have no idea why this check is necessary, but here it is.
+        if arm.attrs.is_empty() {
+            self.space();
+        }
+        self.cbox(INDENT_UNIT);
+        self.ibox(0);
+        self.maybe_print_comment(arm.pat.span.lo());
+        self.print_outer_attributes(&arm.attrs);
+        self.print_pat(&arm.pat);
+        self.space();
+        if let Some(ref e) = arm.guard {
+            self.word_space("if");
+            self.print_expr(e);
+            self.space();
+        }
+        self.word_space("=>");
+
+        match arm.body.kind {
+            ast::ExprKind::Block(ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+
+                // The block will close the pattern's ibox.
+                self.print_block_unclosed_indent(blk);
+
+                // If it is a user-provided unsafe block, print a comma after it.
+                if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
+                    self.word(",");
+                }
+            }
+            _ => {
+                self.end(); // Close the ibox for the pattern.
+                self.print_expr(&arm.body);
+                self.word(",");
+            }
+        }
+        self.end(); // Close enclosing cbox.
+    }
+
+    fn print_closure_binder(&mut self, binder: &ast::ClosureBinder) {
+        match binder {
+            ast::ClosureBinder::NotPresent => {}
+            ast::ClosureBinder::For { generic_params, .. } => {
+                self.print_formal_generic_params(&generic_params)
+            }
+        }
+    }
+
+    fn print_movability(&mut self, movability: ast::Movability) {
+        match movability {
+            ast::Movability::Static => self.word_space("static"),
+            ast::Movability::Movable => {}
+        }
+    }
+
+    fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy) {
+        match capture_clause {
+            ast::CaptureBy::Value => self.word_space("move"),
+            ast::CaptureBy::Ref => {}
+        }
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
new file mode 100644
index 000000000..f1caf22f3
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -0,0 +1,708 @@
+use crate::pp::Breaks::Inconsistent;
+use crate::pprust::state::delimited::IterDelimited;
+use crate::pprust::state::{AnnNode, PrintState, State, INDENT_UNIT};
+
+use rustc_ast as ast;
+use rustc_ast::GenericBound;
+use rustc_ast::ModKind;
+use rustc_span::symbol::Ident;
+
+fn visibility_qualified(vis: &ast::Visibility, s: &str) -> String {
+    format!("{}{}", State::to_string(|s| s.print_visibility(vis)), s)
+}
+
+impl<'a> State<'a> {
+    fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod, attrs: &[ast::Attribute]) {
+        self.print_inner_attributes(attrs);
+        for item in &nmod.items {
+            self.print_foreign_item(item);
+        }
+    }
+
+    pub(crate) fn print_foreign_item(&mut self, item: &ast::ForeignItem) {
+        let ast::Item { id, span, ident, ref attrs, ref kind, ref vis, tokens: _ } = *item;
+        self.ann.pre(self, AnnNode::SubItem(id));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(span.lo());
+        self.print_outer_attributes(attrs);
+        match kind {
+            ast::ForeignItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
+                self.print_fn_full(sig, ident, generics, vis, *defaultness, body.as_deref(), attrs);
+            }
+            ast::ForeignItemKind::Static(ty, mutbl, body) => {
+                let def = ast::Defaultness::Final;
+                self.print_item_const(ident, Some(*mutbl), ty, body.as_deref(), vis, def);
+            }
+            ast::ForeignItemKind::TyAlias(box ast::TyAlias {
+                defaultness,
+                generics,
+                where_clauses,
+                where_predicates_split,
+                bounds,
+                ty,
+            }) => {
+                self.print_associated_type(
+                    ident,
+                    generics,
+                    *where_clauses,
+                    *where_predicates_split,
+                    bounds,
+                    ty.as_deref(),
+                    vis,
+                    *defaultness,
+                );
+            }
+            ast::ForeignItemKind::MacCall(m) => {
+                self.print_mac(m);
+                if m.args.need_semicolon() {
+                    self.word(";");
+                }
+            }
+        }
+        self.ann.post(self, AnnNode::SubItem(id))
+    }
+
+    fn print_item_const(
+        &mut self,
+        ident: Ident,
+        mutbl: Option<ast::Mutability>,
+        ty: &ast::Ty,
+        body: Option<&ast::Expr>,
+        vis: &ast::Visibility,
+        defaultness: ast::Defaultness,
+    ) {
+        self.head("");
+        self.print_visibility(vis);
+        self.print_defaultness(defaultness);
+        let leading = match mutbl {
+            None => "const",
+            Some(ast::Mutability::Not) => "static",
+            Some(ast::Mutability::Mut) => "static mut",
+        };
+        self.word_space(leading);
+        self.print_ident(ident);
+        self.word_space(":");
+        self.print_type(ty);
+        if body.is_some() {
+            self.space();
+        }
+        self.end(); // end the head-ibox
+        if let Some(body) = body {
+            self.word_space("=");
+            self.print_expr(body);
+        }
+        self.word(";");
+        self.end(); // end the outer cbox
+    }
+
+    fn print_associated_type(
+        &mut self,
+        ident: Ident,
+        generics: &ast::Generics,
+        where_clauses: (ast::TyAliasWhereClause, ast::TyAliasWhereClause),
+        where_predicates_split: usize,
+        bounds: &ast::GenericBounds,
+        ty: Option<&ast::Ty>,
+        vis: &ast::Visibility,
+        defaultness: ast::Defaultness,
+    ) {
+        let (before_predicates, after_predicates) =
+            generics.where_clause.predicates.split_at(where_predicates_split);
+        self.head("");
+        self.print_visibility(vis);
+        self.print_defaultness(defaultness);
+        self.word_space("type");
+        self.print_ident(ident);
+        self.print_generic_params(&generics.params);
+        if !bounds.is_empty() {
+            self.word_nbsp(":");
+            self.print_type_bounds(bounds);
+        }
+        self.print_where_clause_parts(where_clauses.0.0, before_predicates);
+        if let Some(ty) = ty {
+            self.space();
+            self.word_space("=");
+            self.print_type(ty);
+        }
+        self.print_where_clause_parts(where_clauses.1.0, after_predicates);
+        self.word(";");
+        self.end(); // end inner head-block
+        self.end(); // end outer head-block
+    }
+
+    /// Pretty-prints an item.
+    pub(crate) fn print_item(&mut self, item: &ast::Item) {
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(item.span.lo());
+        self.print_outer_attributes(&item.attrs);
+        self.ann.pre(self, AnnNode::Item(item));
+        match item.kind {
+            ast::ItemKind::ExternCrate(orig_name) => {
+                self.head(visibility_qualified(&item.vis, "extern crate"));
+                if let Some(orig_name) = orig_name {
+                    self.print_name(orig_name);
+                    self.space();
+                    self.word("as");
+                    self.space();
+                }
+                self.print_ident(item.ident);
+                self.word(";");
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
+            }
+            ast::ItemKind::Use(ref tree) => {
+                self.print_visibility(&item.vis);
+                self.word_nbsp("use");
+                self.print_use_tree(tree);
+                self.word(";");
+            }
+            ast::ItemKind::Static(ref ty, mutbl, ref body) => {
+                let def = ast::Defaultness::Final;
+                self.print_item_const(item.ident, Some(mutbl), ty, body.as_deref(), &item.vis, def);
+            }
+            ast::ItemKind::Const(def, ref ty, ref body) => {
+                self.print_item_const(item.ident, None, ty, body.as_deref(), &item.vis, def);
+            }
+            ast::ItemKind::Fn(box ast::Fn { defaultness, ref sig, ref generics, ref body }) => {
+                let body = body.as_deref();
+                self.print_fn_full(
+                    sig,
+                    item.ident,
+                    generics,
+                    &item.vis,
+                    defaultness,
+                    body,
+                    &item.attrs,
+                );
+            }
+            ast::ItemKind::Mod(unsafety, ref mod_kind) => {
+                self.head(Self::to_string(|s| {
+                    s.print_visibility(&item.vis);
+                    s.print_unsafety(unsafety);
+                    s.word("mod");
+                }));
+                self.print_ident(item.ident);
+
+                match mod_kind {
+                    ModKind::Loaded(items, ..) => {
+                        self.nbsp();
+                        self.bopen();
+                        self.print_inner_attributes(&item.attrs);
+                        for item in items {
+                            self.print_item(item);
+                        }
+                        let empty = item.attrs.is_empty() && items.is_empty();
+                        self.bclose(item.span, empty);
+                    }
+                    ModKind::Unloaded => {
+                        self.word(";");
+                        self.end(); // end inner head-block
+                        self.end(); // end outer head-block
+                    }
+                }
+            }
+            ast::ItemKind::ForeignMod(ref nmod) => {
+                self.head(Self::to_string(|s| {
+                    s.print_unsafety(nmod.unsafety);
+                    s.word("extern");
+                }));
+                if let Some(abi) = nmod.abi {
+                    self.print_literal(&abi.as_lit());
+                    self.nbsp();
+                }
+                self.bopen();
+                self.print_foreign_mod(nmod, &item.attrs);
+                let empty = item.attrs.is_empty() && nmod.items.is_empty();
+                self.bclose(item.span, empty);
+            }
+            ast::ItemKind::GlobalAsm(ref asm) => {
+                self.head(visibility_qualified(&item.vis, "global_asm!"));
+                self.print_inline_asm(asm);
+                self.end();
+            }
+            ast::ItemKind::TyAlias(box ast::TyAlias {
+                defaultness,
+                ref generics,
+                where_clauses,
+                where_predicates_split,
+                ref bounds,
+                ref ty,
+            }) => {
+                let ty = ty.as_deref();
+                self.print_associated_type(
+                    item.ident,
+                    generics,
+                    where_clauses,
+                    where_predicates_split,
+                    bounds,
+                    ty,
+                    &item.vis,
+                    defaultness,
+                );
+            }
+            ast::ItemKind::Enum(ref enum_definition, ref params) => {
+                self.print_enum_def(enum_definition, params, item.ident, item.span, &item.vis);
+            }
+            ast::ItemKind::Struct(ref struct_def, ref generics) => {
+                self.head(visibility_qualified(&item.vis, "struct"));
+                self.print_struct(struct_def, generics, item.ident, item.span, true);
+            }
+            ast::ItemKind::Union(ref struct_def, ref generics) => {
+                self.head(visibility_qualified(&item.vis, "union"));
+                self.print_struct(struct_def, generics, item.ident, item.span, true);
+            }
+            ast::ItemKind::Impl(box ast::Impl {
+                unsafety,
+                polarity,
+                defaultness,
+                constness,
+                ref generics,
+                ref of_trait,
+                ref self_ty,
+                ref items,
+            }) => {
+                self.head("");
+                self.print_visibility(&item.vis);
+                self.print_defaultness(defaultness);
+                self.print_unsafety(unsafety);
+                self.word("impl");
+
+                if generics.params.is_empty() {
+                    self.nbsp();
+                } else {
+                    self.print_generic_params(&generics.params);
+                    self.space();
+                }
+
+                self.print_constness(constness);
+
+                if let ast::ImplPolarity::Negative(_) = polarity {
+                    self.word("!");
+                }
+
+                if let Some(ref t) = *of_trait {
+                    self.print_trait_ref(t);
+                    self.space();
+                    self.word_space("for");
+                }
+
+                self.print_type(self_ty);
+                self.print_where_clause(&generics.where_clause);
+
+                self.space();
+                self.bopen();
+                self.print_inner_attributes(&item.attrs);
+                for impl_item in items {
+                    self.print_assoc_item(impl_item);
+                }
+                let empty = item.attrs.is_empty() && items.is_empty();
+                self.bclose(item.span, empty);
+            }
+            ast::ItemKind::Trait(box ast::Trait {
+                is_auto,
+                unsafety,
+                ref generics,
+                ref bounds,
+                ref items,
+                ..
+            }) => {
+                self.head("");
+                self.print_visibility(&item.vis);
+                self.print_unsafety(unsafety);
+                self.print_is_auto(is_auto);
+                self.word_nbsp("trait");
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
+                let mut real_bounds = Vec::with_capacity(bounds.len());
+                for b in bounds.iter() {
+                    if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
+                        self.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
+                    } else {
+                        real_bounds.push(b.clone());
+                    }
+                }
+                if !real_bounds.is_empty() {
+                    self.word_nbsp(":");
+                    self.print_type_bounds(&real_bounds);
+                }
+                self.print_where_clause(&generics.where_clause);
+                self.word(" ");
+                self.bopen();
+                self.print_inner_attributes(&item.attrs);
+                for trait_item in items {
+                    self.print_assoc_item(trait_item);
+                }
+                let empty = item.attrs.is_empty() && items.is_empty();
+                self.bclose(item.span, empty);
+            }
+            ast::ItemKind::TraitAlias(ref generics, ref bounds) => {
+                self.head(visibility_qualified(&item.vis, "trait"));
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
+                let mut real_bounds = Vec::with_capacity(bounds.len());
+                // FIXME(durka) this seems to be some quite outdated syntax
+                for b in bounds.iter() {
+                    if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
+                        self.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
+                    } else {
+                        real_bounds.push(b.clone());
+                    }
+                }
+                self.nbsp();
+                if !real_bounds.is_empty() {
+                    self.word_nbsp("=");
+                    self.print_type_bounds(&real_bounds);
+                }
+                self.print_where_clause(&generics.where_clause);
+                self.word(";");
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
+            }
+            ast::ItemKind::MacCall(ref mac) => {
+                self.print_mac(mac);
+                if mac.args.need_semicolon() {
+                    self.word(";");
+                }
+            }
+            ast::ItemKind::MacroDef(ref macro_def) => {
+                self.print_mac_def(macro_def, &item.ident, item.span, |state| {
+                    state.print_visibility(&item.vis)
+                });
+            }
+        }
+        self.ann.post(self, AnnNode::Item(item))
+    }
+
+    fn print_enum_def(
+        &mut self,
+        enum_definition: &ast::EnumDef,
+        generics: &ast::Generics,
+        ident: Ident,
+        span: rustc_span::Span,
+        visibility: &ast::Visibility,
+    ) {
+        self.head(visibility_qualified(visibility, "enum"));
+        self.print_ident(ident);
+        self.print_generic_params(&generics.params);
+        self.print_where_clause(&generics.where_clause);
+        self.space();
+        self.print_variants(&enum_definition.variants, span)
+    }
+
+    fn print_variants(&mut self, variants: &[ast::Variant], span: rustc_span::Span) {
+        self.bopen();
+        for v in variants {
+            self.space_if_not_bol();
+            self.maybe_print_comment(v.span.lo());
+            self.print_outer_attributes(&v.attrs);
+            self.ibox(0);
+            self.print_variant(v);
+            self.word(",");
+            self.end();
+            self.maybe_print_trailing_comment(v.span, None);
+        }
+        let empty = variants.is_empty();
+        self.bclose(span, empty)
+    }
+
+    pub(crate) fn print_visibility(&mut self, vis: &ast::Visibility) {
+        match vis.kind {
+            ast::VisibilityKind::Public => self.word_nbsp("pub"),
+            ast::VisibilityKind::Restricted { ref path, .. } => {
+                let path = Self::to_string(|s| s.print_path(path, false, 0));
+                if path == "crate" || path == "self" || path == "super" {
+                    self.word_nbsp(format!("pub({})", path))
+                } else {
+                    self.word_nbsp(format!("pub(in {})", path))
+                }
+            }
+            ast::VisibilityKind::Inherited => {}
+        }
+    }
+
+    fn print_defaultness(&mut self, defaultness: ast::Defaultness) {
+        if let ast::Defaultness::Default(_) = defaultness {
+            self.word_nbsp("default");
+        }
+    }
+
+    fn print_record_struct_body(&mut self, fields: &[ast::FieldDef], span: rustc_span::Span) {
+        self.nbsp();
+        self.bopen();
+
+        let empty = fields.is_empty();
+        if !empty {
+            self.hardbreak_if_not_bol();
+
+            for field in fields {
+                self.hardbreak_if_not_bol();
+                self.maybe_print_comment(field.span.lo());
+                self.print_outer_attributes(&field.attrs);
+                self.print_visibility(&field.vis);
+                self.print_ident(field.ident.unwrap());
+                self.word_nbsp(":");
+                self.print_type(&field.ty);
+                self.word(",");
+            }
+        }
+
+        self.bclose(span, empty);
+    }
+
+    fn print_struct(
+        &mut self,
+        struct_def: &ast::VariantData,
+        generics: &ast::Generics,
+        ident: Ident,
+        span: rustc_span::Span,
+        print_finalizer: bool,
+    ) {
+        self.print_ident(ident);
+        self.print_generic_params(&generics.params);
+        match struct_def {
+            ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
+                if let ast::VariantData::Tuple(..) = struct_def {
+                    self.popen();
+                    self.commasep(Inconsistent, struct_def.fields(), |s, field| {
+                        s.maybe_print_comment(field.span.lo());
+                        s.print_outer_attributes(&field.attrs);
+                        s.print_visibility(&field.vis);
+                        s.print_type(&field.ty)
+                    });
+                    self.pclose();
+                }
+                self.print_where_clause(&generics.where_clause);
+                if print_finalizer {
+                    self.word(";");
+                }
+                self.end();
+                self.end(); // Close the outer-box.
+            }
+            ast::VariantData::Struct(ref fields, ..) => {
+                self.print_where_clause(&generics.where_clause);
+                self.print_record_struct_body(fields, span);
+            }
+        }
+    }
+
+    pub(crate) fn print_variant(&mut self, v: &ast::Variant) {
+        self.head("");
+        self.print_visibility(&v.vis);
+        let generics = ast::Generics::default();
+        self.print_struct(&v.data, &generics, v.ident, v.span, false);
+        if let Some(ref d) = v.disr_expr {
+            self.space();
+            self.word_space("=");
+            self.print_expr(&d.value)
+        }
+    }
+
+    pub(crate) fn print_assoc_item(&mut self, item: &ast::AssocItem) {
+        let ast::Item { id, span, ident, ref attrs, ref kind, ref vis, tokens: _ } = *item;
+        self.ann.pre(self, AnnNode::SubItem(id));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(span.lo());
+        self.print_outer_attributes(attrs);
+        match kind {
+            ast::AssocItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
+                self.print_fn_full(sig, ident, generics, vis, *defaultness, body.as_deref(), attrs);
+            }
+            ast::AssocItemKind::Const(def, ty, body) => {
+                self.print_item_const(ident, None, ty, body.as_deref(), vis, *def);
+            }
+            ast::AssocItemKind::TyAlias(box ast::TyAlias {
+                defaultness,
+                generics,
+                where_clauses,
+                where_predicates_split,
+                bounds,
+                ty,
+            }) => {
+                self.print_associated_type(
+                    ident,
+                    generics,
+                    *where_clauses,
+                    *where_predicates_split,
+                    bounds,
+                    ty.as_deref(),
+                    vis,
+                    *defaultness,
+                );
+            }
+            ast::AssocItemKind::MacCall(m) => {
+                self.print_mac(m);
+                if m.args.need_semicolon() {
+                    self.word(";");
+                }
+            }
+        }
+        self.ann.post(self, AnnNode::SubItem(id))
+    }
+
+    fn print_fn_full(
+        &mut self,
+        sig: &ast::FnSig,
+        name: Ident,
+        generics: &ast::Generics,
+        vis: &ast::Visibility,
+        defaultness: ast::Defaultness,
+        body: Option<&ast::Block>,
+        attrs: &[ast::Attribute],
+    ) {
+        if body.is_some() {
+            self.head("");
+        }
+        self.print_visibility(vis);
+        self.print_defaultness(defaultness);
+        self.print_fn(&sig.decl, sig.header, Some(name), generics);
+        if let Some(body) = body {
+            self.nbsp();
+            self.print_block_with_attrs(body, attrs);
+        } else {
+            self.word(";");
+        }
+    }
+
+    pub(crate) fn print_fn(
+        &mut self,
+        decl: &ast::FnDecl,
+        header: ast::FnHeader,
+        name: Option<Ident>,
+        generics: &ast::Generics,
+    ) {
+        self.print_fn_header_info(header);
+        if let Some(name) = name {
+            self.nbsp();
+            self.print_ident(name);
+        }
+        self.print_generic_params(&generics.params);
+        self.print_fn_params_and_ret(decl, false);
+        self.print_where_clause(&generics.where_clause)
+    }
+
+    pub(crate) fn print_fn_params_and_ret(&mut self, decl: &ast::FnDecl, is_closure: bool) {
+        let (open, close) = if is_closure { ("|", "|") } else { ("(", ")") };
+        self.word(open);
+        self.commasep(Inconsistent, &decl.inputs, |s, param| s.print_param(param, is_closure));
+        self.word(close);
+        self.print_fn_ret_ty(&decl.output)
+    }
+
+    fn print_where_clause(&mut self, where_clause: &ast::WhereClause) {
+        self.print_where_clause_parts(where_clause.has_where_token, &where_clause.predicates);
+    }
+
+    pub(crate) fn print_where_clause_parts(
+        &mut self,
+        has_where_token: bool,
+        predicates: &[ast::WherePredicate],
+    ) {
+        if predicates.is_empty() && !has_where_token {
+            return;
+        }
+
+        self.space();
+        self.word_space("where");
+
+        for (i, predicate) in predicates.iter().enumerate() {
+            if i != 0 {
+                self.word_space(",");
+            }
+
+            self.print_where_predicate(predicate);
+        }
+    }
+
+    pub fn print_where_predicate(&mut self, predicate: &ast::WherePredicate) {
+        match predicate {
+            ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
+                bound_generic_params,
+                bounded_ty,
+                bounds,
+                ..
+            }) => {
+                self.print_formal_generic_params(bound_generic_params);
+                self.print_type(bounded_ty);
+                self.word(":");
+                if !bounds.is_empty() {
+                    self.nbsp();
+                    self.print_type_bounds(bounds);
+                }
+            }
+            ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
+                lifetime,
+                bounds,
+                ..
+            }) => {
+                self.print_lifetime(*lifetime);
+                self.word(":");
+                if !bounds.is_empty() {
+                    self.nbsp();
+                    self.print_lifetime_bounds(bounds);
+                }
+            }
+            ast::WherePredicate::EqPredicate(ast::WhereEqPredicate { lhs_ty, rhs_ty, .. }) => {
+                self.print_type(lhs_ty);
+                self.space();
+                self.word_space("=");
+                self.print_type(rhs_ty);
+            }
+        }
+    }
+
+    fn print_use_tree(&mut self, tree: &ast::UseTree) {
+        match tree.kind {
+            ast::UseTreeKind::Simple(rename, ..) => {
+                self.print_path(&tree.prefix, false, 0);
+                if let Some(rename) = rename {
+                    self.nbsp();
+                    self.word_nbsp("as");
+                    self.print_ident(rename);
+                }
+            }
+            ast::UseTreeKind::Glob => {
+                if !tree.prefix.segments.is_empty() {
+                    self.print_path(&tree.prefix, false, 0);
+                    self.word("::");
+                }
+                self.word("*");
+            }
+            ast::UseTreeKind::Nested(ref items) => {
+                if !tree.prefix.segments.is_empty() {
+                    self.print_path(&tree.prefix, false, 0);
+                    self.word("::");
+                }
+                if items.is_empty() {
+                    self.word("{}");
+                } else if items.len() == 1 {
+                    self.print_use_tree(&items[0].0);
+                } else {
+                    self.cbox(INDENT_UNIT);
+                    self.word("{");
+                    self.zerobreak();
+                    self.ibox(0);
+                    for use_tree in items.iter().delimited() {
+                        self.print_use_tree(&use_tree.0);
+                        if !use_tree.is_last {
+                            self.word(",");
+                            if let ast::UseTreeKind::Nested(_) = use_tree.0.kind {
+                                self.hardbreak();
+                            } else {
+                                self.space();
+                            }
+                        }
+                    }
+                    self.end();
+                    self.trailing_comma();
+                    self.offset(-INDENT_UNIT);
+                    self.word("}");
+                    self.end();
+                }
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_ast_pretty/src/pprust/tests.rs b/compiler/rustc_ast_pretty/src/pprust/tests.rs
new file mode 100644
index 000000000..6c8d42f33
--- /dev/null
+++ b/compiler/rustc_ast_pretty/src/pprust/tests.rs
@@ -0,0 +1,63 @@
+use super::*;
+
+use rustc_ast as ast;
+use rustc_span::create_default_session_globals_then;
+use rustc_span::symbol::Ident;
+
+fn fun_to_string(
+    decl: &ast::FnDecl,
+    header: ast::FnHeader,
+    name: Ident,
+    generics: &ast::Generics,
+) -> String {
+    to_string(|s| {
+        s.head("");
+        s.print_fn(decl, header, Some(name), generics);
+        s.end(); // Close the head box.
+        s.end(); // Close the outer box.
+    })
+}
+
+fn variant_to_string(var: &ast::Variant) -> String {
+    to_string(|s| s.print_variant(var))
+}
+
+#[test]
+fn test_fun_to_string() {
+    create_default_session_globals_then(|| {
+        let abba_ident = Ident::from_str("abba");
+
+        let decl =
+            ast::FnDecl { inputs: Vec::new(), output: ast::FnRetTy::Default(rustc_span::DUMMY_SP) };
+        let generics = ast::Generics::default();
+        assert_eq!(
+            fun_to_string(&decl, ast::FnHeader::default(), abba_ident, &generics),
+            "fn abba()"
+        );
+    })
+}
+
+#[test]
+fn test_variant_to_string() {
+    create_default_session_globals_then(|| {
+        let ident = Ident::from_str("principal_skinner");
+
+        let var = ast::Variant {
+            ident,
+            vis: ast::Visibility {
+                span: rustc_span::DUMMY_SP,
+                kind: ast::VisibilityKind::Inherited,
+                tokens: None,
+            },
+            attrs: ast::AttrVec::new(),
+            id: ast::DUMMY_NODE_ID,
+            data: ast::VariantData::Unit(ast::DUMMY_NODE_ID),
+            disr_expr: None,
+            span: rustc_span::DUMMY_SP,
+            is_placeholder: false,
+        };
+
+        let varstr = variant_to_string(&var);
+        assert_eq!(varstr, "principal_skinner");
+    })
+}