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

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

1 files changed, 2413 insertions, 0 deletions

diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
new file mode 100644
index 000000000..e0179bd3e
--- /dev/null
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -0,0 +1,2413 @@
+#![recursion_limit = "256"]
+
+use rustc_ast as ast;
+use rustc_ast::util::parser::{self, AssocOp, Fixity};
+use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
+use rustc_ast_pretty::pp::{self, Breaks};
+use rustc_ast_pretty::pprust::{Comments, PrintState};
+use rustc_hir as hir;
+use rustc_hir::LifetimeParamKind;
+use rustc_hir::{GenericArg, GenericParam, GenericParamKind, Node, Term};
+use rustc_hir::{GenericBound, PatKind, RangeEnd, TraitBoundModifier};
+use rustc_span::source_map::SourceMap;
+use rustc_span::symbol::{kw, Ident, IdentPrinter, Symbol};
+use rustc_span::{self, FileName};
+use rustc_target::spec::abi::Abi;
+
+use std::cell::Cell;
+use std::vec;
+
+pub fn id_to_string(map: &dyn rustc_hir::intravisit::Map<'_>, hir_id: hir::HirId) -> String {
+    to_string(&map, |s| s.print_node(map.find(hir_id).unwrap()))
+}
+
+pub enum AnnNode<'a> {
+    Name(&'a Symbol),
+    Block(&'a hir::Block<'a>),
+    Item(&'a hir::Item<'a>),
+    SubItem(hir::HirId),
+    Expr(&'a hir::Expr<'a>),
+    Pat(&'a hir::Pat<'a>),
+    Arm(&'a hir::Arm<'a>),
+}
+
+pub enum Nested {
+    Item(hir::ItemId),
+    TraitItem(hir::TraitItemId),
+    ImplItem(hir::ImplItemId),
+    ForeignItem(hir::ForeignItemId),
+    Body(hir::BodyId),
+    BodyParamPat(hir::BodyId, usize),
+}
+
+pub trait PpAnn {
+    fn nested(&self, _state: &mut State<'_>, _nested: Nested) {}
+    fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
+    fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
+}
+
+pub struct NoAnn;
+impl PpAnn for NoAnn {}
+pub const NO_ANN: &dyn PpAnn = &NoAnn;
+
+/// Identical to the `PpAnn` implementation for `hir::Crate`,
+/// except it avoids creating a dependency on the whole crate.
+impl PpAnn for &dyn rustc_hir::intravisit::Map<'_> {
+    fn nested(&self, state: &mut State<'_>, nested: Nested) {
+        match nested {
+            Nested::Item(id) => state.print_item(self.item(id)),
+            Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
+            Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
+            Nested::ForeignItem(id) => state.print_foreign_item(self.foreign_item(id)),
+            Nested::Body(id) => state.print_expr(&self.body(id).value),
+            Nested::BodyParamPat(id, i) => state.print_pat(self.body(id).params[i].pat),
+        }
+    }
+}
+
+pub struct State<'a> {
+    pub s: pp::Printer,
+    comments: Option<Comments<'a>>,
+    attrs: &'a dyn Fn(hir::HirId) -> &'a [ast::Attribute],
+    ann: &'a (dyn PpAnn + 'a),
+}
+
+impl<'a> State<'a> {
+    pub fn print_node(&mut self, node: Node<'_>) {
+        match node {
+            Node::Param(a) => self.print_param(a),
+            Node::Item(a) => self.print_item(a),
+            Node::ForeignItem(a) => self.print_foreign_item(a),
+            Node::TraitItem(a) => self.print_trait_item(a),
+            Node::ImplItem(a) => self.print_impl_item(a),
+            Node::Variant(a) => self.print_variant(a),
+            Node::AnonConst(a) => self.print_anon_const(a),
+            Node::Expr(a) => self.print_expr(a),
+            Node::Stmt(a) => self.print_stmt(a),
+            Node::PathSegment(a) => self.print_path_segment(a),
+            Node::Ty(a) => self.print_type(a),
+            Node::TypeBinding(a) => self.print_type_binding(a),
+            Node::TraitRef(a) => self.print_trait_ref(a),
+            Node::Pat(a) => self.print_pat(a),
+            Node::Arm(a) => self.print_arm(a),
+            Node::Infer(_) => self.word("_"),
+            Node::Block(a) => {
+                // Containing cbox, will be closed by print-block at `}`.
+                self.cbox(INDENT_UNIT);
+                // Head-ibox, will be closed by print-block after `{`.
+                self.ibox(0);
+                self.print_block(a);
+            }
+            Node::Lifetime(a) => self.print_lifetime(a),
+            Node::GenericParam(_) => panic!("cannot print Node::GenericParam"),
+            Node::Field(_) => panic!("cannot print Node::Field"),
+            // These cases do not carry enough information in the
+            // `hir_map` to reconstruct their full structure for pretty
+            // printing.
+            Node::Ctor(..) => panic!("cannot print isolated Ctor"),
+            Node::Local(a) => self.print_local_decl(a),
+            Node::Crate(..) => panic!("cannot print Crate"),
+        }
+    }
+}
+
+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
+    }
+}
+
+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::Name(&ident.name))
+    }
+
+    fn print_generic_args(&mut self, _: &ast::GenericArgs, _colons_before_params: bool) {
+        panic!("AST generic args printed by HIR pretty-printer");
+    }
+}
+
+pub 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: &hir::Mod<'_>,
+    filename: FileName,
+    input: String,
+    attrs: &'a dyn Fn(hir::HirId) -> &'a [ast::Attribute],
+    ann: &'a dyn PpAnn,
+) -> String {
+    let mut s = State::new_from_input(sm, filename, input, attrs, ann);
+
+    // When printing the AST, we sometimes need to inject `#[no_std]` here.
+    // Since you can't compile the HIR, it's not necessary.
+
+    s.print_mod(krate, (*attrs)(hir::CRATE_HIR_ID));
+    s.print_remaining_comments();
+    s.s.eof()
+}
+
+impl<'a> State<'a> {
+    pub fn new_from_input(
+        sm: &'a SourceMap,
+        filename: FileName,
+        input: String,
+        attrs: &'a dyn Fn(hir::HirId) -> &'a [ast::Attribute],
+        ann: &'a dyn PpAnn,
+    ) -> State<'a> {
+        State {
+            s: pp::Printer::new(),
+            comments: Some(Comments::new(sm, filename, input)),
+            attrs,
+            ann,
+        }
+    }
+
+    fn attrs(&self, id: hir::HirId) -> &'a [ast::Attribute] {
+        (self.attrs)(id)
+    }
+}
+
+pub fn to_string<F>(ann: &dyn PpAnn, f: F) -> String
+where
+    F: FnOnce(&mut State<'_>),
+{
+    let mut printer = State { s: pp::Printer::new(), comments: None, attrs: &|_| &[], ann };
+    f(&mut printer);
+    printer.s.eof()
+}
+
+pub fn generic_params_to_string(generic_params: &[GenericParam<'_>]) -> String {
+    to_string(NO_ANN, |s| s.print_generic_params(generic_params))
+}
+
+pub fn bounds_to_string<'b>(bounds: impl IntoIterator<Item = &'b hir::GenericBound<'b>>) -> String {
+    to_string(NO_ANN, |s| s.print_bounds("", bounds))
+}
+
+pub fn ty_to_string(ty: &hir::Ty<'_>) -> String {
+    to_string(NO_ANN, |s| s.print_type(ty))
+}
+
+pub fn path_segment_to_string(segment: &hir::PathSegment<'_>) -> String {
+    to_string(NO_ANN, |s| s.print_path_segment(segment))
+}
+
+pub fn path_to_string(segment: &hir::Path<'_>) -> String {
+    to_string(NO_ANN, |s| s.print_path(segment, false))
+}
+
+pub fn qpath_to_string(segment: &hir::QPath<'_>) -> String {
+    to_string(NO_ANN, |s| s.print_qpath(segment, false))
+}
+
+pub fn fn_to_string(
+    decl: &hir::FnDecl<'_>,
+    header: hir::FnHeader,
+    name: Option<Symbol>,
+    generics: &hir::Generics<'_>,
+    arg_names: &[Ident],
+    body_id: Option<hir::BodyId>,
+) -> String {
+    to_string(NO_ANN, |s| s.print_fn(decl, header, name, generics, arg_names, body_id))
+}
+
+pub fn enum_def_to_string(
+    enum_definition: &hir::EnumDef<'_>,
+    generics: &hir::Generics<'_>,
+    name: Symbol,
+    span: rustc_span::Span,
+) -> String {
+    to_string(NO_ANN, |s| s.print_enum_def(enum_definition, generics, name, span))
+}
+
+impl<'a> State<'a> {
+    pub fn bclose_maybe_open(&mut self, span: rustc_span::Span, close_box: bool) {
+        self.maybe_print_comment(span.hi());
+        self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
+        self.word("}");
+        if close_box {
+            self.end(); // close the outer-box
+        }
+    }
+
+    pub fn bclose(&mut self, span: rustc_span::Span) {
+        self.bclose_maybe_open(span, true)
+    }
+
+    pub 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 fn commasep_exprs(&mut self, b: Breaks, exprs: &[hir::Expr<'_>]) {
+        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span);
+    }
+
+    pub fn print_mod(&mut self, _mod: &hir::Mod<'_>, attrs: &[ast::Attribute]) {
+        self.print_inner_attributes(attrs);
+        for &item_id in _mod.item_ids {
+            self.ann.nested(self, Nested::Item(item_id));
+        }
+    }
+
+    pub fn print_opt_lifetime(&mut self, lifetime: &hir::Lifetime) {
+        if !lifetime.is_elided() {
+            self.print_lifetime(lifetime);
+            self.nbsp();
+        }
+    }
+
+    pub fn print_type(&mut self, ty: &hir::Ty<'_>) {
+        self.maybe_print_comment(ty.span.lo());
+        self.ibox(0);
+        match ty.kind {
+            hir::TyKind::Slice(ty) => {
+                self.word("[");
+                self.print_type(ty);
+                self.word("]");
+            }
+            hir::TyKind::Ptr(ref mt) => {
+                self.word("*");
+                self.print_mt(mt, true);
+            }
+            hir::TyKind::Rptr(ref lifetime, ref mt) => {
+                self.word("&");
+                self.print_opt_lifetime(lifetime);
+                self.print_mt(mt, false);
+            }
+            hir::TyKind::Never => {
+                self.word("!");
+            }
+            hir::TyKind::Tup(elts) => {
+                self.popen();
+                self.commasep(Inconsistent, elts, |s, ty| s.print_type(ty));
+                if elts.len() == 1 {
+                    self.word(",");
+                }
+                self.pclose();
+            }
+            hir::TyKind::BareFn(f) => {
+                self.print_ty_fn(f.abi, f.unsafety, f.decl, None, f.generic_params, f.param_names);
+            }
+            hir::TyKind::OpaqueDef(..) => self.word("/*impl Trait*/"),
+            hir::TyKind::Path(ref qpath) => self.print_qpath(qpath, false),
+            hir::TyKind::TraitObject(bounds, ref lifetime, syntax) => {
+                if syntax == ast::TraitObjectSyntax::Dyn {
+                    self.word_space("dyn");
+                }
+                let mut first = true;
+                for bound in bounds {
+                    if first {
+                        first = false;
+                    } else {
+                        self.nbsp();
+                        self.word_space("+");
+                    }
+                    self.print_poly_trait_ref(bound);
+                }
+                if !lifetime.is_elided() {
+                    self.nbsp();
+                    self.word_space("+");
+                    self.print_lifetime(lifetime);
+                }
+            }
+            hir::TyKind::Array(ty, ref length) => {
+                self.word("[");
+                self.print_type(ty);
+                self.word("; ");
+                self.print_array_length(length);
+                self.word("]");
+            }
+            hir::TyKind::Typeof(ref e) => {
+                self.word("typeof(");
+                self.print_anon_const(e);
+                self.word(")");
+            }
+            hir::TyKind::Err => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
+            hir::TyKind::Infer => {
+                self.word("_");
+            }
+        }
+        self.end()
+    }
+
+    pub fn print_foreign_item(&mut self, item: &hir::ForeignItem<'_>) {
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(item.span.lo());
+        self.print_outer_attributes(self.attrs(item.hir_id()));
+        match item.kind {
+            hir::ForeignItemKind::Fn(decl, arg_names, generics) => {
+                self.head("");
+                self.print_fn(
+                    decl,
+                    hir::FnHeader {
+                        unsafety: hir::Unsafety::Normal,
+                        constness: hir::Constness::NotConst,
+                        abi: Abi::Rust,
+                        asyncness: hir::IsAsync::NotAsync,
+                    },
+                    Some(item.ident.name),
+                    generics,
+                    arg_names,
+                    None,
+                );
+                self.end(); // end head-ibox
+                self.word(";");
+                self.end() // end the outer fn box
+            }
+            hir::ForeignItemKind::Static(t, m) => {
+                self.head("static");
+                if m == hir::Mutability::Mut {
+                    self.word_space("mut");
+                }
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(t);
+                self.word(";");
+                self.end(); // end the head-ibox
+                self.end() // end the outer cbox
+            }
+            hir::ForeignItemKind::Type => {
+                self.head("type");
+                self.print_ident(item.ident);
+                self.word(";");
+                self.end(); // end the head-ibox
+                self.end() // end the outer cbox
+            }
+        }
+    }
+
+    fn print_associated_const(
+        &mut self,
+        ident: Ident,
+        ty: &hir::Ty<'_>,
+        default: Option<hir::BodyId>,
+    ) {
+        self.head("");
+        self.word_space("const");
+        self.print_ident(ident);
+        self.word_space(":");
+        self.print_type(ty);
+        if let Some(expr) = default {
+            self.space();
+            self.word_space("=");
+            self.ann.nested(self, Nested::Body(expr));
+        }
+        self.word(";")
+    }
+
+    fn print_associated_type(
+        &mut self,
+        ident: Ident,
+        generics: &hir::Generics<'_>,
+        bounds: Option<hir::GenericBounds<'_>>,
+        ty: Option<&hir::Ty<'_>>,
+    ) {
+        self.word_space("type");
+        self.print_ident(ident);
+        self.print_generic_params(generics.params);
+        if let Some(bounds) = bounds {
+            self.print_bounds(":", bounds);
+        }
+        self.print_where_clause(generics);
+        if let Some(ty) = ty {
+            self.space();
+            self.word_space("=");
+            self.print_type(ty);
+        }
+        self.word(";")
+    }
+
+    fn print_item_type(
+        &mut self,
+        item: &hir::Item<'_>,
+        generics: &hir::Generics<'_>,
+        inner: impl Fn(&mut Self),
+    ) {
+        self.head("type");
+        self.print_ident(item.ident);
+        self.print_generic_params(generics.params);
+        self.end(); // end the inner ibox
+
+        self.print_where_clause(generics);
+        self.space();
+        inner(self);
+        self.word(";");
+        self.end(); // end the outer ibox
+    }
+
+    /// Pretty-print an item
+    pub fn print_item(&mut self, item: &hir::Item<'_>) {
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(item.span.lo());
+        let attrs = self.attrs(item.hir_id());
+        self.print_outer_attributes(attrs);
+        self.ann.pre(self, AnnNode::Item(item));
+        match item.kind {
+            hir::ItemKind::ExternCrate(orig_name) => {
+                self.head("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
+            }
+            hir::ItemKind::Use(path, kind) => {
+                self.head("use");
+                self.print_path(path, false);
+
+                match kind {
+                    hir::UseKind::Single => {
+                        if path.segments.last().unwrap().ident != item.ident {
+                            self.space();
+                            self.word_space("as");
+                            self.print_ident(item.ident);
+                        }
+                        self.word(";");
+                    }
+                    hir::UseKind::Glob => self.word("::*;"),
+                    hir::UseKind::ListStem => self.word("::{};"),
+                }
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
+            }
+            hir::ItemKind::Static(ty, m, expr) => {
+                self.head("static");
+                if m == hir::Mutability::Mut {
+                    self.word_space("mut");
+                }
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(ty);
+                self.space();
+                self.end(); // end the head-ibox
+
+                self.word_space("=");
+                self.ann.nested(self, Nested::Body(expr));
+                self.word(";");
+                self.end(); // end the outer cbox
+            }
+            hir::ItemKind::Const(ty, expr) => {
+                self.head("const");
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(ty);
+                self.space();
+                self.end(); // end the head-ibox
+
+                self.word_space("=");
+                self.ann.nested(self, Nested::Body(expr));
+                self.word(";");
+                self.end(); // end the outer cbox
+            }
+            hir::ItemKind::Fn(ref sig, param_names, body) => {
+                self.head("");
+                self.print_fn(
+                    sig.decl,
+                    sig.header,
+                    Some(item.ident.name),
+                    param_names,
+                    &[],
+                    Some(body),
+                );
+                self.word(" ");
+                self.end(); // need to close a box
+                self.end(); // need to close a box
+                self.ann.nested(self, Nested::Body(body));
+            }
+            hir::ItemKind::Macro(ref macro_def, _) => {
+                self.print_mac_def(macro_def, &item.ident, item.span, |_| {});
+            }
+            hir::ItemKind::Mod(ref _mod) => {
+                self.head("mod");
+                self.print_ident(item.ident);
+                self.nbsp();
+                self.bopen();
+                self.print_mod(_mod, attrs);
+                self.bclose(item.span);
+            }
+            hir::ItemKind::ForeignMod { abi, items } => {
+                self.head("extern");
+                self.word_nbsp(abi.to_string());
+                self.bopen();
+                self.print_inner_attributes(self.attrs(item.hir_id()));
+                for item in items {
+                    self.ann.nested(self, Nested::ForeignItem(item.id));
+                }
+                self.bclose(item.span);
+            }
+            hir::ItemKind::GlobalAsm(asm) => {
+                self.head("global_asm!");
+                self.print_inline_asm(asm);
+                self.end()
+            }
+            hir::ItemKind::TyAlias(ty, generics) => {
+                self.print_item_type(item, generics, |state| {
+                    state.word_space("=");
+                    state.print_type(ty);
+                });
+            }
+            hir::ItemKind::OpaqueTy(ref opaque_ty) => {
+                self.print_item_type(item, opaque_ty.generics, |state| {
+                    let mut real_bounds = Vec::with_capacity(opaque_ty.bounds.len());
+                    for b in opaque_ty.bounds {
+                        if let GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = b {
+                            state.space();
+                            state.word_space("for ?");
+                            state.print_trait_ref(&ptr.trait_ref);
+                        } else {
+                            real_bounds.push(b);
+                        }
+                    }
+                    state.print_bounds("= impl", real_bounds);
+                });
+            }
+            hir::ItemKind::Enum(ref enum_definition, params) => {
+                self.print_enum_def(enum_definition, params, item.ident.name, item.span);
+            }
+            hir::ItemKind::Struct(ref struct_def, generics) => {
+                self.head("struct");
+                self.print_struct(struct_def, generics, item.ident.name, item.span, true);
+            }
+            hir::ItemKind::Union(ref struct_def, generics) => {
+                self.head("union");
+                self.print_struct(struct_def, generics, item.ident.name, item.span, true);
+            }
+            hir::ItemKind::Impl(&hir::Impl {
+                unsafety,
+                polarity,
+                defaultness,
+                constness,
+                defaultness_span: _,
+                generics,
+                ref of_trait,
+                self_ty,
+                items,
+            }) => {
+                self.head("");
+                self.print_defaultness(defaultness);
+                self.print_unsafety(unsafety);
+                self.word_nbsp("impl");
+
+                if !generics.params.is_empty() {
+                    self.print_generic_params(generics.params);
+                    self.space();
+                }
+
+                if constness == hir::Constness::Const {
+                    self.word_nbsp("const");
+                }
+
+                if let hir::ImplPolarity::Negative(_) = polarity {
+                    self.word("!");
+                }
+
+                if let Some(t) = of_trait {
+                    self.print_trait_ref(t);
+                    self.space();
+                    self.word_space("for");
+                }
+
+                self.print_type(self_ty);
+                self.print_where_clause(generics);
+
+                self.space();
+                self.bopen();
+                self.print_inner_attributes(attrs);
+                for impl_item in items {
+                    self.ann.nested(self, Nested::ImplItem(impl_item.id));
+                }
+                self.bclose(item.span);
+            }
+            hir::ItemKind::Trait(is_auto, unsafety, generics, bounds, trait_items) => {
+                self.head("");
+                self.print_is_auto(is_auto);
+                self.print_unsafety(unsafety);
+                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 {
+                    if let GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = b {
+                        self.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
+                    } else {
+                        real_bounds.push(b);
+                    }
+                }
+                self.print_bounds(":", real_bounds);
+                self.print_where_clause(generics);
+                self.word(" ");
+                self.bopen();
+                for trait_item in trait_items {
+                    self.ann.nested(self, Nested::TraitItem(trait_item.id));
+                }
+                self.bclose(item.span);
+            }
+            hir::ItemKind::TraitAlias(generics, bounds) => {
+                self.head("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 {
+                    if let GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = b {
+                        self.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
+                    } else {
+                        real_bounds.push(b);
+                    }
+                }
+                self.nbsp();
+                self.print_bounds("=", real_bounds);
+                self.print_where_clause(generics);
+                self.word(";");
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
+            }
+        }
+        self.ann.post(self, AnnNode::Item(item))
+    }
+
+    pub fn print_trait_ref(&mut self, t: &hir::TraitRef<'_>) {
+        self.print_path(t.path, false);
+    }
+
+    fn print_formal_generic_params(&mut self, generic_params: &[hir::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: &hir::PolyTraitRef<'_>) {
+        self.print_formal_generic_params(t.bound_generic_params);
+        self.print_trait_ref(&t.trait_ref);
+    }
+
+    pub fn print_enum_def(
+        &mut self,
+        enum_definition: &hir::EnumDef<'_>,
+        generics: &hir::Generics<'_>,
+        name: Symbol,
+        span: rustc_span::Span,
+    ) {
+        self.head("enum");
+        self.print_name(name);
+        self.print_generic_params(generics.params);
+        self.print_where_clause(generics);
+        self.space();
+        self.print_variants(enum_definition.variants, span);
+    }
+
+    pub fn print_variants(&mut self, variants: &[hir::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(self.attrs(v.id));
+            self.ibox(INDENT_UNIT);
+            self.print_variant(v);
+            self.word(",");
+            self.end();
+            self.maybe_print_trailing_comment(v.span, None);
+        }
+        self.bclose(span)
+    }
+
+    pub fn print_defaultness(&mut self, defaultness: hir::Defaultness) {
+        match defaultness {
+            hir::Defaultness::Default { .. } => self.word_nbsp("default"),
+            hir::Defaultness::Final => (),
+        }
+    }
+
+    pub fn print_struct(
+        &mut self,
+        struct_def: &hir::VariantData<'_>,
+        generics: &hir::Generics<'_>,
+        name: Symbol,
+        span: rustc_span::Span,
+        print_finalizer: bool,
+    ) {
+        self.print_name(name);
+        self.print_generic_params(generics.params);
+        match struct_def {
+            hir::VariantData::Tuple(..) | hir::VariantData::Unit(..) => {
+                if let hir::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(s.attrs(field.hir_id));
+                        s.print_type(field.ty);
+                    });
+                    self.pclose();
+                }
+                self.print_where_clause(generics);
+                if print_finalizer {
+                    self.word(";");
+                }
+                self.end();
+                self.end() // close the outer-box
+            }
+            hir::VariantData::Struct(..) => {
+                self.print_where_clause(generics);
+                self.nbsp();
+                self.bopen();
+                self.hardbreak_if_not_bol();
+
+                for field in struct_def.fields() {
+                    self.hardbreak_if_not_bol();
+                    self.maybe_print_comment(field.span.lo());
+                    self.print_outer_attributes(self.attrs(field.hir_id));
+                    self.print_ident(field.ident);
+                    self.word_nbsp(":");
+                    self.print_type(field.ty);
+                    self.word(",");
+                }
+
+                self.bclose(span)
+            }
+        }
+    }
+
+    pub fn print_variant(&mut self, v: &hir::Variant<'_>) {
+        self.head("");
+        let generics = hir::Generics::empty();
+        self.print_struct(&v.data, generics, v.ident.name, v.span, false);
+        if let Some(ref d) = v.disr_expr {
+            self.space();
+            self.word_space("=");
+            self.print_anon_const(d);
+        }
+    }
+    pub fn print_method_sig(
+        &mut self,
+        ident: Ident,
+        m: &hir::FnSig<'_>,
+        generics: &hir::Generics<'_>,
+        arg_names: &[Ident],
+        body_id: Option<hir::BodyId>,
+    ) {
+        self.print_fn(m.decl, m.header, Some(ident.name), generics, arg_names, body_id);
+    }
+
+    pub fn print_trait_item(&mut self, ti: &hir::TraitItem<'_>) {
+        self.ann.pre(self, AnnNode::SubItem(ti.hir_id()));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(ti.span.lo());
+        self.print_outer_attributes(self.attrs(ti.hir_id()));
+        match ti.kind {
+            hir::TraitItemKind::Const(ty, default) => {
+                self.print_associated_const(ti.ident, ty, default);
+            }
+            hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(arg_names)) => {
+                self.print_method_sig(ti.ident, sig, ti.generics, arg_names, None);
+                self.word(";");
+            }
+            hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
+                self.head("");
+                self.print_method_sig(ti.ident, sig, ti.generics, &[], Some(body));
+                self.nbsp();
+                self.end(); // need to close a box
+                self.end(); // need to close a box
+                self.ann.nested(self, Nested::Body(body));
+            }
+            hir::TraitItemKind::Type(bounds, default) => {
+                self.print_associated_type(ti.ident, ti.generics, Some(bounds), default);
+            }
+        }
+        self.ann.post(self, AnnNode::SubItem(ti.hir_id()))
+    }
+
+    pub fn print_impl_item(&mut self, ii: &hir::ImplItem<'_>) {
+        self.ann.pre(self, AnnNode::SubItem(ii.hir_id()));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(ii.span.lo());
+        self.print_outer_attributes(self.attrs(ii.hir_id()));
+
+        match ii.kind {
+            hir::ImplItemKind::Const(ty, expr) => {
+                self.print_associated_const(ii.ident, ty, Some(expr));
+            }
+            hir::ImplItemKind::Fn(ref sig, body) => {
+                self.head("");
+                self.print_method_sig(ii.ident, sig, ii.generics, &[], Some(body));
+                self.nbsp();
+                self.end(); // need to close a box
+                self.end(); // need to close a box
+                self.ann.nested(self, Nested::Body(body));
+            }
+            hir::ImplItemKind::TyAlias(ty) => {
+                self.print_associated_type(ii.ident, ii.generics, None, Some(ty));
+            }
+        }
+        self.ann.post(self, AnnNode::SubItem(ii.hir_id()))
+    }
+
+    pub fn print_local(
+        &mut self,
+        init: Option<&hir::Expr<'_>>,
+        els: Option<&hir::Block<'_>>,
+        decl: impl Fn(&mut Self),
+    ) {
+        self.space_if_not_bol();
+        self.ibox(INDENT_UNIT);
+        self.word_nbsp("let");
+
+        self.ibox(INDENT_UNIT);
+        decl(self);
+        self.end();
+
+        if let Some(init) = init {
+            self.nbsp();
+            self.word_space("=");
+            self.print_expr(init);
+        }
+
+        if let Some(els) = els {
+            self.nbsp();
+            self.word_space("else");
+            self.print_block(els);
+        }
+
+        self.end()
+    }
+
+    pub fn print_stmt(&mut self, st: &hir::Stmt<'_>) {
+        self.maybe_print_comment(st.span.lo());
+        match st.kind {
+            hir::StmtKind::Local(loc) => {
+                self.print_local(loc.init, loc.els, |this| this.print_local_decl(loc));
+            }
+            hir::StmtKind::Item(item) => self.ann.nested(self, Nested::Item(item)),
+            hir::StmtKind::Expr(expr) => {
+                self.space_if_not_bol();
+                self.print_expr(expr);
+            }
+            hir::StmtKind::Semi(expr) => {
+                self.space_if_not_bol();
+                self.print_expr(expr);
+                self.word(";");
+            }
+        }
+        if stmt_ends_with_semi(&st.kind) {
+            self.word(";");
+        }
+        self.maybe_print_trailing_comment(st.span, None)
+    }
+
+    pub fn print_block(&mut self, blk: &hir::Block<'_>) {
+        self.print_block_with_attrs(blk, &[])
+    }
+
+    pub fn print_block_unclosed(&mut self, blk: &hir::Block<'_>) {
+        self.print_block_maybe_unclosed(blk, &[], false)
+    }
+
+    pub fn print_block_with_attrs(&mut self, blk: &hir::Block<'_>, attrs: &[ast::Attribute]) {
+        self.print_block_maybe_unclosed(blk, attrs, true)
+    }
+
+    pub fn print_block_maybe_unclosed(
+        &mut self,
+        blk: &hir::Block<'_>,
+        attrs: &[ast::Attribute],
+        close_box: bool,
+    ) {
+        match blk.rules {
+            hir::BlockCheckMode::UnsafeBlock(..) => self.word_space("unsafe"),
+            hir::BlockCheckMode::DefaultBlock => (),
+        }
+        self.maybe_print_comment(blk.span.lo());
+        self.ann.pre(self, AnnNode::Block(blk));
+        self.bopen();
+
+        self.print_inner_attributes(attrs);
+
+        for st in blk.stmts {
+            self.print_stmt(st);
+        }
+        if let Some(expr) = blk.expr {
+            self.space_if_not_bol();
+            self.print_expr(expr);
+            self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
+        }
+        self.bclose_maybe_open(blk.span, close_box);
+        self.ann.post(self, AnnNode::Block(blk))
+    }
+
+    fn print_else(&mut self, els: Option<&hir::Expr<'_>>) {
+        if let Some(els_inner) = els {
+            match els_inner.kind {
+                // Another `else if` block.
+                hir::ExprKind::If(i, then, e) => {
+                    self.cbox(INDENT_UNIT - 1);
+                    self.ibox(0);
+                    self.word(" else if ");
+                    self.print_expr_as_cond(i);
+                    self.space();
+                    self.print_expr(then);
+                    self.print_else(e);
+                }
+                // Final `else` block.
+                hir::ExprKind::Block(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");
+                }
+            }
+        }
+    }
+
+    pub fn print_if(
+        &mut self,
+        test: &hir::Expr<'_>,
+        blk: &hir::Expr<'_>,
+        elseopt: Option<&hir::Expr<'_>>,
+    ) {
+        self.head("if");
+        self.print_expr_as_cond(test);
+        self.space();
+        self.print_expr(blk);
+        self.print_else(elseopt)
+    }
+
+    pub fn print_array_length(&mut self, len: &hir::ArrayLen) {
+        match len {
+            hir::ArrayLen::Infer(_, _) => self.word("_"),
+            hir::ArrayLen::Body(ct) => self.print_anon_const(ct),
+        }
+    }
+
+    pub fn print_anon_const(&mut self, constant: &hir::AnonConst) {
+        self.ann.nested(self, Nested::Body(constant.body))
+    }
+
+    fn print_call_post(&mut self, args: &[hir::Expr<'_>]) {
+        self.popen();
+        self.commasep_exprs(Inconsistent, args);
+        self.pclose()
+    }
+
+    fn print_expr_maybe_paren(&mut self, expr: &hir::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 { ... }`.
+    pub fn print_expr_as_cond(&mut self, expr: &hir::Expr<'_>) {
+        self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
+    }
+
+    /// Prints `expr` or `(expr)` when `needs_par` holds.
+    fn print_expr_cond_paren(&mut self, expr: &hir::Expr<'_>, needs_par: bool) {
+        if needs_par {
+            self.popen();
+        }
+        if let hir::ExprKind::DropTemps(actual_expr) = expr.kind {
+            self.print_expr(actual_expr);
+        } else {
+            self.print_expr(expr);
+        }
+        if needs_par {
+            self.pclose();
+        }
+    }
+
+    /// Print a `let pat = expr` expression.
+    fn print_let(&mut self, pat: &hir::Pat<'_>, ty: Option<&hir::Ty<'_>>, init: &hir::Expr<'_>) {
+        self.word_space("let");
+        self.print_pat(pat);
+        if let Some(ty) = ty {
+            self.word_space(":");
+            self.print_type(ty);
+        }
+        self.space();
+        self.word_space("=");
+        let npals = || parser::needs_par_as_let_scrutinee(init.precedence().order());
+        self.print_expr_cond_paren(init, Self::cond_needs_par(init) || npals())
+    }
+
+    // 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) {}`.
+    fn cond_needs_par(expr: &hir::Expr<'_>) -> bool {
+        match expr.kind {
+            hir::ExprKind::Break(..) | hir::ExprKind::Closure { .. } | hir::ExprKind::Ret(..) => {
+                true
+            }
+            _ => contains_exterior_struct_lit(expr),
+        }
+    }
+
+    fn print_expr_vec(&mut self, exprs: &[hir::Expr<'_>]) {
+        self.ibox(INDENT_UNIT);
+        self.word("[");
+        self.commasep_exprs(Inconsistent, exprs);
+        self.word("]");
+        self.end()
+    }
+
+    fn print_expr_anon_const(&mut self, anon_const: &hir::AnonConst) {
+        self.ibox(INDENT_UNIT);
+        self.word_space("const");
+        self.print_anon_const(anon_const);
+        self.end()
+    }
+
+    fn print_expr_repeat(&mut self, element: &hir::Expr<'_>, count: &hir::ArrayLen) {
+        self.ibox(INDENT_UNIT);
+        self.word("[");
+        self.print_expr(element);
+        self.word_space(";");
+        self.print_array_length(count);
+        self.word("]");
+        self.end()
+    }
+
+    fn print_expr_struct(
+        &mut self,
+        qpath: &hir::QPath<'_>,
+        fields: &[hir::ExprField<'_>],
+        wth: Option<&hir::Expr<'_>>,
+    ) {
+        self.print_qpath(qpath, true);
+        self.word("{");
+        self.commasep_cmnt(
+            Consistent,
+            fields,
+            |s, field| {
+                s.ibox(INDENT_UNIT);
+                if !field.is_shorthand {
+                    s.print_ident(field.ident);
+                    s.word_space(":");
+                }
+                s.print_expr(field.expr);
+                s.end()
+            },
+            |f| f.span,
+        );
+        if let Some(expr) = wth {
+            self.ibox(INDENT_UNIT);
+            if !fields.is_empty() {
+                self.word(",");
+                self.space();
+            }
+            self.word("..");
+            self.print_expr(expr);
+            self.end();
+        } else if !fields.is_empty() {
+            self.word(",");
+        }
+
+        self.word("}");
+    }
+
+    fn print_expr_tup(&mut self, exprs: &[hir::Expr<'_>]) {
+        self.popen();
+        self.commasep_exprs(Inconsistent, exprs);
+        if exprs.len() == 1 {
+            self.word(",");
+        }
+        self.pclose()
+    }
+
+    fn print_expr_call(&mut self, func: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
+        let prec = match func.kind {
+            hir::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: &hir::PathSegment<'_>, args: &[hir::Expr<'_>]) {
+        let base_args = &args[1..];
+        self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX);
+        self.word(".");
+        self.print_ident(segment.ident);
+
+        let generic_args = segment.args();
+        if !generic_args.args.is_empty() || !generic_args.bindings.is_empty() {
+            self.print_generic_args(generic_args, segment.infer_args, true);
+        }
+
+        self.print_call_post(base_args)
+    }
+
+    fn print_expr_binary(&mut self, op: hir::BinOp, lhs: &hir::Expr<'_>, rhs: &hir::Expr<'_>) {
+        let assoc_op = bin_op_to_assoc_op(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.
+            (&hir::ExprKind::Cast { .. }, hir::BinOpKind::Lt | hir::BinOpKind::Shl) => {
+                parser::PREC_FORCE_PAREN
+            }
+            (&hir::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.as_str());
+        self.print_expr_maybe_paren(rhs, right_prec)
+    }
+
+    fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr<'_>) {
+        self.word(op.as_str());
+        self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
+    }
+
+    fn print_expr_addr_of(
+        &mut self,
+        kind: hir::BorrowKind,
+        mutability: hir::Mutability,
+        expr: &hir::Expr<'_>,
+    ) {
+        self.word("&");
+        match kind {
+            hir::BorrowKind::Ref => self.print_mutability(mutability, false),
+            hir::BorrowKind::Raw => {
+                self.word_nbsp("raw");
+                self.print_mutability(mutability, true);
+            }
+        }
+        self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
+    }
+
+    fn print_literal(&mut self, lit: &hir::Lit) {
+        self.maybe_print_comment(lit.span.lo());
+        self.word(lit.node.to_lit_token().to_string())
+    }
+
+    fn print_inline_asm(&mut self, asm: &hir::InlineAsm<'_>) {
+        enum AsmArg<'a> {
+            Template(String),
+            Operand(&'a hir::InlineAsmOperand<'a>),
+            Options(ast::InlineAsmOptions),
+        }
+
+        let mut args = vec![AsmArg::Template(ast::InlineAsmTemplatePiece::to_string(asm.template))];
+        args.extend(asm.operands.iter().map(|(o, _)| AsmArg::Operand(o)));
+        if !asm.options.is_empty() {
+            args.push(AsmArg::Options(asm.options));
+        }
+
+        self.popen();
+        self.commasep(Consistent, &args, |s, arg| match *arg {
+            AsmArg::Template(ref template) => s.print_string(template, ast::StrStyle::Cooked),
+            AsmArg::Operand(op) => match *op {
+                hir::InlineAsmOperand::In { reg, ref expr } => {
+                    s.word("in");
+                    s.popen();
+                    s.word(format!("{}", reg));
+                    s.pclose();
+                    s.space();
+                    s.print_expr(expr);
+                }
+                hir::InlineAsmOperand::Out { reg, late, ref expr } => {
+                    s.word(if late { "lateout" } else { "out" });
+                    s.popen();
+                    s.word(format!("{}", reg));
+                    s.pclose();
+                    s.space();
+                    match expr {
+                        Some(expr) => s.print_expr(expr),
+                        None => s.word("_"),
+                    }
+                }
+                hir::InlineAsmOperand::InOut { reg, late, ref expr } => {
+                    s.word(if late { "inlateout" } else { "inout" });
+                    s.popen();
+                    s.word(format!("{}", reg));
+                    s.pclose();
+                    s.space();
+                    s.print_expr(expr);
+                }
+                hir::InlineAsmOperand::SplitInOut { reg, late, ref in_expr, ref out_expr } => {
+                    s.word(if late { "inlateout" } else { "inout" });
+                    s.popen();
+                    s.word(format!("{}", 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("_"),
+                    }
+                }
+                hir::InlineAsmOperand::Const { ref anon_const } => {
+                    s.word("const");
+                    s.space();
+                    s.print_anon_const(anon_const);
+                }
+                hir::InlineAsmOperand::SymFn { ref anon_const } => {
+                    s.word("sym_fn");
+                    s.space();
+                    s.print_anon_const(anon_const);
+                }
+                hir::InlineAsmOperand::SymStatic { ref path, def_id: _ } => {
+                    s.word("sym_static");
+                    s.space();
+                    s.print_qpath(path, true);
+                }
+            },
+            AsmArg::Options(opts) => {
+                s.word("options");
+                s.popen();
+                let mut options = vec![];
+                if opts.contains(ast::InlineAsmOptions::PURE) {
+                    options.push("pure");
+                }
+                if opts.contains(ast::InlineAsmOptions::NOMEM) {
+                    options.push("nomem");
+                }
+                if opts.contains(ast::InlineAsmOptions::READONLY) {
+                    options.push("readonly");
+                }
+                if opts.contains(ast::InlineAsmOptions::PRESERVES_FLAGS) {
+                    options.push("preserves_flags");
+                }
+                if opts.contains(ast::InlineAsmOptions::NORETURN) {
+                    options.push("noreturn");
+                }
+                if opts.contains(ast::InlineAsmOptions::NOSTACK) {
+                    options.push("nostack");
+                }
+                if opts.contains(ast::InlineAsmOptions::ATT_SYNTAX) {
+                    options.push("att_syntax");
+                }
+                if opts.contains(ast::InlineAsmOptions::RAW) {
+                    options.push("raw");
+                }
+                if opts.contains(ast::InlineAsmOptions::MAY_UNWIND) {
+                    options.push("may_unwind");
+                }
+                s.commasep(Inconsistent, &options, |s, &opt| {
+                    s.word(opt);
+                });
+                s.pclose();
+            }
+        });
+        self.pclose();
+    }
+
+    pub fn print_expr(&mut self, expr: &hir::Expr<'_>) {
+        self.maybe_print_comment(expr.span.lo());
+        self.print_outer_attributes(self.attrs(expr.hir_id));
+        self.ibox(INDENT_UNIT);
+        self.ann.pre(self, AnnNode::Expr(expr));
+        match expr.kind {
+            hir::ExprKind::Box(expr) => {
+                self.word_space("box");
+                self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
+            }
+            hir::ExprKind::Array(exprs) => {
+                self.print_expr_vec(exprs);
+            }
+            hir::ExprKind::ConstBlock(ref anon_const) => {
+                self.print_expr_anon_const(anon_const);
+            }
+            hir::ExprKind::Repeat(element, ref count) => {
+                self.print_expr_repeat(element, count);
+            }
+            hir::ExprKind::Struct(qpath, fields, wth) => {
+                self.print_expr_struct(qpath, fields, wth);
+            }
+            hir::ExprKind::Tup(exprs) => {
+                self.print_expr_tup(exprs);
+            }
+            hir::ExprKind::Call(func, args) => {
+                self.print_expr_call(func, args);
+            }
+            hir::ExprKind::MethodCall(segment, args, _) => {
+                self.print_expr_method_call(segment, args);
+            }
+            hir::ExprKind::Binary(op, lhs, rhs) => {
+                self.print_expr_binary(op, lhs, rhs);
+            }
+            hir::ExprKind::Unary(op, expr) => {
+                self.print_expr_unary(op, expr);
+            }
+            hir::ExprKind::AddrOf(k, m, expr) => {
+                self.print_expr_addr_of(k, m, expr);
+            }
+            hir::ExprKind::Lit(ref lit) => {
+                self.print_literal(lit);
+            }
+            hir::ExprKind::Cast(expr, 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);
+            }
+            hir::ExprKind::Type(expr, ty) => {
+                let prec = AssocOp::Colon.precedence() as i8;
+                self.print_expr_maybe_paren(expr, prec);
+                self.word_space(":");
+                self.print_type(ty);
+            }
+            hir::ExprKind::DropTemps(init) => {
+                // Print `{`:
+                self.cbox(INDENT_UNIT);
+                self.ibox(0);
+                self.bopen();
+
+                // Print `let _t = $init;`:
+                let temp = Ident::from_str("_t");
+                self.print_local(Some(init), None, |this| this.print_ident(temp));
+                self.word(";");
+
+                // Print `_t`:
+                self.space_if_not_bol();
+                self.print_ident(temp);
+
+                // Print `}`:
+                self.bclose_maybe_open(expr.span, true);
+            }
+            hir::ExprKind::Let(&hir::Let { pat, ty, init, .. }) => {
+                self.print_let(pat, ty, init);
+            }
+            hir::ExprKind::If(test, blk, elseopt) => {
+                self.print_if(test, blk, elseopt);
+            }
+            hir::ExprKind::Loop(blk, opt_label, _, _) => {
+                if let Some(label) = opt_label {
+                    self.print_ident(label.ident);
+                    self.word_space(":");
+                }
+                self.head("loop");
+                self.print_block(blk);
+            }
+            hir::ExprKind::Match(expr, arms, _) => {
+                self.cbox(INDENT_UNIT);
+                self.ibox(INDENT_UNIT);
+                self.word_nbsp("match");
+                self.print_expr_as_cond(expr);
+                self.space();
+                self.bopen();
+                for arm in arms {
+                    self.print_arm(arm);
+                }
+                self.bclose(expr.span);
+            }
+            hir::ExprKind::Closure(&hir::Closure {
+                binder,
+                capture_clause,
+                bound_generic_params,
+                fn_decl,
+                body,
+                fn_decl_span: _,
+                movability: _,
+            }) => {
+                self.print_closure_binder(binder, bound_generic_params);
+                self.print_capture_clause(capture_clause);
+
+                self.print_closure_params(fn_decl, body);
+                self.space();
+
+                // This is a bare expression.
+                self.ann.nested(self, Nested::Body(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);
+            }
+            hir::ExprKind::Block(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(INDENT_UNIT);
+                // head-box, will be closed by print-block after `{`
+                self.ibox(0);
+                self.print_block(blk);
+            }
+            hir::ExprKind::Assign(lhs, 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);
+            }
+            hir::ExprKind::AssignOp(op, lhs, rhs) => {
+                let prec = AssocOp::Assign.precedence() as i8;
+                self.print_expr_maybe_paren(lhs, prec + 1);
+                self.space();
+                self.word(op.node.as_str());
+                self.word_space("=");
+                self.print_expr_maybe_paren(rhs, prec);
+            }
+            hir::ExprKind::Field(expr, ident) => {
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.word(".");
+                self.print_ident(ident);
+            }
+            hir::ExprKind::Index(expr, index) => {
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.word("[");
+                self.print_expr(index);
+                self.word("]");
+            }
+            hir::ExprKind::Path(ref qpath) => self.print_qpath(qpath, true),
+            hir::ExprKind::Break(destination, opt_expr) => {
+                self.word("break");
+                if let Some(label) = destination.label {
+                    self.space();
+                    self.print_ident(label.ident);
+                }
+                if let Some(expr) = opt_expr {
+                    self.space();
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            hir::ExprKind::Continue(destination) => {
+                self.word("continue");
+                if let Some(label) = destination.label {
+                    self.space();
+                    self.print_ident(label.ident);
+                }
+            }
+            hir::ExprKind::Ret(result) => {
+                self.word("return");
+                if let Some(expr) = result {
+                    self.word(" ");
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                }
+            }
+            hir::ExprKind::InlineAsm(asm) => {
+                self.word("asm!");
+                self.print_inline_asm(asm);
+            }
+            hir::ExprKind::Yield(expr, _) => {
+                self.word_space("yield");
+                self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+            }
+            hir::ExprKind::Err => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
+        }
+        self.ann.post(self, AnnNode::Expr(expr));
+        self.end()
+    }
+
+    pub fn print_local_decl(&mut self, loc: &hir::Local<'_>) {
+        self.print_pat(loc.pat);
+        if let Some(ty) = loc.ty {
+            self.word_space(":");
+            self.print_type(ty);
+        }
+    }
+
+    pub fn print_name(&mut self, name: Symbol) {
+        self.print_ident(Ident::with_dummy_span(name))
+    }
+
+    pub fn print_path(&mut self, path: &hir::Path<'_>, colons_before_params: bool) {
+        self.maybe_print_comment(path.span.lo());
+
+        for (i, segment) in path.segments.iter().enumerate() {
+            if i > 0 {
+                self.word("::")
+            }
+            if segment.ident.name != kw::PathRoot {
+                self.print_ident(segment.ident);
+                self.print_generic_args(segment.args(), segment.infer_args, colons_before_params);
+            }
+        }
+    }
+
+    pub fn print_path_segment(&mut self, segment: &hir::PathSegment<'_>) {
+        if segment.ident.name != kw::PathRoot {
+            self.print_ident(segment.ident);
+            self.print_generic_args(segment.args(), segment.infer_args, false);
+        }
+    }
+
+    pub fn print_qpath(&mut self, qpath: &hir::QPath<'_>, colons_before_params: bool) {
+        match *qpath {
+            hir::QPath::Resolved(None, path) => self.print_path(path, colons_before_params),
+            hir::QPath::Resolved(Some(qself), path) => {
+                self.word("<");
+                self.print_type(qself);
+                self.space();
+                self.word_space("as");
+
+                for (i, segment) in path.segments[..path.segments.len() - 1].iter().enumerate() {
+                    if i > 0 {
+                        self.word("::")
+                    }
+                    if segment.ident.name != kw::PathRoot {
+                        self.print_ident(segment.ident);
+                        self.print_generic_args(
+                            segment.args(),
+                            segment.infer_args,
+                            colons_before_params,
+                        );
+                    }
+                }
+
+                self.word(">");
+                self.word("::");
+                let item_segment = path.segments.last().unwrap();
+                self.print_ident(item_segment.ident);
+                self.print_generic_args(
+                    item_segment.args(),
+                    item_segment.infer_args,
+                    colons_before_params,
+                )
+            }
+            hir::QPath::TypeRelative(qself, item_segment) => {
+                // If we've got a compound-qualified-path, let's push an additional pair of angle
+                // brackets, so that we pretty-print `<<A::B>::C>` as `<A::B>::C`, instead of just
+                // `A::B::C` (since the latter could be ambiguous to the user)
+                if let hir::TyKind::Path(hir::QPath::Resolved(None, _)) = qself.kind {
+                    self.print_type(qself);
+                } else {
+                    self.word("<");
+                    self.print_type(qself);
+                    self.word(">");
+                }
+
+                self.word("::");
+                self.print_ident(item_segment.ident);
+                self.print_generic_args(
+                    item_segment.args(),
+                    item_segment.infer_args,
+                    colons_before_params,
+                )
+            }
+            hir::QPath::LangItem(lang_item, span, _) => {
+                self.word("#[lang = \"");
+                self.print_ident(Ident::new(lang_item.name(), span));
+                self.word("\"]");
+            }
+        }
+    }
+
+    fn print_generic_args(
+        &mut self,
+        generic_args: &hir::GenericArgs<'_>,
+        infer_args: bool,
+        colons_before_params: bool,
+    ) {
+        if generic_args.parenthesized {
+            self.word("(");
+            self.commasep(Inconsistent, generic_args.inputs(), |s, ty| s.print_type(ty));
+            self.word(")");
+
+            self.space_if_not_bol();
+            self.word_space("->");
+            self.print_type(generic_args.bindings[0].ty());
+        } else {
+            let start = if colons_before_params { "::<" } else { "<" };
+            let empty = Cell::new(true);
+            let start_or_comma = |this: &mut Self| {
+                if empty.get() {
+                    empty.set(false);
+                    this.word(start)
+                } else {
+                    this.word_space(",")
+                }
+            };
+
+            let mut nonelided_generic_args: bool = false;
+            let elide_lifetimes = generic_args.args.iter().all(|arg| match arg {
+                GenericArg::Lifetime(lt) => lt.is_elided(),
+                _ => {
+                    nonelided_generic_args = true;
+                    true
+                }
+            });
+
+            if nonelided_generic_args {
+                start_or_comma(self);
+                self.commasep(
+                    Inconsistent,
+                    generic_args.args,
+                    |s, generic_arg| match generic_arg {
+                        GenericArg::Lifetime(lt) if !elide_lifetimes => s.print_lifetime(lt),
+                        GenericArg::Lifetime(_) => {}
+                        GenericArg::Type(ty) => s.print_type(ty),
+                        GenericArg::Const(ct) => s.print_anon_const(&ct.value),
+                        GenericArg::Infer(_inf) => s.word("_"),
+                    },
+                );
+            }
+
+            // FIXME(eddyb): this would leak into error messages (e.g.,
+            // "non-exhaustive patterns: `Some::<..>(_)` not covered").
+            if infer_args && false {
+                start_or_comma(self);
+                self.word("..");
+            }
+
+            for binding in generic_args.bindings {
+                start_or_comma(self);
+                self.print_type_binding(binding);
+            }
+
+            if !empty.get() {
+                self.word(">")
+            }
+        }
+    }
+
+    pub fn print_type_binding(&mut self, binding: &hir::TypeBinding<'_>) {
+        self.print_ident(binding.ident);
+        self.print_generic_args(binding.gen_args, false, false);
+        self.space();
+        match binding.kind {
+            hir::TypeBindingKind::Equality { ref term } => {
+                self.word_space("=");
+                match term {
+                    Term::Ty(ty) => self.print_type(ty),
+                    Term::Const(ref c) => self.print_anon_const(c),
+                }
+            }
+            hir::TypeBindingKind::Constraint { bounds } => {
+                self.print_bounds(":", bounds);
+            }
+        }
+    }
+
+    pub fn print_pat(&mut self, pat: &hir::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::Binding(binding_mode, _, ident, sub) => {
+                match binding_mode {
+                    hir::BindingAnnotation::Ref => {
+                        self.word_nbsp("ref");
+                        self.print_mutability(hir::Mutability::Not, false);
+                    }
+                    hir::BindingAnnotation::RefMut => {
+                        self.word_nbsp("ref");
+                        self.print_mutability(hir::Mutability::Mut, false);
+                    }
+                    hir::BindingAnnotation::Unannotated => {}
+                    hir::BindingAnnotation::Mutable => {
+                        self.word_nbsp("mut");
+                    }
+                }
+                self.print_ident(ident);
+                if let Some(p) = sub {
+                    self.word("@");
+                    self.print_pat(p);
+                }
+            }
+            PatKind::TupleStruct(ref qpath, elts, ddpos) => {
+                self.print_qpath(qpath, true);
+                self.popen();
+                if let Some(ddpos) = ddpos {
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p));
+                    if ddpos != 0 {
+                        self.word_space(",");
+                    }
+                    self.word("..");
+                    if ddpos != elts.len() {
+                        self.word(",");
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p));
+                    }
+                } else {
+                    self.commasep(Inconsistent, elts, |s, p| s.print_pat(p));
+                }
+                self.pclose();
+            }
+            PatKind::Path(ref qpath) => {
+                self.print_qpath(qpath, true);
+            }
+            PatKind::Struct(ref qpath, fields, etc) => {
+                self.print_qpath(qpath, true);
+                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::Or(pats) => {
+                self.strsep("|", true, Inconsistent, pats, |s, p| s.print_pat(p));
+            }
+            PatKind::Tuple(elts, ddpos) => {
+                self.popen();
+                if let Some(ddpos) = ddpos {
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p));
+                    if ddpos != 0 {
+                        self.word_space(",");
+                    }
+                    self.word("..");
+                    if ddpos != elts.len() {
+                        self.word(",");
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p));
+                    }
+                } else {
+                    self.commasep(Inconsistent, elts, |s, p| s.print_pat(p));
+                    if elts.len() == 1 {
+                        self.word(",");
+                    }
+                }
+                self.pclose();
+            }
+            PatKind::Box(inner) => {
+                let is_range_inner = matches!(inner.kind, PatKind::Range(..));
+                self.word("box ");
+                if is_range_inner {
+                    self.popen();
+                }
+                self.print_pat(inner);
+                if is_range_inner {
+                    self.pclose();
+                }
+            }
+            PatKind::Ref(inner, mutbl) => {
+                let is_range_inner = matches!(inner.kind, PatKind::Range(..));
+                self.word("&");
+                self.word(mutbl.prefix_str());
+                if is_range_inner {
+                    self.popen();
+                }
+                self.print_pat(inner);
+                if is_range_inner {
+                    self.pclose();
+                }
+            }
+            PatKind::Lit(e) => self.print_expr(e),
+            PatKind::Range(begin, end, end_kind) => {
+                if let Some(expr) = begin {
+                    self.print_expr(expr);
+                }
+                match end_kind {
+                    RangeEnd::Included => self.word("..."),
+                    RangeEnd::Excluded => self.word(".."),
+                }
+                if let Some(expr) = end {
+                    self.print_expr(expr);
+                }
+            }
+            PatKind::Slice(before, slice, after) => {
+                self.word("[");
+                self.commasep(Inconsistent, before, |s, p| s.print_pat(p));
+                if let Some(p) = slice {
+                    if !before.is_empty() {
+                        self.word_space(",");
+                    }
+                    if let PatKind::Wild = p.kind {
+                        // Print nothing.
+                    } else {
+                        self.print_pat(p);
+                    }
+                    self.word("..");
+                    if !after.is_empty() {
+                        self.word_space(",");
+                    }
+                }
+                self.commasep(Inconsistent, after, |s, p| s.print_pat(p));
+                self.word("]");
+            }
+        }
+        self.ann.post(self, AnnNode::Pat(pat))
+    }
+
+    pub fn print_param(&mut self, arg: &hir::Param<'_>) {
+        self.print_outer_attributes(self.attrs(arg.hir_id));
+        self.print_pat(arg.pat);
+    }
+
+    pub fn print_arm(&mut self, arm: &hir::Arm<'_>) {
+        // I have no idea why this check is necessary, but here it
+        // is :(
+        if self.attrs(arm.hir_id).is_empty() {
+            self.space();
+        }
+        self.cbox(INDENT_UNIT);
+        self.ann.pre(self, AnnNode::Arm(arm));
+        self.ibox(0);
+        self.print_outer_attributes(self.attrs(arm.hir_id));
+        self.print_pat(arm.pat);
+        self.space();
+        if let Some(ref g) = arm.guard {
+            match *g {
+                hir::Guard::If(e) => {
+                    self.word_space("if");
+                    self.print_expr(e);
+                    self.space();
+                }
+                hir::Guard::IfLet(&hir::Let { pat, ty, init, .. }) => {
+                    self.word_nbsp("if");
+                    self.print_let(pat, ty, init);
+                }
+            }
+        }
+        self.word_space("=>");
+
+        match arm.body.kind {
+            hir::ExprKind::Block(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(blk);
+
+                // If it is a user-provided unsafe block, print a comma after it
+                if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = blk.rules
+                {
+                    self.word(",");
+                }
+            }
+            _ => {
+                self.end(); // close the ibox for the pattern
+                self.print_expr(arm.body);
+                self.word(",");
+            }
+        }
+        self.ann.post(self, AnnNode::Arm(arm));
+        self.end() // close enclosing cbox
+    }
+
+    pub fn print_fn(
+        &mut self,
+        decl: &hir::FnDecl<'_>,
+        header: hir::FnHeader,
+        name: Option<Symbol>,
+        generics: &hir::Generics<'_>,
+        arg_names: &[Ident],
+        body_id: Option<hir::BodyId>,
+    ) {
+        self.print_fn_header_info(header);
+
+        if let Some(name) = name {
+            self.nbsp();
+            self.print_name(name);
+        }
+        self.print_generic_params(generics.params);
+
+        self.popen();
+        let mut i = 0;
+        // Make sure we aren't supplied *both* `arg_names` and `body_id`.
+        assert!(arg_names.is_empty() || body_id.is_none());
+        self.commasep(Inconsistent, decl.inputs, |s, ty| {
+            s.ibox(INDENT_UNIT);
+            if let Some(arg_name) = arg_names.get(i) {
+                s.word(arg_name.to_string());
+                s.word(":");
+                s.space();
+            } else if let Some(body_id) = body_id {
+                s.ann.nested(s, Nested::BodyParamPat(body_id, i));
+                s.word(":");
+                s.space();
+            }
+            i += 1;
+            s.print_type(ty);
+            s.end()
+        });
+        if decl.c_variadic {
+            self.word(", ...");
+        }
+        self.pclose();
+
+        self.print_fn_output(decl);
+        self.print_where_clause(generics)
+    }
+
+    fn print_closure_params(&mut self, decl: &hir::FnDecl<'_>, body_id: hir::BodyId) {
+        self.word("|");
+        let mut i = 0;
+        self.commasep(Inconsistent, decl.inputs, |s, ty| {
+            s.ibox(INDENT_UNIT);
+
+            s.ann.nested(s, Nested::BodyParamPat(body_id, i));
+            i += 1;
+
+            if let hir::TyKind::Infer = ty.kind {
+                // Print nothing.
+            } else {
+                s.word(":");
+                s.space();
+                s.print_type(ty);
+            }
+            s.end();
+        });
+        self.word("|");
+
+        if let hir::FnRetTy::DefaultReturn(..) = decl.output {
+            return;
+        }
+
+        self.space_if_not_bol();
+        self.word_space("->");
+        match decl.output {
+            hir::FnRetTy::Return(ty) => {
+                self.print_type(ty);
+                self.maybe_print_comment(ty.span.lo());
+            }
+            hir::FnRetTy::DefaultReturn(..) => unreachable!(),
+        }
+    }
+
+    pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureBy) {
+        match capture_clause {
+            hir::CaptureBy::Value => self.word_space("move"),
+            hir::CaptureBy::Ref => {}
+        }
+    }
+
+    pub fn print_closure_binder(
+        &mut self,
+        binder: hir::ClosureBinder,
+        generic_params: &[GenericParam<'_>],
+    ) {
+        let generic_params = generic_params
+            .iter()
+            .filter(|p| {
+                matches!(
+                    p,
+                    GenericParam {
+                        kind: GenericParamKind::Lifetime { kind: LifetimeParamKind::Explicit },
+                        ..
+                    }
+                )
+            })
+            .collect::<Vec<_>>();
+
+        match binder {
+            hir::ClosureBinder::Default => {}
+            // we need to distinguish `|...| {}` from `for<> |...| {}` as `for<>` adds additional restrictions
+            hir::ClosureBinder::For { .. } if generic_params.is_empty() => self.word("for<>"),
+            hir::ClosureBinder::For { .. } => {
+                self.word("for");
+                self.word("<");
+
+                self.commasep(Inconsistent, &generic_params, |s, param| {
+                    s.print_generic_param(param)
+                });
+
+                self.word(">");
+                self.nbsp();
+            }
+        }
+    }
+
+    pub fn print_bounds<'b>(
+        &mut self,
+        prefix: &'static str,
+        bounds: impl IntoIterator<Item = &'b hir::GenericBound<'b>>,
+    ) {
+        let mut first = true;
+        for bound in bounds {
+            if first {
+                self.word(prefix);
+            }
+            if !(first && prefix.is_empty()) {
+                self.nbsp();
+            }
+            if first {
+                first = false;
+            } else {
+                self.word_space("+");
+            }
+
+            match bound {
+                GenericBound::Trait(tref, modifier) => {
+                    if modifier == &TraitBoundModifier::Maybe {
+                        self.word("?");
+                    }
+                    self.print_poly_trait_ref(tref);
+                }
+                GenericBound::LangItemTrait(lang_item, span, ..) => {
+                    self.word("#[lang = \"");
+                    self.print_ident(Ident::new(lang_item.name(), *span));
+                    self.word("\"]");
+                }
+                GenericBound::Outlives(lt) => {
+                    self.print_lifetime(lt);
+                }
+            }
+        }
+    }
+
+    pub fn print_generic_params(&mut self, generic_params: &[GenericParam<'_>]) {
+        if !generic_params.is_empty() {
+            self.word("<");
+
+            self.commasep(Inconsistent, generic_params, |s, param| s.print_generic_param(param));
+
+            self.word(">");
+        }
+    }
+
+    pub fn print_generic_param(&mut self, param: &GenericParam<'_>) {
+        if let GenericParamKind::Const { .. } = param.kind {
+            self.word_space("const");
+        }
+
+        self.print_ident(param.name.ident());
+
+        match param.kind {
+            GenericParamKind::Lifetime { .. } => {}
+            GenericParamKind::Type { default, .. } => {
+                if let Some(default) = default {
+                    self.space();
+                    self.word_space("=");
+                    self.print_type(default);
+                }
+            }
+            GenericParamKind::Const { ty, ref default } => {
+                self.word_space(":");
+                self.print_type(ty);
+                if let Some(default) = default {
+                    self.space();
+                    self.word_space("=");
+                    self.print_anon_const(default);
+                }
+            }
+        }
+    }
+
+    pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) {
+        self.print_ident(lifetime.name.ident())
+    }
+
+    pub fn print_where_clause(&mut self, generics: &hir::Generics<'_>) {
+        if generics.predicates.is_empty() {
+            return;
+        }
+
+        self.space();
+        self.word_space("where");
+
+        for (i, predicate) in generics.predicates.iter().enumerate() {
+            if i != 0 {
+                self.word_space(",");
+            }
+
+            match *predicate {
+                hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
+                    bound_generic_params,
+                    bounded_ty,
+                    bounds,
+                    ..
+                }) => {
+                    self.print_formal_generic_params(bound_generic_params);
+                    self.print_type(bounded_ty);
+                    self.print_bounds(":", bounds);
+                }
+                hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
+                    ref lifetime,
+                    bounds,
+                    ..
+                }) => {
+                    self.print_lifetime(lifetime);
+                    self.word(":");
+
+                    for (i, bound) in bounds.iter().enumerate() {
+                        match bound {
+                            GenericBound::Outlives(lt) => {
+                                self.print_lifetime(lt);
+                            }
+                            _ => panic!(),
+                        }
+
+                        if i != 0 {
+                            self.word(":");
+                        }
+                    }
+                }
+                hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
+                    lhs_ty, rhs_ty, ..
+                }) => {
+                    self.print_type(lhs_ty);
+                    self.space();
+                    self.word_space("=");
+                    self.print_type(rhs_ty);
+                }
+            }
+        }
+    }
+
+    pub fn print_mutability(&mut self, mutbl: hir::Mutability, print_const: bool) {
+        match mutbl {
+            hir::Mutability::Mut => self.word_nbsp("mut"),
+            hir::Mutability::Not => {
+                if print_const {
+                    self.word_nbsp("const")
+                }
+            }
+        }
+    }
+
+    pub fn print_mt(&mut self, mt: &hir::MutTy<'_>, print_const: bool) {
+        self.print_mutability(mt.mutbl, print_const);
+        self.print_type(mt.ty);
+    }
+
+    pub fn print_fn_output(&mut self, decl: &hir::FnDecl<'_>) {
+        if let hir::FnRetTy::DefaultReturn(..) = decl.output {
+            return;
+        }
+
+        self.space_if_not_bol();
+        self.ibox(INDENT_UNIT);
+        self.word_space("->");
+        match decl.output {
+            hir::FnRetTy::DefaultReturn(..) => unreachable!(),
+            hir::FnRetTy::Return(ty) => self.print_type(ty),
+        }
+        self.end();
+
+        if let hir::FnRetTy::Return(output) = decl.output {
+            self.maybe_print_comment(output.span.lo());
+        }
+    }
+
+    pub fn print_ty_fn(
+        &mut self,
+        abi: Abi,
+        unsafety: hir::Unsafety,
+        decl: &hir::FnDecl<'_>,
+        name: Option<Symbol>,
+        generic_params: &[hir::GenericParam<'_>],
+        arg_names: &[Ident],
+    ) {
+        self.ibox(INDENT_UNIT);
+        self.print_formal_generic_params(generic_params);
+        let generics = hir::Generics::empty();
+        self.print_fn(
+            decl,
+            hir::FnHeader {
+                unsafety,
+                abi,
+                constness: hir::Constness::NotConst,
+                asyncness: hir::IsAsync::NotAsync,
+            },
+            name,
+            generics,
+            arg_names,
+            None,
+        );
+        self.end();
+    }
+
+    pub fn print_fn_header_info(&mut self, header: hir::FnHeader) {
+        match header.constness {
+            hir::Constness::NotConst => {}
+            hir::Constness::Const => self.word_nbsp("const"),
+        }
+
+        match header.asyncness {
+            hir::IsAsync::NotAsync => {}
+            hir::IsAsync::Async => self.word_nbsp("async"),
+        }
+
+        self.print_unsafety(header.unsafety);
+
+        if header.abi != Abi::Rust {
+            self.word_nbsp("extern");
+            self.word_nbsp(header.abi.to_string());
+        }
+
+        self.word("fn")
+    }
+
+    pub fn print_unsafety(&mut self, s: hir::Unsafety) {
+        match s {
+            hir::Unsafety::Normal => {}
+            hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
+        }
+    }
+
+    pub fn print_is_auto(&mut self, s: hir::IsAuto) {
+        match s {
+            hir::IsAuto::Yes => self.word_nbsp("auto"),
+            hir::IsAuto::No => {}
+        }
+    }
+}
+
+/// Does this expression require a semicolon to be treated
+/// as a statement? The negation of this: 'can this expression
+/// be used as a statement without a semicolon' -- is used
+/// as an early-bail-out in the parser so that, for instance,
+///     if true {...} else {...}
+///      |x| 5
+/// isn't parsed as (if true {...} else {...} | x) | 5
+//
+// Duplicated from `parse::classify`, but adapted for the HIR.
+fn expr_requires_semi_to_be_stmt(e: &hir::Expr<'_>) -> bool {
+    !matches!(
+        e.kind,
+        hir::ExprKind::If(..)
+            | hir::ExprKind::Match(..)
+            | hir::ExprKind::Block(..)
+            | hir::ExprKind::Loop(..)
+    )
+}
+
+/// This statement requires a semicolon after it.
+/// note that in one case (stmt_semi), we've already
+/// seen the semicolon, and thus don't need another.
+fn stmt_ends_with_semi(stmt: &hir::StmtKind<'_>) -> bool {
+    match *stmt {
+        hir::StmtKind::Local(_) => true,
+        hir::StmtKind::Item(_) => false,
+        hir::StmtKind::Expr(e) => expr_requires_semi_to_be_stmt(e),
+        hir::StmtKind::Semi(..) => false,
+    }
+}
+
+fn bin_op_to_assoc_op(op: hir::BinOpKind) -> AssocOp {
+    use crate::hir::BinOpKind::*;
+    match op {
+        Add => AssocOp::Add,
+        Sub => AssocOp::Subtract,
+        Mul => AssocOp::Multiply,
+        Div => AssocOp::Divide,
+        Rem => AssocOp::Modulus,
+
+        And => AssocOp::LAnd,
+        Or => AssocOp::LOr,
+
+        BitXor => AssocOp::BitXor,
+        BitAnd => AssocOp::BitAnd,
+        BitOr => AssocOp::BitOr,
+        Shl => AssocOp::ShiftLeft,
+        Shr => AssocOp::ShiftRight,
+
+        Eq => AssocOp::Equal,
+        Lt => AssocOp::Less,
+        Le => AssocOp::LessEqual,
+        Ne => AssocOp::NotEqual,
+        Ge => AssocOp::GreaterEqual,
+        Gt => AssocOp::Greater,
+    }
+}
+
+/// Expressions that syntactically contain an "exterior" struct literal, i.e., not surrounded by any
+/// parens or other delimiters, e.g., `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
+/// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
+fn contains_exterior_struct_lit(value: &hir::Expr<'_>) -> bool {
+    match value.kind {
+        hir::ExprKind::Struct(..) => true,
+
+        hir::ExprKind::Assign(lhs, rhs, _)
+        | hir::ExprKind::AssignOp(_, lhs, rhs)
+        | hir::ExprKind::Binary(_, lhs, rhs) => {
+            // `X { y: 1 } + X { y: 2 }`
+            contains_exterior_struct_lit(lhs) || contains_exterior_struct_lit(rhs)
+        }
+        hir::ExprKind::Unary(_, x)
+        | hir::ExprKind::Cast(x, _)
+        | hir::ExprKind::Type(x, _)
+        | hir::ExprKind::Field(x, _)
+        | hir::ExprKind::Index(x, _) => {
+            // `&X { y: 1 }, X { y: 1 }.y`
+            contains_exterior_struct_lit(x)
+        }
+
+        hir::ExprKind::MethodCall(.., exprs, _) => {
+            // `X { y: 1 }.bar(...)`
+            contains_exterior_struct_lit(&exprs[0])
+        }
+
+        _ => false,
+    }
+}