pprust.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use abi;
use ast::{P, RegionTyParamBound, TraitTyParamBound, Required, Provided};
use ast;
use ast_util;
use owned_slice::OwnedSlice;
use attr::{AttrMetaMethods, AttributeMethods};
use codemap::{CodeMap, BytePos};
use codemap;
use diagnostic;
use parse::classify::expr_is_simple_block;
use parse::token::IdentInterner;
use parse::{comments, token};
use parse;
use print::pp::{break_offset, word, space, zerobreak, hardbreak};
use print::pp::{Breaks, Consistent, Inconsistent, eof};
use print::pp;

use std::cast;
use std::char;
use std::io::{IoResult, MemWriter};
use std::io;
use std::rc::Rc;
use std::str;
use std::strbuf::StrBuf;

pub enum AnnNode<'a> {
    NodeBlock(&'a ast::Block),
    NodeItem(&'a ast::Item),
    NodeExpr(&'a ast::Expr),
    NodePat(&'a ast::Pat),
}

pub trait PpAnn {
    fn pre(&self, _state: &mut State, _node: AnnNode) -> IoResult<()> { Ok(()) }
    fn post(&self, _state: &mut State, _node: AnnNode) -> IoResult<()> { Ok(()) }
}

pub struct NoAnn;

impl PpAnn for NoAnn {}

pub struct CurrentCommentAndLiteral {
    cur_cmnt: uint,
    cur_lit: uint,
}

pub struct State<'a> {
    pub s: pp::Printer,
    cm: Option<&'a CodeMap>,
    intr: Rc<token::IdentInterner>,
    comments: Option<Vec<comments::Comment> >,
    literals: Option<Vec<comments::Literal> >,
    cur_cmnt_and_lit: CurrentCommentAndLiteral,
    boxes: Vec<pp::Breaks>,
    ann: &'a PpAnn
}

pub fn rust_printer(writer: ~io::Writer) -> State<'static> {
    static NO_ANN: NoAnn = NoAnn;
    rust_printer_annotated(writer, &NO_ANN)
}

pub fn rust_printer_annotated<'a>(writer: ~io::Writer,
                                  ann: &'a PpAnn) -> State<'a> {
    State {
        s: pp::mk_printer(writer, default_columns),
        cm: None,
        intr: token::get_ident_interner(),
        comments: None,
        literals: None,
        cur_cmnt_and_lit: CurrentCommentAndLiteral {
            cur_cmnt: 0,
            cur_lit: 0
        },
        boxes: Vec::new(),
        ann: ann
    }
}

pub static indent_unit: uint = 4u;

pub static default_columns: uint = 78u;

// Requires you to pass an input filename and reader so that
// it can scan the input text for comments and literals to
// copy forward.
pub fn print_crate<'a>(cm: &'a CodeMap,
                       span_diagnostic: &diagnostic::SpanHandler,
                       krate: &ast::Crate,
                       filename: ~str,
                       input: &mut io::Reader,
                       out: ~io::Writer,
                       ann: &'a PpAnn,
                       is_expanded: bool) -> IoResult<()> {
    let (cmnts, lits) = comments::gather_comments_and_literals(
        span_diagnostic,
        filename,
        input
    );
    let mut s = State {
        s: pp::mk_printer(out, default_columns),
        cm: Some(cm),
        intr: token::get_ident_interner(),
        comments: Some(cmnts),
        // If the code is post expansion, don't use the table of
        // literals, since it doesn't correspond with the literals
        // in the AST anymore.
        literals: if is_expanded {
            None
        } else {
            Some(lits)
        },
        cur_cmnt_and_lit: CurrentCommentAndLiteral {
            cur_cmnt: 0,
            cur_lit: 0
        },
        boxes: Vec::new(),
        ann: ann
    };
    try!(s.print_mod(&krate.module, krate.attrs.as_slice()));
    try!(s.print_remaining_comments());
    eof(&mut s.s)
}

pub fn to_str(f: |&mut State| -> IoResult<()>) -> ~str {
    let mut s = rust_printer(~MemWriter::new());
    f(&mut s).unwrap();
    eof(&mut s.s).unwrap();
    unsafe {
        // FIXME(pcwalton): A nasty function to extract the string from an `io::Writer`
        // that we "know" to be a `MemWriter` that works around the lack of checked
        // downcasts.
        let (_, wr): (uint, ~MemWriter) = cast::transmute_copy(&s.s.out);
        let result = str::from_utf8_owned(wr.get_ref().to_owned()).unwrap();
        cast::forget(wr);
        result
    }
}

pub fn ty_to_str(ty: &ast::Ty) -> ~str {
    to_str(|s| s.print_type(ty))
}

pub fn pat_to_str(pat: &ast::Pat) -> ~str {
    to_str(|s| s.print_pat(pat))
}

pub fn expr_to_str(e: &ast::Expr) -> ~str {
    to_str(|s| s.print_expr(e))
}

pub fn lifetime_to_str(e: &ast::Lifetime) -> ~str {
    to_str(|s| s.print_lifetime(e))
}

pub fn tt_to_str(tt: &ast::TokenTree) -> ~str {
    to_str(|s| s.print_tt(tt))
}

pub fn tts_to_str(tts: &[ast::TokenTree]) -> ~str {
    to_str(|s| s.print_tts(&tts))
}

pub fn stmt_to_str(stmt: &ast::Stmt) -> ~str {
    to_str(|s| s.print_stmt(stmt))
}

pub fn item_to_str(i: &ast::Item) -> ~str {
    to_str(|s| s.print_item(i))
}

pub fn generics_to_str(generics: &ast::Generics) -> ~str {
    to_str(|s| s.print_generics(generics))
}

pub fn ty_method_to_str(p: &ast::TypeMethod) -> ~str {
    to_str(|s| s.print_ty_method(p))
}

pub fn method_to_str(p: &ast::Method) -> ~str {
    to_str(|s| s.print_method(p))
}

pub fn fn_block_to_str(p: &ast::FnDecl) -> ~str {
    to_str(|s| s.print_fn_block_args(p))
}

pub fn path_to_str(p: &ast::Path) -> ~str {
    to_str(|s| s.print_path(p, false))
}

pub fn fun_to_str(decl: &ast::FnDecl, fn_style: ast::FnStyle, name: ast::Ident,
                  opt_explicit_self: Option<ast::ExplicitSelf_>,
                  generics: &ast::Generics) -> ~str {
    to_str(|s| {
        try!(s.print_fn(decl, Some(fn_style), abi::Rust,
                        name, generics, opt_explicit_self, ast::Inherited));
        try!(s.end()); // Close the head box
        s.end() // Close the outer box
    })
}

pub fn block_to_str(blk: &ast::Block) -> ~str {
    to_str(|s| {
        // containing cbox, will be closed by print-block at }
        try!(s.cbox(indent_unit));
        // head-ibox, will be closed by print-block after {
        try!(s.ibox(0u));
        s.print_block(blk)
    })
}

pub fn meta_item_to_str(mi: &ast::MetaItem) -> ~str {
    to_str(|s| s.print_meta_item(mi))
}

pub fn attribute_to_str(attr: &ast::Attribute) -> ~str {
    to_str(|s| s.print_attribute(attr))
}

pub fn lit_to_str(l: &ast::Lit) -> ~str {
    to_str(|s| s.print_literal(l))
}

pub fn explicit_self_to_str(explicit_self: ast::ExplicitSelf_) -> ~str {
    to_str(|s| s.print_explicit_self(explicit_self, ast::MutImmutable).map(|_| {}))
}

pub fn variant_to_str(var: &ast::Variant) -> ~str {
    to_str(|s| s.print_variant(var))
}

pub fn visibility_qualified(vis: ast::Visibility, s: &str) -> ~str {
    match vis {
        ast::Public => format!("pub {}", s),
        ast::Inherited => s.to_owned()
    }
}

impl<'a> State<'a> {
    pub fn ibox(&mut self, u: uint) -> IoResult<()> {
        self.boxes.push(pp::Inconsistent);
        pp::ibox(&mut self.s, u)
    }

    pub fn end(&mut self) -> IoResult<()> {
        self.boxes.pop().unwrap();
        pp::end(&mut self.s)
    }

    pub fn cbox(&mut self, u: uint) -> IoResult<()> {
        self.boxes.push(pp::Consistent);
        pp::cbox(&mut self.s, u)
    }

    // "raw box"
    pub fn rbox(&mut self, u: uint, b: pp::Breaks) -> IoResult<()> {
        self.boxes.push(b);
        pp::rbox(&mut self.s, u, b)
    }

    pub fn nbsp(&mut self) -> IoResult<()> { word(&mut self.s, " ") }

    pub fn word_nbsp(&mut self, w: &str) -> IoResult<()> {
        try!(word(&mut self.s, w));
        self.nbsp()
    }

    pub fn word_space(&mut self, w: &str) -> IoResult<()> {
        try!(word(&mut self.s, w));
        space(&mut self.s)
    }

    pub fn popen(&mut self) -> IoResult<()> { word(&mut self.s, "(") }

    pub fn pclose(&mut self) -> IoResult<()> { word(&mut self.s, ")") }

    pub fn head(&mut self, w: &str) -> IoResult<()> {
        // outer-box is consistent
        try!(self.cbox(indent_unit));
        // head-box is inconsistent
        try!(self.ibox(w.len() + 1));
        // keyword that starts the head
        if !w.is_empty() {
            try!(self.word_nbsp(w));
        }
        Ok(())
    }

    pub fn bopen(&mut self) -> IoResult<()> {
        try!(word(&mut self.s, "{"));
        self.end() // close the head-box
    }

    pub fn bclose_(&mut self, span: codemap::Span,
                   indented: uint) -> IoResult<()> {
        self.bclose_maybe_open(span, indented, true)
    }
    pub fn bclose_maybe_open (&mut self, span: codemap::Span,
                              indented: uint, close_box: bool) -> IoResult<()> {
        try!(self.maybe_print_comment(span.hi));
        try!(self.break_offset_if_not_bol(1u, -(indented as int)));
        try!(word(&mut self.s, "}"));
        if close_box {
            try!(self.end()); // close the outer-box
        }
        Ok(())
    }
    pub fn bclose(&mut self, span: codemap::Span) -> IoResult<()> {
        self.bclose_(span, indent_unit)
    }

    pub fn is_begin(&mut self) -> bool {
        match self.s.last_token() { pp::Begin(_) => true, _ => false }
    }

    pub fn is_end(&mut self) -> bool {
        match self.s.last_token() { pp::End => true, _ => false }
    }

    pub fn is_bol(&mut self) -> bool {
        self.s.last_token().is_eof() || self.s.last_token().is_hardbreak_tok()
    }

    pub fn in_cbox(&self) -> bool {
        match self.boxes.last() {
            Some(&last_box) => last_box == pp::Consistent,
            None => false
        }
    }

    pub fn hardbreak_if_not_bol(&mut self) -> IoResult<()> {
        if !self.is_bol() {
            try!(hardbreak(&mut self.s))
        }
        Ok(())
    }
    pub fn space_if_not_bol(&mut self) -> IoResult<()> {
        if !self.is_bol() { try!(space(&mut self.s)); }
        Ok(())
    }
    pub fn break_offset_if_not_bol(&mut self, n: uint,
                                   off: int) -> IoResult<()> {
        if !self.is_bol() {
            break_offset(&mut self.s, n, off)
        } else {
            if off != 0 && self.s.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.s.replace_last_token(pp::hardbreak_tok_offset(off));
            }
            Ok(())
        }
    }

    // Synthesizes a comment that was not textually present in the original source
    // file.
    pub fn synth_comment(&mut self, text: ~str) -> IoResult<()> {
        try!(word(&mut self.s, "/*"));
        try!(space(&mut self.s));
        try!(word(&mut self.s, text));
        try!(space(&mut self.s));
        word(&mut self.s, "*/")
    }

    pub fn commasep<T>(&mut self, b: Breaks, elts: &[T],
                       op: |&mut State, &T| -> IoResult<()>)
        -> IoResult<()> {
        try!(self.rbox(0u, b));
        let mut first = true;
        for elt in elts.iter() {
            if first { first = false; } else { try!(self.word_space(",")); }
            try!(op(self, elt));
        }
        self.end()
    }


    pub fn commasep_cmnt<T>(
                         &mut self,
                         b: Breaks,
                         elts: &[T],
                         op: |&mut State, &T| -> IoResult<()>,
                         get_span: |&T| -> codemap::Span) -> IoResult<()> {
        try!(self.rbox(0u, b));
        let len = elts.len();
        let mut i = 0u;
        for elt in elts.iter() {
            try!(self.maybe_print_comment(get_span(elt).hi));
            try!(op(self, elt));
            i += 1u;
            if i < len {
                try!(word(&mut self.s, ","));
                try!(self.maybe_print_trailing_comment(get_span(elt),
                                                    Some(get_span(&elts[i]).hi)));
                try!(self.space_if_not_bol());
            }
        }
        self.end()
    }

    pub fn commasep_exprs(&mut self, b: Breaks,
                          exprs: &[@ast::Expr]) -> IoResult<()> {
        self.commasep_cmnt(b, exprs, |s, &e| s.print_expr(e), |e| e.span)
    }

    pub fn print_mod(&mut self, _mod: &ast::Mod,
                     attrs: &[ast::Attribute]) -> IoResult<()> {
        try!(self.print_inner_attributes(attrs));
        for vitem in _mod.view_items.iter() {
            try!(self.print_view_item(vitem));
        }
        for item in _mod.items.iter() {
            try!(self.print_item(*item));
        }
        Ok(())
    }

    pub fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod,
                             attrs: &[ast::Attribute]) -> IoResult<()> {
        try!(self.print_inner_attributes(attrs));
        for vitem in nmod.view_items.iter() {
            try!(self.print_view_item(vitem));
        }
        for item in nmod.items.iter() {
            try!(self.print_foreign_item(*item));
        }
        Ok(())
    }

    pub fn print_opt_lifetime(&mut self,
                              lifetime: &Option<ast::Lifetime>) -> IoResult<()> {
        for l in lifetime.iter() {
            try!(self.print_lifetime(l));
            try!(self.nbsp());
        }
        Ok(())
    }

    pub fn print_type(&mut self, ty: &ast::Ty) -> IoResult<()> {
        try!(self.maybe_print_comment(ty.span.lo));
        try!(self.ibox(0u));
        match ty.node {
            ast::TyNil => try!(word(&mut self.s, "()")),
            ast::TyBot => try!(word(&mut self.s, "!")),
            ast::TyBox(ty) => {
                try!(word(&mut self.s, "@"));
                try!(self.print_type(ty));
            }
            ast::TyUniq(ty) => {
                try!(word(&mut self.s, "~"));
                try!(self.print_type(ty));
            }
            ast::TyVec(ty) => {
                try!(word(&mut self.s, "["));
                try!(self.print_type(ty));
                try!(word(&mut self.s, "]"));
            }
            ast::TyPtr(ref mt) => {
                try!(word(&mut self.s, "*"));
                try!(self.print_mt(mt));
            }
            ast::TyRptr(ref lifetime, ref mt) => {
                try!(word(&mut self.s, "&"));
                try!(self.print_opt_lifetime(lifetime));
                try!(self.print_mt(mt));
            }
            ast::TyTup(ref elts) => {
                try!(self.popen());
                try!(self.commasep(Inconsistent, elts.as_slice(),
                                   |s, ty| s.print_type_ref(ty)));
                if elts.len() == 1 {
                    try!(word(&mut self.s, ","));
                }
                try!(self.pclose());
            }
            ast::TyBareFn(f) => {
                let generics = ast::Generics {
                    lifetimes: f.lifetimes.clone(),
                    ty_params: OwnedSlice::empty()
                };
                try!(self.print_ty_fn(Some(f.abi), None, &None,
                                   f.fn_style, ast::Many, f.decl, None, &None,
                                   Some(&generics), None));
            }
            ast::TyClosure(f, ref region) => {
                let generics = ast::Generics {
                    lifetimes: f.lifetimes.clone(),
                    ty_params: OwnedSlice::empty()
                };
                try!(self.print_ty_fn(None, Some('&'), region, f.fn_style,
                                      f.onceness, f.decl, None, &f.bounds,
                                      Some(&generics), None));
            }
            ast::TyProc(f) => {
                let generics = ast::Generics {
                    lifetimes: f.lifetimes.clone(),
                    ty_params: OwnedSlice::empty()
                };
                try!(self.print_ty_fn(None, Some('~'), &None, f.fn_style,
                                      f.onceness, f.decl, None, &f.bounds,
                                      Some(&generics), None));
            }
            ast::TyPath(ref path, ref bounds, _) => {
                try!(self.print_bounded_path(path, bounds));
            }
            ast::TyFixedLengthVec(ty, v) => {
                try!(word(&mut self.s, "["));
                try!(self.print_type(ty));
                try!(word(&mut self.s, ", .."));
                try!(self.print_expr(v));
                try!(word(&mut self.s, "]"));
            }
            ast::TyTypeof(e) => {
                try!(word(&mut self.s, "typeof("));
                try!(self.print_expr(e));
                try!(word(&mut self.s, ")"));
            }
            ast::TyInfer => {
                try!(word(&mut self.s, "_"));
            }
        }
        self.end()
    }

    pub fn print_type_ref(&mut self, ty: &P<ast::Ty>) -> IoResult<()> {
        self.print_type(*ty)
    }

    pub fn print_foreign_item(&mut self,
                              item: &ast::ForeignItem) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(item.span.lo));
        try!(self.print_outer_attributes(item.attrs.as_slice()));
        match item.node {
            ast::ForeignItemFn(decl, ref generics) => {
                try!(self.print_fn(decl, None, abi::Rust, item.ident, generics,
                None, item.vis));
                try!(self.end()); // end head-ibox
                try!(word(&mut self.s, ";"));
                self.end() // end the outer fn box
            }
            ast::ForeignItemStatic(t, m) => {
                try!(self.head(visibility_qualified(item.vis, "static")));
                if m {
                    try!(self.word_space("mut"));
                }
                try!(self.print_ident(item.ident));
                try!(self.word_space(":"));
                try!(self.print_type(t));
                try!(word(&mut self.s, ";"));
                try!(self.end()); // end the head-ibox
                self.end() // end the outer cbox
            }
        }
    }

    pub fn print_item(&mut self, item: &ast::Item) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(item.span.lo));
        try!(self.print_outer_attributes(item.attrs.as_slice()));
        try!(self.ann.pre(self, NodeItem(item)));
        match item.node {
            ast::ItemStatic(ty, m, expr) => {
                try!(self.head(visibility_qualified(item.vis, "static")));
                if m == ast::MutMutable {
                    try!(self.word_space("mut"));
                }
                try!(self.print_ident(item.ident));
                try!(self.word_space(":"));
                try!(self.print_type(ty));
                try!(space(&mut self.s));
                try!(self.end()); // end the head-ibox

                try!(self.word_space("="));
                try!(self.print_expr(expr));
                try!(word(&mut self.s, ";"));
                try!(self.end()); // end the outer cbox
            }
            ast::ItemFn(decl, fn_style, abi, ref typarams, body) => {
                try!(self.print_fn(
                    decl,
                    Some(fn_style),
                    abi,
                    item.ident,
                    typarams,
                    None,
                    item.vis
                ));
                try!(word(&mut self.s, " "));
                try!(self.print_block_with_attrs(body, item.attrs.as_slice()));
            }
            ast::ItemMod(ref _mod) => {
                try!(self.head(visibility_qualified(item.vis, "mod")));
                try!(self.print_ident(item.ident));
                try!(self.nbsp());
                try!(self.bopen());
                try!(self.print_mod(_mod, item.attrs.as_slice()));
                try!(self.bclose(item.span));
            }
            ast::ItemForeignMod(ref nmod) => {
                try!(self.head("extern"));
                try!(self.word_nbsp(nmod.abi.to_str()));
                try!(self.bopen());
                try!(self.print_foreign_mod(nmod, item.attrs.as_slice()));
                try!(self.bclose(item.span));
            }
            ast::ItemTy(ty, ref params) => {
                try!(self.ibox(indent_unit));
                try!(self.ibox(0u));
                try!(self.word_nbsp(visibility_qualified(item.vis, "type")));
                try!(self.print_ident(item.ident));
                try!(self.print_generics(params));
                try!(self.end()); // end the inner ibox

                try!(space(&mut self.s));
                try!(self.word_space("="));
                try!(self.print_type(ty));
                try!(word(&mut self.s, ";"));
                try!(self.end()); // end the outer ibox
            }
            ast::ItemEnum(ref enum_definition, ref params) => {
                try!(self.print_enum_def(
                    enum_definition,
                    params,
                    item.ident,
                    item.span,
                    item.vis
                ));
            }
            ast::ItemStruct(struct_def, ref generics) => {
                if struct_def.is_virtual {
                    try!(self.word_space("virtual"));
                }
                try!(self.head(visibility_qualified(item.vis, "struct")));
                try!(self.print_struct(struct_def, generics, item.ident, item.span));
            }

            ast::ItemImpl(ref generics, ref opt_trait, ty, ref methods) => {
                try!(self.head(visibility_qualified(item.vis, "impl")));
                if generics.is_parameterized() {
                    try!(self.print_generics(generics));
                    try!(space(&mut self.s));
                }

                match opt_trait {
                    &Some(ref t) => {
                        try!(self.print_trait_ref(t));
                        try!(space(&mut self.s));
                        try!(self.word_space("for"));
                    }
                    &None => {}
                }

                try!(self.print_type(ty));

                try!(space(&mut self.s));
                try!(self.bopen());
                try!(self.print_inner_attributes(item.attrs.as_slice()));
                for meth in methods.iter() {
                    try!(self.print_method(*meth));
                }
                try!(self.bclose(item.span));
            }
            ast::ItemTrait(ref generics, ref sized, ref traits, ref methods) => {
                try!(self.head(visibility_qualified(item.vis, "trait")));
                try!(self.print_ident(item.ident));
                try!(self.print_generics(generics));
                if *sized == ast::DynSize {
                    try!(space(&mut self.s));
                    try!(word(&mut self.s, "for type"));
                }
                if traits.len() != 0u {
                    try!(word(&mut self.s, ":"));
                    for (i, trait_) in traits.iter().enumerate() {
                        try!(self.nbsp());
                        if i != 0 {
                            try!(self.word_space("+"));
                        }
                        try!(self.print_path(&trait_.path, false));
                    }
                }
                try!(word(&mut self.s, " "));
                try!(self.bopen());
                for meth in methods.iter() {
                    try!(self.print_trait_method(meth));
                }
                try!(self.bclose(item.span));
            }
            // I think it's reasonable to hide the context here:
            ast::ItemMac(codemap::Spanned { node: ast::MacInvocTT(ref pth, ref tts, _),
                                            ..}) => {
                try!(self.print_visibility(item.vis));
                try!(self.print_path(pth, false));
                try!(word(&mut self.s, "! "));
                try!(self.print_ident(item.ident));
                try!(self.cbox(indent_unit));
                try!(self.popen());
                try!(self.print_tts(&(tts.as_slice())));
                try!(self.pclose());
                try!(self.end());
            }
        }
        self.ann.post(self, NodeItem(item))
    }

    fn print_trait_ref(&mut self, t: &ast::TraitRef) -> IoResult<()> {
        self.print_path(&t.path, false)
    }

    pub fn print_enum_def(&mut self, enum_definition: &ast::EnumDef,
                          generics: &ast::Generics, ident: ast::Ident,
                          span: codemap::Span,
                          visibility: ast::Visibility) -> IoResult<()> {
        try!(self.head(visibility_qualified(visibility, "enum")));
        try!(self.print_ident(ident));
        try!(self.print_generics(generics));
        try!(space(&mut self.s));
        self.print_variants(enum_definition.variants.as_slice(), span)
    }

    pub fn print_variants(&mut self,
                          variants: &[P<ast::Variant>],
                          span: codemap::Span) -> IoResult<()> {
        try!(self.bopen());
        for &v in variants.iter() {
            try!(self.space_if_not_bol());
            try!(self.maybe_print_comment(v.span.lo));
            try!(self.print_outer_attributes(v.node.attrs.as_slice()));
            try!(self.ibox(indent_unit));
            try!(self.print_variant(v));
            try!(word(&mut self.s, ","));
            try!(self.end());
            try!(self.maybe_print_trailing_comment(v.span, None));
        }
        self.bclose(span)
    }

    pub fn print_visibility(&mut self, vis: ast::Visibility) -> IoResult<()> {
        match vis {
            ast::Public => self.word_nbsp("pub"),
            ast::Inherited => Ok(())
        }
    }

    pub fn print_struct(&mut self,
                        struct_def: &ast::StructDef,
                        generics: &ast::Generics,
                        ident: ast::Ident,
                        span: codemap::Span) -> IoResult<()> {
        try!(self.print_ident(ident));
        try!(self.print_generics(generics));
        match struct_def.super_struct {
            Some(t) => {
                try!(self.word_space(":"));
                try!(self.print_type(t));
            },
            None => {},
        }
        if ast_util::struct_def_is_tuple_like(struct_def) {
            if !struct_def.fields.is_empty() {
                try!(self.popen());
                try!(self.commasep(
                    Inconsistent, struct_def.fields.as_slice(),
                    |s, field| {
                        match field.node.kind {
                            ast::NamedField(..) => fail!("unexpected named field"),
                            ast::UnnamedField(vis) => {
                                try!(s.print_visibility(vis));
                                try!(s.maybe_print_comment(field.span.lo));
                                s.print_type(field.node.ty)
                            }
                        }
                    }
                ));
                try!(self.pclose());
            }
            try!(word(&mut self.s, ";"));
            try!(self.end());
            self.end() // close the outer-box
        } else {
            try!(self.nbsp());
            try!(self.bopen());
            try!(self.hardbreak_if_not_bol());

            for field in struct_def.fields.iter() {
                match field.node.kind {
                    ast::UnnamedField(..) => fail!("unexpected unnamed field"),
                    ast::NamedField(ident, visibility) => {
                        try!(self.hardbreak_if_not_bol());
                        try!(self.maybe_print_comment(field.span.lo));
                        try!(self.print_outer_attributes(field.node.attrs.as_slice()));
                        try!(self.print_visibility(visibility));
                        try!(self.print_ident(ident));
                        try!(self.word_nbsp(":"));
                        try!(self.print_type(field.node.ty));
                        try!(word(&mut self.s, ","));
                    }
                }
            }

            self.bclose(span)
        }
    }

    /// 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.
    pub fn print_tt(&mut self, tt: &ast::TokenTree) -> IoResult<()> {
        match *tt {
            ast::TTDelim(ref tts) => self.print_tts(&(tts.as_slice())),
            ast::TTTok(_, ref tk) => {
                word(&mut self.s, parse::token::to_str(tk))
            }
            ast::TTSeq(_, ref tts, ref sep, zerok) => {
                try!(word(&mut self.s, "$("));
                for tt_elt in (*tts).iter() {
                    try!(self.print_tt(tt_elt));
                }
                try!(word(&mut self.s, ")"));
                match *sep {
                    Some(ref tk) => {
                        try!(word(&mut self.s, parse::token::to_str(tk)));
                    }
                    None => ()
                }
                word(&mut self.s, if zerok { "*" } else { "+" })
            }
            ast::TTNonterminal(_, name) => {
                try!(word(&mut self.s, "$"));
                self.print_ident(name)
            }
        }
    }

    pub fn print_tts(&mut self, tts: & &[ast::TokenTree]) -> IoResult<()> {
        try!(self.ibox(0));
        for (i, tt) in tts.iter().enumerate() {
            if i != 0 {
                try!(space(&mut self.s));
            }
            try!(self.print_tt(tt));
        }
        self.end()
    }

    pub fn print_variant(&mut self, v: &ast::Variant) -> IoResult<()> {
        try!(self.print_visibility(v.node.vis));
        match v.node.kind {
            ast::TupleVariantKind(ref args) => {
                try!(self.print_ident(v.node.name));
                if !args.is_empty() {
                    try!(self.popen());
                    try!(self.commasep(Consistent,
                                       args.as_slice(),
                                       |s, arg| s.print_type(arg.ty)));
                    try!(self.pclose());
                }
            }
            ast::StructVariantKind(struct_def) => {
                try!(self.head(""));
                let generics = ast_util::empty_generics();
                try!(self.print_struct(struct_def, &generics, v.node.name, v.span));
            }
        }
        match v.node.disr_expr {
            Some(d) => {
                try!(space(&mut self.s));
                try!(self.word_space("="));
                self.print_expr(d)
            }
            _ => Ok(())
        }
    }

    pub fn print_ty_method(&mut self, m: &ast::TypeMethod) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(m.span.lo));
        try!(self.print_outer_attributes(m.attrs.as_slice()));
        try!(self.print_ty_fn(None,
                              None,
                              &None,
                              m.fn_style,
                              ast::Many,
                              m.decl,
                              Some(m.ident),
                              &None,
                              Some(&m.generics),
                              Some(m.explicit_self.node)));
        word(&mut self.s, ";")
    }

    pub fn print_trait_method(&mut self,
                              m: &ast::TraitMethod) -> IoResult<()> {
        match *m {
            Required(ref ty_m) => self.print_ty_method(ty_m),
            Provided(m) => self.print_method(m)
        }
    }

    pub fn print_method(&mut self, meth: &ast::Method) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(meth.span.lo));
        try!(self.print_outer_attributes(meth.attrs.as_slice()));
        try!(self.print_fn(meth.decl, Some(meth.fn_style), abi::Rust,
                        meth.ident, &meth.generics, Some(meth.explicit_self.node),
                        meth.vis));
        try!(word(&mut self.s, " "));
        self.print_block_with_attrs(meth.body, meth.attrs.as_slice())
    }

    pub fn print_outer_attributes(&mut self,
                                  attrs: &[ast::Attribute]) -> IoResult<()> {
        let mut count = 0;
        for attr in attrs.iter() {
            match attr.node.style {
                ast::AttrOuter => {
                    try!(self.print_attribute(attr));
                    count += 1;
                }
                _ => {/* fallthrough */ }
            }
        }
        if count > 0 {
            try!(self.hardbreak_if_not_bol());
        }
        Ok(())
    }

    pub fn print_inner_attributes(&mut self,
                                  attrs: &[ast::Attribute]) -> IoResult<()> {
        let mut count = 0;
        for attr in attrs.iter() {
            match attr.node.style {
                ast::AttrInner => {
                    try!(self.print_attribute(attr));
                    count += 1;
                }
                _ => {/* fallthrough */ }
            }
        }
        if count > 0 {
            try!(self.hardbreak_if_not_bol());
        }
        Ok(())
    }

    pub fn print_attribute(&mut self, attr: &ast::Attribute) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(attr.span.lo));
        if attr.node.is_sugared_doc {
            word(&mut self.s, attr.value_str().unwrap().get())
        } else {
            match attr.node.style {
                ast::AttrInner => try!(word(&mut self.s, "#![")),
                ast::AttrOuter => try!(word(&mut self.s, "#[")),
            }
            try!(self.print_meta_item(attr.meta()));
            word(&mut self.s, "]")
        }
    }


    pub fn print_stmt(&mut self, st: &ast::Stmt) -> IoResult<()> {
        try!(self.maybe_print_comment(st.span.lo));
        match st.node {
            ast::StmtDecl(decl, _) => {
                try!(self.print_decl(decl));
            }
            ast::StmtExpr(expr, _) => {
                try!(self.space_if_not_bol());
                try!(self.print_expr(expr));
            }
            ast::StmtSemi(expr, _) => {
                try!(self.space_if_not_bol());
                try!(self.print_expr(expr));
                try!(word(&mut self.s, ";"));
            }
            ast::StmtMac(ref mac, semi) => {
                try!(self.space_if_not_bol());
                try!(self.print_mac(mac));
                if semi {
                    try!(word(&mut self.s, ";"));
                }
            }
        }
        if parse::classify::stmt_ends_with_semi(st) {
            try!(word(&mut self.s, ";"));
        }
        self.maybe_print_trailing_comment(st.span, None)
    }

    pub fn print_block(&mut self, blk: &ast::Block) -> IoResult<()> {
        self.print_block_with_attrs(blk, &[])
    }

    pub fn print_block_unclosed(&mut self, blk: &ast::Block) -> IoResult<()> {
        self.print_block_unclosed_indent(blk, indent_unit)
    }

    pub fn print_block_unclosed_indent(&mut self, blk: &ast::Block,
                                       indented: uint) -> IoResult<()> {
        self.print_block_maybe_unclosed(blk, indented, &[], false)
    }

    pub fn print_block_with_attrs(&mut self,
                                  blk: &ast::Block,
                                  attrs: &[ast::Attribute]) -> IoResult<()> {
        self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
    }

    pub fn print_block_maybe_unclosed(&mut self,
                                      blk: &ast::Block,
                                      indented: uint,
                                      attrs: &[ast::Attribute],
                                      close_box: bool) -> IoResult<()> {
        match blk.rules {
            ast::UnsafeBlock(..) => try!(self.word_space("unsafe")),
            ast::DefaultBlock => ()
        }
        try!(self.maybe_print_comment(blk.span.lo));
        try!(self.ann.pre(self, NodeBlock(blk)));
        try!(self.bopen());

        try!(self.print_inner_attributes(attrs));

        for vi in blk.view_items.iter() {
            try!(self.print_view_item(vi));
        }
        for st in blk.stmts.iter() {
            try!(self.print_stmt(*st));
        }
        match blk.expr {
            Some(expr) => {
                try!(self.space_if_not_bol());
                try!(self.print_expr(expr));
                try!(self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi)));
            }
            _ => ()
        }
        try!(self.bclose_maybe_open(blk.span, indented, close_box));
        self.ann.post(self, NodeBlock(blk))
    }

    fn print_else(&mut self, els: Option<@ast::Expr>) -> IoResult<()> {
        match els {
            Some(_else) => {
                match _else.node {
                    // "another else-if"
                    ast::ExprIf(i, t, e) => {
                        try!(self.cbox(indent_unit - 1u));
                        try!(self.ibox(0u));
                        try!(word(&mut self.s, " else if "));
                        try!(self.print_expr(i));
                        try!(space(&mut self.s));
                        try!(self.print_block(t));
                        self.print_else(e)
                    }
                    // "final else"
                    ast::ExprBlock(b) => {
                        try!(self.cbox(indent_unit - 1u));
                        try!(self.ibox(0u));
                        try!(word(&mut self.s, " else "));
                        self.print_block(b)
                    }
                    // BLEAH, constraints would be great here
                    _ => {
                        fail!("print_if saw if with weird alternative");
                    }
                }
            }
            _ => Ok(())
        }
    }

    pub fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block,
                    elseopt: Option<@ast::Expr>, chk: bool) -> IoResult<()> {
        try!(self.head("if"));
        if chk { try!(self.word_nbsp("check")); }
        try!(self.print_expr(test));
        try!(space(&mut self.s));
        try!(self.print_block(blk));
        self.print_else(elseopt)
    }

    pub fn print_mac(&mut self, m: &ast::Mac) -> IoResult<()> {
        match m.node {
            // I think it's reasonable to hide the ctxt here:
            ast::MacInvocTT(ref pth, ref tts, _) => {
                try!(self.print_path(pth, false));
                try!(word(&mut self.s, "!"));
                try!(self.popen());
                try!(self.print_tts(&tts.as_slice()));
                self.pclose()
            }
        }
    }

    pub fn print_expr_vstore(&mut self, t: ast::ExprVstore) -> IoResult<()> {
        match t {
            ast::ExprVstoreUniq => word(&mut self.s, "~"),
            ast::ExprVstoreSlice => word(&mut self.s, "&"),
            ast::ExprVstoreMutSlice => {
                try!(word(&mut self.s, "&"));
                word(&mut self.s, "mut")
            }
        }
    }

    fn print_call_post(&mut self, args: &[@ast::Expr]) -> IoResult<()> {
        try!(self.popen());
        try!(self.commasep_exprs(Inconsistent, args));
        self.pclose()
    }

    pub fn print_expr(&mut self, expr: &ast::Expr) -> IoResult<()> {
        try!(self.maybe_print_comment(expr.span.lo));
        try!(self.ibox(indent_unit));
        try!(self.ann.pre(self, NodeExpr(expr)));
        match expr.node {
            ast::ExprVstore(e, v) => {
                try!(self.print_expr_vstore(v));
                try!(self.print_expr(e));
            },
            ast::ExprBox(p, e) => {
                try!(word(&mut self.s, "box"));
                try!(word(&mut self.s, "("));
                try!(self.print_expr(p));
                try!(self.word_space(")"));
                try!(self.print_expr(e));
            }
            ast::ExprVec(ref exprs) => {
                try!(self.ibox(indent_unit));
                try!(word(&mut self.s, "["));
                try!(self.commasep_exprs(Inconsistent, exprs.as_slice()));
                try!(word(&mut self.s, "]"));
                try!(self.end());
            }

            ast::ExprRepeat(element, count) => {
                try!(self.ibox(indent_unit));
                try!(word(&mut self.s, "["));
                try!(self.print_expr(element));
                try!(word(&mut self.s, ","));
                try!(word(&mut self.s, ".."));
                try!(self.print_expr(count));
                try!(word(&mut self.s, "]"));
                try!(self.end());
            }

            ast::ExprStruct(ref path, ref fields, wth) => {
                try!(self.print_path(path, true));
                try!(word(&mut self.s, "{"));
                try!(self.commasep_cmnt(
                    Consistent,
                    fields.as_slice(),
                    |s, field| {
                        try!(s.ibox(indent_unit));
                        try!(s.print_ident(field.ident.node));
                        try!(s.word_space(":"));
                        try!(s.print_expr(field.expr));
                        s.end()
                    },
                    |f| f.span));
                match wth {
                    Some(expr) => {
                        try!(self.ibox(indent_unit));
                        if !fields.is_empty() {
                            try!(word(&mut self.s, ","));
                            try!(space(&mut self.s));
                        }
                        try!(word(&mut self.s, ".."));
                        try!(self.print_expr(expr));
                        try!(self.end());
                    }
                    _ => try!(word(&mut self.s, ","))
                }
                try!(word(&mut self.s, "}"));
            }
            ast::ExprTup(ref exprs) => {
                try!(self.popen());
                try!(self.commasep_exprs(Inconsistent, exprs.as_slice()));
                if exprs.len() == 1 {
                    try!(word(&mut self.s, ","));
                }
                try!(self.pclose());
            }
            ast::ExprCall(func, ref args) => {
                try!(self.print_expr(func));
                try!(self.print_call_post(args.as_slice()));
            }
            ast::ExprMethodCall(ident, ref tys, ref args) => {
                let base_args = args.slice_from(1);
                try!(self.print_expr(*args.get(0)));
                try!(word(&mut self.s, "."));
                try!(self.print_ident(ident));
                if tys.len() > 0u {
                    try!(word(&mut self.s, "::<"));
                    try!(self.commasep(Inconsistent, tys.as_slice(),
                                       |s, ty| s.print_type_ref(ty)));
                    try!(word(&mut self.s, ">"));
                }
                try!(self.print_call_post(base_args));
            }
            ast::ExprBinary(op, lhs, rhs) => {
                try!(self.print_expr(lhs));
                try!(space(&mut self.s));
                try!(self.word_space(ast_util::binop_to_str(op)));
                try!(self.print_expr(rhs));
            }
            ast::ExprUnary(op, expr) => {
                try!(word(&mut self.s, ast_util::unop_to_str(op)));
                try!(self.print_expr(expr));
            }
            ast::ExprAddrOf(m, expr) => {
                try!(word(&mut self.s, "&"));
                try!(self.print_mutability(m));
                // Avoid `& &e` => `&&e`.
                match (m, &expr.node) {
                    (ast::MutImmutable, &ast::ExprAddrOf(..)) => try!(space(&mut self.s)),
                    _ => { }
                }
                try!(self.print_expr(expr));
            }
            ast::ExprLit(lit) => try!(self.print_literal(lit)),
            ast::ExprCast(expr, ty) => {
                try!(self.print_expr(expr));
                try!(space(&mut self.s));
                try!(self.word_space("as"));
                try!(self.print_type(ty));
            }
            ast::ExprIf(test, blk, elseopt) => {
                try!(self.print_if(test, blk, elseopt, false));
            }
            ast::ExprWhile(test, blk) => {
                try!(self.head("while"));
                try!(self.print_expr(test));
                try!(space(&mut self.s));
                try!(self.print_block(blk));
            }
            ast::ExprForLoop(pat, iter, blk, opt_ident) => {
                for ident in opt_ident.iter() {
                    try!(word(&mut self.s, "'"));
                    try!(self.print_ident(*ident));
                    try!(self.word_space(":"));
                }
                try!(self.head("for"));
                try!(self.print_pat(pat));
                try!(space(&mut self.s));
                try!(self.word_space("in"));
                try!(self.print_expr(iter));
                try!(space(&mut self.s));
                try!(self.print_block(blk));
            }
            ast::ExprLoop(blk, opt_ident) => {
                for ident in opt_ident.iter() {
                    try!(word(&mut self.s, "'"));
                    try!(self.print_ident(*ident));
                    try!(self.word_space(":"));
                }
                try!(self.head("loop"));
                try!(space(&mut self.s));
                try!(self.print_block(blk));
            }
            ast::ExprMatch(expr, ref arms) => {
                try!(self.cbox(indent_unit));
                try!(self.ibox(4));
                try!(self.word_nbsp("match"));
                try!(self.print_expr(expr));
                try!(space(&mut self.s));
                try!(self.bopen());
                let len = arms.len();
                for (i, arm) in arms.iter().enumerate() {
                    try!(space(&mut self.s));
                    try!(self.cbox(indent_unit));
                    try!(self.ibox(0u));
                    let mut first = true;
                    for p in arm.pats.iter() {
                        if first {
                            first = false;
                        } else {
                            try!(space(&mut self.s));
                            try!(self.word_space("|"));
                        }
                        try!(self.print_pat(*p));
                    }
                    try!(space(&mut self.s));
                    match arm.guard {
                        Some(e) => {
                            try!(self.word_space("if"));
                            try!(self.print_expr(e));
                            try!(space(&mut self.s));
                        }
                        None => ()
                    }
                    try!(self.word_space("=>"));

                    match arm.body.node {
                        ast::ExprBlock(blk) => {
                            // the block will close the pattern's ibox
                            try!(self.print_block_unclosed_indent(blk, indent_unit));
                        }
                        _ => {
                            try!(self.end()); // close the ibox for the pattern
                            try!(self.print_expr(arm.body));
                        }
                    }
                    if !expr_is_simple_block(expr)
                        && i < len - 1 {
                        try!(word(&mut self.s, ","));
                    }
                    try!(self.end()); // close enclosing cbox
                }
                try!(self.bclose_(expr.span, indent_unit));
            }
            ast::ExprFnBlock(decl, body) => {
                // in do/for blocks we don't want to show an empty
                // argument list, but at this point we don't know which
                // we are inside.
                //
                // if !decl.inputs.is_empty() {
                try!(self.print_fn_block_args(decl));
                try!(space(&mut self.s));
                // }

                if !body.stmts.is_empty() || !body.expr.is_some() {
                    try!(self.print_block_unclosed(body));
                } else {
                    // we extract the block, so as not to create another set of boxes
                    match body.expr.unwrap().node {
                        ast::ExprBlock(blk) => {
                            try!(self.print_block_unclosed(blk));
                        }
                        _ => {
                            // this is a bare expression
                            try!(self.print_expr(body.expr.unwrap()));
                            try!(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.
                try!(self.ibox(0));
            }
            ast::ExprProc(decl, body) => {
                // in do/for blocks we don't want to show an empty
                // argument list, but at this point we don't know which
                // we are inside.
                //
                // if !decl.inputs.is_empty() {
                try!(self.print_proc_args(decl));
                try!(space(&mut self.s));
                // }
                assert!(body.stmts.is_empty());
                assert!(body.expr.is_some());
                // we extract the block, so as not to create another set of boxes
                match body.expr.unwrap().node {
                    ast::ExprBlock(blk) => {
                        try!(self.print_block_unclosed(blk));
                    }
                    _ => {
                        // this is a bare expression
                        try!(self.print_expr(body.expr.unwrap()));
                        try!(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.
                try!(self.ibox(0));
            }
            ast::ExprBlock(blk) => {
                // containing cbox, will be closed by print-block at }
                try!(self.cbox(indent_unit));
                // head-box, will be closed by print-block after {
                try!(self.ibox(0u));
                try!(self.print_block(blk));
            }
            ast::ExprAssign(lhs, rhs) => {
                try!(self.print_expr(lhs));
                try!(space(&mut self.s));
                try!(self.word_space("="));
                try!(self.print_expr(rhs));
            }
            ast::ExprAssignOp(op, lhs, rhs) => {
                try!(self.print_expr(lhs));
                try!(space(&mut self.s));
                try!(word(&mut self.s, ast_util::binop_to_str(op)));
                try!(self.word_space("="));
                try!(self.print_expr(rhs));
            }
            ast::ExprField(expr, id, ref tys) => {
                try!(self.print_expr(expr));
                try!(word(&mut self.s, "."));
                try!(self.print_ident(id));
                if tys.len() > 0u {
                    try!(word(&mut self.s, "::<"));
                    try!(self.commasep(
                        Inconsistent, tys.as_slice(),
                        |s, ty| s.print_type_ref(ty)));
                    try!(word(&mut self.s, ">"));
                }
            }
            ast::ExprIndex(expr, index) => {
                try!(self.print_expr(expr));
                try!(word(&mut self.s, "["));
                try!(self.print_expr(index));
                try!(word(&mut self.s, "]"));
            }
            ast::ExprPath(ref path) => try!(self.print_path(path, true)),
            ast::ExprBreak(opt_ident) => {
                try!(word(&mut self.s, "break"));
                try!(space(&mut self.s));
                for ident in opt_ident.iter() {
                    try!(word(&mut self.s, "'"));
                    try!(self.print_ident(*ident));
                    try!(space(&mut self.s));
                }
            }
            ast::ExprAgain(opt_ident) => {
                try!(word(&mut self.s, "continue"));
                try!(space(&mut self.s));
                for ident in opt_ident.iter() {
                    try!(word(&mut self.s, "'"));
                    try!(self.print_ident(*ident));
                    try!(space(&mut self.s))
                }
            }
            ast::ExprRet(result) => {
                try!(word(&mut self.s, "return"));
                match result {
                    Some(expr) => {
                        try!(word(&mut self.s, " "));
                        try!(self.print_expr(expr));
                    }
                    _ => ()
                }
            }
            ast::ExprInlineAsm(ref a) => {
                if a.volatile {
                    try!(word(&mut self.s, "__volatile__ asm!"));
                } else {
                    try!(word(&mut self.s, "asm!"));
                }
                try!(self.popen());
                try!(self.print_string(a.asm.get(), a.asm_str_style));
                try!(self.word_space(":"));
                for &(ref co, o) in a.outputs.iter() {
                    try!(self.print_string(co.get(), ast::CookedStr));
                    try!(self.popen());
                    try!(self.print_expr(o));
                    try!(self.pclose());
                    try!(self.word_space(","));
                }
                try!(self.word_space(":"));
                for &(ref co, o) in a.inputs.iter() {
                    try!(self.print_string(co.get(), ast::CookedStr));
                    try!(self.popen());
                    try!(self.print_expr(o));
                    try!(self.pclose());
                    try!(self.word_space(","));
                }
                try!(self.word_space(":"));
                try!(self.print_string(a.clobbers.get(), ast::CookedStr));
                try!(self.pclose());
            }
            ast::ExprMac(ref m) => try!(self.print_mac(m)),
            ast::ExprParen(e) => {
                try!(self.popen());
                try!(self.print_expr(e));
                try!(self.pclose());
            }
        }
        try!(self.ann.post(self, NodeExpr(expr)));
        self.end()
    }

    pub fn print_local_decl(&mut self, loc: &ast::Local) -> IoResult<()> {
        try!(self.print_pat(loc.pat));
        match loc.ty.node {
            ast::TyInfer => Ok(()),
            _ => {
                try!(self.word_space(":"));
                self.print_type(loc.ty)
            }
        }
    }

    pub fn print_decl(&mut self, decl: &ast::Decl) -> IoResult<()> {
        try!(self.maybe_print_comment(decl.span.lo));
        match decl.node {
            ast::DeclLocal(loc) => {
                try!(self.space_if_not_bol());
                try!(self.ibox(indent_unit));
                try!(self.word_nbsp("let"));

                try!(self.ibox(indent_unit));
                try!(self.print_local_decl(loc));
                try!(self.end());
                match loc.init {
                    Some(init) => {
                        try!(self.nbsp());
                        try!(self.word_space("="));
                        try!(self.print_expr(init));
                    }
                    _ => {}
                }
                self.end()
            }
            ast::DeclItem(item) => self.print_item(item)
        }
    }

    pub fn print_ident(&mut self, ident: ast::Ident) -> IoResult<()> {
        word(&mut self.s, token::get_ident(ident).get())
    }

    pub fn print_name(&mut self, name: ast::Name) -> IoResult<()> {
        word(&mut self.s, token::get_name(name).get())
    }

    pub fn print_for_decl(&mut self, loc: &ast::Local,
                          coll: &ast::Expr) -> IoResult<()> {
        try!(self.print_local_decl(loc));
        try!(space(&mut self.s));
        try!(self.word_space("in"));
        self.print_expr(coll)
    }

    fn print_path_(&mut self,
                   path: &ast::Path,
                   colons_before_params: bool,
                   opt_bounds: &Option<OwnedSlice<ast::TyParamBound>>)
        -> IoResult<()> {
        try!(self.maybe_print_comment(path.span.lo));
        if path.global {
            try!(word(&mut self.s, "::"));
        }

        let mut first = true;
        for segment in path.segments.iter() {
            if first {
                first = false
            } else {
                try!(word(&mut self.s, "::"))
            }

            try!(self.print_ident(segment.identifier));

            if !segment.lifetimes.is_empty() || !segment.types.is_empty() {
                if colons_before_params {
                    try!(word(&mut self.s, "::"))
                }
                try!(word(&mut self.s, "<"));

                let mut comma = false;
                for lifetime in segment.lifetimes.iter() {
                    if comma {
                        try!(self.word_space(","))
                    }
                    try!(self.print_lifetime(lifetime));
                    comma = true;
                }

                if !segment.types.is_empty() {
                    if comma {
                        try!(self.word_space(","))
                    }
                    try!(self.commasep(
                        Inconsistent,
                        segment.types.as_slice(),
                        |s, ty| s.print_type_ref(ty)));
                }

                try!(word(&mut self.s, ">"))
            }
        }

        match *opt_bounds {
            None => Ok(()),
            Some(ref bounds) => self.print_bounds(&None, bounds, true),
        }
    }

    fn print_path(&mut self, path: &ast::Path,
                  colons_before_params: bool) -> IoResult<()> {
        self.print_path_(path, colons_before_params, &None)
    }

    fn print_bounded_path(&mut self, path: &ast::Path,
                          bounds: &Option<OwnedSlice<ast::TyParamBound>>)
        -> IoResult<()> {
        self.print_path_(path, false, bounds)
    }

    pub fn print_pat(&mut self, pat: &ast::Pat) -> IoResult<()> {
        try!(self.maybe_print_comment(pat.span.lo));
        try!(self.ann.pre(self, NodePat(pat)));
        /* Pat isn't normalized, but the beauty of it
         is that it doesn't matter */
        match pat.node {
            ast::PatWild => try!(word(&mut self.s, "_")),
            ast::PatWildMulti => try!(word(&mut self.s, "..")),
            ast::PatIdent(binding_mode, ref path, sub) => {
                match binding_mode {
                    ast::BindByRef(mutbl) => {
                        try!(self.word_nbsp("ref"));
                        try!(self.print_mutability(mutbl));
                    }
                    ast::BindByValue(ast::MutImmutable) => {}
                    ast::BindByValue(ast::MutMutable) => {
                        try!(self.word_nbsp("mut"));
                    }
                }
                try!(self.print_path(path, true));
                match sub {
                    Some(p) => {
                        try!(word(&mut self.s, "@"));
                        try!(self.print_pat(p));
                    }
                    None => ()
                }
            }
            ast::PatEnum(ref path, ref args_) => {
                try!(self.print_path(path, true));
                match *args_ {
                    None => try!(word(&mut self.s, "(..)")),
                    Some(ref args) => {
                        if !args.is_empty() {
                            try!(self.popen());
                            try!(self.commasep(Inconsistent, args.as_slice(),
                                              |s, &p| s.print_pat(p)));
                            try!(self.pclose());
                        }
                    }
                }
            }
            ast::PatStruct(ref path, ref fields, etc) => {
                try!(self.print_path(path, true));
                try!(word(&mut self.s, "{"));
                try!(self.commasep_cmnt(
                    Consistent, fields.as_slice(),
                    |s, f| {
                        try!(s.cbox(indent_unit));
                        try!(s.print_ident(f.ident));
                        try!(s.word_space(":"));
                        try!(s.print_pat(f.pat));
                        s.end()
                    },
                    |f| f.pat.span));
                if etc {
                    if fields.len() != 0u { try!(self.word_space(",")); }
                    try!(word(&mut self.s, ".."));
                }
                try!(word(&mut self.s, "}"));
            }
            ast::PatTup(ref elts) => {
                try!(self.popen());
                try!(self.commasep(Inconsistent,
                                   elts.as_slice(),
                                   |s, &p| s.print_pat(p)));
                if elts.len() == 1 {
                    try!(word(&mut self.s, ","));
                }
                try!(self.pclose());
            }
            ast::PatUniq(inner) => {
                try!(word(&mut self.s, "~"));
                try!(self.print_pat(inner));
            }
            ast::PatRegion(inner) => {
                try!(word(&mut self.s, "&"));
                try!(self.print_pat(inner));
            }
            ast::PatLit(e) => try!(self.print_expr(e)),
            ast::PatRange(begin, end) => {
                try!(self.print_expr(begin));
                try!(space(&mut self.s));
                try!(word(&mut self.s, ".."));
                try!(self.print_expr(end));
            }
            ast::PatVec(ref before, slice, ref after) => {
                try!(word(&mut self.s, "["));
                try!(self.commasep(Inconsistent,
                                   before.as_slice(),
                                   |s, &p| s.print_pat(p)));
                for &p in slice.iter() {
                    if !before.is_empty() { try!(self.word_space(",")); }
                    match *p {
                        ast::Pat { node: ast::PatWildMulti, .. } => {
                            // this case is handled by print_pat
                        }
                        _ => try!(word(&mut self.s, "..")),
                    }
                    try!(self.print_pat(p));
                    if !after.is_empty() { try!(self.word_space(",")); }
                }
                try!(self.commasep(Inconsistent,
                                   after.as_slice(),
                                   |s, &p| s.print_pat(p)));
                try!(word(&mut self.s, "]"));
            }
        }
        self.ann.post(self, NodePat(pat))
    }

    // Returns whether it printed anything
    fn print_explicit_self(&mut self,
                           explicit_self: ast::ExplicitSelf_,
                           mutbl: ast::Mutability) -> IoResult<bool> {
        try!(self.print_mutability(mutbl));
        match explicit_self {
            ast::SelfStatic => { return Ok(false); }
            ast::SelfValue => {
                try!(word(&mut self.s, "self"));
            }
            ast::SelfUniq => {
                try!(word(&mut self.s, "~self"));
            }
            ast::SelfRegion(ref lt, m) => {
                try!(word(&mut self.s, "&"));
                try!(self.print_opt_lifetime(lt));
                try!(self.print_mutability(m));
                try!(word(&mut self.s, "self"));
            }
        }
        return Ok(true);
    }

    pub fn print_fn(&mut self,
                    decl: &ast::FnDecl,
                    fn_style: Option<ast::FnStyle>,
                    abi: abi::Abi,
                    name: ast::Ident,
                    generics: &ast::Generics,
                    opt_explicit_self: Option<ast::ExplicitSelf_>,
                    vis: ast::Visibility) -> IoResult<()> {
        try!(self.head(""));
        try!(self.print_fn_header_info(opt_explicit_self, fn_style, abi, vis));
        try!(self.nbsp());
        try!(self.print_ident(name));
        try!(self.print_generics(generics));
        self.print_fn_args_and_ret(decl, opt_explicit_self)
    }

    pub fn print_fn_args(&mut self, decl: &ast::FnDecl,
                         opt_explicit_self: Option<ast::ExplicitSelf_>)
        -> IoResult<()> {
        // It is unfortunate to duplicate the commasep logic, but we want the
        // self type and the args all in the same box.
        try!(self.rbox(0u, Inconsistent));
        let mut first = true;
        for &explicit_self in opt_explicit_self.iter() {
            let m = match explicit_self {
                ast::SelfStatic => ast::MutImmutable,
                _ => match decl.inputs.get(0).pat.node {
                    ast::PatIdent(ast::BindByValue(m), _, _) => m,
                    _ => ast::MutImmutable
                }
            };
            first = !try!(self.print_explicit_self(explicit_self, m));
        }

        // HACK(eddyb) ignore the separately printed self argument.
        let args = if first {
            decl.inputs.as_slice()
        } else {
            decl.inputs.slice_from(1)
        };

        for arg in args.iter() {
            if first { first = false; } else { try!(self.word_space(",")); }
            try!(self.print_arg(arg));
        }

        self.end()
    }

    pub fn print_fn_args_and_ret(&mut self, decl: &ast::FnDecl,
                                 opt_explicit_self: Option<ast::ExplicitSelf_>)
        -> IoResult<()> {
        try!(self.popen());
        try!(self.print_fn_args(decl, opt_explicit_self));
        if decl.variadic {
            try!(word(&mut self.s, ", ..."));
        }
        try!(self.pclose());

        try!(self.maybe_print_comment(decl.output.span.lo));
        match decl.output.node {
            ast::TyNil => Ok(()),
            _ => {
                try!(self.space_if_not_bol());
                try!(self.word_space("->"));
                self.print_type(decl.output)
            }
        }
    }

    pub fn print_fn_block_args(&mut self,
                               decl: &ast::FnDecl) -> IoResult<()> {
        try!(word(&mut self.s, "|"));
        try!(self.print_fn_args(decl, None));
        try!(word(&mut self.s, "|"));

        match decl.output.node {
            ast::TyInfer => {}
            _ => {
                try!(self.space_if_not_bol());
                try!(self.word_space("->"));
                try!(self.print_type(decl.output));
            }
        }

        self.maybe_print_comment(decl.output.span.lo)
    }

    pub fn print_proc_args(&mut self, decl: &ast::FnDecl) -> IoResult<()> {
        try!(word(&mut self.s, "proc"));
        try!(word(&mut self.s, "("));
        try!(self.print_fn_args(decl, None));
        try!(word(&mut self.s, ")"));

        match decl.output.node {
            ast::TyInfer => {}
            _ => {
                try!(self.space_if_not_bol());
                try!(self.word_space("->"));
                try!(self.print_type(decl.output));
            }
        }

        self.maybe_print_comment(decl.output.span.lo)
    }

    pub fn print_bounds(&mut self,
                        region: &Option<ast::Lifetime>,
                        bounds: &OwnedSlice<ast::TyParamBound>,
                        print_colon_anyway: bool) -> IoResult<()> {
        if !bounds.is_empty() || region.is_some() {
            try!(word(&mut self.s, ":"));
            let mut first = true;
            match *region {
                Some(ref lt) => {
                    let token = token::get_name(lt.name);
                    if token.get() != "static" {
                        try!(self.nbsp());
                        first = false;
                        try!(self.print_lifetime(lt));
                    }
                }
                None => {}
            }
            for bound in bounds.iter() {
                try!(self.nbsp());
                if first {
                    first = false;
                } else {
                    try!(self.word_space("+"));
                }

                try!(match *bound {
                    TraitTyParamBound(ref tref) => self.print_trait_ref(tref),
                    RegionTyParamBound => word(&mut self.s, "'static"),
                })
            }
            Ok(())
        } else if print_colon_anyway {
            word(&mut self.s, ":")
        } else {
            Ok(())
        }
    }

    pub fn print_lifetime(&mut self,
                          lifetime: &ast::Lifetime) -> IoResult<()> {
        try!(word(&mut self.s, "'"));
        self.print_name(lifetime.name)
    }

    pub fn print_generics(&mut self,
                          generics: &ast::Generics) -> IoResult<()> {
        let total = generics.lifetimes.len() + generics.ty_params.len();
        if total > 0 {
            try!(word(&mut self.s, "<"));

            let mut ints = Vec::new();
            for i in range(0u, total) {
                ints.push(i);
            }

            try!(self.commasep(
                Inconsistent, ints.as_slice(),
                |s, &idx| {
                    if idx < generics.lifetimes.len() {
                        let lifetime = generics.lifetimes.get(idx);
                        s.print_lifetime(lifetime)
                    } else {
                        let idx = idx - generics.lifetimes.len();
                        let param = generics.ty_params.get(idx);
                        if param.sized == ast::DynSize {
                            try!(s.word_space("type"));
                        }
                        try!(s.print_ident(param.ident));
                        try!(s.print_bounds(&None, &param.bounds, false));
                        match param.default {
                            Some(default) => {
                                try!(space(&mut s.s));
                                try!(s.word_space("="));
                                s.print_type(default)
                            }
                            _ => Ok(())
                        }
                    }
                }));
            word(&mut self.s, ">")
        } else {
            Ok(())
        }
    }

    pub fn print_meta_item(&mut self, item: &ast::MetaItem) -> IoResult<()> {
        try!(self.ibox(indent_unit));
        match item.node {
            ast::MetaWord(ref name) => {
                try!(word(&mut self.s, name.get()));
            }
            ast::MetaNameValue(ref name, ref value) => {
                try!(self.word_space(name.get()));
                try!(self.word_space("="));
                try!(self.print_literal(value));
            }
            ast::MetaList(ref name, ref items) => {
                try!(word(&mut self.s, name.get()));
                try!(self.popen());
                try!(self.commasep(Consistent,
                                   items.as_slice(),
                                   |s, &i| s.print_meta_item(i)));
                try!(self.pclose());
            }
        }
        self.end()
    }

    pub fn print_view_path(&mut self, vp: &ast::ViewPath) -> IoResult<()> {
        match vp.node {
            ast::ViewPathSimple(ident, ref path, _) => {
                // FIXME(#6993) can't compare identifiers directly here
                if path.segments.last().unwrap().identifier.name != ident.name {
                    try!(self.print_ident(ident));
                    try!(space(&mut self.s));
                    try!(self.word_space("="));
                }
                self.print_path(path, false)
            }

            ast::ViewPathGlob(ref path, _) => {
                try!(self.print_path(path, false));
                word(&mut self.s, "::*")
            }

            ast::ViewPathList(ref path, ref idents, _) => {
                if path.segments.is_empty() {
                    try!(word(&mut self.s, "{"));
                } else {
                    try!(self.print_path(path, false));
                    try!(word(&mut self.s, "::{"));
                }
                try!(self.commasep(Inconsistent, idents.as_slice(), |s, w| {
                    s.print_ident(w.node.name)
                }));
                word(&mut self.s, "}")
            }
        }
    }

    pub fn print_view_paths(&mut self,
                            vps: &[@ast::ViewPath]) -> IoResult<()> {
        self.commasep(Inconsistent, vps, |s, &vp| s.print_view_path(vp))
    }

    pub fn print_view_item(&mut self, item: &ast::ViewItem) -> IoResult<()> {
        try!(self.hardbreak_if_not_bol());
        try!(self.maybe_print_comment(item.span.lo));
        try!(self.print_outer_attributes(item.attrs.as_slice()));
        try!(self.print_visibility(item.vis));
        match item.node {
            ast::ViewItemExternCrate(id, ref optional_path, _) => {
                try!(self.head("extern crate"));
                try!(self.print_ident(id));
                for &(ref p, style) in optional_path.iter() {
                    try!(space(&mut self.s));
                    try!(word(&mut self.s, "="));
                    try!(space(&mut self.s));
                    try!(self.print_string(p.get(), style));
                }
            }

            ast::ViewItemUse(ref vps) => {
                try!(self.head("use"));
                try!(self.print_view_paths(vps.as_slice()));
            }
        }
        try!(word(&mut self.s, ";"));
        try!(self.end()); // end inner head-block
        self.end() // end outer head-block
    }

    pub fn print_mutability(&mut self,
                            mutbl: ast::Mutability) -> IoResult<()> {
        match mutbl {
            ast::MutMutable => self.word_nbsp("mut"),
            ast::MutImmutable => Ok(()),
        }
    }

    pub fn print_mt(&mut self, mt: &ast::MutTy) -> IoResult<()> {
        try!(self.print_mutability(mt.mutbl));
        self.print_type(mt.ty)
    }

    pub fn print_arg(&mut self, input: &ast::Arg) -> IoResult<()> {
        try!(self.ibox(indent_unit));
        match input.ty.node {
            ast::TyInfer => try!(self.print_pat(input.pat)),
            _ => {
                match input.pat.node {
                    ast::PatIdent(_, ref path, _) if
                        path.segments.len() == 1 &&
                        path.segments.get(0).identifier.name ==
                            parse::token::special_idents::invalid.name => {
                        // Do nothing.
                    }
                    _ => {
                        try!(self.print_pat(input.pat));
                        try!(word(&mut self.s, ":"));
                        try!(space(&mut self.s));
                    }
                }
                try!(self.print_type(input.ty));
            }
        }
        self.end()
    }

    pub fn print_ty_fn(&mut self,
                       opt_abi: Option<abi::Abi>,
                       opt_sigil: Option<char>,
                       opt_region: &Option<ast::Lifetime>,
                       fn_style: ast::FnStyle,
                       onceness: ast::Onceness,
                       decl: &ast::FnDecl,
                       id: Option<ast::Ident>,
                       opt_bounds: &Option<OwnedSlice<ast::TyParamBound>>,
                       generics: Option<&ast::Generics>,
                       opt_explicit_self: Option<ast::ExplicitSelf_>)
        -> IoResult<()> {
        try!(self.ibox(indent_unit));

        // Duplicates the logic in `print_fn_header_info()`.  This is because that
        // function prints the sigil in the wrong place.  That should be fixed.
        if opt_sigil == Some('~') && onceness == ast::Once {
            try!(word(&mut self.s, "proc"));
        } else if opt_sigil == Some('&') {
            try!(self.print_extern_opt_abi(opt_abi));
            try!(self.print_fn_style(fn_style));
            try!(self.print_onceness(onceness));
        } else {
            assert!(opt_sigil.is_none());
            try!(self.print_opt_abi_and_extern_if_nondefault(opt_abi));
            try!(self.print_fn_style(fn_style));
            try!(self.print_onceness(onceness));
            try!(word(&mut self.s, "fn"));
        }

        match id {
            Some(id) => {
                try!(word(&mut self.s, " "));
                try!(self.print_ident(id));
            }
            _ => ()
        }

        match generics { Some(g) => try!(self.print_generics(g)), _ => () }
        try!(zerobreak(&mut self.s));

        if opt_sigil == Some('&') {
            try!(word(&mut self.s, "|"));
        } else {
            try!(self.popen());
        }

        try!(self.print_fn_args(decl, opt_explicit_self));

        if opt_sigil == Some('&') {
            try!(word(&mut self.s, "|"));
        } else {
            if decl.variadic {
                try!(word(&mut self.s, ", ..."));
            }
            try!(self.pclose());
        }

        opt_bounds.as_ref().map(|bounds| {
            self.print_bounds(opt_region, bounds, true)
        });

        try!(self.maybe_print_comment(decl.output.span.lo));

        match decl.output.node {
            ast::TyNil => {}
            _ => {
                try!(self.space_if_not_bol());
                try!(self.ibox(indent_unit));
                try!(self.word_space("->"));
                if decl.cf == ast::NoReturn {
                    try!(self.word_nbsp("!"));
                } else {
                    try!(self.print_type(decl.output));
                }
                try!(self.end());
            }
        }

        self.end()
    }

    pub fn maybe_print_trailing_comment(&mut self, span: codemap::Span,
                                        next_pos: Option<BytePos>)
        -> IoResult<()> {
        let cm = match self.cm {
            Some(cm) => cm,
            _ => return Ok(())
        };
        match self.next_comment() {
            Some(ref cmnt) => {
                if (*cmnt).style != comments::Trailing { return Ok(()) }
                let span_line = cm.lookup_char_pos(span.hi);
                let comment_line = cm.lookup_char_pos((*cmnt).pos);
                let mut next = (*cmnt).pos + BytePos(1);
                match next_pos { None => (), Some(p) => next = p }
                if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
                    span_line.line == comment_line.line {
                        try!(self.print_comment(cmnt));
                        self.cur_cmnt_and_lit.cur_cmnt += 1u;
                    }
            }
            _ => ()
        }
        Ok(())
    }

    pub fn print_remaining_comments(&mut self) -> IoResult<()> {
        // 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() {
            try!(hardbreak(&mut self.s));
        }
        loop {
            match self.next_comment() {
                Some(ref cmnt) => {
                    try!(self.print_comment(cmnt));
                    self.cur_cmnt_and_lit.cur_cmnt += 1u;
                }
                _ => break
            }
        }
        Ok(())
    }

    pub fn print_literal(&mut self, lit: &ast::Lit) -> IoResult<()> {
        try!(self.maybe_print_comment(lit.span.lo));
        match self.next_lit(lit.span.lo) {
            Some(ref ltrl) => {
                return word(&mut self.s, (*ltrl).lit);
            }
            _ => ()
        }
        match lit.node {
            ast::LitStr(ref st, style) => self.print_string(st.get(), style),
            ast::LitChar(ch) => {
                let mut res = StrBuf::from_str("'");
                char::from_u32(ch).unwrap().escape_default(|c| res.push_char(c));
                res.push_char('\'');
                word(&mut self.s, res.into_owned())
            }
            ast::LitInt(i, t) => {
                word(&mut self.s, ast_util::int_ty_to_str(t, Some(i)))
            }
            ast::LitUint(u, t) => {
                word(&mut self.s, ast_util::uint_ty_to_str(t, Some(u)))
            }
            ast::LitIntUnsuffixed(i) => {
                word(&mut self.s, format!("{}", i))
            }
            ast::LitFloat(ref f, t) => {
                word(&mut self.s, f.get() + ast_util::float_ty_to_str(t))
            }
            ast::LitFloatUnsuffixed(ref f) => word(&mut self.s, f.get()),
            ast::LitNil => word(&mut self.s, "()"),
            ast::LitBool(val) => {
                if val { word(&mut self.s, "true") } else { word(&mut self.s, "false") }
            }
            ast::LitBinary(ref arr) => {
                try!(self.ibox(indent_unit));
                try!(word(&mut self.s, "["));
                try!(self.commasep_cmnt(Inconsistent, arr.as_slice(),
                                        |s, u| word(&mut s.s, format!("{}", *u)),
                                        |_| lit.span));
                try!(word(&mut self.s, "]"));
                self.end()
            }
        }
    }

    pub fn next_lit(&mut self, pos: BytePos) -> Option<comments::Literal> {
        match self.literals {
            Some(ref lits) => {
                while self.cur_cmnt_and_lit.cur_lit < lits.len() {
                    let ltrl = (*(*lits).get(self.cur_cmnt_and_lit.cur_lit)).clone();
                    if ltrl.pos > pos { return None; }
                    self.cur_cmnt_and_lit.cur_lit += 1u;
                    if ltrl.pos == pos { return Some(ltrl); }
                }
                None
            }
            _ => None
        }
    }

    pub fn maybe_print_comment(&mut self, pos: BytePos) -> IoResult<()> {
        loop {
            match self.next_comment() {
                Some(ref cmnt) => {
                    if (*cmnt).pos < pos {
                        try!(self.print_comment(cmnt));
                        self.cur_cmnt_and_lit.cur_cmnt += 1u;
                    } else { break; }
                }
                _ => break
            }
        }
        Ok(())
    }

    pub fn print_comment(&mut self,
                         cmnt: &comments::Comment) -> IoResult<()> {
        match cmnt.style {
            comments::Mixed => {
                assert_eq!(cmnt.lines.len(), 1u);
                try!(zerobreak(&mut self.s));
                try!(word(&mut self.s, *cmnt.lines.get(0)));
                zerobreak(&mut self.s)
            }
            comments::Isolated => {
                try!(self.hardbreak_if_not_bol());
                for line in cmnt.lines.iter() {
                    // Don't print empty lines because they will end up as trailing
                    // whitespace
                    if !line.is_empty() {
                        try!(word(&mut self.s, *line));
                    }
                    try!(hardbreak(&mut self.s));
                }
                Ok(())
            }
            comments::Trailing => {
                try!(word(&mut self.s, " "));
                if cmnt.lines.len() == 1u {
                    try!(word(&mut self.s, *cmnt.lines.get(0)));
                    hardbreak(&mut self.s)
                } else {
                    try!(self.ibox(0u));
                    for line in cmnt.lines.iter() {
                        if !line.is_empty() {
                            try!(word(&mut self.s, *line));
                        }
                        try!(hardbreak(&mut self.s));
                    }
                    self.end()
                }
            }
            comments::BlankLine => {
                // We need to do at least one, possibly two hardbreaks.
                let is_semi = match self.s.last_token() {
                    pp::String(s, _) => ";" == s,
                    _ => false
                };
                if is_semi || self.is_begin() || self.is_end() {
                    try!(hardbreak(&mut self.s));
                }
                hardbreak(&mut self.s)
            }
        }
    }

    pub fn print_string(&mut self, st: &str,
                        style: ast::StrStyle) -> IoResult<()> {
        let st = match style {
            ast::CookedStr => format!("\"{}\"", st.escape_default()),
            ast::RawStr(n) => format!("r{delim}\"{string}\"{delim}",
                                      delim="#".repeat(n), string=st)
        };
        word(&mut self.s, st)
    }

    pub fn next_comment(&mut self) -> Option<comments::Comment> {
        match self.comments {
            Some(ref cmnts) => {
                if self.cur_cmnt_and_lit.cur_cmnt < cmnts.len() {
                    Some((*cmnts.get(self.cur_cmnt_and_lit.cur_cmnt)).clone())
                } else {
                    None
                }
            }
            _ => None
        }
    }

    pub fn print_opt_fn_style(&mut self,
                            opt_fn_style: Option<ast::FnStyle>) -> IoResult<()> {
        match opt_fn_style {
            Some(fn_style) => self.print_fn_style(fn_style),
            None => Ok(())
        }
    }

    pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
                                                  opt_abi: Option<abi::Abi>)
        -> IoResult<()> {
        match opt_abi {
            Some(abi::Rust) => Ok(()),
            Some(abi) => {
                try!(self.word_nbsp("extern"));
                self.word_nbsp(abi.to_str())
            }
            None => Ok(())
        }
    }

    pub fn print_extern_opt_abi(&mut self,
                                opt_abi: Option<abi::Abi>) -> IoResult<()> {
        match opt_abi {
            Some(abi) => {
                try!(self.word_nbsp("extern"));
                self.word_nbsp(abi.to_str())
            }
            None => Ok(())
        }
    }

    pub fn print_fn_header_info(&mut self,
                                _opt_explicit_self: Option<ast::ExplicitSelf_>,
                                opt_fn_style: Option<ast::FnStyle>,
                                abi: abi::Abi,
                                vis: ast::Visibility) -> IoResult<()> {
        try!(word(&mut self.s, visibility_qualified(vis, "")));

        if abi != abi::Rust {
            try!(self.word_nbsp("extern"));
            try!(self.word_nbsp(abi.to_str()));

            if opt_fn_style != Some(ast::ExternFn) {
                try!(self.print_opt_fn_style(opt_fn_style));
            }
        } else {
            try!(self.print_opt_fn_style(opt_fn_style));
        }

        word(&mut self.s, "fn")
    }

    pub fn print_fn_style(&mut self, s: ast::FnStyle) -> IoResult<()> {
        match s {
            ast::NormalFn => Ok(()),
            ast::UnsafeFn => self.word_nbsp("unsafe"),
            ast::ExternFn => self.word_nbsp("extern")
        }
    }

    pub fn print_onceness(&mut self, o: ast::Onceness) -> IoResult<()> {
        match o {
            ast::Once => self.word_nbsp("once"),
            ast::Many => Ok(())
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;

    use ast;
    use ast_util;
    use codemap;
    use parse::token;

    #[test]
    fn test_fun_to_str() {
        let abba_ident = token::str_to_ident("abba");

        let decl = ast::FnDecl {
            inputs: Vec::new(),
            output: ast::P(ast::Ty {id: 0,
                                    node: ast::TyNil,
                                    span: codemap::DUMMY_SP}),
            cf: ast::Return,
            variadic: false
        };
        let generics = ast_util::empty_generics();
        assert_eq!(&fun_to_str(&decl, ast::NormalFn, abba_ident,
                               None, &generics),
                   &"fn abba()".to_owned());
    }

    #[test]
    fn test_variant_to_str() {
        let ident = token::str_to_ident("principal_skinner");

        let var = codemap::respan(codemap::DUMMY_SP, ast::Variant_ {
            name: ident,
            attrs: Vec::new(),
            // making this up as I go.... ?
            kind: ast::TupleVariantKind(Vec::new()),
            id: 0,
            disr_expr: None,
            vis: ast::Public,
        });

        let varstr = variant_to_str(&var);
        assert_eq!(&varstr,&"pub principal_skinner".to_owned());
    }
}