rust/src/libsyntax/print/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 core::prelude::*;

use abi::AbiSet;
use ast::{RegionTyParamBound, TraitTyParamBound, required, provided};
use ast;
use ast_util;
use opt_vec::OptVec;
use opt_vec;
use attr;
use codemap::{CodeMap, BytePos};
use codemap;
use diagnostic;
use parse::classify::expr_is_simple_block;
use parse::token::{ident_interner, ident_to_str};
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 print::pprust;

use core::char;
use core::io;
use core::u64;
use core::uint;

// The @ps is stored here to prevent recursive type.
pub enum ann_node<'self> {
    node_block(@ps, &'self ast::blk),
    node_item(@ps, @ast::item),
    node_expr(@ps, @ast::expr),
    node_pat(@ps, @ast::pat),
}
pub struct pp_ann {
    pre: @fn(ann_node),
    post: @fn(ann_node)
}

pub fn no_ann() -> pp_ann {
    fn ignore(_node: ann_node) { }
    return pp_ann {pre: ignore, post: ignore};
}

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

pub struct ps {
    s: @mut pp::Printer,
    cm: Option<@CodeMap>,
    intr: @token::ident_interner,
    comments: Option<~[comments::cmnt]>,
    literals: Option<~[comments::lit]>,
    cur_cmnt_and_lit: @mut CurrentCommentAndLiteral,
    boxes: @mut ~[pp::breaks],
    ann: pp_ann
}

pub fn ibox(s: @ps, u: uint) {
    s.boxes.push(pp::inconsistent);
    pp::ibox(s.s, u);
}

pub fn end(s: @ps) {
    s.boxes.pop();
    pp::end(s.s);
}

pub fn rust_printer(writer: @io::Writer, intr: @ident_interner) -> @ps {
    return rust_printer_annotated(writer, intr, no_ann());
}

pub fn rust_printer_annotated(writer: @io::Writer,
                              intr: @ident_interner,
                              ann: pp_ann) -> @ps {
    return @ps {
        s: pp::mk_printer(writer, default_columns),
        cm: None::<@CodeMap>,
        intr: intr,
        comments: None::<~[comments::cmnt]>,
        literals: None::<~[comments::lit]>,
        cur_cmnt_and_lit: @mut CurrentCommentAndLiteral {
            cur_cmnt: 0,
            cur_lit: 0
        },
        boxes: @mut ~[],
        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(cm: @CodeMap,
                   intr: @ident_interner,
                   span_diagnostic: @diagnostic::span_handler,
                   crate: @ast::crate,
                   filename: @str,
                   in: @io::Reader,
                   out: @io::Writer,
                   ann: pp_ann,
                   is_expanded: bool) {
    let (cmnts, lits) = comments::gather_comments_and_literals(
        span_diagnostic,
        filename,
        in
    );
    let s = @ps {
        s: pp::mk_printer(out, default_columns),
        cm: Some(cm),
        intr: intr,
        comments: Some(copy 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(copy lits) },
        cur_cmnt_and_lit: @mut CurrentCommentAndLiteral {
            cur_cmnt: 0,
            cur_lit: 0
        },
        boxes: @mut ~[],
        ann: ann
    };
    print_crate_(s, crate);
}

pub fn print_crate_(s: @ps, crate: @ast::crate) {
    print_mod(s, &crate.node.module, crate.node.attrs);
    print_remaining_comments(s);
    eof(s.s);
}

pub fn ty_to_str(ty: @ast::Ty, intr: @ident_interner) -> ~str {
    to_str(ty, print_type, intr)
}

pub fn pat_to_str(pat: @ast::pat, intr: @ident_interner) -> ~str {
    to_str(pat, print_irrefutable_pat, intr)
}

pub fn expr_to_str(e: @ast::expr, intr: @ident_interner) -> ~str {
    to_str(e, print_expr, intr)
}

pub fn lifetime_to_str(e: &ast::Lifetime, intr: @ident_interner) -> ~str {
    to_str(e, print_lifetime, intr)
}

pub fn tt_to_str(tt: ast::token_tree, intr: @ident_interner) -> ~str {
    to_str(&tt, print_tt, intr)
}

pub fn tts_to_str(tts: &[ast::token_tree], intr: @ident_interner) -> ~str {
    to_str(tts, print_tts, intr)
}

pub fn stmt_to_str(s: &ast::stmt, intr: @ident_interner) -> ~str {
    to_str(s, print_stmt, intr)
}

pub fn item_to_str(i: @ast::item, intr: @ident_interner) -> ~str {
    to_str(i, print_item, intr)
}

pub fn generics_to_str(generics: &ast::Generics,
                       intr: @ident_interner) -> ~str {
    to_str(generics, print_generics, intr)
}

pub fn path_to_str(p: @ast::Path, intr: @ident_interner) -> ~str {
    to_str(p, |a,b| print_path(a, b, false), intr)
}

pub fn fun_to_str(decl: &ast::fn_decl, purity: ast::purity, name: ast::ident,
                  opt_explicit_self: Option<ast::explicit_self_>,
                  generics: &ast::Generics, intr: @ident_interner) -> ~str {
    do io::with_str_writer |wr| {
        let s = rust_printer(wr, intr);
        print_fn(s, decl, Some(purity), AbiSet::Rust(),
                 name, generics, opt_explicit_self, ast::inherited);
        end(s); // Close the head box
        end(s); // Close the outer box
        eof(s.s);
    }
}

pub fn block_to_str(blk: &ast::blk, intr: @ident_interner) -> ~str {
    do io::with_str_writer |wr| {
        let s = rust_printer(wr, intr);
        // containing cbox, will be closed by print-block at }
        cbox(s, indent_unit);
        // head-ibox, will be closed by print-block after {
        ibox(s, 0u);
        print_block(s, blk);
        eof(s.s);
    }
}

pub fn meta_item_to_str(mi: @ast::meta_item, intr: @ident_interner) -> ~str {
    to_str(mi, print_meta_item, intr)
}

pub fn attribute_to_str(attr: ast::attribute, intr: @ident_interner) -> ~str {
    to_str(attr, print_attribute, intr)
}

pub fn variant_to_str(var: &ast::variant, intr: @ident_interner) -> ~str {
    to_str(var, print_variant, intr)
}

pub fn cbox(s: @ps, u: uint) {
    s.boxes.push(pp::consistent);
    pp::cbox(s.s, u);
}

pub fn box(s: @ps, u: uint, b: pp::breaks) {
    s.boxes.push(b);
    pp::box(s.s, u, b);
}

pub fn nbsp(s: @ps) { word(s.s, " "); }

pub fn word_nbsp(s: @ps, w: &str) { word(s.s, w); nbsp(s); }

pub fn word_space(s: @ps, w: &str) { word(s.s, w); space(s.s); }

pub fn popen(s: @ps) { word(s.s, "("); }

pub fn pclose(s: @ps) { word(s.s, ")"); }

pub fn head(s: @ps, w: &str) {
    // outer-box is consistent
    cbox(s, indent_unit);
    // head-box is inconsistent
    ibox(s, w.len() + 1);
    // keyword that starts the head
    if !w.is_empty() {
        word_nbsp(s, w);
    }
}

pub fn bopen(s: @ps) {
    word(s.s, "{");
    end(s); // close the head-box
}

pub fn bclose_(s: @ps, span: codemap::span, indented: uint) {
    bclose_maybe_open(s, span, indented, true);
}
pub fn bclose_maybe_open (s: @ps, span: codemap::span, indented: uint,
                          close_box: bool) {
    maybe_print_comment(s, span.hi);
    break_offset_if_not_bol(s, 1u, -(indented as int));
    word(s.s, "}");
    if close_box {
        end(s); // close the outer-box
    }
}
pub fn bclose(s: @ps, span: codemap::span) { bclose_(s, span, indent_unit); }

pub fn is_begin(s: @ps) -> bool {
    match s.s.last_token() { pp::BEGIN(_) => true, _ => false }
}

pub fn is_end(s: @ps) -> bool {
    match s.s.last_token() { pp::END => true, _ => false }
}

pub fn is_bol(s: @ps) -> bool {
    return s.s.last_token().is_eof() || s.s.last_token().is_hardbreak_tok();
}

pub fn in_cbox(s: @ps) -> bool {
    let boxes = &*s.boxes;
    let len = boxes.len();
    if len == 0u { return false; }
    return boxes[len - 1u] == pp::consistent;
}

pub fn hardbreak_if_not_bol(s: @ps) { if !is_bol(s) { hardbreak(s.s); } }
pub fn space_if_not_bol(s: @ps) { if !is_bol(s) { space(s.s); } }
pub fn break_offset_if_not_bol(s: @ps, n: uint, off: int) {
    if !is_bol(s) {
        break_offset(s.s, n, off);
    } else {
        if off != 0 && s.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.
            s.s.replace_last_token(pp::hardbreak_tok_offset(off));
        }
    }
}

// Synthesizes a comment that was not textually present in the original source
// file.
pub fn synth_comment(s: @ps, text: ~str) {
    word(s.s, "/*");
    space(s.s);
    word(s.s, text);
    space(s.s);
    word(s.s, "*/");
}

pub fn commasep<IN: Copy>(s: @ps, b: breaks, elts: &[IN], op: &fn(@ps, IN)) {
    box(s, 0u, b);
    let mut first = true;
    for elts.each |elt| {
        if first { first = false; } else { word_space(s, ","); }
        op(s, copy *elt);
    }
    end(s);
}


pub fn commasep_cmnt<IN: Copy>(s: @ps, b: breaks, elts: &[IN], op: &fn(@ps, IN),
                               get_span: &fn(IN) -> codemap::span) {
    box(s, 0u, b);
    let len = elts.len();
    let mut i = 0u;
    for elts.each |elt| {
        maybe_print_comment(s, get_span(copy *elt).hi);
        op(s, copy *elt);
        i += 1u;
        if i < len {
            word(s.s, ",");
            maybe_print_trailing_comment(s, get_span(copy *elt),
                                         Some(get_span(copy elts[i]).hi));
            space_if_not_bol(s);
        }
    }
    end(s);
}

pub fn commasep_exprs(s: @ps, b: breaks, exprs: &[@ast::expr]) {
    fn expr_span(expr: @ast::expr) -> codemap::span { return expr.span; }
    commasep_cmnt(s, b, exprs, print_expr, expr_span);
}

pub fn print_mod(s: @ps, _mod: &ast::_mod, attrs: &[ast::attribute]) {
    print_inner_attributes(s, attrs);
    for _mod.view_items.each |vitem| {
        print_view_item(s, *vitem);
    }
    for _mod.items.each |item| { print_item(s, *item); }
}

pub fn print_foreign_mod(s: @ps, nmod: &ast::foreign_mod,
                         attrs: &[ast::attribute]) {
    print_inner_attributes(s, attrs);
    for nmod.view_items.each |vitem| {
        print_view_item(s, *vitem);
    }
    for nmod.items.each |item| { print_foreign_item(s, *item); }
}

pub fn print_opt_lifetime(s: @ps, lifetime: Option<@ast::Lifetime>) {
    for lifetime.iter().advance |l| {
        print_lifetime(s, *l);
        nbsp(s);
    }
}

pub fn print_type(s: @ps, ty: @ast::Ty) {
    maybe_print_comment(s, ty.span.lo);
    ibox(s, 0u);
    match ty.node {
      ast::ty_nil => word(s.s, "()"),
      ast::ty_bot => word(s.s, "!"),
      ast::ty_box(ref mt) => { word(s.s, "@"); print_mt(s, mt); }
      ast::ty_uniq(ref mt) => { word(s.s, "~"); print_mt(s, mt); }
      ast::ty_vec(ref mt) => {
        word(s.s, "[");
        match mt.mutbl {
          ast::m_mutbl => word_space(s, "mut"),
          ast::m_const => word_space(s, "const"),
          ast::m_imm => ()
        }
        print_type(s, mt.ty);
        word(s.s, "]");
      }
      ast::ty_ptr(ref mt) => { word(s.s, "*"); print_mt(s, mt); }
      ast::ty_rptr(lifetime, ref mt) => {
          word(s.s, "&");
          print_opt_lifetime(s, lifetime);
          print_mt(s, mt);
      }
      ast::ty_tup(ref elts) => {
        popen(s);
        commasep(s, inconsistent, *elts, print_type);
        if elts.len() == 1 {
            word(s.s, ",");
        }
        pclose(s);
      }
      ast::ty_bare_fn(f) => {
          let generics = ast::Generics {lifetimes: copy f.lifetimes,
                                        ty_params: opt_vec::Empty};
          print_ty_fn(s, Some(f.abis), None, None,
                      f.purity, ast::Many, &f.decl, None,
                      Some(&generics), None);
      }
      ast::ty_closure(f) => {
          let generics = ast::Generics {lifetimes: copy f.lifetimes,
                                        ty_params: opt_vec::Empty};
          print_ty_fn(s, None, Some(f.sigil), f.region,
                      f.purity, f.onceness, &f.decl, None,
                      Some(&generics), None);
      }
      ast::ty_path(path, _) => print_path(s, path, false),
      ast::ty_fixed_length_vec(ref mt, v) => {
        word(s.s, "[");
        match mt.mutbl {
            ast::m_mutbl => word_space(s, "mut"),
            ast::m_const => word_space(s, "const"),
            ast::m_imm => ()
        }
        print_type(s, mt.ty);
        word(s.s, ", ..");
        print_expr(s, v);
        word(s.s, "]");
      }
      ast::ty_mac(_) => {
          fail!("print_type doesn't know how to print a ty_mac");
      }
      ast::ty_infer => {
          fail!("print_type shouldn't see a ty_infer");
      }

    }
    end(s);
}

pub fn print_foreign_item(s: @ps, item: @ast::foreign_item) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, item.span.lo);
    print_outer_attributes(s, item.attrs);
    match item.node {
      ast::foreign_item_fn(ref decl, purity, ref generics) => {
        print_fn(s, decl, Some(purity), AbiSet::Rust(), item.ident, generics, None,
                 ast::inherited);
        end(s); // end head-ibox
        word(s.s, ";");
        end(s); // end the outer fn box
      }
      ast::foreign_item_const(t) => {
        head(s, "static");
        print_ident(s, item.ident);
        word_space(s, ":");
        print_type(s, t);
        word(s.s, ";");
        end(s); // end the head-ibox
        end(s); // end the outer cbox
      }
    }
}

pub fn print_item(s: @ps, item: @ast::item) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, item.span.lo);
    print_outer_attributes(s, item.attrs);
    let ann_node = node_item(s, item);
    (s.ann.pre)(ann_node);
    match item.node {
      ast::item_const(ty, expr) => {
        head(s, visibility_qualified(item.vis, "static"));
        print_ident(s, item.ident);
        word_space(s, ":");
        print_type(s, ty);
        space(s.s);
        end(s); // end the head-ibox

        word_space(s, "=");
        print_expr(s, expr);
        word(s.s, ";");
        end(s); // end the outer cbox

      }
      ast::item_fn(ref decl, purity, abi, ref typarams, ref body) => {
        print_fn(
            s,
            decl,
            Some(purity),
            abi,
            item.ident,
            typarams,
            None,
            item.vis
        );
        word(s.s, " ");
        print_block_with_attrs(s, body, item.attrs);
      }
      ast::item_mod(ref _mod) => {
        head(s, visibility_qualified(item.vis, "mod"));
        print_ident(s, item.ident);
        nbsp(s);
        bopen(s);
        print_mod(s, _mod, item.attrs);
        bclose(s, item.span);
      }
      ast::item_foreign_mod(ref nmod) => {
        head(s, visibility_qualified(item.vis, "extern"));
        word_nbsp(s, nmod.abis.to_str());
        match nmod.sort {
            ast::named => {
                word_nbsp(s, "mod");
                print_ident(s, item.ident);
                nbsp(s);
            }
            ast::anonymous => {}
        }
        bopen(s);
        print_foreign_mod(s, nmod, item.attrs);
        bclose(s, item.span);
      }
      ast::item_ty(ty, ref params) => {
        ibox(s, indent_unit);
        ibox(s, 0u);
        word_nbsp(s, visibility_qualified(item.vis, "type"));
        print_ident(s, item.ident);
        print_generics(s, params);
        end(s); // end the inner ibox

        space(s.s);
        word_space(s, "=");
        print_type(s, ty);
        word(s.s, ";");
        end(s); // end the outer ibox
      }
      ast::item_enum(ref enum_definition, ref params) => {
        print_enum_def(
            s,
            enum_definition,
            params,
            item.ident,
            item.span,
            item.vis
        );
      }
      ast::item_struct(struct_def, ref generics) => {
          head(s, visibility_qualified(item.vis, "struct"));
          print_struct(s, struct_def, generics, item.ident, item.span);
      }

      ast::item_impl(ref generics, opt_trait, ty, ref methods) => {
        head(s, visibility_qualified(item.vis, "impl"));
        if generics.is_parameterized() {
            print_generics(s, generics);
            space(s.s);
        }

        match opt_trait {
            Some(t) => {
                print_trait_ref(s, t);
                space(s.s);
                word_space(s, "for");
            }
            None => ()
        };

        print_type(s, ty);
        space(s.s);

        if methods.len() == 0 {
            word(s.s, ";");
        } else {
            bopen(s);
            for methods.each |meth| {
               print_method(s, *meth);
            }
            bclose(s, item.span);
        }
      }
      ast::item_trait(ref generics, ref traits, ref methods) => {
        head(s, visibility_qualified(item.vis, "trait"));
        print_ident(s, item.ident);
        print_generics(s, generics);
        if traits.len() != 0u {
            word(s.s, ":");
            for traits.iter().enumerate().advance |(i, trait_)| {
                nbsp(s);
                if i != 0 {
                    word_space(s, "+");
                }
                print_path(s, trait_.path, false);
            }
        }
        word(s.s, " ");
        bopen(s);
        for methods.each |meth| {
            print_trait_method(s, meth);
        }
        bclose(s, item.span);
      }
      ast::item_mac(codemap::spanned { node: ast::mac_invoc_tt(pth, ref tts),
                                   _}) => {
        print_visibility(s, item.vis);
        print_path(s, pth, false);
        word(s.s, "! ");
        print_ident(s, item.ident);
        cbox(s, indent_unit);
        popen(s);
        print_tts(s, *tts);
        pclose(s);
        end(s);
      }
    }
    (s.ann.post)(ann_node);
}

fn print_trait_ref(s: @ps, t: &ast::trait_ref) {
    print_path(s, t.path, false);
}

pub fn print_enum_def(s: @ps, enum_definition: &ast::enum_def,
                      generics: &ast::Generics, ident: ast::ident,
                      span: codemap::span, visibility: ast::visibility) {
    head(s, visibility_qualified(visibility, "enum"));
    print_ident(s, ident);
    print_generics(s, generics);
    space(s.s);
    print_variants(s, enum_definition.variants, span);
}

pub fn print_variants(s: @ps,
                      variants: &[ast::variant],
                      span: codemap::span) {
    bopen(s);
    for variants.each |v| {
        space_if_not_bol(s);
        maybe_print_comment(s, v.span.lo);
        print_outer_attributes(s, v.node.attrs);
        ibox(s, indent_unit);
        print_variant(s, v);
        word(s.s, ",");
        end(s);
        maybe_print_trailing_comment(s, v.span, None);
    }
    bclose(s, span);
}

pub fn visibility_to_str(vis: ast::visibility) -> ~str {
    match vis {
        ast::private => ~"priv",
        ast::public => ~"pub",
        ast::inherited => ~""
    }
}

pub fn visibility_qualified(vis: ast::visibility, s: &str) -> ~str {
    match vis {
        ast::private | ast::public => visibility_to_str(vis) + " " + s,
        ast::inherited => s.to_owned()
    }
}

pub fn print_visibility(s: @ps, vis: ast::visibility) {
    match vis {
        ast::private | ast::public =>
        word_nbsp(s, visibility_to_str(vis)),
        ast::inherited => ()
    }
}

pub fn print_struct(s: @ps,
                    struct_def: @ast::struct_def,
                    generics: &ast::Generics,
                    ident: ast::ident,
                    span: codemap::span) {
    print_ident(s, ident);
    print_generics(s, generics);
    if ast_util::struct_def_is_tuple_like(struct_def) {
        if !struct_def.fields.is_empty() {
            popen(s);
            do commasep(s, inconsistent, struct_def.fields) |s, field| {
                match field.node.kind {
                    ast::named_field(*) => fail!("unexpected named field"),
                    ast::unnamed_field => {
                        maybe_print_comment(s, field.span.lo);
                        print_type(s, field.node.ty);
                    }
                }
            }
            pclose(s);
        }
        word(s.s, ";");
        end(s);
        end(s); // close the outer-box
    } else {
        nbsp(s);
        bopen(s);
        hardbreak_if_not_bol(s);

        for struct_def.fields.each |field| {
            match field.node.kind {
                ast::unnamed_field => fail!("unexpected unnamed field"),
                ast::named_field(ident, visibility) => {
                    hardbreak_if_not_bol(s);
                    maybe_print_comment(s, field.span.lo);
                    print_outer_attributes(s, field.node.attrs);
                    print_visibility(s, visibility);
                    print_ident(s, ident);
                    word_nbsp(s, ":");
                    print_type(s, field.node.ty);
                    word(s.s, ",");
                }
            }
        }

        bclose(s, 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(s: @ps, tt: &ast::token_tree) {
    match *tt {
      ast::tt_delim(ref tts) => print_tts(s, *tts),
      ast::tt_tok(_, ref tk) => {
          word(s.s, parse::token::to_str(s.intr, tk));
      }
      ast::tt_seq(_, ref tts, ref sep, zerok) => {
        word(s.s, "$(");
        for (*tts).each() |tt_elt| { print_tt(s, tt_elt); }
        word(s.s, ")");
        match (*sep) {
          Some(ref tk) => word(s.s, parse::token::to_str(s.intr, tk)),
          None => ()
        }
        word(s.s, if zerok { "*" } else { "+" });
      }
      ast::tt_nonterminal(_, name) => {
        word(s.s, "$");
        print_ident(s, name);
      }
    }
}

pub fn print_tts(s: @ps, tts: &[ast::token_tree]) {
    ibox(s, 0);
    for tts.iter().enumerate().advance |(i, tt)| {
        if i != 0 {
            space(s.s);
        }
        print_tt(s, tt);
    }
    end(s);
}

pub fn print_variant(s: @ps, v: &ast::variant) {
    print_visibility(s, v.node.vis);
    match v.node.kind {
        ast::tuple_variant_kind(ref args) => {
            print_ident(s, v.node.name);
            if !args.is_empty() {
                popen(s);
                fn print_variant_arg(s: @ps, arg: ast::variant_arg) {
                    print_type(s, arg.ty);
                }
                commasep(s, consistent, *args, print_variant_arg);
                pclose(s);
            }
        }
        ast::struct_variant_kind(struct_def) => {
            head(s, "");
            let generics = ast_util::empty_generics();
            print_struct(s, struct_def, &generics, v.node.name, v.span);
        }
    }
    match v.node.disr_expr {
      Some(d) => {
        space(s.s);
        word_space(s, "=");
        print_expr(s, d);
      }
      _ => ()
    }
}

pub fn print_ty_method(s: @ps, m: &ast::ty_method) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, m.span.lo);
    print_outer_attributes(s, m.attrs);
    print_ty_fn(s, None, None, None, m.purity, ast::Many,
                &m.decl, Some(m.ident), Some(&m.generics),
                Some(/*bad*/ copy m.explicit_self.node));
    word(s.s, ";");
}

pub fn print_trait_method(s: @ps, m: &ast::trait_method) {
    match *m {
        required(ref ty_m) => print_ty_method(s, ty_m),
        provided(m) => print_method(s, m)
    }
}

pub fn print_method(s: @ps, meth: @ast::method) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, meth.span.lo);
    print_outer_attributes(s, meth.attrs);
    print_fn(s, &meth.decl, Some(meth.purity), AbiSet::Rust(),
             meth.ident, &meth.generics, Some(meth.explicit_self.node),
             meth.vis);
    word(s.s, " ");
    print_block_with_attrs(s, &meth.body, meth.attrs);
}

pub fn print_outer_attributes(s: @ps, attrs: &[ast::attribute]) {
    let mut count = 0;
    for attrs.each |attr| {
        match attr.node.style {
          ast::attr_outer => { print_attribute(s, *attr); count += 1; }
          _ => {/* fallthrough */ }
        }
    }
    if count > 0 { hardbreak_if_not_bol(s); }
}

pub fn print_inner_attributes(s: @ps, attrs: &[ast::attribute]) {
    let mut count = 0;
    for attrs.each |attr| {
        match attr.node.style {
          ast::attr_inner => {
            print_attribute(s, *attr);
            if !attr.node.is_sugared_doc {
                word(s.s, ";");
            }
            count += 1;
          }
          _ => {/* fallthrough */ }
        }
    }
    if count > 0 { hardbreak_if_not_bol(s); }
}

pub fn print_attribute(s: @ps, attr: ast::attribute) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, attr.span.lo);
    if attr.node.is_sugared_doc {
        let meta = attr::attr_meta(attr);
        let comment = attr::get_meta_item_value_str(meta).get();
        word(s.s, comment);
    } else {
        word(s.s, "#[");
        print_meta_item(s, attr.node.value);
        word(s.s, "]");
    }
}


pub fn print_stmt(s: @ps, st: &ast::stmt) {
    maybe_print_comment(s, st.span.lo);
    match st.node {
      ast::stmt_decl(decl, _) => {
        print_decl(s, decl);
      }
      ast::stmt_expr(expr, _) => {
        space_if_not_bol(s);
        print_expr(s, expr);
      }
      ast::stmt_semi(expr, _) => {
        space_if_not_bol(s);
        print_expr(s, expr);
        word(s.s, ";");
      }
      ast::stmt_mac(ref mac, semi) => {
        space_if_not_bol(s);
        print_mac(s, mac);
        if semi { word(s.s, ";"); }
      }
    }
    if parse::classify::stmt_ends_with_semi(st) { word(s.s, ";"); }
    maybe_print_trailing_comment(s, st.span, None);
}

pub fn print_block(s: @ps, blk: &ast::blk) {
    print_possibly_embedded_block(s, blk, block_normal, indent_unit);
}

pub fn print_block_unclosed(s: @ps, blk: &ast::blk) {
    print_possibly_embedded_block_(s, blk, block_normal, indent_unit, &[],
                                 false);
}

pub fn print_block_unclosed_indent(s: @ps, blk: &ast::blk, indented: uint) {
    print_possibly_embedded_block_(s, blk, block_normal, indented, &[],
                                   false);
}

pub fn print_block_with_attrs(s: @ps,
                              blk: &ast::blk,
                              attrs: &[ast::attribute]) {
    print_possibly_embedded_block_(s, blk, block_normal, indent_unit, attrs,
                                  true);
}

pub enum embed_type { block_block_fn, block_normal, }

pub fn print_possibly_embedded_block(s: @ps,
                                     blk: &ast::blk,
                                     embedded: embed_type,
                                     indented: uint) {
    print_possibly_embedded_block_(
        s, blk, embedded, indented, &[], true);
}

pub fn print_possibly_embedded_block_(s: @ps,
                                      blk: &ast::blk,
                                      embedded: embed_type,
                                      indented: uint,
                                      attrs: &[ast::attribute],
                                      close_box: bool) {
    match blk.node.rules {
      ast::unsafe_blk => word_space(s, "unsafe"),
      ast::default_blk => ()
    }
    maybe_print_comment(s, blk.span.lo);
    let ann_node = node_block(s, blk);
    (s.ann.pre)(ann_node);
    match embedded {
      block_block_fn => end(s),
      block_normal => bopen(s)
    }

    print_inner_attributes(s, attrs);

    for blk.node.view_items.each |vi| { print_view_item(s, *vi); }
    for blk.node.stmts.each |st| {
        print_stmt(s, *st);
    }
    match blk.node.expr {
      Some(expr) => {
        space_if_not_bol(s);
        print_expr(s, expr);
        maybe_print_trailing_comment(s, expr.span, Some(blk.span.hi));
      }
      _ => ()
    }
    bclose_maybe_open(s, blk.span, indented, close_box);
    (s.ann.post)(ann_node);
}

pub fn print_if(s: @ps, test: @ast::expr, blk: &ast::blk,
                elseopt: Option<@ast::expr>, chk: bool) {
    head(s, "if");
    if chk { word_nbsp(s, "check"); }
    print_expr(s, test);
    space(s.s);
    print_block(s, blk);
    fn do_else(s: @ps, els: Option<@ast::expr>) {
        match els {
          Some(_else) => {
            match _else.node {
              // "another else-if"
              ast::expr_if(i, ref t, e) => {
                cbox(s, indent_unit - 1u);
                ibox(s, 0u);
                word(s.s, " else if ");
                print_expr(s, i);
                space(s.s);
                print_block(s, t);
                do_else(s, e);
              }
              // "final else"
              ast::expr_block(ref b) => {
                cbox(s, indent_unit - 1u);
                ibox(s, 0u);
                word(s.s, " else ");
                print_block(s, b);
              }
              // BLEAH, constraints would be great here
              _ => {
                  fail!("print_if saw if with weird alternative");
              }
            }
          }
          _ => {/* fall through */ }
        }
    }
    do_else(s, elseopt);
}

pub fn print_mac(s: @ps, m: &ast::mac) {
    match m.node {
      ast::mac_invoc_tt(pth, ref tts) => {
        print_path(s, pth, false);
        word(s.s, "!");
        popen(s);
        print_tts(s, *tts);
        pclose(s);
      }
    }
}

pub fn print_vstore(s: @ps, t: ast::vstore) {
    match t {
        ast::vstore_fixed(Some(i)) => word(s.s, fmt!("%u", i)),
        ast::vstore_fixed(None) => word(s.s, "_"),
        ast::vstore_uniq => word(s.s, "~"),
        ast::vstore_box => word(s.s, "@"),
        ast::vstore_slice(r) => {
            word(s.s, "&");
            print_opt_lifetime(s, r);
        }
    }
}

pub fn print_expr_vstore(s: @ps, t: ast::expr_vstore) {
    match t {
      ast::expr_vstore_uniq => word(s.s, "~"),
      ast::expr_vstore_box => word(s.s, "@"),
      ast::expr_vstore_mut_box => {
        word(s.s, "@");
        word(s.s, "mut");
      }
      ast::expr_vstore_slice => word(s.s, "&"),
      ast::expr_vstore_mut_slice => {
        word(s.s, "&");
        word(s.s, "mut");
      }
    }
}

pub fn print_call_pre(s: @ps,
                      sugar: ast::CallSugar,
                      base_args: &mut ~[@ast::expr])
                   -> Option<@ast::expr> {
    match sugar {
        ast::DoSugar => {
            head(s, "do");
            Some(base_args.pop())
        }
        ast::ForSugar => {
            head(s, "for");
            Some(base_args.pop())
        }
        ast::NoSugar => None
    }
}

pub fn print_call_post(s: @ps,
                       sugar: ast::CallSugar,
                       blk: &Option<@ast::expr>,
                       base_args: &mut ~[@ast::expr]) {
    if sugar == ast::NoSugar || !base_args.is_empty() {
        popen(s);
        commasep_exprs(s, inconsistent, *base_args);
        pclose(s);
    }
    if sugar != ast::NoSugar {
        nbsp(s);
        match blk.get().node {
          // need to handle closures specifically
          ast::expr_do_body(e) | ast::expr_loop_body(e) => {
            end(s); // we close our head box; closure
                    // will create it's own.
            print_expr(s, e);
            end(s); // close outer box, as closures don't
          }
          _ => {
            // not sure if this can happen.
            print_expr(s, blk.get());
          }
        }
    }
}

pub fn print_expr(s: @ps, expr: @ast::expr) {
    fn print_field(s: @ps, field: ast::field) {
        ibox(s, indent_unit);
        print_ident(s, field.node.ident);
        word_space(s, ":");
        print_expr(s, field.node.expr);
        end(s);
    }
    fn get_span(field: ast::field) -> codemap::span { return field.span; }

    maybe_print_comment(s, expr.span.lo);
    ibox(s, indent_unit);
    let ann_node = node_expr(s, expr);
    (s.ann.pre)(ann_node);
    match expr.node {
        ast::expr_vstore(e, v) => {
            print_expr_vstore(s, v);
            print_expr(s, e);
        },
      ast::expr_vec(ref exprs, mutbl) => {
        ibox(s, indent_unit);
        word(s.s, "[");
        if mutbl == ast::m_mutbl {
            word(s.s, "mut");
            if exprs.len() > 0u { nbsp(s); }
        }
        commasep_exprs(s, inconsistent, *exprs);
        word(s.s, "]");
        end(s);
      }

      ast::expr_repeat(element, count, mutbl) => {
        ibox(s, indent_unit);
        word(s.s, "[");
        if mutbl == ast::m_mutbl {
            word(s.s, "mut");
            nbsp(s);
        }
        print_expr(s, element);
        word(s.s, ",");
        word(s.s, "..");
        print_expr(s, count);
        word(s.s, "]");
        end(s);
      }

      ast::expr_struct(path, ref fields, wth) => {
        print_path(s, path, true);
        word(s.s, "{");
        commasep_cmnt(s, consistent, (*fields), print_field, get_span);
        match wth {
            Some(expr) => {
                ibox(s, indent_unit);
                word(s.s, ",");
                space(s.s);
                word(s.s, "..");
                print_expr(s, expr);
                end(s);
            }
            _ => (word(s.s, ","))
        }
        word(s.s, "}");
      }
      ast::expr_tup(ref exprs) => {
        popen(s);
        commasep_exprs(s, inconsistent, *exprs);
        if exprs.len() == 1 {
            word(s.s, ",");
        }
        pclose(s);
      }
      ast::expr_call(func, ref args, sugar) => {
        let mut base_args = copy *args;
        let blk = print_call_pre(s, sugar, &mut base_args);
        print_expr(s, func);
        print_call_post(s, sugar, &blk, &mut base_args);
      }
      ast::expr_method_call(_, func, ident, ref tys, ref args, sugar) => {
        let mut base_args = copy *args;
        let blk = print_call_pre(s, sugar, &mut base_args);
        print_expr(s, func);
        word(s.s, ".");
        print_ident(s, ident);
        if tys.len() > 0u {
            word(s.s, "::<");
            commasep(s, inconsistent, *tys, print_type);
            word(s.s, ">");
        }
        print_call_post(s, sugar, &blk, &mut base_args);
      }
      ast::expr_binary(_, op, lhs, rhs) => {
        print_expr(s, lhs);
        space(s.s);
        word_space(s, ast_util::binop_to_str(op));
        print_expr(s, rhs);
      }
      ast::expr_unary(_, op, expr) => {
        word(s.s, ast_util::unop_to_str(op));
        print_expr(s, expr);
      }
      ast::expr_addr_of(m, expr) => {
        word(s.s, "&");
        print_mutability(s, m);
        // Avoid `& &e` => `&&e`.
        match (m, &expr.node) {
            (ast::m_imm, &ast::expr_addr_of(*)) => space(s.s),
            _ => { }
        }
        print_expr(s, expr);
      }
      ast::expr_lit(lit) => print_literal(s, lit),
      ast::expr_cast(expr, ty) => {
        print_expr(s, expr);
        space(s.s);
        word_space(s, "as");
        print_type(s, ty);
      }
      ast::expr_if(test, ref blk, elseopt) => {
        print_if(s, test, blk, elseopt, false);
      }
      ast::expr_while(test, ref blk) => {
        head(s, "while");
        print_expr(s, test);
        space(s.s);
        print_block(s, blk);
      }
      ast::expr_loop(ref blk, opt_ident) => {
        for opt_ident.iter().advance |ident| {
            word(s.s, "'");
            print_ident(s, *ident);
            word_space(s, ":");
        }
        head(s, "loop");
        space(s.s);
        print_block(s, blk);
      }
      ast::expr_match(expr, ref arms) => {
        cbox(s, indent_unit);
        ibox(s, 4);
        word_nbsp(s, "match");
        print_expr(s, expr);
        space(s.s);
        bopen(s);
        let len = arms.len();
        for arms.iter().enumerate().advance |(i, arm)| {
            space(s.s);
            cbox(s, indent_unit);
            ibox(s, 0u);
            let mut first = true;
            for arm.pats.each |p| {
                if first {
                    first = false;
                } else { space(s.s); word_space(s, "|"); }
                print_refutable_pat(s, *p);
            }
            space(s.s);
            match arm.guard {
              Some(e) => {
                word_space(s, "if");
                print_expr(s, e);
                space(s.s);
              }
              None => ()
            }
            word_space(s, "=>");

            // Extract the expression from the extra block the parser adds
            // in the case of foo => expr
            if arm.body.node.view_items.is_empty() &&
                arm.body.node.stmts.is_empty() &&
                arm.body.node.rules == ast::default_blk &&
                arm.body.node.expr.is_some()
            {
                match arm.body.node.expr {
                    Some(expr) => {
                        match expr.node {
                            ast::expr_block(ref blk) => {
                                // the block will close the pattern's ibox
                                print_block_unclosed_indent(
                                    s, blk, indent_unit);
                            }
                            _ => {
                                end(s); // close the ibox for the pattern
                                print_expr(s, expr);
                            }
                        }
                        if !expr_is_simple_block(expr)
                            && i < len - 1 {
                            word(s.s, ",");
                        }
                        end(s); // close enclosing cbox
                    }
                    None => fail!()
                }
            } else {
                // the block will close the pattern's ibox
                print_block_unclosed_indent(s, &arm.body, indent_unit);
            }
        }
        bclose_(s, expr.span, indent_unit);
      }
      ast::expr_fn_block(ref decl, ref 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() {
        print_fn_block_args(s, decl);
        space(s.s);
        // }
        assert!(body.node.stmts.is_empty());
        assert!(body.node.expr.is_some());
        // we extract the block, so as not to create another set of boxes
        match body.node.expr.get().node {
            ast::expr_block(ref blk) => {
                print_block_unclosed(s, blk);
            }
            _ => {
                // this is a bare expression
                print_expr(s, body.node.expr.get());
                end(s); // 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.
        ibox(s, 0);
      }
      ast::expr_loop_body(body) => {
        print_expr(s, body);
      }
      ast::expr_do_body(body) => {
        print_expr(s, body);
      }
      ast::expr_block(ref blk) => {
        // containing cbox, will be closed by print-block at }
        cbox(s, indent_unit);
        // head-box, will be closed by print-block after {
        ibox(s, 0u);
        print_block(s, blk);
      }
      ast::expr_copy(e) => { word_space(s, "copy"); print_expr(s, e); }
      ast::expr_assign(lhs, rhs) => {
        print_expr(s, lhs);
        space(s.s);
        word_space(s, "=");
        print_expr(s, rhs);
      }
      ast::expr_assign_op(_, op, lhs, rhs) => {
        print_expr(s, lhs);
        space(s.s);
        word(s.s, ast_util::binop_to_str(op));
        word_space(s, "=");
        print_expr(s, rhs);
      }
      ast::expr_field(expr, id, ref tys) => {
        print_expr(s, expr);
        word(s.s, ".");
        print_ident(s, id);
        if tys.len() > 0u {
            word(s.s, "::<");
            commasep(s, inconsistent, *tys, print_type);
            word(s.s, ">");
        }
      }
      ast::expr_index(_, expr, index) => {
        print_expr(s, expr);
        word(s.s, "[");
        print_expr(s, index);
        word(s.s, "]");
      }
      ast::expr_path(path) => print_path(s, path, true),
      ast::expr_self => word(s.s, "self"),
      ast::expr_break(opt_ident) => {
        word(s.s, "break");
        space(s.s);
        for opt_ident.iter().advance |ident| {
            word(s.s, "'");
            print_ident(s, *ident);
            space(s.s);
        }
      }
      ast::expr_again(opt_ident) => {
        word(s.s, "loop");
        space(s.s);
        for opt_ident.iter().advance |ident| {
            word(s.s, "'");
            print_ident(s, *ident);
            space(s.s)
        }
      }
      ast::expr_ret(result) => {
        word(s.s, "return");
        match result {
          Some(expr) => { word(s.s, " "); print_expr(s, expr); }
          _ => ()
        }
      }
      ast::expr_log(lexp, expr) => {
        word(s.s, "__log");
        popen(s);
        print_expr(s, lexp);
        word(s.s, ",");
        space_if_not_bol(s);
        print_expr(s, expr);
        pclose(s);
      }
      ast::expr_inline_asm(ref a) => {
        if a.volatile {
            word(s.s, "__volatile__ asm!");
        } else {
            word(s.s, "asm!");
        }
        popen(s);
        print_string(s, a.asm);
        word_space(s, ":");
        for a.outputs.each |&(co, o)| {
            print_string(s, co);
            popen(s);
            print_expr(s, o);
            pclose(s);
            word_space(s, ",");
        }
        word_space(s, ":");
        for a.inputs.each |&(co, o)| {
            print_string(s, co);
            popen(s);
            print_expr(s, o);
            pclose(s);
            word_space(s, ",");
        }
        word_space(s, ":");
        print_string(s, a.clobbers);
        pclose(s);
      }
      ast::expr_mac(ref m) => print_mac(s, m),
      ast::expr_paren(e) => {
          popen(s);
          print_expr(s, e);
          pclose(s);
      }
    }
    (s.ann.post)(ann_node);
    end(s);
}

pub fn print_local_decl(s: @ps, loc: @ast::local) {
    print_irrefutable_pat(s, loc.node.pat);
    match loc.node.ty.node {
      ast::ty_infer => (),
      _ => { word_space(s, ":"); print_type(s, loc.node.ty); }
    }
}

pub fn print_decl(s: @ps, decl: @ast::decl) {
    maybe_print_comment(s, decl.span.lo);
    match decl.node {
      ast::decl_local(ref loc) => {
        space_if_not_bol(s);
        ibox(s, indent_unit);
        word_nbsp(s, "let");

        if loc.node.is_mutbl {
            word_nbsp(s, "mut");
        }

        fn print_local(s: @ps, loc: @ast::local) {
            ibox(s, indent_unit);
            print_local_decl(s, loc);
            end(s);
            match loc.node.init {
              Some(init) => {
                nbsp(s);
                word_space(s, "=");
                print_expr(s, init);
              }
              _ => ()
            }
        }

        print_local(s, *loc);
        end(s);
      }
      ast::decl_item(item) => print_item(s, item)
    }
}

pub fn print_ident(s: @ps, ident: ast::ident) {
    word(s.s, ident_to_str(&ident));
}

pub fn print_for_decl(s: @ps, loc: @ast::local, coll: @ast::expr) {
    print_local_decl(s, loc);
    space(s.s);
    word_space(s, "in");
    print_expr(s, coll);
}

pub fn print_path(s: @ps, path: @ast::Path, colons_before_params: bool) {
    maybe_print_comment(s, path.span.lo);
    if path.global { word(s.s, "::"); }
    let mut first = true;
    for path.idents.each |id| {
        if first { first = false; } else { word(s.s, "::"); }
        print_ident(s, *id);
    }
    if path.rp.is_some() || !path.types.is_empty() {
        if colons_before_params { word(s.s, "::"); }

        if path.rp.is_some() || !path.types.is_empty() {
            word(s.s, "<");

            for path.rp.iter().advance |r| {
                print_lifetime(s, *r);
                if !path.types.is_empty() {
                    word_space(s, ",");
                }
            }

            commasep(s, inconsistent, path.types, print_type);

            word(s.s, ">");
        }
    }
}

pub fn print_irrefutable_pat(s: @ps, pat: @ast::pat) {
    print_pat(s, pat, false)
}

pub fn print_refutable_pat(s: @ps, pat: @ast::pat) {
    print_pat(s, pat, true)
}

pub fn print_pat(s: @ps, pat: @ast::pat, refutable: bool) {
    maybe_print_comment(s, pat.span.lo);
    let ann_node = node_pat(s, pat);
    (s.ann.pre)(ann_node);
    /* Pat isn't normalized, but the beauty of it
     is that it doesn't matter */
    match pat.node {
      ast::pat_wild => word(s.s, "_"),
      ast::pat_ident(binding_mode, path, sub) => {
          if refutable {
              match binding_mode {
                  ast::bind_by_ref(mutbl) => {
                      word_nbsp(s, "ref");
                      print_mutability(s, mutbl);
                  }
                  ast::bind_infer => {}
              }
          }
          print_path(s, path, true);
          match sub {
              Some(p) => {
                  word(s.s, "@");
                  print_pat(s, p, refutable);
              }
              None => ()
          }
      }
      ast::pat_enum(path, ref args_) => {
        print_path(s, path, true);
        match *args_ {
          None => word(s.s, "(*)"),
          Some(ref args) => {
            if !args.is_empty() {
              popen(s);
              commasep(s, inconsistent, *args,
                       |s, p| print_pat(s, p, refutable));
              pclose(s);
            } else { }
          }
        }
      }
      ast::pat_struct(path, ref fields, etc) => {
        print_path(s, path, true);
        word(s.s, "{");
        fn print_field(s: @ps, f: ast::field_pat, refutable: bool) {
            cbox(s, indent_unit);
            print_ident(s, f.ident);
            word_space(s, ":");
            print_pat(s, f.pat, refutable);
            end(s);
        }
        fn get_span(f: ast::field_pat) -> codemap::span { return f.pat.span; }
        commasep_cmnt(s, consistent, *fields,
                      |s, f| print_field(s,f,refutable),
                      get_span);
        if etc {
            if fields.len() != 0u { word_space(s, ","); }
            word(s.s, "_");
        }
        word(s.s, "}");
      }
      ast::pat_tup(ref elts) => {
        popen(s);
        commasep(s, inconsistent, *elts, |s, p| print_pat(s, p, refutable));
        if elts.len() == 1 {
            word(s.s, ",");
        }
        pclose(s);
      }
      ast::pat_box(inner) => {
          word(s.s, "@");
          print_pat(s, inner, refutable);
      }
      ast::pat_uniq(inner) => {
          word(s.s, "~");
          print_pat(s, inner, refutable);
      }
      ast::pat_region(inner) => {
          word(s.s, "&");
          print_pat(s, inner, refutable);
      }
      ast::pat_lit(e) => print_expr(s, e),
      ast::pat_range(begin, end) => {
        print_expr(s, begin);
        space(s.s);
        word(s.s, "..");
        print_expr(s, end);
      }
      ast::pat_vec(ref before, slice, ref after) => {
        word(s.s, "[");
        do commasep(s, inconsistent, *before) |s, p| {
            print_pat(s, p, refutable);
        }
        for slice.iter().advance |&p| {
            if !before.is_empty() { word_space(s, ","); }
            word(s.s, "..");
            print_pat(s, p, refutable);
            if !after.is_empty() { word_space(s, ","); }
        }
        do commasep(s, inconsistent, *after) |s, p| {
            print_pat(s, p, refutable);
        }
        word(s.s, "]");
      }
    }
    (s.ann.post)(ann_node);
}

pub fn explicit_self_to_str(explicit_self: ast::explicit_self_, intr: @ident_interner) -> ~str {
    to_str(explicit_self, |a, b| { print_explicit_self(a, b); () }, intr)
}

// Returns whether it printed anything
pub fn print_explicit_self(s: @ps, explicit_self: ast::explicit_self_) -> bool {
    match explicit_self {
        ast::sty_static => { return false; }
        ast::sty_value => { word(s.s, "self"); }
        ast::sty_region(lt, m) => {
            word(s.s, "&");
            print_opt_lifetime(s, lt);
            print_mutability(s, m);
            word(s.s, "self");
        }
        ast::sty_box(m) => {
            word(s.s, "@"); print_mutability(s, m); word(s.s, "self");
        }
        ast::sty_uniq(m) => {
            word(s.s, "~"); print_mutability(s, m); word(s.s, "self");
        }
    }
    return true;
}

pub fn print_fn(s: @ps,
                decl: &ast::fn_decl,
                purity: Option<ast::purity>,
                abis: AbiSet,
                name: ast::ident,
                generics: &ast::Generics,
                opt_explicit_self: Option<ast::explicit_self_>,
                vis: ast::visibility) {
    head(s, "");
    print_fn_header_info(s, opt_explicit_self, purity, abis, ast::Many, None, vis);
    nbsp(s);
    print_ident(s, name);
    print_generics(s, generics);
    print_fn_args_and_ret(s, decl, opt_explicit_self);
}

pub fn print_fn_args(s: @ps, decl: &ast::fn_decl,
                 opt_explicit_self: Option<ast::explicit_self_>) {
    // It is unfortunate to duplicate the commasep logic, but we want the
    // self type and the args all in the same box.
    box(s, 0u, inconsistent);
    let mut first = true;
    for opt_explicit_self.iter().advance |explicit_self| {
        first = !print_explicit_self(s, *explicit_self);
    }

    for decl.inputs.each |arg| {
        if first { first = false; } else { word_space(s, ","); }
        print_arg(s, *arg);
    }

    end(s);
}

pub fn print_fn_args_and_ret(s: @ps, decl: &ast::fn_decl,
                             opt_explicit_self: Option<ast::explicit_self_>) {
    popen(s);
    print_fn_args(s, decl, opt_explicit_self);
    pclose(s);

    maybe_print_comment(s, decl.output.span.lo);
    match decl.output.node {
        ast::ty_nil => {}
        _ => {
            space_if_not_bol(s);
            word_space(s, "->");
            print_type(s, decl.output);
        }
    }
}

pub fn print_fn_block_args(s: @ps, decl: &ast::fn_decl) {
    word(s.s, "|");
    print_fn_args(s, decl, None);
    word(s.s, "|");

    match decl.output.node {
        ast::ty_infer => {}
        _ => {
            space_if_not_bol(s);
            word_space(s, "->");
            print_type(s, decl.output);
        }
    }

    maybe_print_comment(s, decl.output.span.lo);
}

pub fn print_bounds(s: @ps, bounds: @OptVec<ast::TyParamBound>) {
    if !bounds.is_empty() {
        word(s.s, ":");
        let mut first = true;
        for bounds.each |bound| {
            nbsp(s);
            if first {
                first = false;
            } else {
                word_space(s, "+");
            }

            match *bound {
                TraitTyParamBound(tref) => print_trait_ref(s, tref),
                RegionTyParamBound => word(s.s, "'static"),
            }
        }
    }
}

pub fn print_lifetime(s: @ps, lifetime: &ast::Lifetime) {
    word(s.s, "'");
    print_ident(s, lifetime.ident);
}

pub fn print_generics(s: @ps, generics: &ast::Generics) {
    let total = generics.lifetimes.len() + generics.ty_params.len();
    if total > 0 {
        word(s.s, "<");
        fn print_item(s: @ps, generics: &ast::Generics, idx: uint) {
            if idx < generics.lifetimes.len() {
                let lifetime = generics.lifetimes.get(idx);
                print_lifetime(s, lifetime);
            } else {
                let idx = idx - generics.lifetimes.len();
                let param = generics.ty_params.get(idx);
                print_ident(s, param.ident);
                print_bounds(s, param.bounds);
            }
        }

        let mut ints = ~[];
        for uint::range(0, total) |i| {
            ints.push(i);
        }

        commasep(s, inconsistent, ints,
                 |s, i| print_item(s, generics, i));
        word(s.s, ">");
    }
}

pub fn print_meta_item(s: @ps, item: @ast::meta_item) {
    ibox(s, indent_unit);
    match item.node {
      ast::meta_word(name) => word(s.s, name),
      ast::meta_name_value(name, value) => {
        word_space(s, name);
        word_space(s, "=");
        print_literal(s, @value);
      }
      ast::meta_list(name, ref items) => {
        word(s.s, name);
        popen(s);
        commasep(
            s,
            consistent,
            /* FIXME (#2543) */ copy *items,
            print_meta_item
        );
        pclose(s);
      }
    }
    end(s);
}

pub fn print_view_path(s: @ps, vp: @ast::view_path) {
    match vp.node {
      ast::view_path_simple(ident, path, _) => {
        if path.idents[path.idents.len()-1u] != ident {
            print_ident(s, ident);
            space(s.s);
            word_space(s, "=");
        }
        print_path(s, path, false);
      }

      ast::view_path_glob(path, _) => {
        print_path(s, path, false);
        word(s.s, "::*");
      }

      ast::view_path_list(path, ref idents, _) => {
        print_path(s, path, false);
        word(s.s, "::{");
        do commasep(s, inconsistent, (*idents)) |s, w| {
            print_ident(s, w.node.name);
        }
        word(s.s, "}");
      }
    }
}

pub fn print_view_paths(s: @ps, vps: &[@ast::view_path]) {
    commasep(s, inconsistent, vps, print_view_path);
}

pub fn print_view_item(s: @ps, item: @ast::view_item) {
    hardbreak_if_not_bol(s);
    maybe_print_comment(s, item.span.lo);
    print_outer_attributes(s, item.attrs);
    print_visibility(s, item.vis);
    match item.node {
        ast::view_item_extern_mod(id, ref mta, _) => {
            head(s, "extern mod");
            print_ident(s, id);
            if !mta.is_empty() {
                popen(s);
                commasep(s, consistent, *mta, print_meta_item);
                pclose(s);
            }
        }

        ast::view_item_use(ref vps) => {
            head(s, "use");
            print_view_paths(s, *vps);
        }
    }
    word(s.s, ";");
    end(s); // end inner head-block
    end(s); // end outer head-block
}

pub fn print_mutability(s: @ps, mutbl: ast::mutability) {
    match mutbl {
      ast::m_mutbl => word_nbsp(s, "mut"),
      ast::m_const => word_nbsp(s, "const"),
      ast::m_imm => {/* nothing */ }
    }
}

pub fn print_mt(s: @ps, mt: &ast::mt) {
    print_mutability(s, mt.mutbl);
    print_type(s, mt.ty);
}

pub fn print_arg(s: @ps, input: ast::arg) {
    ibox(s, indent_unit);
    if input.is_mutbl {
        word_space(s, "mut");
    }
    match input.ty.node {
      ast::ty_infer => print_irrefutable_pat(s, input.pat),
      _ => {
        match input.pat.node {
            ast::pat_ident(_, path, _) if
                path.idents.len() == 1 &&
                path.idents[0] == parse::token::special_idents::invalid => {
                // Do nothing.
            }
            _ => {
                print_irrefutable_pat(s, input.pat);
                word(s.s, ":");
                space(s.s);
            }
        }
        print_type(s, input.ty);
      }
    }
    end(s);
}

pub fn print_ty_fn(s: @ps,
                   opt_abis: Option<AbiSet>,
                   opt_sigil: Option<ast::Sigil>,
                   opt_region: Option<@ast::Lifetime>,
                   purity: ast::purity,
                   onceness: ast::Onceness,
                   decl: &ast::fn_decl,
                   id: Option<ast::ident>,
                   generics: Option<&ast::Generics>,
                   opt_explicit_self: Option<ast::explicit_self_>) {
    ibox(s, 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.
    print_extern_opt_abis(s, opt_abis);
    print_opt_sigil(s, opt_sigil);
    print_opt_lifetime(s, opt_region);
    print_purity(s, purity);
    print_onceness(s, onceness);
    word(s.s, "fn");
    match id { Some(id) => { word(s.s, " "); print_ident(s, id); } _ => () }
    match generics { Some(g) => print_generics(s, g), _ => () }
    zerobreak(s.s);

    popen(s);
    // It is unfortunate to duplicate the commasep logic, but we want the
    // self type and the args all in the same box.
    box(s, 0u, inconsistent);
    let mut first = true;
    for opt_explicit_self.iter().advance |explicit_self| {
        first = !print_explicit_self(s, *explicit_self);
    }
    for decl.inputs.each |arg| {
        if first { first = false; } else { word_space(s, ","); }
        print_arg(s, *arg);
    }
    end(s);
    pclose(s);

    maybe_print_comment(s, decl.output.span.lo);

    match decl.output.node {
        ast::ty_nil => {}
        _ => {
            space_if_not_bol(s);
            ibox(s, indent_unit);
            word_space(s, "->");
            if decl.cf == ast::noreturn { word_nbsp(s, "!"); }
            else { print_type(s, decl.output); }
            end(s);
        }
    }

    end(s);
}

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

pub fn print_remaining_comments(s: @ps) {
    // If there aren't any remaining comments, then we need to manually
    // make sure there is a line break at the end.
    if next_comment(s).is_none() { hardbreak(s.s); }
    loop {
        match next_comment(s) {
          Some(ref cmnt) => {
            print_comment(s, cmnt);
            s.cur_cmnt_and_lit.cur_cmnt += 1u;
          }
          _ => break
        }
    }
}

pub fn print_literal(s: @ps, lit: @ast::lit) {
    maybe_print_comment(s, lit.span.lo);
    match next_lit(s, lit.span.lo) {
      Some(ref ltrl) => {
        word(s.s, (*ltrl).lit);
        return;
      }
      _ => ()
    }
    match lit.node {
      ast::lit_str(st) => print_string(s, st),
      ast::lit_int(ch, ast::ty_char) => {
        word(s.s, ~"'" + char::escape_default(ch as char) + "'");
      }
      ast::lit_int(i, t) => {
        if i < 0_i64 {
            word(s.s,
                 ~"-" + u64::to_str_radix(-i as u64, 10u)
                 + ast_util::int_ty_to_str(t));
        } else {
            word(s.s,
                 u64::to_str_radix(i as u64, 10u)
                 + ast_util::int_ty_to_str(t));
        }
      }
      ast::lit_uint(u, t) => {
        word(s.s,
             u64::to_str_radix(u, 10u)
             + ast_util::uint_ty_to_str(t));
      }
      ast::lit_int_unsuffixed(i) => {
        if i < 0_i64 {
            word(s.s, ~"-" + u64::to_str_radix(-i as u64, 10u));
        } else {
            word(s.s, u64::to_str_radix(i as u64, 10u));
        }
      }
      ast::lit_float(f, t) => {
        word(s.s, f.to_owned() + ast_util::float_ty_to_str(t));
      }
      ast::lit_float_unsuffixed(f) => word(s.s, f),
      ast::lit_nil => word(s.s, "()"),
      ast::lit_bool(val) => {
        if val { word(s.s, "true"); } else { word(s.s, "false"); }
      }
    }
}

pub fn lit_to_str(l: @ast::lit) -> ~str {
    return to_str(l, print_literal, parse::token::mk_fake_ident_interner());
}

pub fn next_lit(s: @ps, pos: BytePos) -> Option<comments::lit> {
    match s.literals {
      Some(ref lits) => {
        while s.cur_cmnt_and_lit.cur_lit < lits.len() {
            let ltrl = /*bad*/ copy (*lits)[s.cur_cmnt_and_lit.cur_lit];
            if ltrl.pos > pos { return None; }
            s.cur_cmnt_and_lit.cur_lit += 1u;
            if ltrl.pos == pos { return Some(ltrl); }
        }
        return None;
      }
      _ => return None
    }
}

pub fn maybe_print_comment(s: @ps, pos: BytePos) {
    loop {
        match next_comment(s) {
          Some(ref cmnt) => {
            if (*cmnt).pos < pos {
                print_comment(s, cmnt);
                s.cur_cmnt_and_lit.cur_cmnt += 1u;
            } else { break; }
          }
          _ => break
        }
    }
}

pub fn print_comment(s: @ps, cmnt: &comments::cmnt) {
    match cmnt.style {
      comments::mixed => {
        assert_eq!(cmnt.lines.len(), 1u);
        zerobreak(s.s);
        word(s.s, cmnt.lines[0]);
        zerobreak(s.s);
      }
      comments::isolated => {
        pprust::hardbreak_if_not_bol(s);
        for cmnt.lines.each |line| {
            // Don't print empty lines because they will end up as trailing
            // whitespace
            if !line.is_empty() { word(s.s, *line); }
            hardbreak(s.s);
        }
      }
      comments::trailing => {
        word(s.s, " ");
        if cmnt.lines.len() == 1u {
            word(s.s, cmnt.lines[0]);
            hardbreak(s.s);
        } else {
            ibox(s, 0u);
            for cmnt.lines.each |line| {
                if !line.is_empty() { word(s.s, *line); }
                hardbreak(s.s);
            }
            end(s);
        }
      }
      comments::blank_line => {
        // We need to do at least one, possibly two hardbreaks.
        let is_semi =
            match s.s.last_token() {
              pp::STRING(s, _) => ";" == s,
              _ => false
            };
        if is_semi || is_begin(s) || is_end(s) { hardbreak(s.s); }
        hardbreak(s.s);
      }
    }
}

pub fn print_string(s: @ps, st: &str) {
    word(s.s, "\"");
    word(s.s, st.escape_default());
    word(s.s, "\"");
}

pub fn to_str<T: Copy>(t: T, f: @fn(@ps, T), intr: @ident_interner) -> ~str {
    do io::with_str_writer |wr| {
        let s = rust_printer(wr, intr);
        f(s, copy t);
        eof(s.s);
    }
}

pub fn next_comment(s: @ps) -> Option<comments::cmnt> {
    match s.comments {
      Some(ref cmnts) => {
        if s.cur_cmnt_and_lit.cur_cmnt < cmnts.len() {
            return Some(copy cmnts[s.cur_cmnt_and_lit.cur_cmnt]);
        } else { return None::<comments::cmnt>; }
      }
      _ => return None::<comments::cmnt>
    }
}

pub fn print_opt_purity(s: @ps, opt_purity: Option<ast::purity>) {
    match opt_purity {
        Some(ast::impure_fn) => { }
        Some(purity) => {
            word_nbsp(s, purity_to_str(purity));
        }
        None => {}
    }
}

pub fn print_extern_opt_abis(s: @ps, opt_abis: Option<AbiSet>) {
    match opt_abis {
        Some(abis) => {
            word_nbsp(s, "extern");
            word_nbsp(s, abis.to_str());
        }
        None => {}
    };
}

pub fn print_opt_sigil(s: @ps, opt_sigil: Option<ast::Sigil>) {
    match opt_sigil {
        Some(ast::BorrowedSigil) => { word(s.s, "&"); }
        Some(ast::OwnedSigil) => { word(s.s, "~"); }
        Some(ast::ManagedSigil) => { word(s.s, "@"); }
        None => {}
    };
}

pub fn print_fn_header_info(s: @ps,
                            _opt_explicit_self: Option<ast::explicit_self_>,
                            opt_purity: Option<ast::purity>,
                            abis: AbiSet,
                            onceness: ast::Onceness,
                            opt_sigil: Option<ast::Sigil>,
                            vis: ast::visibility) {
    word(s.s, visibility_qualified(vis, ""));

    if abis != AbiSet::Rust() {
        word_nbsp(s, "extern");
        word_nbsp(s, abis.to_str());

        if opt_purity != Some(ast::extern_fn) {
            print_opt_purity(s, opt_purity);
        }
    } else {
        print_opt_purity(s, opt_purity);
    }

    print_onceness(s, onceness);
    word(s.s, "fn");
    print_opt_sigil(s, opt_sigil);
}

pub fn opt_sigil_to_str(opt_p: Option<ast::Sigil>) -> ~str {
    match opt_p {
      None => ~"fn",
      Some(p) => fmt!("fn%s", p.to_str())
    }
}

pub fn purity_to_str(p: ast::purity) -> ~str {
    match p {
      ast::impure_fn => ~"impure",
      ast::unsafe_fn => ~"unsafe",
      ast::pure_fn => ~"pure",
      ast::extern_fn => ~"extern"
    }
}

pub fn onceness_to_str(o: ast::Onceness) -> ~str {
    match o {
        ast::Once => ~"once",
        ast::Many => ~"many"
    }
}

pub fn print_purity(s: @ps, p: ast::purity) {
    match p {
      ast::impure_fn => (),
      _ => word_nbsp(s, purity_to_str(p))
    }
}

pub fn print_onceness(s: @ps, o: ast::Onceness) {
    match o {
        ast::Once => { word_nbsp(s, "once"); }
        ast::Many => {}
    }
}

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

    use ast;
    use ast_util;
    use codemap;
    use core::cmp::Eq;
    use core::option::None;
    use parse::token;

    fn string_check<T:Eq> (given : &T, expected: &T) {
        if !(given == expected) {
            fail!("given %?, expected %?", given, expected);
        }
    }

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

        let decl = ast::fn_decl {
            inputs: ~[],
            output: @ast::Ty {id: 0,
                              node: ast::ty_nil,
                              span: codemap::dummy_sp()},
            cf: ast::return_val
        };
        let generics = ast_util::empty_generics();
        assert_eq!(&fun_to_str(&decl, ast::impure_fn, abba_ident,
                               None, &generics, token::get_ident_interner()),
                   &~"fn abba()");
    }

    #[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: ~[],
            // making this up as I go.... ?
            kind: ast::tuple_variant_kind(~[]),
            id: 0,
            disr_expr: None,
            vis: ast::public,
        });

        let varstr = variant_to_str(&var,token::get_ident_interner());
        assert_eq!(&varstr,&~"pub principal_skinner");
    }
}