rust/src/comp/pretty/pprust.rs

import std._vec;
import std._str;
import std.io;
import std.option;
import front.ast;
import front.lexer;
import pp.end; import pp.wrd; import pp.space; import pp.line;

const uint indent_unit = 4u;
const int as_prec = 5;
const uint default_columns = 78u;

type ps = @rec(pp.ps s,
               option.t[vec[lexer.cmnt]] comments,
               mutable uint cur_cmnt);

impure fn print_file(ast._mod _mod, str filename, io.writer out) {
    auto cmnts = lexer.gather_comments(filename);
    auto s = @rec(s=pp.mkstate(out, default_columns),
                  comments=option.some[vec[lexer.cmnt]](cmnts),
                  mutable cur_cmnt=0u);
    print_mod(s, _mod);
}

fn ty_to_str(&@ast.ty ty) -> str {
    auto writer = io.string_writer();
    auto s = @rec(s=pp.mkstate(writer.get_writer(), 0u),
                  comments=option.none[vec[lexer.cmnt]],
                  mutable cur_cmnt=0u);
    print_type(s, ty);
    ret writer.get_str();
}

impure fn hbox(ps s) {
    pp.hbox(s.s, indent_unit);
}
impure fn wrd1(ps s, str word) {
    wrd(s.s, word);
    space(s.s);
}
impure fn popen(ps s) {
    wrd(s.s, "(");
    pp.abox(s.s);
}
impure fn popen_h(ps s) {
    wrd(s.s, "(");
    pp.hbox(s.s, 0u);
}
impure fn pclose(ps s) {
    end(s.s);
    wrd(s.s, ")");
}
impure fn bopen(ps s) {
    wrd(s.s, "{");
    pp.vbox(s.s, indent_unit);
    line(s.s);
}
impure fn bclose(ps s) {
    end(s.s);
    pp.cwrd(s.s, "}");
}
impure fn bclose_c(ps s, util.common.span span) {
    maybe_print_comment(s, span.hi);
    bclose(s);
}
impure fn commasep[IN](ps s, vec[IN] elts, impure fn (ps, &IN) op) {
    auto first = true;
    for (IN elt in elts) {
        if (first) {first = false;}
        else {wrd1(s, ",");}
        op(s, elt);
    }
}

impure fn print_mod(ps s, ast._mod _mod) {
    for (@ast.view_item vitem in _mod.view_items) {print_view_item(s, vitem);}
    line(s.s);
    for (@ast.item item in _mod.items) {print_item(s, item);}
    print_remaining_comments(s);
}

impure fn print_type(ps s, &@ast.ty ty) {
    maybe_print_comment(s, ty.span.lo);
    hbox(s);
    alt (ty.node) {
        case (ast.ty_nil) {wrd(s.s, "()");}
        case (ast.ty_bool) {wrd(s.s, "bool");}
        case (ast.ty_int) {wrd(s.s, "int");}
        case (ast.ty_uint) {wrd(s.s, "uint");}
        case (ast.ty_machine(?tm)) {wrd(s.s, util.common.ty_mach_to_str(tm));}
        case (ast.ty_char) {wrd(s.s, "char");}
        case (ast.ty_str) {wrd(s.s, "str");}
        case (ast.ty_box(?mt)) {wrd(s.s, "@"); print_mt(s, mt);}
        case (ast.ty_vec(?mt)) {
            wrd(s.s, "vec["); print_mt(s, mt); wrd(s.s, "]");
        }
        case (ast.ty_port(?t)) {
            wrd(s.s, "port["); print_type(s, t); wrd(s.s, "]");
        }
        case (ast.ty_chan(?t)) {
            wrd(s.s, "chan["); print_type(s, t); wrd(s.s, "]");
        }
        case (ast.ty_type) {wrd(s.s, "type");}
        case (ast.ty_tup(?elts)) {
            wrd(s.s, "tup");
            popen(s);
            auto f = print_mt;
            commasep[ast.mt](s, elts, f);
            pclose(s);
        }
        case (ast.ty_rec(?fields)) {
            wrd(s.s, "rec");
            popen(s);
            impure fn print_field(ps s, &ast.ty_field f) {
                hbox(s);
                print_mt(s, f.mt);
                space(s.s);
                wrd(s.s, f.ident);
                end(s.s);
            }
            auto f = print_field;
            commasep[ast.ty_field](s, fields, f);
            pclose(s);
        }
        case (ast.ty_obj(?methods)) {
            wrd1(s, "obj");
            bopen(s);
            for (ast.ty_method m in methods) {
                hbox(s);
                print_ty_fn(s, m.proto, option.some[str](m.ident),
                            m.inputs, m.output);
                wrd(s.s, ";");
                end(s.s);
                line(s.s);
            }
            bclose_c(s, ty.span);
        }
        case (ast.ty_fn(?proto,?inputs,?output)) {
            print_ty_fn(s, proto, option.none[str], inputs, output);
        }
        case (ast.ty_path(?path,_)) {
            print_path(s, path);
        }
    }
    end(s.s);
}

impure fn print_item(ps s, @ast.item item) {
    maybe_print_comment(s, item.span.lo);
    hbox(s);
    alt (item.node) {
        case (ast.item_const(?id, ?ty, ?expr, _, _)) {
            wrd1(s, "const");
            print_type(s, ty);
            space(s.s);
            wrd1(s, id);
            wrd1(s, "=");
            print_expr(s, expr);
            wrd(s.s, ";");
        }
        case (ast.item_fn(?name,?_fn,?typarams,_,_)) {
            print_fn(s, _fn.decl, name, typarams);
            space(s.s);
            print_block(s, _fn.body);
        }
        case (ast.item_mod(?id,?_mod,_)) {
            wrd1(s, "mod");
            wrd1(s, id);
            bopen(s);
            for (@ast.item itm in _mod.items) {print_item(s, itm);}
            bclose_c(s, item.span);
        }
        case (ast.item_native_mod(?id,?nmod,_)) {
            wrd1(s, "native");
            alt (nmod.abi) {
                case (ast.native_abi_rust) {wrd1(s, "\"rust\"");}
                case (ast.native_abi_cdecl) {wrd1(s, "\"cdecl\"");}
            }
            wrd1(s, "mod");
            wrd1(s, id);
            bopen(s);
            for (@ast.native_item item in nmod.items) {
                hbox(s);
                maybe_print_comment(s, item.span.lo);
                alt (item.node) {
                    case (ast.native_item_ty(?id,_)) {
                        wrd1(s, "type");
                        wrd(s.s, id);
                    }
                    case (ast.native_item_fn(?id,?lname,?decl,
                                             ?typarams,_,_)) {
                        print_fn(s, decl, id, typarams);
                        alt (lname) {
                            case (option.none[str]) {}
                            case (option.some[str](?ss)) {
                                print_string(s, ss);
                            }
                        }
                    }
                }
                wrd(s.s, ";");
                end(s.s);
            }
            bclose_c(s, item.span);
        }
        case (ast.item_ty(?id,?ty,?params,_,_)) {
            wrd1(s, "type");
            wrd(s.s, id);
            print_type_params(s, params);
            space(s.s);
            wrd1(s, "=");
            print_type(s, ty);
            wrd(s.s, ";");
        }
        case (ast.item_tag(?id,?variants,?params,_)) {
            wrd1(s, "tag");
            wrd(s.s, id);
            print_type_params(s, params);
            space(s.s);
            bopen(s);
            for (ast.variant v in variants) {
                wrd(s.s, v.name);
                if (_vec.len[ast.variant_arg](v.args) > 0u) {
                    popen(s);
                    impure fn print_variant_arg(ps s, &ast.variant_arg arg) {
                        print_type(s, arg.ty);
                    }
                    auto f = print_variant_arg;
                    commasep[ast.variant_arg](s, v.args, f);
                    pclose(s);
                }
                wrd(s.s, ";");
                line(s.s);
            }
            bclose_c(s, item.span);
        }
        case (ast.item_obj(?id,?_obj,?params,_,_)) {
            wrd1(s, "obj");
            wrd(s.s, id);
            print_type_params(s, params);
            popen(s);
            impure fn print_field(ps s, &ast.obj_field field) {
                hbox(s);
                print_type(s, field.ty);
                space(s.s);
                wrd(s.s, field.ident);
                end(s.s);
            }
            auto f = print_field;
            commasep[ast.obj_field](s, _obj.fields, f);
            pclose(s);
            space(s.s);
            bopen(s);
            for (@ast.method meth in _obj.methods) {
                hbox(s);
                let vec[ast.ty_param] typarams = vec();
                maybe_print_comment(s, meth.span.lo);
                print_fn(s, meth.node.meth.decl, meth.node.ident, typarams);
                space(s.s);
                print_block(s, meth.node.meth.body);
                end(s.s);
                line(s.s);
            }
            alt (_obj.dtor) {
                case (option.some[ast.block](?dtor)) {
                    hbox(s);
                    wrd1(s, "close");
                    print_block(s, dtor);
                    end(s.s);
                    line(s.s);
                }
                case (_) {}
            }
            bclose_c(s, item.span);
        }
    }
    end(s.s);
    line(s.s);
    line(s.s);
}

impure fn print_block(ps s, ast.block blk) {
    auto cur_line = 0u;
    maybe_print_comment(s, blk.span.lo);
    bopen(s);
    for (@ast.stmt st in blk.node.stmts) {
        if (cur_line != 0u && blk.span.lo.line > cur_line + 1u) {
            line(s.s);
        }
        cur_line = blk.span.hi.line;
        maybe_print_comment(s, st.span.lo);
        alt (st.node) {
            case (ast.stmt_decl(?decl)) {print_decl(s, decl);}
            case (ast.stmt_expr(?expr)) {print_expr(s, expr);}
        }
        if (front.parser.stmt_ends_with_semi(st)) {wrd(s.s, ";");}
        if (!maybe_print_stmt_comment(s, st.span)) {line(s.s);}
    }
    alt (blk.node.expr) {
        case (option.some[@ast.expr](?expr)) {
            if (cur_line != 0u && blk.span.lo.line > cur_line + 1u) {
                line(s.s);
            }
            print_expr(s, expr);
            if (!maybe_print_stmt_comment(s, expr.span)) {line(s.s);}
        }
        case (_) {}
    }
    bclose_c(s, blk.span);
}

impure fn print_literal(ps s, @ast.lit lit) {
    maybe_print_comment(s, lit.span.lo);
    alt (lit.node) {
        case (ast.lit_str(?st)) {print_string(s, st);}
        case (ast.lit_char(?ch)) {
            wrd(s.s, "'" + escape_str(_str.from_bytes(vec(ch as u8)), '\'')
                + "'");
        }
        case (ast.lit_int(?val)) {
            wrd(s.s, util.common.istr(val));
        }
        case (ast.lit_uint(?val)) { // FIXME clipping? uistr?
            wrd(s.s, util.common.istr(val as int) + "u");
        }
        case (ast.lit_float(?fstr)) {
            wrd(s.s, fstr);
        }
        case (ast.lit_mach_int(?mach,?val)) {
            wrd(s.s, util.common.istr(val as int));
            wrd(s.s, util.common.ty_mach_to_str(mach));
        }
        case (ast.lit_nil) {wrd(s.s, "()");}
        case (ast.lit_bool(?val)) {
            if (val) {wrd(s.s, "true");} else {wrd(s.s, "false");}
        }
    }
}

impure fn print_expr(ps s, &@ast.expr expr) {
    maybe_print_comment(s, expr.span.lo);
    auto pe = print_expr;
    hbox(s);
    alt (expr.node) {
        case (ast.expr_vec(?exprs,?mut,_)) {
            if (mut == ast.mut) {
                wrd1(s, "mutable");
            }
            wrd(s.s, "vec");
            popen(s);
            commasep[@ast.expr](s, exprs, pe);
            pclose(s);
        }
        case (ast.expr_tup(?exprs,_)) {
            impure fn printElt(ps s, &ast.elt elt) {
                hbox(s);
                if (elt.mut == ast.mut) {wrd1(s, "mutable");}
                print_expr(s, elt.expr);
                end(s.s);
            }
            wrd(s.s, "tup");
            popen(s);
            auto f = printElt;
            commasep[ast.elt](s, exprs, f);
            pclose(s);
        }
        case (ast.expr_rec(?fields,?wth,_)) {
            impure fn print_field(ps s, &ast.field field) {
                hbox(s);
                if (field.mut == ast.mut) {wrd1(s, "mutable");}
                wrd(s.s, field.ident);
                wrd(s.s, "=");
                print_expr(s, field.expr);
                end(s.s);
            }
            wrd(s.s, "rec");
            popen(s);
            auto f = print_field;
            commasep[ast.field](s, fields, f);
            alt (wth) {
                case (option.some[@ast.expr](?expr)) {
                    if (_vec.len[ast.field](fields) > 0u) {space(s.s);}
                    hbox(s);
                    wrd1(s, "with");
                    print_expr(s, expr);
                    end(s.s);
                }
                case (_) {}
            }
            pclose(s);
        }
        case (ast.expr_call(?func,?args,_)) {
            print_expr(s, func);
            popen(s);
            commasep[@ast.expr](s, args, pe);
            pclose(s);
        }
        case (ast.expr_bind(?func,?args,_)) {
            impure fn print_opt(ps s, &option.t[@ast.expr] expr) {
                alt (expr) {
                    case (option.some[@ast.expr](?expr)) {
                        print_expr(s, expr);
                    }
                    case (_) {wrd(s.s, "_");}
                }
            }
            wrd1(s, "bind");
            print_expr(s, func);
            popen(s);
            auto f = print_opt;
            commasep[option.t[@ast.expr]](s, args, f);
            pclose(s);
        }
        case (ast.expr_binary(?op,?lhs,?rhs,_)) {
            auto prec = operator_prec(op);
            print_maybe_parens(s, lhs, prec);
            space(s.s);
            wrd1(s, ast.binop_to_str(op));
            print_maybe_parens(s, rhs, prec + 1);
        }
        case (ast.expr_unary(?op,?expr,_)) {
            wrd(s.s, ast.unop_to_str(op));
            print_expr(s, expr);
        }
        case (ast.expr_lit(?lit,_)) {
            print_literal(s, lit);
        }
        case (ast.expr_cast(?expr,?ty,_)) {
            print_maybe_parens(s, expr, as_prec);
            space(s.s);
            wrd1(s, "as");
            print_type(s, ty);
        }
        case (ast.expr_if(?test,?block,?elseopt,_)) {
            wrd1(s, "if");
            popen_h(s);
            print_expr(s, test);
            pclose(s);
            space(s.s);
            print_block(s, block);
            alt (elseopt) {
                case (option.some[@ast.expr](?_else)) {
                    space(s.s);
                    wrd1(s, "else");
                    print_expr(s, _else);
                }
                case (_) { /* fall through */ }
            }
        }
        case (ast.expr_while(?test,?block,_)) {
            wrd1(s, "while");
            popen_h(s);
            print_expr(s, test);
            pclose(s);
            space(s.s);
            print_block(s, block);
        }
        case (ast.expr_for(?decl,?expr,?block,_)) {
            wrd1(s, "for");
            popen_h(s);
            print_for_decl(s, decl);
            space(s.s);
            wrd1(s, "in");
            print_expr(s, expr);
            pclose(s);
            space(s.s);
            print_block(s, block);
        }
        case (ast.expr_for_each(?decl,?expr,?block,_)) {
            wrd1(s, "for each");
            popen_h(s);
            print_for_decl(s, decl);
            space(s.s);
            wrd1(s, "in");
            print_expr(s, expr);
            pclose(s);
            space(s.s);
            print_block(s, block);
        }
        case (ast.expr_do_while(?block,?expr,_)) {
            wrd1(s, "do");
            space(s.s);
            print_block(s, block);
            space(s.s);
            wrd1(s, "while");
            popen_h(s);
            print_expr(s, expr);
            pclose(s);
        }
        case (ast.expr_alt(?expr,?arms,_)) {
            wrd1(s, "alt");
            popen_h(s);
            print_expr(s, expr);
            pclose(s);
            space(s.s);
            bopen(s);
            for (ast.arm arm in arms) {
                hbox(s);
                wrd1(s, "case");
                popen_h(s);
                print_pat(s, arm.pat);
                pclose(s);
                space(s.s);
                print_block(s, arm.block);
                end(s.s);
                line(s.s);
            }
            bclose_c(s, expr.span);
        }
        case (ast.expr_block(?block,_)) {
            print_block(s, block);
        }
        case (ast.expr_assign(?lhs,?rhs,_)) {
            print_expr(s, lhs);
            space(s.s);
            wrd1(s, "=");
            print_expr(s, rhs);
        }
        case (ast.expr_assign_op(?op,?lhs,?rhs,_)) {
            print_expr(s, lhs);
            space(s.s);
            wrd(s.s, ast.binop_to_str(op));
            wrd1(s, "=");
            print_expr(s, rhs);
        }
        case (ast.expr_send(?lhs, ?rhs, _)) {
            print_expr(s, lhs);
            space(s.s);
            wrd1(s, "<|");
            print_expr(s, rhs);
        }
        case (ast.expr_recv(?lhs, ?rhs, _)) {
            print_expr(s, lhs);
            space(s.s);
            wrd1(s, "<-");
            print_expr(s, rhs);
        }
        case (ast.expr_field(?expr,?id,_)) {
            print_expr(s, expr);
            wrd(s.s, ".");
            wrd(s.s, id);
        }
        case (ast.expr_index(?expr,?index,_)) {
            print_expr(s, expr);
            wrd(s.s, ".");
            popen_h(s);
            print_expr(s, index);
            pclose(s);
        }
        case (ast.expr_path(?path,_,_)) {
            print_path(s, path);
        }
        case (ast.expr_fail) {
            wrd(s.s, "fail");
        }
        case (ast.expr_ret(?result)) {
            wrd(s.s, "ret");
            alt (result) {
                case (option.some[@ast.expr](?expr)) {
                    space(s.s);
                    print_expr(s, expr);
                }
                case (_) {}
            }
        }
        case (ast.expr_put(?result)) {
            wrd(s.s, "put");
            alt (result) {
                case (option.some[@ast.expr](?expr)) {
                    space(s.s);
                    print_expr(s, expr);
                }
                case (_) {}
            }
        }
        case (ast.expr_be(?result)) {
            wrd1(s, "be");
            print_expr(s, result);
        }
        case (ast.expr_log(?expr)) {
            wrd1(s, "log");
            print_expr(s, expr);
        }
        case (ast.expr_check_expr(?expr)) {
            wrd1(s, "check");
            popen_h(s);
            print_expr(s, expr);
            pclose(s);
        }
        case (ast.expr_ext(?path, ?args, ?body, _, _)) {
            wrd(s.s, "#");
            print_path(s, path);
            if (_vec.len[@ast.expr](args) > 0u) {
                popen(s);
                commasep[@ast.expr](s, args, pe);
                pclose(s);
            }
            // FIXME: extension 'body'
        }
        case (ast.expr_port(_)) {
            wrd(s.s, "port");
            popen_h(s);
            pclose(s);
        }
        case (ast.expr_chan(?expr, _)) {
            wrd(s.s, "chan");
            popen_h(s);
            print_expr(s, expr);
            pclose(s);
        }
    }
    end(s.s);
}

impure fn print_decl(ps s, @ast.decl decl) {
    maybe_print_comment(s, decl.span.lo);
    hbox(s);
    alt (decl.node) {
        case (ast.decl_local(?loc)) {
            alt (loc.ty) {
                case (option.some[@ast.ty](?ty)) {
                    wrd1(s, "let");
                    print_type(s, ty);
                    space(s.s);
                }
                case (_) {
                    wrd1(s, "auto");
                }
            }
            wrd(s.s, loc.ident);
            alt (loc.init) {
                case (option.some[ast.initializer](?init)) {
                    space(s.s);
                    alt (init.op) {
                        case (ast.init_assign) {
                            wrd1(s, "=");
                        }
                        case (ast.init_recv) {
                            wrd1(s, "<-");
                        }
                    }
                    print_expr(s, init.expr);
                }
                case (_) {}
            }
        }
        case (ast.decl_item(?item)) {
            print_item(s, item);
        }
    }
    end(s.s);
}

impure fn print_for_decl(ps s, @ast.decl decl) {
    alt (decl.node) {
        case (ast.decl_local(?loc)) {
            print_type(s, option.get[@ast.ty](loc.ty));
            space(s.s);
            wrd(s.s, loc.ident);
        }
    }
}

impure fn print_path(ps s, ast.path path) {
    maybe_print_comment(s, path.span.lo);
    auto first = true;
    for (str id in path.node.idents) {
        if (first) {first = false;}
        else {wrd(s.s, ".");}
        wrd(s.s, id);
    }
    if (_vec.len[@ast.ty](path.node.types) > 0u) {
        wrd(s.s, "[");
        auto f = print_type;
        commasep[@ast.ty](s, path.node.types, f);
        wrd(s.s, "]");
    }
}

impure fn print_pat(ps s, &@ast.pat pat) {
    maybe_print_comment(s, pat.span.lo);
    alt (pat.node) {
        case (ast.pat_wild(_)) {wrd(s.s, "_");}
        case (ast.pat_bind(?id,_,_)) {wrd(s.s, "?" + id);}
        case (ast.pat_lit(?lit,_)) {print_literal(s, lit);}
        case (ast.pat_tag(?path,?args,_,_)) {
            print_path(s, path);
            if (_vec.len[@ast.pat](args) > 0u) {
                popen_h(s);
                auto f = print_pat;
                commasep[@ast.pat](s, args, f);
                pclose(s);
            }
        }
    }
}

impure fn print_fn(ps s, ast.fn_decl decl, str name,
                   vec[ast.ty_param] typarams) {
    alt (decl.effect) {
        case (ast.eff_impure) {wrd1(s, "impure");}
        case (ast.eff_unsafe) {wrd1(s, "unsafe");}
        case (_) {}
    }
    wrd1(s, "fn");
    wrd(s.s, name);
    print_type_params(s, typarams);
    popen(s);
    impure fn print_arg(ps s, &ast.arg x) {
        hbox(s);
        if (x.mode == ast.alias) {wrd(s.s, "&");}
        print_type(s, x.ty);
        space(s.s);
        wrd(s.s, x.ident);
        end(s.s);
    }
    auto f = print_arg;
    commasep[ast.arg](s, decl.inputs, f);
    pclose(s);
    maybe_print_comment(s, decl.output.span.lo);
    if (decl.output.node != ast.ty_nil) {
        space(s.s);
        hbox(s);
        wrd1(s, "->");
        print_type(s, decl.output);
        end(s.s);
    }
}

impure fn print_type_params(ps s, vec[ast.ty_param] params) {
    if (_vec.len[ast.ty_param](params) > 0u) {
        wrd(s.s, "[");
        impure fn printParam(ps s, &ast.ty_param param) {
            wrd(s.s, param.ident);
        }
        auto f = printParam;
        commasep[ast.ty_param](s, params, f);
        wrd(s.s, "]");
    }
}

impure fn print_view_item(ps s, @ast.view_item item) {
    maybe_print_comment(s, item.span.lo);
    hbox(s);
    alt (item.node) {
        case (ast.view_item_use(?id,?mta,_,_)) {
            wrd1(s, "use");
            wrd(s.s, id);
            if (_vec.len[@ast.meta_item](mta) > 0u) {
                popen(s);
                impure fn print_meta(ps s, &@ast.meta_item item) {
                    hbox(s);
                    wrd1(s, item.node.name);
                    wrd1(s, "=");
                    print_string(s, item.node.value);
                    end(s.s);
                }
                auto f = print_meta;
                commasep[@ast.meta_item](s, mta, f);
                pclose(s);
            }
        }
        case (ast.view_item_import(?id,?ids,_,_)) {
            wrd1(s, "import");
            if (!_str.eq(id, ids.(_vec.len[str](ids)-1u))) {
                wrd1(s, id);
                wrd1(s, "=");
            }
            auto first = true;
            for (str elt in ids) {
                if (first) {first = false;}
                else {wrd(s.s, ".");}
                wrd(s.s, elt);
            }
        }
        case (ast.view_item_export(?id)) {
            wrd1(s, "export");
            wrd(s.s, id);
        }
    }
    end(s.s);
    wrd(s.s, ";");
    line(s.s);
}

// FIXME: The fact that this builds up the table anew for every call is
// not good. Eventually, table should be a const.
fn operator_prec(ast.binop op) -> int {
    for (front.parser.op_spec spec in front.parser.prec_table()) {
        if (spec.op == op) {ret spec.prec;}
    }
    fail;
}

impure fn print_maybe_parens(ps s, @ast.expr expr, int outer_prec) {
    auto add_them;
    alt (expr.node) {
        case (ast.expr_binary(?op,_,_,_)) {
            add_them = operator_prec(op) < outer_prec;
        }
        case (ast.expr_cast(_,_,_)) {
            add_them = as_prec < outer_prec;
        }
        case (_) {
            add_them = false;
        }
    }
    if (add_them) {popen(s);}
    print_expr(s, expr);
    if (add_them) {pclose(s);}
}

fn escape_str(str st, char to_escape) -> str {
    let str out = "";
    auto len = _str.byte_len(st);
    auto i = 0u;
    while (i < len) {
        alt (st.(i) as char) {
            case ('\n') {out += "\\n";}
            case ('\t') {out += "\\t";}
            case ('\r') {out += "\\r";}
            case ('\\') {out += "\\\\";}
            case (?cur) {
                if (cur == to_escape) {out += "\\";}
                _str.push_byte(out, cur as u8);
            }
        }
        i += 1u;
    }
    ret out;
}

impure fn print_mt(ps s, &ast.mt mt) {
    alt (mt.mut) {
        case (ast.mut)       { wrd1(s, "mutable");  }
        case (ast.maybe_mut) { wrd1(s, "mutable?"); }
        case (ast.imm)       { /* nothing */        }
    }
    print_type(s, mt.ty);
}

impure fn print_string(ps s, str st) {
    wrd(s.s, "\""); wrd(s.s, escape_str(st, '"')); wrd(s.s, "\"");
}

impure fn print_ty_fn(ps s, ast.proto proto, option.t[str] id,
                      vec[ast.ty_arg] inputs, @ast.ty output) {
    if (proto == ast.proto_fn) {wrd(s.s, "fn");}
    else {wrd(s.s, "iter");}
    alt (id) {
        case (option.some[str](?id)) {space(s.s); wrd(s.s, id);}
        case (_) {}
    }
    popen_h(s);
    impure fn print_arg(ps s, &ast.ty_arg input) {
        if (middle.ty.mode_is_alias(input.mode)) {wrd(s.s, "&");}
        print_type(s, input.ty);
    }
    auto f = print_arg;
    commasep[ast.ty_arg](s, inputs, f);
    pclose(s);
    maybe_print_comment(s, output.span.lo);
    if (output.node != ast.ty_nil) {
        space(s.s);
        hbox(s);
        wrd1(s, "->");
        print_type(s, output);
        end(s.s);
    }
}

fn next_comment(ps s) -> option.t[lexer.cmnt] {
    alt (s.comments) {
        case (option.some[vec[lexer.cmnt]](?cmnts)) {
            if (s.cur_cmnt < _vec.len[lexer.cmnt](cmnts)) {
                ret option.some[lexer.cmnt](cmnts.(s.cur_cmnt));
            } else {ret option.none[lexer.cmnt];}
        }
        case (_) {ret option.none[lexer.cmnt];}
    }
}

impure fn maybe_print_comment(ps s, util.common.pos pos) {
    while (true) {
        alt (next_comment(s)) {
            case (option.some[lexer.cmnt](?cmnt)) {
                if (cmnt.pos.line < pos.line ||
                    (cmnt.pos.line == pos.line && cmnt.pos.col < pos.col)) {
                    print_comment(s, cmnt.val);
                    if (cmnt.space_after) {line(s.s);}
                    s.cur_cmnt += 1u;
                } else { break; }
            }
            case (_) {break;}
        }
    }
}

impure fn maybe_print_stmt_comment(ps s, util.common.span span) -> bool {
    alt (next_comment(s)) {
        case (option.some[lexer.cmnt](?cmnt)) {
            if (span.hi.line == cmnt.pos.line) {
                wrd(s.s, " ");
                print_comment(s, cmnt.val);
                s.cur_cmnt += 1u;
                ret true;
            }
        }
        case (_) {}
    }
    ret false;
}

impure fn print_remaining_comments(ps s) {
    while (true) {
        alt (next_comment(s)) {
            case (option.some[lexer.cmnt](?cmnt)) {
                print_comment(s, cmnt.val);
                if (cmnt.space_after) {line(s.s);}
                s.cur_cmnt += 1u;
            }
            case (_) {break;}
        }
    }
}

impure fn print_comment(ps s, lexer.cmnt_ cmnt) {
    alt (cmnt) {
        case (lexer.cmnt_line(?val)) {
            wrd(s.s, "// " + val);
            pp.hardbreak(s.s);
        }
        case (lexer.cmnt_block(?lines)) {
            pp.abox(s.s);
            wrd(s.s, "/* ");
            pp.abox(s.s);
            auto first = true;
            for (str ln in lines) {
                if (first) {first = false;}
                else {pp.hardbreak(s.s);}
                wrd(s.s, ln);
            }
            end(s.s);
            wrd(s.s, "*/");
            end(s.s);
            line(s.s);
        }
    }
}