Move src/comp to src/rustc

src/rustc/metadata/astencode.rs

@@ -0,0 +1,925 @@
+import syntax::ast;
+import syntax::fold;
+import syntax::visit;
+import syntax::ast_util;
+import syntax::ast_util::inlined_item_methods;
+import syntax::codemap::span;
+import std::map::map;
+import std::smallintmap::map;
+import std::ebml;
+import std::ebml::writer;
+import std::serialization;
+import std::serialization::serializer;
+import std::serialization::deserializer;
+import std::serialization::serializer_helpers;
+import std::serialization::deserializer_helpers;
+import middle::trans::common::maps;
+import middle::{ty, typeck, last_use, ast_map};
+import middle::typeck::method_origin;
+import middle::typeck::dict_res;
+import middle::typeck::dict_origin;
+import driver::session::session;
+import middle::freevars::freevar_entry;
+import c = common;
+import e = encoder;
+
+// used in testing:
+import std::io;
+import driver::diagnostic;
+import syntax::codemap;
+import syntax::parse::parser;
+import syntax::print::pprust;
+
+export encode_inlined_item;
+export decode_inlined_item;
+
+type decode_ctxt = @{
+    cdata: cstore::crate_metadata,
+    tcx: ty::ctxt,
+    maps: maps
+};
+
+type extended_decode_ctxt = @{
+    dcx: decode_ctxt,
+    from_id_range: id_range,
+    to_id_range: id_range
+};
+
+iface tr {
+    fn tr(xcx: extended_decode_ctxt) -> self;
+}
+
+// ______________________________________________________________________
+// Top-level methods.
+
+fn encode_inlined_item(ecx: @e::encode_ctxt,
+                       ebml_w: ebml::writer,
+                       path: ast_map::path,
+                       ii: ast::inlined_item) {
+    #debug["> Encoding inlined item: %s::%s (%u)",
+           ast_map::path_to_str(path), ii.ident(),
+           ebml_w.writer.tell()];
+
+    let id_range = compute_id_range(ii);
+    ebml_w.wr_tag(c::tag_ast as uint) {||
+        encode_id_range(ebml_w, id_range);
+        encode_ast(ebml_w, ii);
+        encode_side_tables_for_ii(ecx, ebml_w, ii);
+    }
+
+    #debug["< Encoded inlined fn: %s::%s (%u)",
+           ast_map::path_to_str(path), ii.ident(),
+           ebml_w.writer.tell()];
+}
+
+fn decode_inlined_item(cdata: cstore::crate_metadata,
+                       tcx: ty::ctxt,
+                       maps: maps,
+                       path: ast_map::path,
+                       par_doc: ebml::doc) -> option<ast::inlined_item> {
+    let dcx = @{cdata: cdata, tcx: tcx, maps: maps};
+    alt par_doc.opt_child(c::tag_ast) {
+      none { none }
+      some(ast_doc) {
+        #debug["> Decoding inlined fn: %s::?", ast_map::path_to_str(path)];
+        let from_id_range = decode_id_range(ast_doc);
+        let to_id_range = reserve_id_range(dcx.tcx.sess, from_id_range);
+        let xcx = @{dcx: dcx,
+                    from_id_range: from_id_range,
+                    to_id_range: to_id_range};
+        let raw_ii = decode_ast(ast_doc);
+        let ii = renumber_ast(xcx, raw_ii);
+        ast_map::map_decoded_item(dcx.tcx.items, path, ii);
+        #debug["Fn named: %s", ii.ident()];
+        decode_side_tables(xcx, ast_doc);
+        #debug["< Decoded inlined fn: %s::%s",
+               ast_map::path_to_str(path), ii.ident()];
+        some(ii)
+      }
+    }
+}
+
+// ______________________________________________________________________
+// Enumerating the IDs which appear in an AST
+
+type id_range = {min: ast::node_id, max: ast::node_id};
+
+fn empty(range: id_range) -> bool {
+    range.min >= range.max
+}
+
+fn visit_ids(item: ast::inlined_item, vfn: fn@(ast::node_id)) {
+    let visitor = visit::mk_simple_visitor(@{
+        visit_mod: fn@(_m: ast::_mod, _sp: span, id: ast::node_id) {
+            vfn(id)
+        },
+
+        visit_view_item: fn@(vi: @ast::view_item) {
+            alt vi.node {
+              ast::view_item_use(_, _, id) { vfn(id) }
+              ast::view_item_import(vps) | ast::view_item_export(vps) {
+                vec::iter(vps) {|vp|
+                    alt vp.node {
+                      ast::view_path_simple(_, _, id) { vfn(id) }
+                      ast::view_path_glob(_, id) { vfn(id) }
+                      ast::view_path_list(_, _, id) { vfn(id) }
+                    }
+                }
+              }
+            }
+        },
+
+        visit_native_item: fn@(ni: @ast::native_item) {
+            vfn(ni.id)
+        },
+
+        visit_item: fn@(i: @ast::item) {
+            vfn(i.id);
+        },
+
+        visit_local: fn@(l: @ast::local) {
+            vfn(l.node.id);
+        },
+
+        visit_block: fn@(b: ast::blk) {
+            vfn(b.node.id);
+        },
+
+        visit_stmt: fn@(s: @ast::stmt) {
+            vfn(ast_util::stmt_id(*s));
+        },
+
+        visit_arm: fn@(_a: ast::arm) { },
+
+        visit_pat: fn@(p: @ast::pat) {
+            vfn(p.id)
+        },
+
+        visit_decl: fn@(_d: @ast::decl) {
+        },
+
+        visit_expr: fn@(e: @ast::expr) {
+            vfn(e.id);
+            alt e.node {
+              ast::expr_unary(_, _) | ast::expr_binary(_, _, _) {
+                vfn(ast_util::op_expr_callee_id(e));
+              }
+              _ { /* fallthrough */ }
+            }
+        },
+
+        visit_ty: fn@(t: @ast::ty) {
+            alt t.node {
+              ast::ty_path(_, id) {
+                vfn(id)
+              }
+              _ { /* fall through */ }
+            }
+        },
+
+        visit_ty_params: fn@(ps: [ast::ty_param]) {
+            vec::iter(ps) {|p| vfn(p.id) }
+        },
+
+        visit_constr: fn@(_p: @ast::path, _sp: span, id: ast::node_id) {
+            vfn(id);
+        },
+
+        visit_fn: fn@(fk: visit::fn_kind, d: ast::fn_decl,
+                      _b: ast::blk, _sp: span, id: ast::node_id) {
+            vfn(id);
+
+            alt fk {
+              visit::fk_item_fn(_, tps) |
+              visit::fk_method(_, tps) |
+              visit::fk_res(_, tps) {
+                vec::iter(tps) {|tp| vfn(tp.id)}
+              }
+              visit::fk_anon(_) |
+              visit::fk_fn_block {
+              }
+            }
+
+            vec::iter(d.inputs) {|arg|
+                vfn(arg.id)
+            }
+        },
+
+        visit_class_item: fn@(_s: span, _p: ast::privacy,
+                              c: ast::class_member) {
+            alt c {
+              ast::instance_var(_, _, _, id) {
+                vfn(id)
+              }
+              ast::class_method(_) {
+              }
+            }
+        }
+    });
+
+    item.accept((), visitor)
+}
+
+fn compute_id_range(item: ast::inlined_item) -> id_range {
+    let min = @mutable int::max_value;
+    let max = @mutable int::min_value;
+    visit_ids(item) {|id|
+        *min = int::min(*min, id);
+        *max = int::max(*max, id + 1);
+    }
+    ret {min:*min, max:*max};
+}
+
+fn encode_id_range(ebml_w: ebml::writer, id_range: id_range) {
+    ebml_w.wr_tag(c::tag_id_range as uint) {||
+        ebml_w.emit_tup(2u) {||
+            ebml_w.emit_tup_elt(0u) {|| ebml_w.emit_int(id_range.min) }
+            ebml_w.emit_tup_elt(1u) {|| ebml_w.emit_int(id_range.max) }
+        }
+    }
+}
+
+fn decode_id_range(par_doc: ebml::doc) -> id_range {
+    let range_doc = par_doc[c::tag_id_range];
+    let dsr = serialization::mk_ebml_deserializer(range_doc);
+    dsr.read_tup(2u) {||
+        {min: dsr.read_tup_elt(0u) {|| dsr.read_int() },
+         max: dsr.read_tup_elt(1u) {|| dsr.read_int() }}
+    }
+}
+
+fn reserve_id_range(sess: session,
+                    from_id_range: id_range) -> id_range {
+    // Handle the case of an empty range:
+    if empty(from_id_range) { ret from_id_range; }
+    let cnt = from_id_range.max - from_id_range.min;
+    let to_id_min = sess.parse_sess.next_id;
+    let to_id_max = sess.parse_sess.next_id + cnt;
+    sess.parse_sess.next_id = to_id_max;
+    ret {min: to_id_min, max: to_id_min};
+}
+
+impl translation_routines for extended_decode_ctxt {
+    fn tr_id(id: ast::node_id) -> ast::node_id {
+        // from_id_range should be non-empty
+        assert !empty(self.from_id_range);
+        (id - self.from_id_range.min + self.to_id_range.min)
+    }
+    fn tr_def_id(did: ast::def_id) -> ast::def_id {
+        decoder::translate_def_id(self.dcx.cdata, did)
+    }
+    fn tr_intern_def_id(did: ast::def_id) -> ast::def_id {
+        assert did.crate == ast::local_crate;
+        {crate: ast::local_crate, node: self.tr_id(did.node)}
+    }
+    fn tr_span(_span: span) -> span {
+        ast_util::dummy_sp() // TODO...
+    }
+}
+
+impl of tr for ast::def_id {
+    fn tr(xcx: extended_decode_ctxt) -> ast::def_id {
+        xcx.tr_def_id(self)
+    }
+    fn tr_intern(xcx: extended_decode_ctxt) -> ast::def_id {
+        xcx.tr_intern_def_id(self)
+    }
+}
+
+impl of tr for span {
+    fn tr(xcx: extended_decode_ctxt) -> span {
+        xcx.tr_span(self)
+    }
+}
+
+impl serializer_helpers<S: serialization::serializer> for S {
+    fn emit_def_id(did: ast::def_id) {
+        astencode_gen::serialize_syntax_ast_def_id(self, did)
+    }
+}
+
+impl deserializer_helpers<D: serialization::deserializer> for D {
+    fn read_def_id(xcx: extended_decode_ctxt) -> ast::def_id {
+        let did = astencode_gen::deserialize_syntax_ast_def_id(self);
+        did.tr(xcx)
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding the AST itself
+//
+// The hard work is done by an autogenerated module astencode_gen.  To
+// regenerate astencode_gen, run src/etc/gen-astencode.  It will
+// replace astencode_gen with a dummy file and regenerate its
+// contents.  If you get compile errors, the dummy file
+// remains---resolve the errors and then rerun astencode_gen.
+// Annoying, I know, but hopefully only temporary.
+//
+// When decoding, we have to renumber the AST so that the node ids that
+// appear within are disjoint from the node ids in our existing ASTs.
+// We also have to adjust the spans: for now we just insert a dummy span,
+// but eventually we should add entries to the local codemap as required.
+
+fn encode_ast(ebml_w: ebml::writer, item: ast::inlined_item) {
+    ebml_w.wr_tag(c::tag_tree as uint) {||
+        astencode_gen::serialize_syntax_ast_inlined_item(ebml_w, item)
+    }
+}
+
+fn decode_ast(par_doc: ebml::doc) -> ast::inlined_item {
+    let chi_doc = par_doc[c::tag_tree];
+    let d = serialization::mk_ebml_deserializer(chi_doc);
+    astencode_gen::deserialize_syntax_ast_inlined_item(d)
+}
+
+fn renumber_ast(xcx: extended_decode_ctxt, ii: ast::inlined_item)
+    -> ast::inlined_item {
+    let fld = fold::make_fold({
+        new_id: xcx.tr_id(_),
+        new_span: xcx.tr_span(_)
+        with *fold::default_ast_fold()
+    });
+
+    alt ii {
+      ast::ii_item(i) {
+        ast::ii_item(fld.fold_item(i))
+      }
+      ast::ii_method(d, m) {
+        ast::ii_method(xcx.tr_def_id(d), fld.fold_method(m))
+      }
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding of ast::def
+
+fn encode_def(ebml_w: ebml::writer, def: ast::def) {
+    astencode_gen::serialize_syntax_ast_def(ebml_w, def)
+}
+
+fn decode_def(xcx: extended_decode_ctxt, doc: ebml::doc) -> ast::def {
+    let dsr = serialization::mk_ebml_deserializer(doc);
+    let def = astencode_gen::deserialize_syntax_ast_def(dsr);
+    def.tr(xcx)
+}
+
+impl of tr for ast::def {
+    fn tr(xcx: extended_decode_ctxt) -> ast::def {
+        alt self {
+          ast::def_fn(did, p) { ast::def_fn(did.tr(xcx), p) }
+          ast::def_self(nid) { ast::def_self(xcx.tr_id(nid)) }
+          ast::def_mod(did) { ast::def_mod(did.tr(xcx)) }
+          ast::def_native_mod(did) { ast::def_native_mod(did.tr(xcx)) }
+          ast::def_const(did) { ast::def_const(did.tr(xcx)) }
+          ast::def_arg(nid, m) { ast::def_arg(xcx.tr_id(nid), m) }
+          ast::def_local(nid, b) { ast::def_local(xcx.tr_id(nid), b) }
+          ast::def_variant(e_did, v_did) {
+            ast::def_variant(e_did.tr(xcx), v_did.tr(xcx))
+          }
+          ast::def_ty(did) { ast::def_ty(did.tr(xcx)) }
+          ast::def_prim_ty(p) { ast::def_prim_ty(p) }
+          ast::def_ty_param(did, v) { ast::def_ty_param(did.tr(xcx), v) }
+          ast::def_binding(nid) { ast::def_binding(xcx.tr_id(nid)) }
+          ast::def_use(did) { ast::def_use(did.tr(xcx)) }
+          ast::def_upvar(nid1, def, nid2) {
+            ast::def_upvar(xcx.tr_id(nid1), @(*def).tr(xcx), xcx.tr_id(nid2))
+          }
+          ast::def_class(did) {
+            ast::def_class(did.tr(xcx))
+          }
+          ast::def_class_field(did0, did1) {
+            ast::def_class_field(did0.tr(xcx), did1.tr(xcx))
+          }
+          ast::def_class_method(did0, did1) {
+            ast::def_class_method(did0.tr(xcx), did1.tr(xcx))
+          }
+        }
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding of freevar information
+
+fn encode_freevar_entry(ebml_w: ebml::writer, fv: freevar_entry) {
+    astencode_gen::serialize_middle_freevars_freevar_entry(ebml_w, fv)
+}
+
+impl helper for serialization::ebml_deserializer {
+    fn read_freevar_entry(xcx: extended_decode_ctxt) -> freevar_entry {
+        let fv =
+            astencode_gen::deserialize_middle_freevars_freevar_entry(self);
+        fv.tr(xcx)
+    }
+}
+
+impl of tr for freevar_entry {
+    fn tr(xcx: extended_decode_ctxt) -> freevar_entry {
+        {def: self.def.tr(xcx), span: self.span.tr(xcx)}
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding of method_origin
+
+fn encode_method_origin(ebml_w: ebml::writer, mo: method_origin) {
+    astencode_gen::serialize_middle_typeck_method_origin(ebml_w, mo)
+}
+
+impl helper for serialization::ebml_deserializer {
+    fn read_method_origin(xcx: extended_decode_ctxt) -> method_origin {
+        let fv = astencode_gen::deserialize_middle_typeck_method_origin(self);
+        fv.tr(xcx)
+    }
+}
+
+impl of tr for method_origin {
+    fn tr(xcx: extended_decode_ctxt) -> method_origin {
+        alt self {
+          typeck::method_static(did) {
+            typeck::method_static(did.tr(xcx))
+          }
+          typeck::method_param(did, m, p, b) {
+            typeck::method_param(did.tr(xcx), m, p, b)
+          }
+          typeck::method_iface(did, m) {
+            typeck::method_iface(did.tr(xcx), m)
+          }
+        }
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding dict_res
+
+fn encode_dict_res(ecx: @e::encode_ctxt,
+                   ebml_w: ebml::writer,
+                   dr: typeck::dict_res) {
+    // can't autogenerate this code because automatic serialization of
+    // ty::t doesn't work, and there is no way (atm) to have
+    // hand-written serialization routines combine with auto-generated
+    // ones.  perhaps we should fix this.
+    ebml_w.emit_from_vec(*dr) {|dict_origin|
+        encode_dict_origin(ecx, ebml_w, dict_origin)
+    }
+}
+
+fn encode_dict_origin(ecx: @e::encode_ctxt,
+                      ebml_w: ebml::writer,
+                      dict_origin: typeck::dict_origin) {
+    ebml_w.emit_enum("dict_origin") {||
+        alt dict_origin {
+          typeck::dict_static(def_id, tys, dict_res) {
+            ebml_w.emit_enum_variant("dict_static", 0u, 3u) {||
+                ebml_w.emit_enum_variant_arg(0u) {||
+                    ebml_w.emit_def_id(def_id)
+                }
+                ebml_w.emit_enum_variant_arg(1u) {||
+                    ebml_w.emit_tys(ecx, tys);
+                }
+                ebml_w.emit_enum_variant_arg(2u) {||
+                    encode_dict_res(ecx, ebml_w, dict_res);
+                }
+            }
+          }
+          typeck::dict_param(pn, bn) {
+            ebml_w.emit_enum_variant("dict_param", 1u, 2u) {||
+                ebml_w.emit_enum_variant_arg(0u) {||
+                    ebml_w.emit_uint(pn);
+                }
+                ebml_w.emit_enum_variant_arg(1u) {||
+                    ebml_w.emit_uint(bn);
+                }
+            }
+          }
+          typeck::dict_iface(def_id) {
+            ebml_w.emit_enum_variant("dict_iface", 1u, 3u) {||
+                ebml_w.emit_enum_variant_arg(0u) {||
+                    ebml_w.emit_def_id(def_id)
+                }
+            }
+          }
+        }
+    }
+
+}
+
+impl helpers for serialization::ebml_deserializer {
+    fn read_dict_res(xcx: extended_decode_ctxt) -> typeck::dict_res {
+        @self.read_to_vec {|| self.read_dict_origin(xcx) }
+    }
+
+    fn read_dict_origin(xcx: extended_decode_ctxt) -> typeck::dict_origin {
+        self.read_enum("dict_origin") {||
+            self.read_enum_variant {|i|
+                alt check i {
+                  0u {
+                    typeck::dict_static(
+                        self.read_enum_variant_arg(0u) {||
+                            self.read_def_id(xcx)
+                        },
+                        self.read_enum_variant_arg(1u) {||
+                            self.read_tys(xcx)
+                        },
+                        self.read_enum_variant_arg(2u) {||
+                            self.read_dict_res(xcx)
+                        }
+                    )
+                  }
+                  1u {
+                    typeck::dict_param(
+                        self.read_enum_variant_arg(0u) {||
+                            self.read_uint()
+                        },
+                        self.read_enum_variant_arg(1u) {||
+                            self.read_uint()
+                        }
+                    )
+                  }
+                  2u {
+                    typeck::dict_iface(
+                        self.read_enum_variant_arg(0u) {||
+                            self.read_def_id(xcx)
+                        }
+                    )
+                  }
+                }
+            }
+        }
+    }
+}
+
+// ______________________________________________________________________
+// Encoding and decoding the side tables
+
+impl helpers for @e::encode_ctxt {
+    fn ty_str_ctxt() -> @tyencode::ctxt {
+        @{ds: e::def_to_str,
+          tcx: self.ccx.tcx,
+          abbrevs: tyencode::ac_use_abbrevs(self.type_abbrevs)}
+    }
+}
+
+impl helpers for ebml::writer {
+    fn emit_ty(ecx: @e::encode_ctxt, ty: ty::t) {
+        e::write_type(ecx, self, ty)
+    }
+
+    fn emit_tys(ecx: @e::encode_ctxt, tys: [ty::t]) {
+        self.emit_from_vec(tys) {|ty|
+            e::write_type(ecx, self, ty)
+        }
+    }
+
+    fn emit_bounds(ecx: @e::encode_ctxt, bs: ty::param_bounds) {
+        tyencode::enc_bounds(self.writer, ecx.ty_str_ctxt(), bs)
+    }
+
+    fn emit_tpbt(ecx: @e::encode_ctxt, tpbt: ty::ty_param_bounds_and_ty) {
+        self.emit_rec {||
+            self.emit_rec_field("bounds", 0u) {||
+                self.emit_from_vec(*tpbt.bounds) {|bs|
+                    self.emit_bounds(ecx, bs)
+                }
+            }
+            self.emit_rec_field("ty", 0u) {||
+                self.emit_ty(ecx, tpbt.ty);
+            }
+        }
+    }
+}
+
+impl writer for ebml::writer {
+    fn tag(tag_id: c::astencode_tag, f: fn()) {
+        self.wr_tag(tag_id as uint) {|| f() }
+    }
+
+    fn id(id: ast::node_id) {
+        self.wr_tagged_u64(c::tag_table_id as uint, id as u64)
+    }
+}
+
+fn encode_side_tables_for_ii(ecx: @e::encode_ctxt,
+                             ebml_w: ebml::writer,
+                             ii: ast::inlined_item) {
+    ebml_w.wr_tag(c::tag_table as uint) {||
+        visit_ids(ii, fn@(id: ast::node_id) {
+            // Note: this will cause a copy of ebml_w, which is bad as
+            // it has mutable fields.  But I believe it's harmless since
+            // we generate balanced EBML.
+            encode_side_tables_for_id(ecx, ebml_w, id)
+        });
+    }
+}
+
+fn encode_side_tables_for_id(ecx: @e::encode_ctxt,
+                             ebml_w: ebml::writer,
+                             id: ast::node_id) {
+
+    let ccx = ecx.ccx;
+    let tcx = ccx.tcx;
+
+    #debug["Encoding side tables for id %d", id];
+
+    option::may(tcx.def_map.find(id)) {|def|
+        ebml_w.tag(c::tag_table_def) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                astencode_gen::serialize_syntax_ast_def(ebml_w, def)
+            }
+        }
+    }
+    option::may((*tcx.node_types).find(id as uint)) {|ty|
+        ebml_w.tag(c::tag_table_node_type) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                e::write_type(ecx, ebml_w, ty)
+            }
+        }
+    }
+
+    option::may(tcx.node_type_substs.find(id)) {|tys|
+        ebml_w.tag(c::tag_table_node_type_subst) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                ebml_w.emit_tys(ecx, tys)
+            }
+        }
+    }
+
+    option::may(tcx.freevars.find(id)) {|fv|
+        ebml_w.tag(c::tag_table_freevars) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                ebml_w.emit_from_vec(*fv) {|fv_entry|
+                    encode_freevar_entry(ebml_w, *fv_entry)
+                }
+            }
+        }
+    }
+
+    let lid = {crate: ast::local_crate, node: id};
+    option::may(tcx.tcache.find(lid)) {|tpbt|
+        ebml_w.tag(c::tag_table_tcache) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                ebml_w.emit_tpbt(ecx, tpbt);
+            }
+        }
+    }
+
+    option::may(tcx.ty_param_bounds.find(id)) {|pbs|
+        ebml_w.tag(c::tag_table_param_bounds) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                ebml_w.emit_bounds(ecx, pbs)
+            }
+        }
+    }
+
+    // I believe it is not necessary to encode this information.  The
+    // ids will appear in the AST but in the *type* information, which
+    // is what we actually use in trans, all modes will have been
+    // resolved.
+    //
+    //option::may(tcx.inferred_modes.find(id)) {|m|
+    //    ebml_w.tag(c::tag_table_inferred_modes) {||
+    //        ebml_w.id(id);
+    //        ebml_w.tag(c::tag_table_val) {||
+    //            tyencode::enc_mode(ebml_w.writer, ty_str_ctxt(), m);
+    //        }
+    //    }
+    //}
+
+    option::may(ccx.maps.mutbl_map.find(id)) {|_m|
+        ebml_w.tag(c::tag_table_mutbl) {||
+            ebml_w.id(id);
+        }
+    }
+
+    option::may(ccx.maps.copy_map.find(id)) {|_m|
+        ebml_w.tag(c::tag_table_copy) {||
+            ebml_w.id(id);
+        }
+    }
+
+    option::may(ccx.maps.last_uses.find(id)) {|_m|
+        ebml_w.tag(c::tag_table_last_use) {||
+            ebml_w.id(id);
+        }
+    }
+
+    // impl_map is not used except when emitting metadata,
+    // don't need to keep it.
+
+    option::may(ccx.maps.method_map.find(id)) {|mo|
+        ebml_w.tag(c::tag_table_method_map) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                astencode_gen::
+                    serialize_middle_typeck_method_origin(ebml_w, mo)
+            }
+        }
+    }
+
+    option::may(ccx.maps.dict_map.find(id)) {|dr|
+        ebml_w.tag(c::tag_table_dict_map) {||
+            ebml_w.id(id);
+            ebml_w.tag(c::tag_table_val) {||
+                encode_dict_res(ecx, ebml_w, dr);
+            }
+        }
+    }
+}
+
+impl decoder for ebml::doc {
+    fn as_int() -> int { ebml::doc_as_u64(self) as int }
+    fn [](tag: c::astencode_tag) -> ebml::doc {
+        ebml::get_doc(self, tag as uint)
+    }
+    fn opt_child(tag: c::astencode_tag) -> option<ebml::doc> {
+        ebml::maybe_get_doc(self, tag as uint)
+    }
+}
+
+impl decoder for serialization::ebml_deserializer {
+    fn read_ty(xcx: extended_decode_ctxt) -> ty::t {
+        tydecode::parse_ty_data(
+            self.parent.data, xcx.dcx.cdata.cnum, self.pos, xcx.dcx.tcx,
+            xcx.tr_def_id(_))
+    }
+
+    fn read_tys(xcx: extended_decode_ctxt) -> [ty::t] {
+        self.read_to_vec {|| self.read_ty(xcx) }
+    }
+
+    fn read_bounds(xcx: extended_decode_ctxt) -> @[ty::param_bound] {
+        tydecode::parse_bounds_data(
+            self.parent.data, self.pos, xcx.dcx.cdata.cnum, xcx.dcx.tcx,
+            xcx.tr_def_id(_))
+    }
+
+    fn read_ty_param_bounds_and_ty(xcx: extended_decode_ctxt)
+        -> ty::ty_param_bounds_and_ty {
+        self.read_rec {||
+            {
+                bounds: self.read_rec_field("bounds", 0u) {||
+                    @self.read_to_vec {|| self.read_bounds(xcx) }
+                },
+                ty: self.read_rec_field("ty", 1u) {||
+                    self.read_ty(xcx)
+                }
+            }
+        }
+    }
+}
+
+fn decode_side_tables(xcx: extended_decode_ctxt,
+                      ast_doc: ebml::doc) {
+    let dcx = xcx.dcx;
+    let tbl_doc = ast_doc[c::tag_table];
+    ebml::docs(tbl_doc) {|tag, entry_doc|
+        let id0 = entry_doc[c::tag_table_id].as_int();
+        let id = xcx.tr_id(id0);
+
+        #debug[">> Side table document with tag 0x%x \
+                found for id %d (orig %d)",
+               tag, id, id0];
+
+        if tag == (c::tag_table_mutbl as uint) {
+            dcx.maps.mutbl_map.insert(id, ());
+        } else if tag == (c::tag_table_copy as uint) {
+            dcx.maps.copy_map.insert(id, ());
+        } else if tag == (c::tag_table_last_use as uint) {
+            dcx.maps.last_uses.insert(id, last_use::is_last_use);
+        } else {
+            let val_doc = entry_doc[c::tag_table_val];
+            let val_dsr = serialization::mk_ebml_deserializer(val_doc);
+            if tag == (c::tag_table_def as uint) {
+                let def = decode_def(xcx, val_doc);
+                dcx.tcx.def_map.insert(id, def);
+            } else if tag == (c::tag_table_node_type as uint) {
+                let ty = val_dsr.read_ty(xcx);
+                (*dcx.tcx.node_types).insert(id as uint, ty);
+            } else if tag == (c::tag_table_node_type_subst as uint) {
+                let tys = val_dsr.read_tys(xcx);
+                dcx.tcx.node_type_substs.insert(id, tys);
+            } else if tag == (c::tag_table_freevars as uint) {
+                let fv_info = @val_dsr.read_to_vec {||
+                    @val_dsr.read_freevar_entry(xcx)
+                };
+                dcx.tcx.freevars.insert(id, fv_info);
+            } else if tag == (c::tag_table_tcache as uint) {
+                let tpbt = val_dsr.read_ty_param_bounds_and_ty(xcx);
+                let lid = {crate: ast::local_crate, node: id};
+                dcx.tcx.tcache.insert(lid, tpbt);
+            } else if tag == (c::tag_table_param_bounds as uint) {
+                let bounds = val_dsr.read_bounds(xcx);
+                dcx.tcx.ty_param_bounds.insert(id, bounds);
+            } else if tag == (c::tag_table_method_map as uint) {
+                dcx.maps.method_map.insert(id,
+                                           val_dsr.read_method_origin(xcx));
+            } else if tag == (c::tag_table_dict_map as uint) {
+                dcx.maps.dict_map.insert(id,
+                                         val_dsr.read_dict_res(xcx));
+            } else {
+                xcx.dcx.tcx.sess.bug(
+                    #fmt["Unknown tag found in side tables: %x", tag]);
+            }
+        }
+
+        #debug[">< Side table doc loaded"];
+    }
+}
+
+// ______________________________________________________________________
+// Testing of astencode_gen
+
+#[cfg(test)]
+fn encode_item_ast(ebml_w: ebml::writer, item: @ast::item) {
+    ebml_w.wr_tag(c::tag_tree as uint) {||
+        astencode_gen::serialize_syntax_ast_item(ebml_w, *item);
+    }
+}
+
+#[cfg(test)]
+fn decode_item_ast(par_doc: ebml::doc) -> @ast::item {
+    let chi_doc = par_doc[c::tag_tree];
+    let d = serialization::mk_ebml_deserializer(chi_doc);
+    @astencode_gen::deserialize_syntax_ast_item(d)
+}
+
+#[cfg(test)]
+fn new_parse_sess() -> parser::parse_sess {
+    let cm = codemap::new_codemap();
+    let handler = diagnostic::mk_handler(option::none);
+    let sess = @{
+        cm: cm,
+        mutable next_id: 1,
+        span_diagnostic: diagnostic::mk_span_handler(handler, cm),
+        mutable chpos: 0u,
+        mutable byte_pos: 0u
+    };
+    ret sess;
+}
+
+#[cfg(test)]
+iface fake_ext_ctxt {
+    fn session() -> fake_session;
+}
+
+#[cfg(test)]
+type fake_options = {cfg: ast::crate_cfg};
+
+#[cfg(test)]
+type fake_session = {opts: @fake_options,
+                     parse_sess: parser::parse_sess};
+
+#[cfg(test)]
+impl of fake_ext_ctxt for fake_session {
+    fn session() -> fake_session {self}
+}
+
+#[cfg(test)]
+fn mk_ctxt() -> fake_ext_ctxt {
+    let opts : fake_options = {cfg: []};
+    {opts: @opts, parse_sess: new_parse_sess()} as fake_ext_ctxt
+}
+
+#[cfg(test)]
+fn roundtrip(in_item: @ast::item) {
+    #debug["in_item = %s", pprust::item_to_str(in_item)];
+    let mbuf = io::mk_mem_buffer();
+    let ebml_w = ebml::mk_writer(io::mem_buffer_writer(mbuf));
+    encode_item_ast(ebml_w, in_item);
+    let ebml_doc = ebml::new_doc(@io::mem_buffer_buf(mbuf));
+    let out_item = decode_item_ast(ebml_doc);
+    #debug["out_item = %s", pprust::item_to_str(out_item)];
+    assert in_item == out_item;
+}
+
+#[test]
+fn test_basic() {
+    let ext_cx = mk_ctxt();
+    roundtrip(#ast(item){
+        fn foo() {}
+    });
+}
+
+#[test]
+fn test_smalltalk() {
+    let ext_cx = mk_ctxt();
+    roundtrip(#ast(item){
+        fn foo() -> int { 3 + 4 } // first smalltalk program ever executed.
+    });
+}
+
+#[test]
+fn test_more() {
+    let ext_cx = mk_ctxt();
+    roundtrip(#ast(item){
+        fn foo(x: uint, y: uint) -> uint {
+            let z = x + y;
+            ret z;
+        }
+    });
+}