Revert "Remove old auto_serialize2 code (needs snapshot)"

This reverts commit 0bd6da8a8c93143325cb45e8a074ccf7121ca168.

3 files changed, 1052 insertions, 2 deletions

diff --git a/src/libsyntax/ext/auto_serialize2.rs b/src/libsyntax/ext/auto_serialize2.rs
new file mode 100644
index 00000000000..b3102f8b4f7
--- /dev/null
+++ b/src/libsyntax/ext/auto_serialize2.rs
@@ -0,0 +1,991 @@
+/*
+
+The compiler code necessary to implement the #[auto_serialize2] and
+#[auto_deserialize2] extension.  The idea here is that type-defining items may
+be tagged with #[auto_serialize2] and #[auto_deserialize2], which will cause
+us to generate a little companion module with the same name as the item.
+
+For example, a type like:
+
+    #[auto_serialize2]
+    #[auto_deserialize2]
+    struct Node {id: uint}
+
+would generate two implementations like:
+
+    impl Node: Serializable {
+        fn serialize<S: Serializer>(s: &S) {
+            do s.emit_struct("Node") {
+                s.emit_field("id", 0, || s.emit_uint(self))
+            }
+        }
+    }
+
+    impl node_id: Deserializable {
+        static fn deserialize<D: Deserializer>(d: &D) -> Node {
+            do d.read_struct("Node") {
+                Node {
+                    id: d.read_field(~"x", 0, || deserialize(d))
+                }
+            }
+        }
+    }
+
+Other interesting scenarios are whe the item has type parameters or
+references other non-built-in types.  A type definition like:
+
+    #[auto_serialize2]
+    #[auto_deserialize2]
+    type spanned<T> = {node: T, span: span};
+
+would yield functions like:
+
+    impl<T: Serializable> spanned<T>: Serializable {
+        fn serialize<S: Serializer>(s: &S) {
+            do s.emit_rec {
+                s.emit_field("node", 0, || self.node.serialize(s));
+                s.emit_field("span", 1, || self.span.serialize(s));
+            }
+        }
+    }
+
+    impl<T: Deserializable> spanned<T>: Deserializable {
+        static fn deserialize<D: Deserializer>(d: &D) -> spanned<T> {
+            do d.read_rec {
+                {
+                    node: d.read_field(~"node", 0, || deserialize(d)),
+                    span: d.read_field(~"span", 1, || deserialize(d)),
+                }
+            }
+        }
+    }
+
+FIXME (#2810)--Hygiene. Search for "__" strings.  We also assume "std" is the
+standard library.
+
+Misc notes:
+-----------
+
+I use move mode arguments for ast nodes that will get inserted as is
+into the tree.  This is intended to prevent us from inserting the same
+node twice.
+
+*/
+
+use base::*;
+use codemap::span;
+use std::map;
+use std::map::HashMap;
+
+export expand_auto_serialize;
+export expand_auto_deserialize;
+
+// Transitional reexports so qquote can find the paths it is looking for
+mod syntax {
+    pub use ext;
+    pub use parse;
+}
+
+fn expand_auto_serialize(
+    cx: ext_ctxt,
+    span: span,
+    _mitem: ast::meta_item,
+    in_items: ~[@ast::item]
+) -> ~[@ast::item] {
+    fn is_auto_serialize2(a: &ast::attribute) -> bool {
+        attr::get_attr_name(*a) == ~"auto_serialize2"
+    }
+
+    fn filter_attrs(item: @ast::item) -> @ast::item {
+        @{attrs: vec::filter(item.attrs, |a| !is_auto_serialize2(a)),
+          .. *item}
+    }
+
+    do vec::flat_map(in_items) |item| {
+        if item.attrs.any(is_auto_serialize2) {
+            match item.node {
+                ast::item_ty(@{node: ast::ty_rec(fields), _}, tps) => {
+                    let ser_impl = mk_rec_ser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        fields,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), ser_impl]
+                },
+                ast::item_class(@{ fields, _}, tps) => {
+                    let ser_impl = mk_struct_ser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        fields,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), ser_impl]
+                },
+                ast::item_enum(enum_def, tps) => {
+                    let ser_impl = mk_enum_ser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        enum_def,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), ser_impl]
+                },
+                _ => {
+                    cx.span_err(span, ~"#[auto_serialize2] can only be \
+                                        applied to structs, record types, \
+                                        and enum definitions");
+                    ~[*item]
+                }
+            }
+        } else {
+            ~[*item]
+        }
+    }
+}
+
+fn expand_auto_deserialize(
+    cx: ext_ctxt,
+    span: span,
+    _mitem: ast::meta_item,
+    in_items: ~[@ast::item]
+) -> ~[@ast::item] {
+    fn is_auto_deserialize2(a: &ast::attribute) -> bool {
+        attr::get_attr_name(*a) == ~"auto_deserialize2"
+    }
+
+    fn filter_attrs(item: @ast::item) -> @ast::item {
+        @{attrs: vec::filter(item.attrs, |a| !is_auto_deserialize2(a)),
+          .. *item}
+    }
+
+    do vec::flat_map(in_items) |item| {
+        if item.attrs.any(is_auto_deserialize2) {
+            match item.node {
+                ast::item_ty(@{node: ast::ty_rec(fields), _}, tps) => {
+                    let deser_impl = mk_rec_deser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        fields,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), deser_impl]
+                },
+                ast::item_class(@{ fields, _}, tps) => {
+                    let deser_impl = mk_struct_deser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        fields,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), deser_impl]
+                },
+                ast::item_enum(enum_def, tps) => {
+                    let deser_impl = mk_enum_deser_impl(
+                        cx,
+                        item.span,
+                        item.ident,
+                        enum_def,
+                        tps
+                    );
+
+                    ~[filter_attrs(*item), deser_impl]
+                },
+                _ => {
+                    cx.span_err(span, ~"#[auto_deserialize2] can only be \
+                                        applied to structs, record types, \
+                                        and enum definitions");
+                    ~[*item]
+                }
+            }
+        } else {
+            ~[*item]
+        }
+    }
+}
+
+fn mk_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    path: @ast::path,
+    tps: ~[ast::ty_param],
+    f: fn(@ast::ty) -> @ast::method
+) -> @ast::item {
+    // All the type parameters need to bound to the trait.
+    let trait_tps = do tps.map |tp| {
+        let t_bound = ast::bound_trait(@{
+            id: cx.next_id(),
+            node: ast::ty_path(path, cx.next_id()),
+            span: span,
+        });
+
+        {
+            ident: tp.ident,
+            id: cx.next_id(),
+            bounds: @vec::append(~[t_bound], *tp.bounds)
+        }
+    };
+
+    let opt_trait = Some(@{
+        path: path,
+        ref_id: cx.next_id(),
+        impl_id: cx.next_id(),
+    });
+
+    let ty = cx.ty_path(
+        span,
+        ~[ident],
+        tps.map(|tp| cx.ty_path(span, ~[tp.ident], ~[]))
+    );
+
+    @{
+        // This is a new-style impl declaration.
+        // XXX: clownshoes
+        ident: ast::token::special_idents::clownshoes_extensions,
+        attrs: ~[],
+        id: cx.next_id(),
+        node: ast::item_impl(trait_tps, opt_trait, ty, ~[f(ty)]),
+        vis: ast::public,
+        span: span,
+    }
+}
+
+fn mk_ser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    tps: ~[ast::ty_param],
+    body: @ast::expr
+) -> @ast::item {
+    // Make a path to the std::serialization2::Serializable trait.
+    let path = cx.path(
+        span,
+        ~[
+            cx.ident_of(~"std"),
+            cx.ident_of(~"serialization2"),
+            cx.ident_of(~"Serializable"),
+        ]
+    );
+
+    mk_impl(
+        cx,
+        span,
+        ident,
+        path,
+        tps,
+        |_ty| mk_ser_method(cx, span, cx.expr_blk(body))
+    )
+}
+
+fn mk_deser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    tps: ~[ast::ty_param],
+    body: @ast::expr
+) -> @ast::item {
+    // Make a path to the std::serialization2::Deserializable trait.
+    let path = cx.path(
+        span,
+        ~[
+            cx.ident_of(~"std"),
+            cx.ident_of(~"serialization2"),
+            cx.ident_of(~"Deserializable"),
+        ]
+    );
+
+    mk_impl(
+        cx,
+        span,
+        ident,
+        path,
+        tps,
+        |ty| mk_deser_method(cx, span, ty, cx.expr_blk(body))
+    )
+}
+
+fn mk_ser_method(
+    cx: ext_ctxt,
+    span: span,
+    ser_body: ast::blk
+) -> @ast::method {
+    let ser_bound = cx.ty_path(
+        span,
+        ~[
+            cx.ident_of(~"std"),
+            cx.ident_of(~"serialization2"),
+            cx.ident_of(~"Serializer"),
+        ],
+        ~[]
+    );
+
+    let ser_tps = ~[{
+        ident: cx.ident_of(~"__S"),
+        id: cx.next_id(),
+        bounds: @~[ast::bound_trait(ser_bound)],
+    }];
+
+    let ty_s = @{
+        id: cx.next_id(),
+        node: ast::ty_rptr(
+            @{
+                id: cx.next_id(),
+                node: ast::re_anon,
+            },
+            {
+                ty: cx.ty_path(span, ~[cx.ident_of(~"__S")], ~[]),
+                mutbl: ast::m_imm
+            }
+        ),
+        span: span,
+    };
+
+    let ser_inputs = ~[{
+        mode: ast::infer(cx.next_id()),
+        ty: ty_s,
+        ident: cx.ident_of(~"__s"),
+        id: cx.next_id(),
+    }];
+
+    let ser_output = @{
+        id: cx.next_id(),
+        node: ast::ty_nil,
+        span: span,
+    };
+
+    let ser_decl = {
+        inputs: ser_inputs,
+        output: ser_output,
+        cf: ast::return_val,
+    };
+
+    @{
+        ident: cx.ident_of(~"serialize"),
+        attrs: ~[],
+        tps: ser_tps,
+        self_ty: { node: ast::sty_region(ast::m_imm), span: span },
+        purity: ast::impure_fn,
+        decl: ser_decl,
+        body: ser_body,
+        id: cx.next_id(),
+        span: span,
+        self_id: cx.next_id(),
+        vis: ast::public,
+    }
+}
+
+fn mk_deser_method(
+    cx: ext_ctxt,
+    span: span,
+    ty: @ast::ty,
+    deser_body: ast::blk
+) -> @ast::method {
+    let deser_bound = cx.ty_path(
+        span,
+        ~[
+            cx.ident_of(~"std"),
+            cx.ident_of(~"serialization2"),
+            cx.ident_of(~"Deserializer"),
+        ],
+        ~[]
+    );
+
+    let deser_tps = ~[{
+        ident: cx.ident_of(~"__D"),
+        id: cx.next_id(),
+        bounds: @~[ast::bound_trait(deser_bound)],
+    }];
+
+    let ty_d = @{
+        id: cx.next_id(),
+        node: ast::ty_rptr(
+            @{
+                id: cx.next_id(),
+                node: ast::re_anon,
+            },
+            {
+                ty: cx.ty_path(span, ~[cx.ident_of(~"__D")], ~[]),
+                mutbl: ast::m_imm
+            }
+        ),
+        span: span,
+    };
+
+    let deser_inputs = ~[{
+        mode: ast::infer(cx.next_id()),
+        ty: ty_d,
+        ident: cx.ident_of(~"__d"),
+        id: cx.next_id(),
+    }];
+
+    let deser_decl = {
+        inputs: deser_inputs,
+        output: ty,
+        cf: ast::return_val,
+    };
+
+    @{
+        ident: cx.ident_of(~"deserialize"),
+        attrs: ~[],
+        tps: deser_tps,
+        self_ty: { node: ast::sty_static, span: span },
+        purity: ast::impure_fn,
+        decl: deser_decl,
+        body: deser_body,
+        id: cx.next_id(),
+        span: span,
+        self_id: cx.next_id(),
+        vis: ast::public,
+    }
+}
+
+fn mk_rec_ser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    fields: ~[ast::ty_field],
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let fields = mk_ser_fields(cx, span, mk_rec_fields(fields));
+
+    // ast for `__s.emit_rec(|| $(fields))`
+    let body = cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__s"),
+            cx.ident_of(~"emit_rec")
+        ),
+        ~[cx.lambda_stmts(span, fields)]
+    );
+
+    mk_ser_impl(cx, span, ident, tps, body)
+}
+
+fn mk_rec_deser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    fields: ~[ast::ty_field],
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let fields = mk_deser_fields(cx, span, mk_rec_fields(fields));
+
+    // ast for `read_rec(|| $(fields))`
+    let body = cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__d"),
+            cx.ident_of(~"read_rec")
+        ),
+        ~[
+            cx.lambda_expr(
+                cx.expr(
+                    span,
+                    ast::expr_rec(fields, None)
+                )
+            )
+        ]
+    );
+
+    mk_deser_impl(cx, span, ident, tps, body)
+}
+
+fn mk_struct_ser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    fields: ~[@ast::struct_field],
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let fields = mk_ser_fields(cx, span, mk_struct_fields(fields));
+
+    // ast for `__s.emit_struct($(name), || $(fields))`
+    let ser_body = cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__s"),
+            cx.ident_of(~"emit_struct")
+        ),
+        ~[
+            cx.lit_str(span, @cx.str_of(ident)),
+            cx.lambda_stmts(span, fields),
+        ]
+    );
+
+    mk_ser_impl(cx, span, ident, tps, ser_body)
+}
+
+fn mk_struct_deser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    fields: ~[@ast::struct_field],
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let fields = mk_deser_fields(cx, span, mk_struct_fields(fields));
+
+    // ast for `read_struct($(name), || $(fields))`
+    let body = cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__d"),
+            cx.ident_of(~"read_struct")
+        ),
+        ~[
+            cx.lit_str(span, @cx.str_of(ident)),
+            cx.lambda_expr(
+                cx.expr(
+                    span,
+                    ast::expr_struct(
+                        cx.path(span, ~[ident]),
+                        fields,
+                        None
+                    )
+                )
+            ),
+        ]
+    );
+
+    mk_deser_impl(cx, span, ident, tps, body)
+}
+
+// Records and structs don't have the same fields types, but they share enough
+// that if we extract the right subfields out we can share the serialization
+// generator code.
+type field = { span: span, ident: ast::ident, mutbl: ast::mutability };
+
+fn mk_rec_fields(fields: ~[ast::ty_field]) -> ~[field] {
+    do fields.map |field| {
+        {
+            span: field.span,
+            ident: field.node.ident,
+            mutbl: field.node.mt.mutbl,
+        }
+    }
+}
+
+fn mk_struct_fields(fields: ~[@ast::struct_field]) -> ~[field] {
+    do fields.map |field| {
+        let (ident, mutbl) = match field.node.kind {
+            ast::named_field(ident, mutbl, _) => (ident, mutbl),
+            _ => fail ~"[auto_serialize2] does not support \
+                        unnamed fields",
+        };
+
+        {
+            span: field.span,
+            ident: ident,
+            mutbl: match mutbl {
+                ast::class_mutable => ast::m_mutbl,
+                ast::class_immutable => ast::m_imm,
+            },
+        }
+    }
+}
+
+fn mk_ser_fields(
+    cx: ext_ctxt,
+    span: span,
+    fields: ~[field]
+) -> ~[@ast::stmt] {
+    do fields.mapi |idx, field| {
+        // ast for `|| self.$(name).serialize(__s)`
+        let expr_lambda = cx.lambda_expr(
+            cx.expr_call(
+                span,
+                cx.expr_field(
+                    span,
+                    cx.expr_field(
+                        span,
+                        cx.expr_var(span, ~"self"),
+                        field.ident
+                    ),
+                    cx.ident_of(~"serialize")
+                ),
+                ~[cx.expr_var(span, ~"__s")]
+            )
+        );
+
+        // ast for `__s.emit_field($(name), $(idx), $(expr_lambda))`
+        cx.stmt(
+            cx.expr_call(
+                span,
+                cx.expr_field(
+                    span,
+                    cx.expr_var(span, ~"__s"),
+                    cx.ident_of(~"emit_field")
+                ),
+                ~[
+                    cx.lit_str(span, @cx.str_of(field.ident)),
+                    cx.lit_uint(span, idx),
+                    expr_lambda,
+                ]
+            )
+        )
+    }
+}
+
+fn mk_deser_fields(
+    cx: ext_ctxt,
+    span: span,
+    fields: ~[{ span: span, ident: ast::ident, mutbl: ast::mutability }]
+) -> ~[ast::field] {
+    do fields.mapi |idx, field| {
+        // ast for `|| std::serialization2::deserialize(__d)`
+        let expr_lambda = cx.lambda(
+            cx.expr_blk(
+                cx.expr_call(
+                    span,
+                    cx.expr_path(span, ~[
+                        cx.ident_of(~"std"),
+                        cx.ident_of(~"serialization2"),
+                        cx.ident_of(~"deserialize"),
+                    ]),
+                    ~[cx.expr_var(span, ~"__d")]
+                )
+            )
+        );
+
+        // ast for `__d.read_field($(name), $(idx), $(expr_lambda))`
+        let expr: @ast::expr = cx.expr_call(
+            span,
+            cx.expr_field(
+                span,
+                cx.expr_var(span, ~"__d"),
+                cx.ident_of(~"read_field")
+            ),
+            ~[
+                cx.lit_str(span, @cx.str_of(field.ident)),
+                cx.lit_uint(span, idx),
+                expr_lambda,
+            ]
+        );
+
+        {
+            node: { mutbl: field.mutbl, ident: field.ident, expr: expr },
+            span: span,
+        }
+    }
+}
+
+fn mk_enum_ser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    enum_def: ast::enum_def,
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let body = mk_enum_ser_body(
+        cx,
+        span,
+        ident,
+        enum_def.variants
+    );
+
+    mk_ser_impl(cx, span, ident, tps, body)
+}
+
+fn mk_enum_deser_impl(
+    cx: ext_ctxt,
+    span: span,
+    ident: ast::ident,
+    enum_def: ast::enum_def,
+    tps: ~[ast::ty_param]
+) -> @ast::item {
+    let body = mk_enum_deser_body(
+        cx,
+        span,
+        ident,
+        enum_def.variants
+    );
+
+    mk_deser_impl(cx, span, ident, tps, body)
+}
+
+fn ser_variant(
+    cx: ext_ctxt,
+    span: span,
+    v_name: ast::ident,
+    v_idx: uint,
+    args: ~[ast::variant_arg]
+) -> ast::arm {
+    // Name the variant arguments.
+    let names = args.mapi(|i, _arg| cx.ident_of(fmt!("__v%u", i)));
+
+    // Bind the names to the variant argument type.
+    let pats = args.mapi(|i, arg| cx.binder_pat(arg.ty.span, names[i]));
+
+    let pat_node = if pats.is_empty() {
+        ast::pat_ident(
+            ast::bind_by_implicit_ref,
+            cx.path(span, ~[v_name]),
+            None
+        )
+    } else {
+        ast::pat_enum(
+            cx.path(span, ~[v_name]),
+            Some(pats)
+        )
+    };
+
+    let pat = @{
+        id: cx.next_id(),
+        node: pat_node,
+        span: span,
+    };
+
+    let stmts = do args.mapi |a_idx, _arg| {
+        // ast for `__s.emit_enum_variant_arg`
+        let expr_emit = cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__s"),
+            cx.ident_of(~"emit_enum_variant_arg")
+        );
+
+        // ast for `|| $(v).serialize(__s)`
+        let expr_serialize = cx.lambda_expr(
+             cx.expr_call(
+                span,
+                cx.expr_field(
+                    span,
+                    cx.expr_path(span, ~[names[a_idx]]),
+                    cx.ident_of(~"serialize")
+                ),
+                ~[cx.expr_var(span, ~"__s")]
+            )
+        );
+
+        // ast for `$(expr_emit)($(a_idx), $(expr_serialize))`
+        cx.stmt(
+            cx.expr_call(
+                span,
+                expr_emit,
+                ~[cx.lit_uint(span, a_idx), expr_serialize]
+            )
+        )
+    };
+
+    // ast for `__s.emit_enum_variant($(name), $(idx), $(sz), $(lambda))`
+    let body = cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__s"),
+            cx.ident_of(~"emit_enum_variant")
+        ),
+        ~[
+            cx.lit_str(span, @cx.str_of(v_name)),
+            cx.lit_uint(span, v_idx),
+            cx.lit_uint(span, stmts.len()),
+            cx.lambda_stmts(span, stmts),
+        ]
+    );
+
+    { pats: ~[pat], guard: None, body: cx.expr_blk(body) }
+}
+
+fn mk_enum_ser_body(
+    cx: ext_ctxt,
+    span: span,
+    name: ast::ident,
+    variants: ~[ast::variant]
+) -> @ast::expr {
+    let arms = do variants.mapi |v_idx, variant| {
+        match variant.node.kind {
+            ast::tuple_variant_kind(args) =>
+                ser_variant(cx, span, variant.node.name, v_idx, args),
+            ast::struct_variant_kind(*) =>
+                fail ~"struct variants unimplemented",
+            ast::enum_variant_kind(*) =>
+                fail ~"enum variants unimplemented",
+        }
+    };
+
+    // ast for `match *self { $(arms) }`
+    let match_expr = cx.expr(
+        span,
+        ast::expr_match(
+            cx.expr(
+                span,
+                ast::expr_unary(ast::deref, cx.expr_var(span, ~"self"))
+            ),
+            arms
+        )
+    );
+
+    // ast for `__s.emit_enum($(name), || $(match_expr))`
+    cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__s"),
+            cx.ident_of(~"emit_enum")
+        ),
+        ~[
+            cx.lit_str(span, @cx.str_of(name)),
+            cx.lambda_expr(match_expr),
+        ]
+    )
+}
+
+fn mk_enum_deser_variant_nary(
+    cx: ext_ctxt,
+    span: span,
+    name: ast::ident,
+    args: ~[ast::variant_arg]
+) -> @ast::expr {
+    let args = do args.mapi |idx, _arg| {
+        // ast for `|| std::serialization2::deserialize(__d)`
+        let expr_lambda = cx.lambda_expr(
+            cx.expr_call(
+                span,
+                cx.expr_path(span, ~[
+                    cx.ident_of(~"std"),
+                    cx.ident_of(~"serialization2"),
+                    cx.ident_of(~"deserialize"),
+                ]),
+                ~[cx.expr_var(span, ~"__d")]
+            )
+        );
+
+        // ast for `__d.read_enum_variant_arg($(a_idx), $(expr_lambda))`
+        cx.expr_call(
+            span,
+            cx.expr_field(
+                span,
+                cx.expr_var(span, ~"__d"),
+                cx.ident_of(~"read_enum_variant_arg")
+            ),
+            ~[cx.lit_uint(span, idx), expr_lambda]
+        )
+    };
+
+    // ast for `$(name)($(args))`
+    cx.expr_call(span, cx.expr_path(span, ~[name]), args)
+}
+
+fn mk_enum_deser_body(
+    cx: ext_ctxt,
+    span: span,
+    name: ast::ident,
+    variants: ~[ast::variant]
+) -> @ast::expr {
+    let mut arms = do variants.mapi |v_idx, variant| {
+        let body = match variant.node.kind {
+            ast::tuple_variant_kind(args) => {
+                if args.is_empty() {
+                    // for a nullary variant v, do "v"
+                    cx.expr_path(span, ~[variant.node.name])
+                } else {
+                    // for an n-ary variant v, do "v(a_1, ..., a_n)"
+                    mk_enum_deser_variant_nary(
+                        cx,
+                        span,
+                        variant.node.name,
+                        args
+                    )
+                }
+            },
+            ast::struct_variant_kind(*) =>
+                fail ~"struct variants unimplemented",
+            ast::enum_variant_kind(*) =>
+                fail ~"enum variants unimplemented",
+        };
+
+        let pat = @{
+            id: cx.next_id(),
+            node: ast::pat_lit(cx.lit_uint(span, v_idx)),
+            span: span,
+        };
+
+        {
+            pats: ~[pat],
+            guard: None,
+            body: cx.expr_blk(body),
+        }
+    };
+
+    let impossible_case = {
+        pats: ~[@{ id: cx.next_id(), node: ast::pat_wild, span: span}],
+        guard: None,
+
+        // FIXME(#3198): proper error message
+        body: cx.expr_blk(cx.expr(span, ast::expr_fail(None))),
+    };
+
+    arms.push(impossible_case);
+
+    // ast for `|i| { match i { $(arms) } }`
+    let expr_lambda = cx.expr(
+        span,
+        ast::expr_fn_block(
+            {
+                inputs: ~[{
+                    mode: ast::infer(cx.next_id()),
+                    ty: @{
+                        id: cx.next_id(),
+                        node: ast::ty_infer,
+                        span: span
+                    },
+                    ident: cx.ident_of(~"i"),
+                    id: cx.next_id(),
+                }],
+                output: @{
+                    id: cx.next_id(),
+                    node: ast::ty_infer,
+                    span: span,
+                },
+                cf: ast::return_val,
+            },
+            cx.expr_blk(
+                cx.expr(
+                    span,
+                    ast::expr_match(cx.expr_var(span, ~"i"), arms)
+                )
+            ),
+            @~[]
+        )
+    );
+
+    // ast for `__d.read_enum_variant($(expr_lambda))`
+    let expr_lambda = cx.lambda_expr(
+        cx.expr_call(
+            span,
+            cx.expr_field(
+                span,
+                cx.expr_var(span, ~"__d"),
+                cx.ident_of(~"read_enum_variant")
+            ),
+            ~[expr_lambda]
+        )
+    );
+
+    // ast for `__d.read_enum($(e_name), $(expr_lambda))`
+    cx.expr_call(
+        span,
+        cx.expr_field(
+            span,
+            cx.expr_var(span, ~"__d"),
+            cx.ident_of(~"read_enum")
+        ),
+        ~[
+            cx.lit_str(span, @cx.str_of(name)),
+            expr_lambda
+        ]
+    )
+}
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index c106042b9a3..ab56b6bb322 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -54,7 +54,7 @@ enum syntax_extension {
     // macro_defining() is obsolete, remove when #old_macros go away.
     macro_defining(macro_definer),
 
-    // #[auto_serialize] and such. will probably survive death of #old_macros
+    // #[auto_serialize2] and such. will probably survive death of #old_macros
     item_decorator(item_decorator),
 
     // Token-tree expanders
@@ -64,6 +64,65 @@ enum syntax_extension {
 
 // A temporary hard-coded map of methods for expanding syntax extension
 // AST nodes into full ASTs
+#[cfg(stage0)]
+fn syntax_expander_table() -> HashMap<~str, syntax_extension> {
+    fn builtin(f: syntax_expander_) -> syntax_extension
+        {normal({expander: f, span: None})}
+    fn builtin_expr_tt(f: syntax_expander_tt_) -> syntax_extension {
+        expr_tt({expander: f, span: None})
+    }
+    fn builtin_item_tt(f: syntax_expander_tt_item_) -> syntax_extension {
+        item_tt({expander: f, span: None})
+    }
+    let syntax_expanders = HashMap();
+    syntax_expanders.insert(~"macro",
+                            macro_defining(ext::simplext::add_new_extension));
+    syntax_expanders.insert(~"macro_rules",
+                            builtin_item_tt(
+                                ext::tt::macro_rules::add_new_extension));
+    syntax_expanders.insert(~"fmt", builtin(ext::fmt::expand_syntax_ext));
+    syntax_expanders.insert(
+        ~"auto_serialize2",
+        item_decorator(ext::auto_serialize2::expand_auto_serialize));
+    syntax_expanders.insert(
+        ~"auto_deserialize2",
+        item_decorator(ext::auto_serialize2::expand_auto_deserialize));
+    syntax_expanders.insert(~"env", builtin(ext::env::expand_syntax_ext));
+    syntax_expanders.insert(~"concat_idents",
+                            builtin(ext::concat_idents::expand_syntax_ext));
+    syntax_expanders.insert(~"ident_to_str",
+                            builtin(ext::ident_to_str::expand_syntax_ext));
+    syntax_expanders.insert(~"log_syntax",
+                            builtin_expr_tt(
+                                ext::log_syntax::expand_syntax_ext));
+    syntax_expanders.insert(~"ast",
+                            builtin(ext::qquote::expand_ast));
+    syntax_expanders.insert(~"line",
+                            builtin(ext::source_util::expand_line));
+    syntax_expanders.insert(~"col",
+                            builtin(ext::source_util::expand_col));
+    syntax_expanders.insert(~"file",
+                            builtin(ext::source_util::expand_file));
+    syntax_expanders.insert(~"stringify",
+                            builtin(ext::source_util::expand_stringify));
+    syntax_expanders.insert(~"include",
+                            builtin(ext::source_util::expand_include));
+    syntax_expanders.insert(~"include_str",
+                            builtin(ext::source_util::expand_include_str));
+    syntax_expanders.insert(~"include_bin",
+                            builtin(ext::source_util::expand_include_bin));
+    syntax_expanders.insert(~"module_path",
+                            builtin(ext::source_util::expand_mod));
+    syntax_expanders.insert(~"proto",
+                            builtin_item_tt(ext::pipes::expand_proto));
+    syntax_expanders.insert(
+        ~"trace_macros",
+        builtin_expr_tt(ext::trace_macros::expand_trace_macros));
+    return syntax_expanders;
+}
+
+#[cfg(stage1)]
+#[cfg(stage2)]
 fn syntax_expander_table() -> HashMap<~str, syntax_extension> {
     fn builtin(f: syntax_expander_) -> syntax_extension
         {normal({expander: f, span: None})}
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 22e2cfcde6b..2d0b2f4c80a 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -124,7 +124,7 @@ fn expand_expr(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
 }
 
 // This is a secondary mechanism for invoking syntax extensions on items:
-// "decorator" attributes, such as #[auto_serialize]. These are invoked by an
+// "decorator" attributes, such as #[auto_serialize2]. These are invoked by an
 // attribute prefixing an item, and are interpreted by feeding the item
 // through the named attribute _as a syntax extension_ and splicing in the
 // resulting item vec into place in favour of the decorator. Note that