1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! The compiler code necessary to implement the `#[derive(Encodable)]`
12 //! (and `Decodable`, in decodable.rs) extension. The idea here is that
13 //! type-defining items may be tagged with `#[derive(Encodable, Decodable)]`.
15 //! For example, a type like:
18 //! #[derive(Encodable, Decodable)]
19 //! struct Node { id: usize }
22 //! would generate two implementations like:
25 //! # struct Node { id: usize }
26 //! impl<S: Encoder<E>, E> Encodable<S, E> for Node {
27 //! fn encode(&self, s: &mut S) -> Result<(), E> {
28 //! s.emit_struct("Node", 1, |this| {
29 //! this.emit_struct_field("id", 0, |this| {
30 //! Encodable::encode(&self.id, this)
31 //! /* this.emit_usize(self.id) can also be used */
37 //! impl<D: Decoder<E>, E> Decodable<D, E> for Node {
38 //! fn decode(d: &mut D) -> Result<Node, E> {
39 //! d.read_struct("Node", 1, |this| {
40 //! match this.read_struct_field("id", 0, |this| Decodable::decode(this)) {
41 //! Ok(id) => Ok(Node { id: id }),
49 //! Other interesting scenarios are when the item has type parameters or
50 //! references other non-built-in types. A type definition like:
53 //! # #[derive(Encodable, Decodable)] struct Span;
54 //! #[derive(Encodable, Decodable)]
55 //! struct Spanned<T> { node: T, span: Span }
58 //! would yield functions like:
61 //! # #[derive(Encodable, Decodable)] struct Span;
62 //! # struct Spanned<T> { node: T, span: Span }
66 //! T: Encodable<S, E>
67 //! > Encodable<S, E> for Spanned<T> {
68 //! fn encode(&self, s: &mut S) -> Result<(), E> {
69 //! s.emit_struct("Spanned", 2, |this| {
70 //! this.emit_struct_field("node", 0, |this| self.node.encode(this))
72 //! this.emit_struct_field("span", 1, |this| self.span.encode(this))
80 //! T: Decodable<D, E>
81 //! > Decodable<D, E> for Spanned<T> {
82 //! fn decode(d: &mut D) -> Result<Spanned<T>, E> {
83 //! d.read_struct("Spanned", 2, |this| {
85 //! node: this.read_struct_field("node", 0, |this| Decodable::decode(this))
87 //! span: this.read_struct_field("span", 1, |this| Decodable::decode(this))
95 use deriving::{self, pathvec_std};
96 use deriving::generic::*;
97 use deriving::generic::ty::*;
98 use deriving::warn_if_deprecated;
100 use syntax::ast::{Expr, ExprKind, MetaItem, Mutability};
101 use syntax::ext::base::{Annotatable, ExtCtxt};
102 use syntax::ext::build::AstBuilder;
104 use syntax::symbol::Symbol;
105 use syntax_pos::Span;
107 pub fn expand_deriving_rustc_encodable(cx: &mut ExtCtxt,
111 push: &mut FnMut(Annotatable)) {
112 expand_deriving_encodable_imp(cx, span, mitem, item, push, "rustc_serialize")
115 pub fn expand_deriving_encodable(cx: &mut ExtCtxt,
119 push: &mut FnMut(Annotatable)) {
120 warn_if_deprecated(cx, span, "Encodable");
121 expand_deriving_encodable_imp(cx, span, mitem, item, push, "serialize")
124 fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
128 push: &mut FnMut(Annotatable),
129 krate: &'static str) {
130 let typaram = &*deriving::hygienic_type_parameter(item, "__S");
132 let trait_def = TraitDef {
134 attributes: Vec::new(),
135 path: Path::new_(vec![krate, "Encodable"], None, vec![], PathKind::Global),
136 additional_bounds: Vec::new(),
137 generics: LifetimeBounds::empty(),
139 supports_unions: false,
143 generics: LifetimeBounds {
144 lifetimes: Vec::new(),
147 vec![Path::new_(vec![krate, "Encoder"], None, vec![], PathKind::Global)])
150 explicit_self: borrowed_explicit_self(),
151 args: vec![Ptr(Box::new(Literal(Path::new_local(typaram))),
152 Borrowed(None, Mutability::Mutable))],
153 ret_ty: Literal(Path::new_(
154 pathvec_std!(cx, result::Result),
156 vec![Box::new(Tuple(Vec::new())), Box::new(Literal(Path::new_(
157 vec![typaram, "Error"], None, vec![], PathKind::Local
161 attributes: Vec::new(),
163 unify_fieldless_variants: false,
164 combine_substructure: combine_substructure(Box::new(|a, b, c| {
165 encodable_substructure(a, b, c, krate)
169 associated_types: Vec::new(),
172 trait_def.expand(cx, mitem, item, push)
175 fn encodable_substructure(cx: &mut ExtCtxt,
177 substr: &Substructure,
180 let encoder = substr.nonself_args[0].clone();
181 // throw an underscore in front to suppress unused variable warnings
182 let blkarg = cx.ident_of("_e");
183 let blkencoder = cx.expr_ident(trait_span, blkarg);
184 let fn_path = cx.expr_path(cx.path_global(trait_span,
185 vec![cx.ident_of(krate),
186 cx.ident_of("Encodable"),
187 cx.ident_of("encode")]));
189 return match *substr.fields {
190 Struct(_, ref fields) => {
191 let emit_struct_field = cx.ident_of("emit_struct_field");
192 let mut stmts = Vec::new();
193 for (i, &FieldInfo { name, ref self_, span, .. }) in fields.iter().enumerate() {
194 let name = match name {
196 None => Symbol::intern(&format!("_field{}", i)),
198 let self_ref = cx.expr_addr_of(span, self_.clone());
199 let enc = cx.expr_call(span, fn_path.clone(), vec![self_ref, blkencoder.clone()]);
200 let lambda = cx.lambda1(span, enc, blkarg);
201 let call = cx.expr_method_call(span,
204 vec![cx.expr_str(span, name),
205 cx.expr_usize(span, i),
208 // last call doesn't need a try!
209 let last = fields.len() - 1;
210 let call = if i != last {
211 cx.expr_try(span, call)
213 cx.expr(span, ExprKind::Ret(Some(call)))
215 stmts.push(cx.stmt_expr(call));
218 // unit structs have no fields and need to return Ok()
219 if stmts.is_empty() {
220 let ok = cx.expr_ok(trait_span, cx.expr_tuple(trait_span, vec![]));
221 let ret_ok = cx.expr(trait_span, ExprKind::Ret(Some(ok)));
222 stmts.push(cx.stmt_expr(ret_ok));
225 let blk = cx.lambda_stmts_1(trait_span, stmts, blkarg);
226 cx.expr_method_call(trait_span,
228 cx.ident_of("emit_struct"),
229 vec![cx.expr_str(trait_span, substr.type_ident.name),
230 cx.expr_usize(trait_span, fields.len()),
234 EnumMatching(idx, _, variant, ref fields) => {
235 // We're not generating an AST that the borrow checker is expecting,
236 // so we need to generate a unique local variable to take the
237 // mutable loan out on, otherwise we get conflicts which don't
239 let me = cx.stmt_let(trait_span, false, blkarg, encoder);
240 let encoder = cx.expr_ident(trait_span, blkarg);
241 let emit_variant_arg = cx.ident_of("emit_enum_variant_arg");
242 let mut stmts = Vec::new();
243 if !fields.is_empty() {
244 let last = fields.len() - 1;
245 for (i, &FieldInfo { ref self_, span, .. }) in fields.iter().enumerate() {
246 let self_ref = cx.expr_addr_of(span, self_.clone());
248 cx.expr_call(span, fn_path.clone(), vec![self_ref, blkencoder.clone()]);
249 let lambda = cx.lambda1(span, enc, blkarg);
250 let call = cx.expr_method_call(span,
253 vec![cx.expr_usize(span, i), lambda]);
254 let call = if i != last {
255 cx.expr_try(span, call)
257 cx.expr(span, ExprKind::Ret(Some(call)))
259 stmts.push(cx.stmt_expr(call));
262 let ok = cx.expr_ok(trait_span, cx.expr_tuple(trait_span, vec![]));
263 let ret_ok = cx.expr(trait_span, ExprKind::Ret(Some(ok)));
264 stmts.push(cx.stmt_expr(ret_ok));
267 let blk = cx.lambda_stmts_1(trait_span, stmts, blkarg);
268 let name = cx.expr_str(trait_span, variant.node.name.name);
269 let call = cx.expr_method_call(trait_span,
271 cx.ident_of("emit_enum_variant"),
273 cx.expr_usize(trait_span, idx),
274 cx.expr_usize(trait_span, fields.len()),
276 let blk = cx.lambda1(trait_span, call, blkarg);
277 let ret = cx.expr_method_call(trait_span,
279 cx.ident_of("emit_enum"),
280 vec![cx.expr_str(trait_span ,substr.type_ident.name),
282 cx.expr_block(cx.block(trait_span, vec![me, cx.stmt_expr(ret)]))
285 _ => cx.bug("expected Struct or EnumMatching in derive(Encodable)"),