compiler/rustc_serialize/src/serialize.rs

   1 //! Support code for encoding and decoding types.
   2
   3 /*
   4 Core encoding and decoding interfaces.
   5 */
   6
   7 use std::borrow::Cow;
   8 use std::cell::{Cell, RefCell};
   9 use std::marker::PhantomData;
  10 use std::path;
  11 use std::rc::Rc;
  12 use std::sync::Arc;
  13
  14 pub trait Encoder {
  15     type Error;
  16
  17     // Primitive types:
  18     fn emit_unit(&mut self) -> Result<(), Self::Error>;
  19     fn emit_usize(&mut self, v: usize) -> Result<(), Self::Error>;
  20     fn emit_u128(&mut self, v: u128) -> Result<(), Self::Error>;
  21     fn emit_u64(&mut self, v: u64) -> Result<(), Self::Error>;
  22     fn emit_u32(&mut self, v: u32) -> Result<(), Self::Error>;
  23     fn emit_u16(&mut self, v: u16) -> Result<(), Self::Error>;
  24     fn emit_u8(&mut self, v: u8) -> Result<(), Self::Error>;
  25     fn emit_isize(&mut self, v: isize) -> Result<(), Self::Error>;
  26     fn emit_i128(&mut self, v: i128) -> Result<(), Self::Error>;
  27     fn emit_i64(&mut self, v: i64) -> Result<(), Self::Error>;
  28     fn emit_i32(&mut self, v: i32) -> Result<(), Self::Error>;
  29     fn emit_i16(&mut self, v: i16) -> Result<(), Self::Error>;
  30     fn emit_i8(&mut self, v: i8) -> Result<(), Self::Error>;
  31     fn emit_bool(&mut self, v: bool) -> Result<(), Self::Error>;
  32     fn emit_f64(&mut self, v: f64) -> Result<(), Self::Error>;
  33     fn emit_f32(&mut self, v: f32) -> Result<(), Self::Error>;
  34     fn emit_char(&mut self, v: char) -> Result<(), Self::Error>;
  35     fn emit_str(&mut self, v: &str) -> Result<(), Self::Error>;
  36     fn emit_raw_bytes(&mut self, s: &[u8]) -> Result<(), Self::Error>;
  37
  38     // Compound types:
  39     #[inline]
  40     fn emit_enum<F>(&mut self, f: F) -> Result<(), Self::Error>
  41     where
  42         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
  43     {
  44         f(self)
  45     }
  46
  47     fn emit_enum_variant<F>(
  48         &mut self,
  49         _v_name: &str,
  50         v_id: usize,
  51         _len: usize,
  52         f: F,
  53     ) -> Result<(), Self::Error>
  54     where
  55         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
  56     {
  57         self.emit_usize(v_id)?;
  58         f(self)
  59     }
  60
  61     // We put the field index in a const generic to allow the emit_usize to be
  62     // compiled into a more efficient form. In practice, the variant index is
  63     // known at compile-time, and that knowledge allows much more efficient
  64     // codegen than we'd otherwise get. LLVM isn't always able to make the
  65     // optimization that would otherwise be necessary here, likely due to the
  66     // multiple levels of inlining and const-prop that are needed.
  67     #[inline]
  68     fn emit_fieldless_enum_variant<const ID: usize>(
  69         &mut self,
  70         _v_name: &str,
  71     ) -> Result<(), Self::Error> {
  72         self.emit_usize(ID)
  73     }
  74
  75     #[inline]
  76     fn emit_enum_variant_arg<F>(&mut self, _first: bool, f: F) -> Result<(), Self::Error>
  77     where
  78         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
  79     {
  80         f(self)
  81     }
  82
  83     #[inline]
  84     fn emit_struct<F>(&mut self, _no_fields: bool, f: F) -> Result<(), Self::Error>
  85     where
  86         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
  87     {
  88         f(self)
  89     }
  90
  91     #[inline]
  92     fn emit_struct_field<F>(&mut self, _f_name: &str, _first: bool, f: F) -> Result<(), Self::Error>
  93     where
  94         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
  95     {
  96         f(self)
  97     }
  98
  99     #[inline]
 100     fn emit_tuple<F>(&mut self, _len: usize, f: F) -> Result<(), Self::Error>
 101     where
 102         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 103     {
 104         f(self)
 105     }
 106
 107     #[inline]
 108     fn emit_tuple_arg<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
 109     where
 110         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 111     {
 112         f(self)
 113     }
 114
 115     // Specialized types:
 116     fn emit_option<F>(&mut self, f: F) -> Result<(), Self::Error>
 117     where
 118         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 119     {
 120         self.emit_enum(f)
 121     }
 122
 123     #[inline]
 124     fn emit_option_none(&mut self) -> Result<(), Self::Error> {
 125         self.emit_enum_variant("None", 0, 0, |_| Ok(()))
 126     }
 127
 128     fn emit_option_some<F>(&mut self, f: F) -> Result<(), Self::Error>
 129     where
 130         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 131     {
 132         self.emit_enum_variant("Some", 1, 1, f)
 133     }
 134
 135     fn emit_seq<F>(&mut self, len: usize, f: F) -> Result<(), Self::Error>
 136     where
 137         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 138     {
 139         self.emit_usize(len)?;
 140         f(self)
 141     }
 142
 143     #[inline]
 144     fn emit_seq_elt<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
 145     where
 146         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 147     {
 148         f(self)
 149     }
 150
 151     fn emit_map<F>(&mut self, len: usize, f: F) -> Result<(), Self::Error>
 152     where
 153         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 154     {
 155         self.emit_usize(len)?;
 156         f(self)
 157     }
 158
 159     #[inline]
 160     fn emit_map_elt_key<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
 161     where
 162         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 163     {
 164         f(self)
 165     }
 166
 167     #[inline]
 168     fn emit_map_elt_val<F>(&mut self, f: F) -> Result<(), Self::Error>
 169     where
 170         F: FnOnce(&mut Self) -> Result<(), Self::Error>,
 171     {
 172         f(self)
 173     }
 174 }
 175
 176 pub trait Decoder {
 177     type Error;
 178
 179     // Primitive types:
 180     fn read_nil(&mut self) -> Result<(), Self::Error>;
 181     fn read_usize(&mut self) -> Result<usize, Self::Error>;
 182     fn read_u128(&mut self) -> Result<u128, Self::Error>;
 183     fn read_u64(&mut self) -> Result<u64, Self::Error>;
 184     fn read_u32(&mut self) -> Result<u32, Self::Error>;
 185     fn read_u16(&mut self) -> Result<u16, Self::Error>;
 186     fn read_u8(&mut self) -> Result<u8, Self::Error>;
 187     fn read_isize(&mut self) -> Result<isize, Self::Error>;
 188     fn read_i128(&mut self) -> Result<i128, Self::Error>;
 189     fn read_i64(&mut self) -> Result<i64, Self::Error>;
 190     fn read_i32(&mut self) -> Result<i32, Self::Error>;
 191     fn read_i16(&mut self) -> Result<i16, Self::Error>;
 192     fn read_i8(&mut self) -> Result<i8, Self::Error>;
 193     fn read_bool(&mut self) -> Result<bool, Self::Error>;
 194     fn read_f64(&mut self) -> Result<f64, Self::Error>;
 195     fn read_f32(&mut self) -> Result<f32, Self::Error>;
 196     fn read_char(&mut self) -> Result<char, Self::Error>;
 197     fn read_str(&mut self) -> Result<Cow<'_, str>, Self::Error>;
 198     fn read_raw_bytes_into(&mut self, s: &mut [u8]) -> Result<(), Self::Error>;
 199
 200     // Compound types:
 201     #[inline]
 202     fn read_enum<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 203     where
 204         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 205     {
 206         f(self)
 207     }
 208
 209     #[inline]
 210     fn read_enum_variant<T, F>(&mut self, _names: &[&str], mut f: F) -> Result<T, Self::Error>
 211     where
 212         F: FnMut(&mut Self, usize) -> Result<T, Self::Error>,
 213     {
 214         let disr = self.read_usize()?;
 215         f(self, disr)
 216     }
 217
 218     #[inline]
 219     fn read_enum_variant_arg<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 220     where
 221         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 222     {
 223         f(self)
 224     }
 225
 226     #[inline]
 227     fn read_struct<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 228     where
 229         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 230     {
 231         f(self)
 232     }
 233
 234     #[inline]
 235     fn read_struct_field<T, F>(&mut self, _f_name: &str, f: F) -> Result<T, Self::Error>
 236     where
 237         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 238     {
 239         f(self)
 240     }
 241
 242     #[inline]
 243     fn read_tuple<T, F>(&mut self, _len: usize, f: F) -> Result<T, Self::Error>
 244     where
 245         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 246     {
 247         f(self)
 248     }
 249
 250     #[inline]
 251     fn read_tuple_arg<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 252     where
 253         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 254     {
 255         f(self)
 256     }
 257
 258     // Specialized types:
 259     fn read_option<T, F>(&mut self, mut f: F) -> Result<T, Self::Error>
 260     where
 261         F: FnMut(&mut Self, bool) -> Result<T, Self::Error>,
 262     {
 263         self.read_enum(move |this| {
 264             this.read_enum_variant(&["None", "Some"], move |this, idx| match idx {
 265                 0 => f(this, false),
 266                 1 => f(this, true),
 267                 _ => Err(this.error("read_option: expected 0 for None or 1 for Some")),
 268             })
 269         })
 270     }
 271
 272     fn read_seq<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 273     where
 274         F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>,
 275     {
 276         let len = self.read_usize()?;
 277         f(self, len)
 278     }
 279
 280     #[inline]
 281     fn read_seq_elt<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 282     where
 283         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 284     {
 285         f(self)
 286     }
 287
 288     fn read_map<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 289     where
 290         F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>,
 291     {
 292         let len = self.read_usize()?;
 293         f(self, len)
 294     }
 295
 296     #[inline]
 297     fn read_map_elt_key<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 298     where
 299         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 300     {
 301         f(self)
 302     }
 303
 304     #[inline]
 305     fn read_map_elt_val<T, F>(&mut self, f: F) -> Result<T, Self::Error>
 306     where
 307         F: FnOnce(&mut Self) -> Result<T, Self::Error>,
 308     {
 309         f(self)
 310     }
 311
 312     // Failure
 313     fn error(&mut self, err: &str) -> Self::Error;
 314 }
 315
 316 /// Trait for types that can be serialized
 317 ///
 318 /// This can be implemented using the `Encodable`, `TyEncodable` and
 319 /// `MetadataEncodable` macros.
 320 ///
 321 /// * `Encodable` should be used in crates that don't depend on
 322 ///   `rustc_middle`.
 323 /// * `MetadataEncodable` is used in `rustc_metadata` for types that contain
 324 ///   `rustc_metadata::rmeta::Lazy`.
 325 /// * `TyEncodable` should be used for types that are only serialized in crate
 326 ///   metadata or the incremental cache. This is most types in `rustc_middle`.
 327 pub trait Encodable<S: Encoder> {
 328     fn encode(&self, s: &mut S) -> Result<(), S::Error>;
 329 }
 330
 331 /// Trait for types that can be deserialized
 332 ///
 333 /// This can be implemented using the `Decodable`, `TyDecodable` and
 334 /// `MetadataDecodable` macros.
 335 ///
 336 /// * `Decodable` should be used in crates that don't depend on
 337 ///   `rustc_middle`.
 338 /// * `MetadataDecodable` is used in `rustc_metadata` for types that contain
 339 ///   `rustc_metadata::rmeta::Lazy`.
 340 /// * `TyDecodable` should be used for types that are only serialized in crate
 341 ///   metadata or the incremental cache. This is most types in `rustc_middle`.
 342 pub trait Decodable<D: Decoder>: Sized {
 343     fn decode(d: &mut D) -> Result<Self, D::Error>;
 344 }
 345
 346 macro_rules! direct_serialize_impls {
 347     ($($ty:ident $emit_method:ident $read_method:ident),*) => {
 348         $(
 349             impl<S: Encoder> Encodable<S> for $ty {
 350                 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 351                     s.$emit_method(*self)
 352                 }
 353             }
 354
 355             impl<D: Decoder> Decodable<D> for $ty {
 356                 fn decode(d: &mut D) -> Result<$ty, D::Error> {
 357                     d.$read_method()
 358                 }
 359             }
 360         )*
 361     }
 362 }
 363
 364 direct_serialize_impls! {
 365     usize emit_usize read_usize,
 366     u8 emit_u8 read_u8,
 367     u16 emit_u16 read_u16,
 368     u32 emit_u32 read_u32,
 369     u64 emit_u64 read_u64,
 370     u128 emit_u128 read_u128,
 371     isize emit_isize read_isize,
 372     i8 emit_i8 read_i8,
 373     i16 emit_i16 read_i16,
 374     i32 emit_i32 read_i32,
 375     i64 emit_i64 read_i64,
 376     i128 emit_i128 read_i128,
 377     f32 emit_f32 read_f32,
 378     f64 emit_f64 read_f64,
 379     bool emit_bool read_bool,
 380     char emit_char read_char
 381 }
 382
 383 impl<S: Encoder> Encodable<S> for ! {
 384     fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
 385         unreachable!()
 386     }
 387 }
 388
 389 impl<D: Decoder> Decodable<D> for ! {
 390     fn decode(_d: &mut D) -> Result<!, D::Error> {
 391         unreachable!()
 392     }
 393 }
 394
 395 impl<S: Encoder> Encodable<S> for ::std::num::NonZeroU32 {
 396     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 397         s.emit_u32(self.get())
 398     }
 399 }
 400
 401 impl<D: Decoder> Decodable<D> for ::std::num::NonZeroU32 {
 402     fn decode(d: &mut D) -> Result<Self, D::Error> {
 403         d.read_u32().map(|d| ::std::num::NonZeroU32::new(d).unwrap())
 404     }
 405 }
 406
 407 impl<S: Encoder> Encodable<S> for str {
 408     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 409         s.emit_str(self)
 410     }
 411 }
 412
 413 impl<S: Encoder> Encodable<S> for &str {
 414     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 415         s.emit_str(self)
 416     }
 417 }
 418
 419 impl<S: Encoder> Encodable<S> for String {
 420     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 421         s.emit_str(&self[..])
 422     }
 423 }
 424
 425 impl<D: Decoder> Decodable<D> for String {
 426     fn decode(d: &mut D) -> Result<String, D::Error> {
 427         Ok(d.read_str()?.into_owned())
 428     }
 429 }
 430
 431 impl<S: Encoder> Encodable<S> for () {
 432     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 433         s.emit_unit()
 434     }
 435 }
 436
 437 impl<D: Decoder> Decodable<D> for () {
 438     fn decode(d: &mut D) -> Result<(), D::Error> {
 439         d.read_nil()
 440     }
 441 }
 442
 443 impl<S: Encoder, T> Encodable<S> for PhantomData<T> {
 444     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 445         s.emit_unit()
 446     }
 447 }
 448
 449 impl<D: Decoder, T> Decodable<D> for PhantomData<T> {
 450     fn decode(d: &mut D) -> Result<PhantomData<T>, D::Error> {
 451         d.read_nil()?;
 452         Ok(PhantomData)
 453     }
 454 }
 455
 456 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<[T]> {
 457     fn decode(d: &mut D) -> Result<Box<[T]>, D::Error> {
 458         let v: Vec<T> = Decodable::decode(d)?;
 459         Ok(v.into_boxed_slice())
 460     }
 461 }
 462
 463 impl<S: Encoder, T: Encodable<S>> Encodable<S> for Rc<T> {
 464     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 465         (**self).encode(s)
 466     }
 467 }
 468
 469 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<T> {
 470     fn decode(d: &mut D) -> Result<Rc<T>, D::Error> {
 471         Ok(Rc::new(Decodable::decode(d)?))
 472     }
 473 }
 474
 475 impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T] {
 476     default fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 477         s.emit_seq(self.len(), |s| {
 478             for (i, e) in self.iter().enumerate() {
 479                 s.emit_seq_elt(i, |s| e.encode(s))?
 480             }
 481             Ok(())
 482         })
 483     }
 484 }
 485
 486 impl<S: Encoder, T: Encodable<S>> Encodable<S> for Vec<T> {
 487     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 488         let slice: &[T] = self;
 489         slice.encode(s)
 490     }
 491 }
 492
 493 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Vec<T> {
 494     default fn decode(d: &mut D) -> Result<Vec<T>, D::Error> {
 495         d.read_seq(|d, len| {
 496             let mut v = Vec::with_capacity(len);
 497             for _ in 0..len {
 498                 v.push(d.read_seq_elt(|d| Decodable::decode(d))?);
 499             }
 500             Ok(v)
 501         })
 502     }
 503 }
 504
 505 impl<S: Encoder, T: Encodable<S>, const N: usize> Encodable<S> for [T; N] {
 506     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 507         let slice: &[T] = self;
 508         slice.encode(s)
 509     }
 510 }
 511
 512 impl<D: Decoder, const N: usize> Decodable<D> for [u8; N] {
 513     fn decode(d: &mut D) -> Result<[u8; N], D::Error> {
 514         d.read_seq(|d, len| {
 515             assert!(len == N);
 516             let mut v = [0u8; N];
 517             for i in 0..len {
 518                 v[i] = d.read_seq_elt(|d| Decodable::decode(d))?;
 519             }
 520             Ok(v)
 521         })
 522     }
 523 }
 524
 525 impl<'a, S: Encoder, T: Encodable<S>> Encodable<S> for Cow<'a, [T]>
 526 where
 527     [T]: ToOwned<Owned = Vec<T>>,
 528 {
 529     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 530         let slice: &[T] = self;
 531         slice.encode(s)
 532     }
 533 }
 534
 535 impl<D: Decoder, T: Decodable<D> + ToOwned> Decodable<D> for Cow<'static, [T]>
 536 where
 537     [T]: ToOwned<Owned = Vec<T>>,
 538 {
 539     fn decode(d: &mut D) -> Result<Cow<'static, [T]>, D::Error> {
 540         let v: Vec<T> = Decodable::decode(d)?;
 541         Ok(Cow::Owned(v))
 542     }
 543 }
 544
 545 impl<S: Encoder, T: Encodable<S>> Encodable<S> for Option<T> {
 546     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 547         s.emit_option(|s| match *self {
 548             None => s.emit_option_none(),
 549             Some(ref v) => s.emit_option_some(|s| v.encode(s)),
 550         })
 551     }
 552 }
 553
 554 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Option<T> {
 555     fn decode(d: &mut D) -> Result<Option<T>, D::Error> {
 556         d.read_option(|d, b| if b { Ok(Some(Decodable::decode(d)?)) } else { Ok(None) })
 557     }
 558 }
 559
 560 impl<S: Encoder, T1: Encodable<S>, T2: Encodable<S>> Encodable<S> for Result<T1, T2> {
 561     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 562         s.emit_enum(|s| match *self {
 563             Ok(ref v) => {
 564                 s.emit_enum_variant("Ok", 0, 1, |s| s.emit_enum_variant_arg(true, |s| v.encode(s)))
 565             }
 566             Err(ref v) => {
 567                 s.emit_enum_variant("Err", 1, 1, |s| s.emit_enum_variant_arg(true, |s| v.encode(s)))
 568             }
 569         })
 570     }
 571 }
 572
 573 impl<D: Decoder, T1: Decodable<D>, T2: Decodable<D>> Decodable<D> for Result<T1, T2> {
 574     fn decode(d: &mut D) -> Result<Result<T1, T2>, D::Error> {
 575         d.read_enum(|d| {
 576             d.read_enum_variant(&["Ok", "Err"], |d, disr| match disr {
 577                 0 => Ok(Ok(d.read_enum_variant_arg(|d| T1::decode(d))?)),
 578                 1 => Ok(Err(d.read_enum_variant_arg(|d| T2::decode(d))?)),
 579                 _ => {
 580                     panic!(
 581                         "Encountered invalid discriminant while \
 582                                 decoding `Result`."
 583                     );
 584                 }
 585             })
 586         })
 587     }
 588 }
 589
 590 macro_rules! peel {
 591     ($name:ident, $($other:ident,)*) => (tuple! { $($other,)* })
 592 }
 593
 594 /// Evaluates to the number of tokens passed to it.
 595 ///
 596 /// Logarithmic counting: every one or two recursive expansions, the number of
 597 /// tokens to count is divided by two, instead of being reduced by one.
 598 /// Therefore, the recursion depth is the binary logarithm of the number of
 599 /// tokens to count, and the expanded tree is likewise very small.
 600 macro_rules! count {
 601     ()                     => (0usize);
 602     ($one:tt)              => (1usize);
 603     ($($pairs:tt $_p:tt)*) => (count!($($pairs)*) << 1usize);
 604     ($odd:tt $($rest:tt)*) => (count!($($rest)*) | 1usize);
 605 }
 606
 607 macro_rules! tuple {
 608     () => ();
 609     ( $($name:ident,)+ ) => (
 610         impl<D: Decoder, $($name: Decodable<D>),+> Decodable<D> for ($($name,)+) {
 611             #[allow(non_snake_case)]
 612             fn decode(d: &mut D) -> Result<($($name,)+), D::Error> {
 613                 let len: usize = count!($($name)+);
 614                 d.read_tuple(len, |d| {
 615                     let ret = ($(d.read_tuple_arg(|d| -> Result<$name, D::Error> {
 616                         Decodable::decode(d)
 617                     })?,)+);
 618                     Ok(ret)
 619                 })
 620             }
 621         }
 622         impl<S: Encoder, $($name: Encodable<S>),+> Encodable<S> for ($($name,)+) {
 623             #[allow(non_snake_case)]
 624             fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 625                 let ($(ref $name,)+) = *self;
 626                 let mut n = 0;
 627                 $(let $name = $name; n += 1;)+
 628                 s.emit_tuple(n, |s| {
 629                     let mut i = 0;
 630                     $(s.emit_tuple_arg({ i+=1; i-1 }, |s| $name.encode(s))?;)+
 631                     Ok(())
 632                 })
 633             }
 634         }
 635         peel! { $($name,)+ }
 636     )
 637 }
 638
 639 tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
 640
 641 impl<S: Encoder> Encodable<S> for path::Path {
 642     fn encode(&self, e: &mut S) -> Result<(), S::Error> {
 643         self.to_str().unwrap().encode(e)
 644     }
 645 }
 646
 647 impl<S: Encoder> Encodable<S> for path::PathBuf {
 648     fn encode(&self, e: &mut S) -> Result<(), S::Error> {
 649         path::Path::encode(self, e)
 650     }
 651 }
 652
 653 impl<D: Decoder> Decodable<D> for path::PathBuf {
 654     fn decode(d: &mut D) -> Result<path::PathBuf, D::Error> {
 655         let bytes: String = Decodable::decode(d)?;
 656         Ok(path::PathBuf::from(bytes))
 657     }
 658 }
 659
 660 impl<S: Encoder, T: Encodable<S> + Copy> Encodable<S> for Cell<T> {
 661     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 662         self.get().encode(s)
 663     }
 664 }
 665
 666 impl<D: Decoder, T: Decodable<D> + Copy> Decodable<D> for Cell<T> {
 667     fn decode(d: &mut D) -> Result<Cell<T>, D::Error> {
 668         Ok(Cell::new(Decodable::decode(d)?))
 669     }
 670 }
 671
 672 // FIXME: #15036
 673 // Should use `try_borrow`, returning an
 674 // `encoder.error("attempting to Encode borrowed RefCell")`
 675 // from `encode` when `try_borrow` returns `None`.
 676
 677 impl<S: Encoder, T: Encodable<S>> Encodable<S> for RefCell<T> {
 678     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 679         self.borrow().encode(s)
 680     }
 681 }
 682
 683 impl<D: Decoder, T: Decodable<D>> Decodable<D> for RefCell<T> {
 684     fn decode(d: &mut D) -> Result<RefCell<T>, D::Error> {
 685         Ok(RefCell::new(Decodable::decode(d)?))
 686     }
 687 }
 688
 689 impl<S: Encoder, T: Encodable<S>> Encodable<S> for Arc<T> {
 690     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 691         (**self).encode(s)
 692     }
 693 }
 694
 695 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<T> {
 696     fn decode(d: &mut D) -> Result<Arc<T>, D::Error> {
 697         Ok(Arc::new(Decodable::decode(d)?))
 698     }
 699 }
 700
 701 impl<S: Encoder, T: ?Sized + Encodable<S>> Encodable<S> for Box<T> {
 702     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
 703         (**self).encode(s)
 704     }
 705 }
 706 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<T> {
 707     fn decode(d: &mut D) -> Result<Box<T>, D::Error> {
 708         Ok(Box::new(Decodable::decode(d)?))
 709     }
 710 }