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