1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! This module implements the `Any` trait, which enables dynamic typing
//! of any `'static` type through runtime reflection.
//!
//! `Any` itself can be used to get a `TypeId`, and has more features when used
//! as a trait object. As `&Any` (a borrowed trait object), it has the `is` and
//! `downcast_ref` methods, to test if the contained value is of a given type,
//! and to get a reference to the inner value as a type. As `&mut Any`, there
//! is also the `downcast_mut` method, for getting a mutable reference to the
//! inner value. `Box<Any>` adds the `downcast` method, which attempts to
//! convert to a `Box<T>`. See the [`Box`] documentation for the full details.
//!
//! Note that &Any is limited to testing whether a value is of a specified
//! concrete type, and cannot be used to test whether a type implements a trait.
//!
//! [`Box`]: ../../std/boxed/struct.Box.html
//!
//! # Examples
//!
//! Consider a situation where we want to log out a value passed to a function.
//! We know the value we're working on implements Debug, but we don't know its
//! concrete type.  We want to give special treatment to certain types: in this
//! case printing out the length of String values prior to their value.
//! We don't know the concrete type of our value at compile time, so we need to
//! use runtime reflection instead.
//!
//! ```rust
//! use std::fmt::Debug;
//! use std::any::Any;
//!
//! // Logger function for any type that implements Debug.
//! fn log<T: Any + Debug>(value: &T) {
//!     let value_any = value as &Any;
//!
//!     // try to convert our value to a String.  If successful, we want to
//!     // output the String's length as well as its value.  If not, it's a
//!     // different type: just print it out unadorned.
//!     match value_any.downcast_ref::<String>() {
//!         Some(as_string) => {
//!             println!("String ({}): {}", as_string.len(), as_string);
//!         }
//!         None => {
//!             println!("{:?}", value);
//!         }
//!     }
//! }
//!
//! // This function wants to log its parameter out prior to doing work with it.
//! fn do_work<T: Any + Debug>(value: &T) {
//!     log(value);
//!     // ...do some other work
//! }
//!
//! fn main() {
//!     let my_string = "Hello World".to_string();
//!     do_work(&my_string);
//!
//!     let my_i8: i8 = 100;
//!     do_work(&my_i8);
//! }
//! ```

#![stable(feature = "rust1", since = "1.0.0")]

use fmt;
use intrinsics;

///////////////////////////////////////////////////////////////////////////////
// Any trait
///////////////////////////////////////////////////////////////////////////////

/// A type to emulate dynamic typing.
///
/// Most types implement `Any`. However, any type which contains a non-`'static` reference does not.
/// See the [module-level documentation][mod] for more details.
///
/// [mod]: index.html
#[stable(feature = "rust1", since = "1.0.0")]
pub trait Any: 'static {
    /// Gets the `TypeId` of `self`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(get_type_id)]
    ///
    /// use std::any::{Any, TypeId};
    ///
    /// fn is_string(s: &Any) -> bool {
    ///     TypeId::of::<String>() == s.get_type_id()
    /// }
    ///
    /// fn main() {
    ///     assert_eq!(is_string(&0), false);
    ///     assert_eq!(is_string(&"cookie monster".to_string()), true);
    /// }
    /// ```
    #[unstable(feature = "get_type_id",
               reason = "this method will likely be replaced by an associated static",
               issue = "27745")]
    fn get_type_id(&self) -> TypeId;
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: 'static + ?Sized > Any for T {
    fn get_type_id(&self) -> TypeId { TypeId::of::<T>() }
}

///////////////////////////////////////////////////////////////////////////////
// Extension methods for Any trait objects.
///////////////////////////////////////////////////////////////////////////////

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for Any {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Any")
    }
}

// Ensure that the result of e.g. joining a thread can be printed and
// hence used with `unwrap`. May eventually no longer be needed if
// dispatch works with upcasting.
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for Any + Send {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Any")
    }
}

#[stable(feature = "any_send_sync_methods", since = "1.28.0")]
impl fmt::Debug for Any + Send + Sync {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Any")
    }
}

impl Any {
    /// Returns `true` if the boxed type is the same as `T`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn is_string(s: &Any) {
    ///     if s.is::<String>() {
    ///         println!("It's a string!");
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     is_string(&0);
    ///     is_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn is<T: Any>(&self) -> bool {
        // Get TypeId of the type this function is instantiated with
        let t = TypeId::of::<T>();

        // Get TypeId of the type in the trait object
        let boxed = self.get_type_id();

        // Compare both TypeIds on equality
        t == boxed
    }

    /// Returns some reference to the boxed value if it is of type `T`, or
    /// `None` if it isn't.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn print_if_string(s: &Any) {
    ///     if let Some(string) = s.downcast_ref::<String>() {
    ///         println!("It's a string({}): '{}'", string.len(), string);
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     print_if_string(&0);
    ///     print_if_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
        if self.is::<T>() {
            unsafe {
                Some(&*(self as *const Any as *const T))
            }
        } else {
            None
        }
    }

    /// Returns some mutable reference to the boxed value if it is of type `T`, or
    /// `None` if it isn't.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn modify_if_u32(s: &mut Any) {
    ///     if let Some(num) = s.downcast_mut::<u32>() {
    ///         *num = 42;
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let mut x = 10u32;
    ///     let mut s = "starlord".to_string();
    ///
    ///     modify_if_u32(&mut x);
    ///     modify_if_u32(&mut s);
    ///
    ///     assert_eq!(x, 42);
    ///     assert_eq!(&s, "starlord");
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
        if self.is::<T>() {
            unsafe {
                Some(&mut *(self as *mut Any as *mut T))
            }
        } else {
            None
        }
    }
}

impl Any+Send {
    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn is_string(s: &(Any + Send)) {
    ///     if s.is::<String>() {
    ///         println!("It's a string!");
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     is_string(&0);
    ///     is_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn is<T: Any>(&self) -> bool {
        Any::is::<T>(self)
    }

    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn print_if_string(s: &(Any + Send)) {
    ///     if let Some(string) = s.downcast_ref::<String>() {
    ///         println!("It's a string({}): '{}'", string.len(), string);
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     print_if_string(&0);
    ///     print_if_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
        Any::downcast_ref::<T>(self)
    }

    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn modify_if_u32(s: &mut (Any + Send)) {
    ///     if let Some(num) = s.downcast_mut::<u32>() {
    ///         *num = 42;
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let mut x = 10u32;
    ///     let mut s = "starlord".to_string();
    ///
    ///     modify_if_u32(&mut x);
    ///     modify_if_u32(&mut s);
    ///
    ///     assert_eq!(x, 42);
    ///     assert_eq!(&s, "starlord");
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[inline]
    pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
        Any::downcast_mut::<T>(self)
    }
}

impl Any+Send+Sync {
    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn is_string(s: &(Any + Send + Sync)) {
    ///     if s.is::<String>() {
    ///         println!("It's a string!");
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     is_string(&0);
    ///     is_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "any_send_sync_methods", since = "1.28.0")]
    #[inline]
    pub fn is<T: Any>(&self) -> bool {
        Any::is::<T>(self)
    }

    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn print_if_string(s: &(Any + Send + Sync)) {
    ///     if let Some(string) = s.downcast_ref::<String>() {
    ///         println!("It's a string({}): '{}'", string.len(), string);
    ///     } else {
    ///         println!("Not a string...");
    ///     }
    /// }
    ///
    /// fn main() {
    ///     print_if_string(&0);
    ///     print_if_string(&"cookie monster".to_string());
    /// }
    /// ```
    #[stable(feature = "any_send_sync_methods", since = "1.28.0")]
    #[inline]
    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
        Any::downcast_ref::<T>(self)
    }

    /// Forwards to the method defined on the type `Any`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::Any;
    ///
    /// fn modify_if_u32(s: &mut (Any + Send + Sync)) {
    ///     if let Some(num) = s.downcast_mut::<u32>() {
    ///         *num = 42;
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let mut x = 10u32;
    ///     let mut s = "starlord".to_string();
    ///
    ///     modify_if_u32(&mut x);
    ///     modify_if_u32(&mut s);
    ///
    ///     assert_eq!(x, 42);
    ///     assert_eq!(&s, "starlord");
    /// }
    /// ```
    #[stable(feature = "any_send_sync_methods", since = "1.28.0")]
    #[inline]
    pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
        Any::downcast_mut::<T>(self)
    }
}

///////////////////////////////////////////////////////////////////////////////
// TypeID and its methods
///////////////////////////////////////////////////////////////////////////////

/// A `TypeId` represents a globally unique identifier for a type.
///
/// Each `TypeId` is an opaque object which does not allow inspection of what's
/// inside but does allow basic operations such as cloning, comparison,
/// printing, and showing.
///
/// A `TypeId` is currently only available for types which ascribe to `'static`,
/// but this limitation may be removed in the future.
///
/// While `TypeId` implements `Hash`, `PartialOrd`, and `Ord`, it is worth
/// noting that the hashes and ordering will vary between Rust releases. Beware
/// of relying on them outside of your code!
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct TypeId {
    t: u64,
}

impl TypeId {
    /// Returns the `TypeId` of the type this generic function has been
    /// instantiated with.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::any::{Any, TypeId};
    ///
    /// fn is_string<T: ?Sized + Any>(_s: &T) -> bool {
    ///     TypeId::of::<String>() == TypeId::of::<T>()
    /// }
    ///
    /// fn main() {
    ///     assert_eq!(is_string(&0), false);
    ///     assert_eq!(is_string(&"cookie monster".to_string()), true);
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature="const_type_id")]
    pub const fn of<T: ?Sized + 'static>() -> TypeId {
        TypeId {
            t: unsafe { intrinsics::type_id::<T>() },
        }
    }
}