bevy_reflect/
type_info.rs

1use crate::{
2    ArrayInfo, DynamicArray, DynamicEnum, DynamicList, DynamicMap, DynamicStruct, DynamicTuple,
3    DynamicTupleStruct, EnumInfo, Generics, ListInfo, MapInfo, PartialReflect, Reflect,
4    ReflectKind, SetInfo, StructInfo, TupleInfo, TupleStructInfo, TypePath, TypePathTable,
5};
6use core::{
7    any::{Any, TypeId},
8    fmt::{Debug, Formatter},
9    hash::Hash,
10};
11use thiserror::Error;
12
13/// A static accessor to compile-time type information.
14///
15/// This trait is automatically implemented by the [`#[derive(Reflect)]`](derive@crate::Reflect) macro
16/// and allows type information to be processed without an instance of that type.
17///
18/// If you need to use this trait as a generic bound along with other reflection traits,
19/// for your convenience, consider using [`Reflectable`] instead.
20///
21/// # Implementing
22///
23/// While it is recommended to leave implementing this trait to the `#[derive(Reflect)]` macro,
24/// it is possible to implement this trait manually. If a manual implementation is needed,
25/// you _must_ ensure that the information you provide is correct, otherwise various systems that
26/// rely on this trait may fail in unexpected ways.
27///
28/// Implementors may have difficulty in generating a reference to [`TypeInfo`] with a static
29/// lifetime. Luckily, this crate comes with some [utility] structs, to make generating these
30/// statics much simpler.
31///
32/// # Example
33///
34/// ```
35/// # use core::any::Any;
36/// # use bevy_reflect::{DynamicTypePath, NamedField, PartialReflect, Reflect, ReflectMut, ReflectOwned, ReflectRef, StructInfo, TypeInfo, TypePath, OpaqueInfo, ApplyError};
37/// # use bevy_reflect::utility::NonGenericTypeInfoCell;
38/// use bevy_reflect::Typed;
39///
40/// struct MyStruct {
41///   foo: usize,
42///   bar: (f32, f32)
43/// }
44///
45/// impl Typed for MyStruct {
46///   fn type_info() -> &'static TypeInfo {
47///     static CELL: NonGenericTypeInfoCell = NonGenericTypeInfoCell::new();
48///     CELL.get_or_set(|| {
49///       let fields = [
50///         NamedField::new::<usize >("foo"),
51///         NamedField::new::<(f32, f32) >("bar"),
52///       ];
53///       let info = StructInfo::new::<Self>(&fields);
54///       TypeInfo::Struct(info)
55///     })
56///   }
57/// }
58///
59/// # impl TypePath for MyStruct {
60/// #     fn type_path() -> &'static str { todo!() }
61/// #     fn short_type_path() -> &'static str { todo!() }
62/// # }
63/// # impl PartialReflect for MyStruct {
64/// #     fn get_represented_type_info(&self) -> Option<&'static TypeInfo> { todo!() }
65/// #     fn into_partial_reflect(self: Box<Self>) -> Box<dyn PartialReflect> { todo!() }
66/// #     fn as_partial_reflect(&self) -> &dyn PartialReflect { todo!() }
67/// #     fn as_partial_reflect_mut(&mut self) -> &mut dyn PartialReflect { todo!() }
68/// #     fn try_into_reflect(self: Box<Self>) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>> { todo!() }
69/// #     fn try_as_reflect(&self) -> Option<&dyn Reflect> { todo!() }
70/// #     fn try_as_reflect_mut(&mut self) -> Option<&mut dyn Reflect> { todo!() }
71/// #     fn try_apply(&mut self, value: &dyn PartialReflect) -> Result<(), ApplyError> { todo!() }
72/// #     fn reflect_ref(&self) -> ReflectRef { todo!() }
73/// #     fn reflect_mut(&mut self) -> ReflectMut { todo!() }
74/// #     fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
75/// # }
76/// # impl Reflect for MyStruct {
77/// #     fn into_any(self: Box<Self>) -> Box<dyn Any> { todo!() }
78/// #     fn as_any(&self) -> &dyn Any { todo!() }
79/// #     fn as_any_mut(&mut self) -> &mut dyn Any { todo!() }
80/// #     fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> { todo!() }
81/// #     fn as_reflect(&self) -> &dyn Reflect { todo!() }
82/// #     fn as_reflect_mut(&mut self) -> &mut dyn Reflect { todo!() }
83/// #     fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
84/// # }
85/// ```
86///
87/// [`Reflectable`]: crate::Reflectable
88/// [utility]: crate::utility
89#[diagnostic::on_unimplemented(
90    message = "`{Self}` does not implement `Typed` so cannot provide static type information",
91    note = "consider annotating `{Self}` with `#[derive(Reflect)]`"
92)]
93pub trait Typed: Reflect + TypePath {
94    /// Returns the compile-time [info] for the underlying type.
95    ///
96    /// [info]: TypeInfo
97    fn type_info() -> &'static TypeInfo;
98}
99
100/// A wrapper trait around [`Typed`].
101///
102/// This trait is used to provide a way to get compile-time type information for types that
103/// do implement `Typed` while also allowing for types that do not implement `Typed` to be used.
104/// It's used instead of `Typed` directly to avoid making dynamic types also
105/// implement `Typed` in order to be used as active fields.
106///
107/// This trait has a blanket implementation for all types that implement `Typed`
108/// and manual implementations for all dynamic types (which simply return `None`).
109#[doc(hidden)]
110#[diagnostic::on_unimplemented(
111    message = "`{Self}` does not implement `Typed` so cannot provide static type information",
112    note = "consider annotating `{Self}` with `#[derive(Reflect)]`"
113)]
114pub trait MaybeTyped: PartialReflect {
115    /// Returns the compile-time [info] for the underlying type, if it exists.
116    ///
117    /// [info]: TypeInfo
118    fn maybe_type_info() -> Option<&'static TypeInfo> {
119        None
120    }
121}
122
123impl<T: Typed> MaybeTyped for T {
124    fn maybe_type_info() -> Option<&'static TypeInfo> {
125        Some(T::type_info())
126    }
127}
128
129impl MaybeTyped for DynamicEnum {}
130
131impl MaybeTyped for DynamicTupleStruct {}
132
133impl MaybeTyped for DynamicStruct {}
134
135impl MaybeTyped for DynamicMap {}
136
137impl MaybeTyped for DynamicList {}
138
139impl MaybeTyped for DynamicArray {}
140
141impl MaybeTyped for DynamicTuple {}
142
143/// Dynamic dispatch for [`Typed`].
144///
145/// Since this is a supertrait of [`Reflect`] its methods can be called on a `dyn Reflect`.
146///
147/// [`Reflect`]: crate::Reflect
148#[diagnostic::on_unimplemented(
149    message = "`{Self}` can not provide dynamic type information through reflection",
150    note = "consider annotating `{Self}` with `#[derive(Reflect)]`"
151)]
152pub trait DynamicTyped {
153    /// See [`Typed::type_info`].
154    fn reflect_type_info(&self) -> &'static TypeInfo;
155}
156
157impl<T: Typed> DynamicTyped for T {
158    #[inline]
159    fn reflect_type_info(&self) -> &'static TypeInfo {
160        Self::type_info()
161    }
162}
163
164/// A [`TypeInfo`]-specific error.
165#[derive(Debug, Error)]
166pub enum TypeInfoError {
167    /// Caused when a type was expected to be of a certain [kind], but was not.
168    ///
169    /// [kind]: ReflectKind
170    #[error("kind mismatch: expected {expected:?}, received {received:?}")]
171    KindMismatch {
172        expected: ReflectKind,
173        received: ReflectKind,
174    },
175}
176
177/// Compile-time type information for various reflected types.
178///
179/// Generally, for any given type, this value can be retrieved in one of four ways:
180///
181/// 1. [`Typed::type_info`]
182/// 2. [`DynamicTyped::reflect_type_info`]
183/// 3. [`PartialReflect::get_represented_type_info`]
184/// 4. [`TypeRegistry::get_type_info`]
185///
186/// Each return a static reference to [`TypeInfo`], but they all have their own use cases.
187/// For example, if you know the type at compile time, [`Typed::type_info`] is probably
188/// the simplest. If you have a `dyn Reflect` you can use [`DynamicTyped::reflect_type_info`].
189/// If all you have is a `dyn PartialReflect`, you'll probably want [`PartialReflect::get_represented_type_info`].
190/// Lastly, if all you have is a [`TypeId`] or [type path], you will need to go through
191/// [`TypeRegistry::get_type_info`].
192///
193/// You may also opt to use [`TypeRegistry::get_type_info`] in place of the other methods simply because
194/// it can be more performant. This is because those other methods may require attaining a lock on
195/// the static [`TypeInfo`], while the registry simply checks a map.
196///
197/// [`TypeRegistry::get_type_info`]: crate::TypeRegistry::get_type_info
198/// [`PartialReflect::get_represented_type_info`]: crate::PartialReflect::get_represented_type_info
199/// [type path]: TypePath::type_path
200#[derive(Debug, Clone)]
201pub enum TypeInfo {
202    Struct(StructInfo),
203    TupleStruct(TupleStructInfo),
204    Tuple(TupleInfo),
205    List(ListInfo),
206    Array(ArrayInfo),
207    Map(MapInfo),
208    Set(SetInfo),
209    Enum(EnumInfo),
210    Opaque(OpaqueInfo),
211}
212
213impl TypeInfo {
214    /// The underlying Rust [type].
215    ///
216    /// [type]: Type
217    pub fn ty(&self) -> &Type {
218        match self {
219            Self::Struct(info) => info.ty(),
220            Self::TupleStruct(info) => info.ty(),
221            Self::Tuple(info) => info.ty(),
222            Self::List(info) => info.ty(),
223            Self::Array(info) => info.ty(),
224            Self::Map(info) => info.ty(),
225            Self::Set(info) => info.ty(),
226            Self::Enum(info) => info.ty(),
227            Self::Opaque(info) => info.ty(),
228        }
229    }
230
231    /// The [`TypeId`] of the underlying type.
232    #[inline]
233    pub fn type_id(&self) -> TypeId {
234        self.ty().id()
235    }
236
237    /// A representation of the type path of the underlying type.
238    ///
239    /// Provides dynamic access to all methods on [`TypePath`].
240    pub fn type_path_table(&self) -> &TypePathTable {
241        self.ty().type_path_table()
242    }
243
244    /// The [stable, full type path] of the underlying type.
245    ///
246    /// Use [`type_path_table`] if you need access to the other methods on [`TypePath`].
247    ///
248    /// [stable, full type path]: TypePath
249    /// [`type_path_table`]: Self::type_path_table
250    pub fn type_path(&self) -> &'static str {
251        self.ty().path()
252    }
253
254    /// Check if the given type matches this one.
255    ///
256    /// This only compares the [`TypeId`] of the types
257    /// and does not verify they share the same [`TypePath`]
258    /// (though it implies they do).
259    pub fn is<T: Any>(&self) -> bool {
260        self.ty().is::<T>()
261    }
262
263    /// The docstring of the underlying type, if any.
264    #[cfg(feature = "documentation")]
265    pub fn docs(&self) -> Option<&str> {
266        match self {
267            Self::Struct(info) => info.docs(),
268            Self::TupleStruct(info) => info.docs(),
269            Self::Tuple(info) => info.docs(),
270            Self::List(info) => info.docs(),
271            Self::Array(info) => info.docs(),
272            Self::Map(info) => info.docs(),
273            Self::Set(info) => info.docs(),
274            Self::Enum(info) => info.docs(),
275            Self::Opaque(info) => info.docs(),
276        }
277    }
278
279    /// Returns the [kind] of this `TypeInfo`.
280    ///
281    /// [kind]: ReflectKind
282    pub fn kind(&self) -> ReflectKind {
283        match self {
284            Self::Struct(_) => ReflectKind::Struct,
285            Self::TupleStruct(_) => ReflectKind::TupleStruct,
286            Self::Tuple(_) => ReflectKind::Tuple,
287            Self::List(_) => ReflectKind::List,
288            Self::Array(_) => ReflectKind::Array,
289            Self::Map(_) => ReflectKind::Map,
290            Self::Set(_) => ReflectKind::Set,
291            Self::Enum(_) => ReflectKind::Enum,
292            Self::Opaque(_) => ReflectKind::Opaque,
293        }
294    }
295
296    impl_generic_info_methods!(self => {
297        match self {
298            Self::Struct(info) => info.generics(),
299            Self::TupleStruct(info) => info.generics(),
300            Self::Tuple(info) => info.generics(),
301            Self::List(info) => info.generics(),
302            Self::Array(info) => info.generics(),
303            Self::Map(info) => info.generics(),
304            Self::Set(info) => info.generics(),
305            Self::Enum(info) => info.generics(),
306            Self::Opaque(info) => info.generics(),
307        }
308    });
309}
310
311macro_rules! impl_cast_method {
312    ($name:ident : $kind:ident => $info:ident) => {
313        #[doc = concat!("Attempts a cast to [`", stringify!($info), "`].")]
314        #[doc = concat!("\n\nReturns an error if `self` is not [`TypeInfo::", stringify!($kind), "`].")]
315        pub fn $name(&self) -> Result<&$info, TypeInfoError> {
316            match self {
317                Self::$kind(info) => Ok(info),
318                _ => Err(TypeInfoError::KindMismatch {
319                    expected: ReflectKind::$kind,
320                    received: self.kind(),
321                }),
322            }
323        }
324    };
325}
326
327/// Conversion convenience methods for [`TypeInfo`].
328impl TypeInfo {
329    impl_cast_method!(as_struct: Struct => StructInfo);
330    impl_cast_method!(as_tuple_struct: TupleStruct => TupleStructInfo);
331    impl_cast_method!(as_tuple: Tuple => TupleInfo);
332    impl_cast_method!(as_list: List => ListInfo);
333    impl_cast_method!(as_array: Array => ArrayInfo);
334    impl_cast_method!(as_map: Map => MapInfo);
335    impl_cast_method!(as_enum: Enum => EnumInfo);
336    impl_cast_method!(as_opaque: Opaque => OpaqueInfo);
337}
338
339/// The base representation of a Rust type.
340///
341/// When possible, it is recommended to use [`&'static TypeInfo`] instead of this
342/// as it provides more information as well as being smaller
343/// (since a reference only takes the same number of bytes as a `usize`).
344///
345/// However, where a static reference to [`TypeInfo`] is not possible,
346/// such as with trait objects and other types that can't implement [`Typed`],
347/// this type can be used instead.
348///
349/// It only requires that the type implements [`TypePath`].
350///
351/// And unlike [`TypeInfo`], this type implements [`Copy`], [`Eq`], and [`Hash`],
352/// making it useful as a key type.
353///
354/// It's especially helpful when compared to [`TypeId`] as it can provide the
355/// actual [type path] when debugging, while still having the same performance
356/// as hashing/comparing [`TypeId`] directly—at the cost of a little more memory.
357///
358/// # Examples
359///
360/// ```
361/// use bevy_reflect::{Type, TypePath};
362///
363/// fn assert_char<T: ?Sized + TypePath>(t: &T) -> Result<(), String> {
364///     let ty = Type::of::<T>();
365///     if Type::of::<char>() == ty {
366///         Ok(())
367///     } else {
368///         Err(format!("expected `char`, got `{}`", ty.path()))
369///     }
370/// }
371///
372/// assert_eq!(
373///     assert_char(&'a'),
374///     Ok(())
375/// );
376/// assert_eq!(
377///     assert_char(&String::from("Hello, world!")),
378///     Err(String::from("expected `char`, got `alloc::string::String`"))
379/// );
380/// ```
381///
382/// [`&'static TypeInfo`]: TypeInfo
383#[derive(Copy, Clone)]
384pub struct Type {
385    type_path_table: TypePathTable,
386    type_id: TypeId,
387}
388
389impl Type {
390    /// Create a new [`Type`] from a type that implements [`TypePath`].
391    pub fn of<T: TypePath + ?Sized>() -> Self {
392        Self {
393            type_path_table: TypePathTable::of::<T>(),
394            type_id: TypeId::of::<T>(),
395        }
396    }
397
398    /// Returns the [`TypeId`] of the type.
399    #[inline]
400    pub fn id(&self) -> TypeId {
401        self.type_id
402    }
403
404    /// See [`TypePath::type_path`].
405    pub fn path(&self) -> &'static str {
406        self.type_path_table.path()
407    }
408
409    /// See [`TypePath::short_type_path`].
410    pub fn short_path(&self) -> &'static str {
411        self.type_path_table.short_path()
412    }
413
414    /// See [`TypePath::type_ident`].
415    pub fn ident(&self) -> Option<&'static str> {
416        self.type_path_table.ident()
417    }
418
419    /// See [`TypePath::crate_name`].
420    pub fn crate_name(&self) -> Option<&'static str> {
421        self.type_path_table.crate_name()
422    }
423
424    /// See [`TypePath::module_path`].
425    pub fn module_path(&self) -> Option<&'static str> {
426        self.type_path_table.module_path()
427    }
428
429    /// A representation of the type path of this.
430    ///
431    /// Provides dynamic access to all methods on [`TypePath`].
432    pub fn type_path_table(&self) -> &TypePathTable {
433        &self.type_path_table
434    }
435
436    /// Check if the given type matches this one.
437    ///
438    /// This only compares the [`TypeId`] of the types
439    /// and does not verify they share the same [`TypePath`]
440    /// (though it implies they do).
441    pub fn is<T: Any>(&self) -> bool {
442        TypeId::of::<T>() == self.type_id
443    }
444}
445
446/// This implementation will only output the [type path] of the type.
447///
448/// If you need to include the [`TypeId`] in the output,
449/// you can access it through [`Type::id`].
450///
451/// [type path]: TypePath
452impl Debug for Type {
453    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
454        write!(f, "{}", self.type_path_table.path())
455    }
456}
457
458impl Eq for Type {}
459
460/// This implementation purely relies on the [`TypeId`] of the type,
461/// and not on the [type path].
462///
463/// [type path]: TypePath
464impl PartialEq for Type {
465    #[inline]
466    fn eq(&self, other: &Self) -> bool {
467        self.type_id == other.type_id
468    }
469}
470
471/// This implementation purely relies on the [`TypeId`] of the type,
472/// and not on the [type path].
473///
474/// [type path]: TypePath
475impl Hash for Type {
476    #[inline]
477    fn hash<H: core::hash::Hasher>(&self, state: &mut H) {
478        self.type_id.hash(state);
479    }
480}
481
482macro_rules! impl_type_methods {
483    // Generates the type methods based off a single field.
484    ($field:ident) => {
485        $crate::type_info::impl_type_methods!(self => {
486            &self.$field
487        });
488    };
489    // Generates the type methods based off a custom expression.
490    ($self:ident => $expr:expr) => {
491        /// The underlying Rust [type].
492        ///
493        /// [type]: crate::type_info::Type
494        pub fn ty(&$self) -> &$crate::type_info::Type {
495            $expr
496        }
497
498        /// The [`TypeId`] of this type.
499        ///
500        /// [`TypeId`]: core::any::TypeId
501        pub fn type_id(&self) -> ::core::any::TypeId {
502            self.ty().id()
503        }
504
505        /// The [stable, full type path] of this type.
506        ///
507        /// Use [`type_path_table`] if you need access to the other methods on [`TypePath`].
508        ///
509        /// [stable, full type path]: TypePath
510        /// [`type_path_table`]: Self::type_path_table
511        pub fn type_path(&self) -> &'static str {
512            self.ty().path()
513        }
514
515        /// A representation of the type path of this type.
516        ///
517        /// Provides dynamic access to all methods on [`TypePath`].
518        ///
519        /// [`TypePath`]: crate::type_path::TypePath
520        pub fn type_path_table(&self) -> &$crate::type_path::TypePathTable {
521            &self.ty().type_path_table()
522        }
523
524        /// Check if the given type matches this one.
525        ///
526        /// This only compares the [`TypeId`] of the types
527        /// and does not verify they share the same [`TypePath`]
528        /// (though it implies they do).
529        ///
530        /// [`TypeId`]: core::any::TypeId
531        /// [`TypePath`]: crate::type_path::TypePath
532        pub fn is<T: ::core::any::Any>(&self) -> bool {
533            self.ty().is::<T>()
534        }
535    };
536}
537
538use crate::generics::impl_generic_info_methods;
539pub(crate) use impl_type_methods;
540
541/// A container for compile-time info related to reflection-opaque types, including primitives.
542///
543/// This typically represents a type which cannot be broken down any further. This is often
544/// due to technical reasons (or by definition), but it can also be a purposeful choice.
545///
546/// For example, [`i32`] cannot be broken down any further, so it is represented by an [`OpaqueInfo`].
547/// And while [`String`] itself is a struct, its fields are private, so we don't really treat
548/// it _as_ a struct. It therefore makes more sense to represent it as an [`OpaqueInfo`].
549///
550/// [`String`]: alloc::string::String
551#[derive(Debug, Clone)]
552pub struct OpaqueInfo {
553    ty: Type,
554    generics: Generics,
555    #[cfg(feature = "documentation")]
556    docs: Option<&'static str>,
557}
558
559impl OpaqueInfo {
560    pub fn new<T: Reflect + TypePath + ?Sized>() -> Self {
561        Self {
562            ty: Type::of::<T>(),
563            generics: Generics::new(),
564            #[cfg(feature = "documentation")]
565            docs: None,
566        }
567    }
568
569    /// Sets the docstring for this type.
570    #[cfg(feature = "documentation")]
571    pub fn with_docs(self, doc: Option<&'static str>) -> Self {
572        Self { docs: doc, ..self }
573    }
574
575    impl_type_methods!(ty);
576
577    /// The docstring of this dynamic type, if any.
578    #[cfg(feature = "documentation")]
579    pub fn docs(&self) -> Option<&'static str> {
580        self.docs
581    }
582
583    impl_generic_info_methods!(generics);
584}
585
586#[cfg(test)]
587mod tests {
588    use super::*;
589    use alloc::vec::Vec;
590
591    #[test]
592    fn should_return_error_on_invalid_cast() {
593        let info = <Vec<i32> as Typed>::type_info();
594        assert!(matches!(
595            info.as_struct(),
596            Err(TypeInfoError::KindMismatch {
597                expected: ReflectKind::Struct,
598                received: ReflectKind::List
599            })
600        ));
601    }
602}
bevy_reflect/type_info.rs

bevy_reflect/
type_info.rs
