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//! An implementation of detailed type information and reflection. //! //! This library provides simple access to type information at runtime, as well as the ability to //! manipulate data whose type is not statically known. //! //! # Type information //! //! By deriving the `TypeInfo` trait, you get access to type information about the type at runtime. //! //! ``` //! #![feature(const_type_id)] //! //! extern crate type_info; //! #[macro_use] //! extern crate type_info_derive; //! //! use type_info::TypeInfo; //! //! #[derive(TypeInfo)] //! struct Person { //! name: String, //! age: u32, //! } //! //! fn main() { //! let ty = Person::TYPE; //! //! assert_eq!("Person", ty.ident); //! assert_eq!(vec!["name", "age"], ty.fields().iter().map(|f| f.ident.unwrap()).collect::<Vec<_>>()); //! } //! ``` //! //! # Static dispatch //! //! This example shows how to use the main `TypeInfo` trait with generic parameters (i.e. not trait //! objects): //! //! ``` //! # #![feature(const_type_id)] //! # //! # extern crate type_info; //! # #[macro_use] //! # extern crate type_info_derive; //! # //! # #[derive(TypeInfo)] //! # struct Person { //! # name: String, //! # age: u32, //! # } //! // Person is defined like in the above example... //! //! // A function that can take any type that has a field called "name" of type String. //! fn add_smith_to_name<A>(anything: &mut A) where A: type_info::TypeInfo { //! let name = anything.field_mut::<String>(type_info::FieldId::Named("name")).unwrap(); //! name.push_str(" Smith"); //! } //! //! fn main() { //! let mut person = Person { //! name: "Lisa".to_owned(), //! age: 23, //! }; //! //! add_smith_to_name(&mut person); //! //! assert_eq!("Lisa Smith", person.name.as_str()); //! } //! ``` //! //! # Dynamic dispatch //! //! This example shows how to use the `DynamicTypeInfo` trait when you don't want to introduce a //! type parameter to specialize a function, but instead prefer to use a trait object: //! //! ``` //! # #![feature(const_type_id)] //! # //! # extern crate type_info; //! # #[macro_use] //! # extern crate type_info_derive; //! # //! # #[derive(TypeInfo)] //! # struct Person { //! # name: String, //! # age: u32, //! # } //! // Person is defined like in the above example... //! //! // A function that can take any type that has a field called "name" of type String. //! fn add_smith_to_name(anything: &mut type_info::DynamicTypeInfo) { //! let field = anything.field_any_mut(type_info::FieldId::Named("name")).unwrap(); //! let name = field.downcast_mut::<String>().unwrap(); //! name.push_str(" Smith"); //! } //! //! fn main() { //! let mut person = Person { //! name: "Lisa".to_owned(), //! age: 23, //! }; //! //! add_smith_to_name(&mut person); //! //! assert_eq!("Lisa Smith", person.name.as_str()); //! } //! ``` #![feature(const_type_id)] #![feature(specialization)] #![deny( missing_docs, missing_debug_implementations, missing_copy_implementations, trivial_casts, trivial_numeric_casts, unsafe_code, unused_import_braces, unused_qualifications )] use std::any; use std::fmt; /// A globally unique identifier for a type. pub type TypeId = any::TypeId; /// A locally unique identifier for a field within a certain type. #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)] pub enum FieldId<'a> { /// An unnamed field with the specified index in a tuple-like struct; e.g. the `0` in `foo.0`. Unnamed(usize), /// A named field in a struct, e.g. the `name` in `foo.name`. Named(&'a str), } /// A type that has compile-time static type information associated with it. pub trait TypeInfo: DynamicTypeInfo { /// The constant statically known type information for this type. const TYPE: Type; /// Get a reference to the value of a field on this type with the given field id. /// /// This method will return the current value of the given field if possible, or `None` if the /// given field does not exist or does not have a type matching the supplied type. fn field<A>(&self, _id: FieldId) -> Option<&A> where A: any::Any, { None } /// Get a mutable reference to the value of a field on this type with the given field id. /// /// This method will return the current value of the given field if possible, or `None` if the /// given field does not exist or does not have a type matching the supplied type. fn field_mut<A>(&mut self, _id: FieldId) -> Option<&mut A> where A: any::Any, { None } } /// A type that has compile-time dynamic type information associated with it. /// /// This trait is built to be compatible with being a trait object. pub trait DynamicTypeInfo { /// The dynamic statically known type information for this type. fn type_ref(&self) -> &'static Type; /// Get the id of the currently active variant of this type, or `None` if the type is not /// an `enum`. fn variant(&self) -> Option<&str> { None } /// Get a dynamic reference to the value of a field on this type with the given field id. /// /// This method will return the current value of the given field if possible, or `None` if the /// given field does not exist or does not have a type matching the supplied type. fn field_any(&self, _id: FieldId) -> Option<&any::Any> { None } /// Get a mutable dynamic reference to the value of a field on this type with the given field id. /// /// This method will return the current value of the given field if possible, or `None` if the /// given field does not exist or does not have a type matching the supplied type. fn field_any_mut(&mut self, _id: FieldId) -> Option<&mut any::Any> { None } } /// A trait that is implemented for every type to conditionally determine whether it exposes type /// information. pub trait TryTypeInfo { /// The constant statically known type information for this type, or `None` if the type does not /// implement `TypeInfo`. const TRY_TYPE: Option<&'static Type>; } impl<T> TryTypeInfo for T { default const TRY_TYPE: Option<&'static Type> = None; } impl<T> TryTypeInfo for T where T: TypeInfo, { const TRY_TYPE: Option<&'static Type> = Some(&T::TYPE); } /// Type information for a type that implements `TypeInfo`. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct Type { /// The globally unique identifier for this type. pub id: TypeId, /// The module in which this type was defined. /// This is using unrooted syntax à la `foo::bar`. pub module: &'static str, /// The identifier of this type within its module. pub ident: &'static str, /// Additional data about this type definition. pub data: Data, } /// Data associated with type information. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub enum Data { /// The associated type is a primitive type. Primitive, /// The associated type is a `struct`. Struct(DataStruct), /// The associated type is an `enum`. Enum(DataEnum), /// The associated type is an `union`. Union(DataUnion), } /// Data associated with `struct` type information. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct DataStruct { /// The fields that this `struct` consists of. pub fields: Fields, } /// Data associated with `enum` type information. #[allow(missing_copy_implementations)] #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct DataEnum { /// The variants that this `enum` consists of. pub variants: &'static [Variant], } /// Data associated with `union` type information. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct DataUnion { /// The fields that this `union` consists of. pub fields: FieldsNamed, } /// A specific `enum` variant. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct Variant { /// The identifier of the enum variant. pub ident: &'static str, /// The fields that are associated with a particular `enum` variant. pub fields: Fields, } /// A set of fields associated with a type or `enum` variant. #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub enum Fields { /// A set of named fields. Named(FieldsNamed), /// A set of index-addressed fields Unnamed(FieldsUnnamed), /// The empty set of fields, applicable to unit structs or enum variants. Unit, } /// A set of named fields associated with a type or `enum` variant. #[allow(missing_copy_implementations)] #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct FieldsNamed { /// The related set of named fields. pub named: &'static [Field], } /// A set of unnamed fields associated with a type or `enum` variant. #[allow(missing_copy_implementations)] #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct FieldsUnnamed { /// The related set of unnamed fields. pub unnamed: &'static [Field], } /// A field that is associated with a type or `enum` variant. #[allow(missing_copy_implementations)] #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] pub struct Field { /// The type or variant local unique identifier for the field. pub id: FieldId<'static>, /// The field's identifier, if it is named. pub ident: Option<&'static str>, /// The type of the field, if it has any associated `TypeInfo`. pub ty: Option<&'static Type>, } impl Type { /// Convenience method for getting all of the struct fields of this type. pub fn fields(&self) -> &'static [Field] { match self.data { Data::Struct(DataStruct { ref fields, .. }) => fields.fields(), _ => &[], } } /// Convenience method for getting all of the enum variants of this type. pub fn variants(&self) -> &'static [Variant] { match self.data { Data::Enum(DataEnum { ref variants, .. }) => variants, _ => &[], } } } impl Fields { /// Convenience method for getting all of the fields, ignoring whether they are named or /// unnamed. pub fn fields(&self) -> &'static [Field] { match *self { Fields::Unit => &[], Fields::Named(FieldsNamed { named, .. }) => named, Fields::Unnamed(FieldsUnnamed { unnamed, .. }) => unnamed, } } } impl<'a> fmt::Display for FieldId<'a> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { FieldId::Unnamed(idx) => idx.fmt(f), FieldId::Named(name) => name.fmt(f), } } } macro_rules! impl_primitive { ($t:ty) => { impl TypeInfo for $t { const TYPE: Type = Type { id: TypeId::of::<$t>(), module: "", ident: stringify!($t), data: Data::Primitive, }; } impl DynamicTypeInfo for $t { fn type_ref(&self) -> &'static Type { &<Self as TypeInfo>::TYPE } } }; } impl_primitive!(u8); impl_primitive!(u16); impl_primitive!(u32); impl_primitive!(u64); impl_primitive!(usize); impl_primitive!(i8); impl_primitive!(i16); impl_primitive!(i32); impl_primitive!(i64); impl_primitive!(isize); impl_primitive!(f32); impl_primitive!(f64); impl_primitive!(bool); impl_primitive!(char);