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#[doc(keyword = "as")] // /// Cast between types, or rename an import. /// /// `as` is most commonly used to turn primitive types into other primitive types, but it has other /// uses that include turning pointers into addresses, addresses into pointers, and pointers into /// other pointers. /// /// ```rust /// let thing1: u8 = 89.0 as u8; /// assert_eq!('B' as u32, 66); /// assert_eq!(thing1 as char, 'Y'); /// let thing2: f32 = thing1 as f32 + 10.5; /// assert_eq!(true as u8 + thing2 as u8, 100); /// ``` /// /// In general, any cast that can be performed via ascribing the type can also be done using `as`, /// so instead of writing `let x: u32 = 123`, you can write `let x = 123 as u32` (Note: `let x: u32 /// = 123` would be best in that situation). The same is not true in the other direction, however, /// explicitly using `as` allows a few more coercions that aren't allowed implicitly, such as /// changing the type of a raw pointer or turning closures into raw pointers. /// /// Other places `as` is used include as extra syntax for [`crate`] and `use`, to change the name /// something is imported as. /// /// For more information on what `as` is capable of, see the [Reference] /// /// [Reference]: ../reference/expressions/operator-expr.html#type-cast-expressions /// [`crate`]: keyword.crate.html mod as_keyword { } #[doc(keyword = "break")] // /// Exit early from a loop. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod break_keyword { } #[doc(keyword = "const")] // /// Compile-time constants and deterministic functions. /// /// Sometimes a certain value is used many times throughout a program, and it can become /// inconvenient to copy it over and over. What's more, it's not always possible or desirable to /// make it a variable that gets carried around to each function that needs it. In these cases, the /// `const` keyword provides a convenient alternative to code duplication. /// /// ```rust /// const THING: u32 = 0xABAD1DEA; /// /// let foo = 123 + THING; /// ``` /// /// Constants must be explicitly typed, unlike with `let` you can't ignore its type and let the /// compiler figure it out. Any constant value can be defined in a const, which in practice happens /// to be most things that would be reasonable to have a constant (barring `const fn`s). For /// example, you can't have a File as a `const`. /// /// The only lifetime allowed in a constant is `'static`, which is the lifetime that encompasses /// all others in a Rust program. For example, if you wanted to define a constant string, it would /// look like this: /// /// ```rust /// const WORDS: &str = "hello rust!"; /// ``` /// /// Thanks to static lifetime elision, you usually don't have to explicitly use 'static: /// /// ```rust /// const WORDS: &str = "hello convenience!"; /// ``` /// /// `const` items looks remarkably similar to `static` items, which introduces some confusion as /// to which one should be used at which times. To put it simply, constants are inlined wherever /// they're used, making using them identical to simply replacing the name of the const with its /// value. Static variables on the other hand point to a single location in memory, which all /// accesses share. This means that, unlike with constants, they can't have destructors, and act as /// a single value across the entire codebase. /// /// Constants, as with statics, should always be in SCREAMING_SNAKE_CASE. /// /// The `const` keyword is also used in raw pointers in combination with `mut`, as seen in `*const /// T` and `*mut T`. More about that can be read at the [pointer] primitive part of the Rust docs. /// /// For more detail on `const`, see the [Rust Book] or the [Reference] /// /// [pointer]: primitive.pointer.html /// [Rust Book]: /// ../book/ch03-01-variables-and-mutability.html#differences-between-variables-and-constants /// [Reference]: ../reference/items/constant-items.html mod const_keyword { } #[doc(keyword = "continue")] // /// Skip to the next iteration of a loop. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod continue_keyword { } #[doc(keyword = "crate")] // /// A Rust binary or library. /// /// The primary use of the `crate` keyword is as a part of `extern crate` declarations, which are /// used to specify a dependency on a crate external to the one it's declared in. Crates are the /// fundamental compilation unit of Rust code, and can be seen as libraries or projects. More can /// be read about crates in the [Reference]. /// /// ```rust ignore /// extern crate rand; /// extern crate my_crate as thing; /// extern crate std; // implicitly added to the root of every Rust project /// ``` /// /// The `as` keyword can be used to change what the crate is referred to as in your project. If a /// crate name includes a dash, it is implicitly imported with the dashes replaced by underscores. /// /// `crate` is also used as in conjunction with `pub` to signify that the item it's attached to /// is public only to other members of the same crate it's in. /// /// ```rust /// # #[allow(unused_imports)] /// pub(crate) use std::io::Error as IoError; /// pub(crate) enum CoolMarkerType { } /// pub struct PublicThing { /// pub(crate) semi_secret_thing: bool, /// } /// ``` /// /// [Reference]: ../reference/items/extern-crates.html mod crate_keyword { } #[doc(keyword = "else")] // /// What to do when an [`if`] condition does not hold. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`if`]: keyword.if.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod else_keyword { } #[doc(keyword = "enum")] // /// A type that can be any one of several variants. /// /// Enums in Rust are similar to those of other compiled languages like C, but have important /// differences that make them considerably more powerful. What Rust calls enums are more commonly /// known as [Algebraic Data Types][ADT] if you're coming from a functional programming background. /// The important detail is that each enum variant can have data to go along with it. /// /// ```rust /// # struct Coord; /// enum SimpleEnum { /// FirstVariant, /// SecondVariant, /// ThirdVariant, /// } /// /// enum Location { /// Unknown, /// Anonymous, /// Known(Coord), /// } /// /// enum ComplexEnum { /// Nothing, /// Something(u32), /// LotsOfThings { /// usual_struct_stuff: bool, /// blah: String, /// } /// } /// /// enum EmptyEnum { } /// ``` /// /// The first enum shown is the usual kind of enum you'd find in a C-style language. The second /// shows off a hypothetical example of something storing location data, with `Coord` being any /// other type that's needed, for example a struct. The third example demonstrates the kind of /// data a variant can store, ranging from nothing, to a tuple, to an anonymous struct. /// /// Instantiating enum variants involves explicitly using the enum's name as its namespace, /// followed by one of its variants. `SimpleEnum::SecondVariant` would be an example from above. /// When data follows along with a variant, such as with rust's built-in [`Option`] type, the data /// is added as the type describes, for example `Option::Some(123)`. The same follows with /// struct-like variants, with things looking like `ComplexEnum::LotsOfThings { usual_struct_stuff: /// true, blah: "hello!".to_string(), }`. Empty Enums are similar to () in that they cannot be /// instantiated at all, and are used mainly to mess with the type system in interesting ways. /// /// For more information, take a look at the [Rust Book] or the [Reference] /// /// [ADT]: https://en.wikipedia.org/wiki/Algebraic_data_type /// [`Option`]: option/enum.Option.html /// [Rust Book]: ../book/ch06-01-defining-an-enum.html /// [Reference]: ../reference/items/enumerations.html mod enum_keyword { } #[doc(keyword = "extern")] // /// Link to or import external code. /// /// The `extern` keyword is used in two places in Rust. One is in conjunction with the [`crate`] /// keyword to make your Rust code aware of other Rust crates in your project, i.e., `extern crate /// lazy_static;`. The other use is in foreign function interfaces (FFI). /// /// `extern` is used in two different contexts within FFI. The first is in the form of external /// blocks, for declaring function interfaces that Rust code can call foreign code by. /// /// ```rust ignore /// #[link(name = "my_c_library")] /// extern "C" { /// fn my_c_function(x: i32) -> bool; /// } /// ``` /// /// This code would attempt to link with `libmy_c_library.so` on unix-like systems and /// `my_c_library.dll` on Windows at runtime, and panic if it can't find something to link to. Rust /// code could then use `my_c_function` as if it were any other unsafe Rust function. Working with /// non-Rust languages and FFI is inherently unsafe, so wrappers are usually built around C APIs. /// /// The mirror use case of FFI is also done via the `extern` keyword: /// /// ```rust /// #[no_mangle] /// pub extern fn callable_from_c(x: i32) -> bool { /// x % 3 == 0 /// } /// ``` /// /// If compiled as a dylib, the resulting .so could then be linked to from a C library, and the /// function could be used as if it was from any other library. /// /// For more information on FFI, check the [Rust book] or the [Reference]. /// /// [Rust book]: /// ../book/ch19-01-unsafe-rust.html#using-extern-functions-to-call-external-code /// [Reference]: ../reference/items/external-blocks.html mod extern_keyword { } #[doc(keyword = "false")] // /// A value of type [`bool`] representing logical **false**. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`bool`]: primitive.bool.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod false_keyword { } #[doc(keyword = "fn")] // /// A function or function pointer. /// /// Functions are the primary way code is executed within Rust. Function blocks, usually just /// called functions, can be defined in a variety of different places and be assigned many /// different attributes and modifiers. /// /// Standalone functions that just sit within a module not attached to anything else are common, /// but most functions will end up being inside [`impl`] blocks, either on another type itself, or /// as a trait impl for that type. /// /// ```rust /// fn standalone_function() { /// // code /// } /// /// pub fn public_thing(argument: bool) -> String { /// // code /// # "".to_string() /// } /// /// struct Thing { /// foo: i32, /// } /// /// impl Thing { /// pub fn new() -> Self { /// Self { /// foo: 42, /// } /// } /// } /// ``` /// /// In addition to presenting fixed types in the form of `fn name(arg: type, ..) -> return_type`, /// functions can also declare a list of type parameters along with trait bounds that they fall /// into. /// /// ```rust /// fn generic_function<T: Clone>(x: T) -> (T, T, T) { /// (x.clone(), x.clone(), x.clone()) /// } /// /// fn generic_where<T>(x: T) -> T /// where T: std::ops::Add<Output = T> + Copy /// { /// x + x + x /// } /// ``` /// /// Declaring trait bounds in the angle brackets is functionally identical to using a `where` /// clause. It's up to the programmer to decide which works better in each situation, but `where` /// tends to be better when things get longer than one line. /// /// Along with being made public via `pub`, `fn` can also have an [`extern`] added for use in /// FFI. /// /// For more information on the various types of functions and how they're used, consult the [Rust /// book] or the [Reference]. /// /// [`impl`]: keyword.impl.html /// [`extern`]: keyword.extern.html /// [Rust book]: ../book/ch03-03-how-functions-work.html /// [Reference]: ../reference/items/functions.html mod fn_keyword { } #[doc(keyword = "for")] // /// Iteration with [`in`], trait implementation with [`impl`], or [higher-ranked trait bounds] /// (`for<'a>`). /// /// The `for` keyword is used in many syntactic locations: /// /// * `for` is used in for-in-loops (see below). /// * `for` is used when implementing traits as in `impl Trait for Type` (see [`impl`] for more info /// on that). /// * `for` is also used for [higher-ranked trait bounds] as in `for<'a> &'a T: PartialEq<i32>`. /// /// for-in-loops, or to be more precise, iterator loops, are a simple syntactic sugar over a common /// practice within Rust, which is to loop over an iterator until that iterator returns `None` (or /// `break` is called). /// /// ```rust /// for i in 0..5 { /// println!("{}", i * 2); /// } /// /// for i in std::iter::repeat(5) { /// println!("turns out {} never stops being 5", i); /// break; // would loop forever otherwise /// } /// /// 'outer: for x in 5..50 { /// for y in 0..10 { /// if x == y { /// break 'outer; /// } /// } /// } /// ``` /// /// As shown in the example above, `for` loops (along with all other loops) can be tagged, using /// similar syntax to lifetimes (only visually similar, entirely distinct in practice). Giving the /// same tag to `break` breaks the tagged loop, which is useful for inner loops. It is definitely /// not a goto. /// /// A `for` loop expands as shown: /// /// ```rust /// # fn code() { } /// # let iterator = 0..2; /// for loop_variable in iterator { /// code() /// } /// ``` /// /// ```rust /// # fn code() { } /// # let iterator = 0..2; /// { /// let mut _iter = std::iter::IntoIterator::into_iter(iterator); /// loop { /// match _iter.next() { /// Some(loop_variable) => { /// code() /// }, /// None => break, /// } /// } /// } /// ``` /// /// More details on the functionality shown can be seen at the [`IntoIterator`] docs. /// /// For more information on for-loops, see the [Rust book] or the [Reference]. /// /// [`in`]: keyword.in.html /// [`impl`]: keyword.impl.html /// [higher-ranked trait bounds]: ../reference/trait-bounds.html#higher-ranked-trait-bounds /// [`IntoIterator`]: iter/trait.IntoIterator.html /// [Rust book]: /// ../book/ch03-05-control-flow.html#looping-through-a-collection-with-for /// [Reference]: ../reference/expressions/loop-expr.html#iterator-loops mod for_keyword { } #[doc(keyword = "if")] // /// Evaluate a block if a condition holds. /// /// `if` is a familiar construct to most programmers, and is the main way you'll often do logic in /// your code. However, unlike in most languages, `if` blocks can also act as expressions. /// /// ```rust /// # let rude = true; /// if 1 == 2 { /// println!("whoops, mathematics broke"); /// } else { /// println!("everything's fine!"); /// } /// /// let greeting = if rude { /// "sup nerd." /// } else { /// "hello, friend!" /// }; /// /// if let Ok(x) = "123".parse::<i32>() { /// println!("{} double that and you get {}!", greeting, x * 2); /// } /// ``` /// /// Shown above are the three typical forms an `if` block comes in. First is the usual kind of /// thing you'd see in many languages, with an optional `else` block. Second uses `if` as an /// expression, which is only possible if all branches return the same type. An `if` expression can /// be used everywhere you'd expect. The third kind of `if` block is an `if let` block, which /// behaves similarly to using a `match` expression: /// /// ```rust /// if let Some(x) = Some(123) { /// // code /// # let _ = x; /// } else { /// // something else /// } /// /// match Some(123) { /// Some(x) => { /// // code /// # let _ = x; /// }, /// _ => { /// // something else /// }, /// } /// ``` /// /// Each kind of `if` expression can be mixed and matched as needed. /// /// ```rust /// if true == false { /// println!("oh no"); /// } else if "something" == "other thing" { /// println!("oh dear"); /// } else if let Some(200) = "blarg".parse::<i32>().ok() { /// println!("uh oh"); /// } else { /// println!("phew, nothing's broken"); /// } /// ``` /// /// The `if` keyword is used in one other place in Rust, namely as a part of pattern matching /// itself, allowing patterns such as `Some(x) if x > 200` to be used. /// /// For more information on `if` expressions, see the [Rust book] or the [Reference]. /// /// [Rust book]: ../book/ch03-05-control-flow.html#if-expressions /// [Reference]: ../reference/expressions/if-expr.html mod if_keyword { } #[doc(keyword = "impl")] // /// Implement some functionality for a type. /// /// The `impl` keyword is primarily used to define implementations on types. Inherent /// implementations are standalone, while trait implementations are used to implement traits for /// types, or other traits. /// /// Functions and consts can both be defined in an implementation. A function defined in an /// `impl` block can be standalone, meaning it would be called like `Foo::bar()`. If the function /// takes `self`, `&self`, or `&mut self` as its first argument, it can also be called using /// method-call syntax, a familiar feature to any object oriented programmer, like `foo.bar()`. /// /// ```rust /// struct Example { /// number: i32, /// } /// /// impl Example { /// fn boo() { /// println!("boo! Example::boo() was called!"); /// } /// /// fn answer(&mut self) { /// self.number += 42; /// } /// /// fn get_number(&self) -> i32 { /// self.number /// } /// } /// /// trait Thingy { /// fn do_thingy(&self); /// } /// /// impl Thingy for Example { /// fn do_thingy(&self) { /// println!("doing a thing! also, number is {}!", self.number); /// } /// } /// ``` /// /// For more information on implementations, see the [Rust book][book1] or the [Reference]. /// /// The other use of the `impl` keyword is in `impl Trait` syntax, which can be seen as a shorthand /// for "a concrete type that implements this trait". Its primary use is working with closures, /// which have type definitions generated at compile time that can't be simply typed out. /// /// ```rust /// fn thing_returning_closure() -> impl Fn(i32) -> bool { /// println!("here's a closure for you!"); /// |x: i32| x % 3 == 0 /// } /// ``` /// /// For more information on `impl Trait` syntax, see the [Rust book][book2]. /// /// [book1]: ../book/ch05-03-method-syntax.html /// [Reference]: ../reference/items/implementations.html /// [book2]: ../book/ch10-02-traits.html#returning-types-that-implement-traits mod impl_keyword { } #[doc(keyword = "in")] // /// Iterate over a series of values with [`for`]. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`for`]: keyword.for.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod in_keyword { } #[doc(keyword = "let")] // /// Bind a value to a variable. /// /// The primary use for the `let` keyword is in `let` statements, which are used to introduce a new /// set of variables into the current scope, as given by a pattern. /// /// ```rust /// # #![allow(unused_assignments)] /// let thing1: i32 = 100; /// let thing2 = 200 + thing1; /// /// let mut changing_thing = true; /// changing_thing = false; /// /// let (part1, part2) = ("first", "second"); /// /// struct Example { /// a: bool, /// b: u64, /// } /// /// let Example { a, b: _ } = Example { /// a: true, /// b: 10004, /// }; /// assert!(a); /// ``` /// /// The pattern is most commonly a single variable, which means no pattern matching is done and /// the expression given is bound to the variable. Apart from that, patterns used in `let` bindings /// can be as complicated as needed, given that the pattern is exhaustive. See the [Rust /// book][book1] for more information on pattern matching. The type of the pattern is optionally /// given afterwards, but if left blank is automatically inferred by the compiler if possible. /// /// Variables in Rust are immutable by default, and require the `mut` keyword to be made mutable. /// /// Multiple variables can be defined with the same name, known as shadowing. This doesn't affect /// the original variable in any way beyond being unable to directly access it beyond the point of /// shadowing. It continues to remain in scope, getting dropped only when it falls out of scope. /// Shadowed variables don't need to have the same type as the variables shadowing them. /// /// ```rust /// let shadowing_example = true; /// let shadowing_example = 123.4; /// let shadowing_example = shadowing_example as u32; /// let mut shadowing_example = format!("cool! {}", shadowing_example); /// shadowing_example += " something else!"; // not shadowing /// ``` /// /// Other places the `let` keyword is used include along with [`if`], in the form of `if let` /// expressions. They're useful if the pattern being matched isn't exhaustive, such as with /// enumerations. `while let` also exists, which runs a loop with a pattern matched value until /// that pattern can't be matched. /// /// For more information on the `let` keyword, see the [Rust book][book2] or the [Reference] /// /// [book1]: ../book/ch06-02-match.html /// [`if`]: keyword.if.html /// [book2]: ../book/ch18-01-all-the-places-for-patterns.html#let-statements /// [Reference]: ../reference/statements.html#let-statements mod let_keyword { } #[doc(keyword = "loop")] // /// Loop indefinitely. /// /// `loop` is used to define the simplest kind of loop supported in Rust. It runs the code inside /// it until the code uses `break` or the program exits. /// /// ```rust /// loop { /// println!("hello world forever!"); /// # break; /// } /// /// let mut i = 0; /// loop { /// println!("i is {}", i); /// if i > 10 { /// break; /// } /// i += 1; /// } /// ``` /// /// Unlike the other kinds of loops in Rust (`while`, `while let`, and `for`), loops can be used as /// expressions that return values via `break`. /// /// ```rust /// let mut i = 1; /// let something = loop { /// i *= 2; /// if i > 100 { /// break i; /// } /// }; /// assert_eq!(something, 128); /// ``` /// /// Every `break` in a loop has to have the same type. When it's not explicitly giving something, /// `break;` returns `()`. /// /// For more information on `loop` and loops in general, see the [Reference]. /// /// [Reference]: ../reference/expressions/loop-expr.html mod loop_keyword { } #[doc(keyword = "match")] // /// Control flow based on pattern matching. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod match_keyword { } #[doc(keyword = "mod")] // /// Organize code into [modules]. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [modules]: ../reference/items/modules.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod mod_keyword { } #[doc(keyword = "move")] // /// Capture a [closure]'s environment by value. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [closure]: ../book/second-edition/ch13-01-closures.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod move_keyword { } #[doc(keyword = "mut")] // /// A mutable binding, reference, or pointer. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod mut_keyword { } #[doc(keyword = "pub")] // /// Make an item visible to others. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod pub_keyword { } #[doc(keyword = "ref")] // /// Bind by reference during pattern matching. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod ref_keyword { } #[doc(keyword = "return")] // /// Return a value from a function. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod return_keyword { } #[doc(keyword = "self")] // /// The receiver of a method, or the current module. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod self_keyword { } #[doc(keyword = "Self")] // /// The implementing type within a [`trait`] or [`impl`] block, or the current type within a type /// definition. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`impl`]: keyword.impl.html /// [`trait`]: keyword.trait.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod self_upper_keyword { } #[doc(keyword = "static")] // /// A place that is valid for the duration of a program. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod static_keyword { } #[doc(keyword = "struct")] // /// A type that is composed of other types. /// /// Structs in Rust come in three flavors: Structs with named fields, tuple structs, and unit /// structs. /// /// ```rust /// struct Regular { /// field1: f32, /// field2: String, /// pub field3: bool /// } /// /// struct Tuple(u32, String); /// /// struct Unit; /// ``` /// /// Regular structs are the most commonly used. Each field defined within them has a name and a /// type, and once defined can be accessed using `example_struct.field` syntax. The fields of a /// struct share its mutability, so `foo.bar = 2;` would only be valid if `foo` was mutable. Adding /// `pub` to a field makes it visible to code in other modules, as well as allowing it to be /// directly accessed and modified. /// /// Tuple structs are similar to regular structs, but its fields have no names. They are used like /// tuples, with deconstruction possible via `let TupleStruct(x, y) = foo;` syntax. For accessing /// individual variables, the same syntax is used as with regular tuples, namely `foo.0`, `foo.1`, /// etc, starting at zero. /// /// Unit structs are most commonly used as marker. They have a size of zero bytes, but unlike empty /// enums they can be instantiated, making them isomorphic to the unit type `()`. Unit structs are /// useful when you need to implement a trait on something, but don't need to store any data inside /// it. /// /// # Instantiation /// /// Structs can be instantiated in different ways, all of which can be mixed and /// matched as needed. The most common way to make a new struct is via a constructor method such as /// `new()`, but when that isn't available (or you're writing the constructor itself), struct /// literal syntax is used: /// /// ```rust /// # struct Foo { field1: f32, field2: String, etc: bool } /// let example = Foo { /// field1: 42.0, /// field2: "blah".to_string(), /// etc: true, /// }; /// ``` /// /// It's only possible to directly instantiate a struct using struct literal syntax when all of its /// fields are visible to you. /// /// There are a handful of shortcuts provided to make writing constructors more convenient, most /// common of which is the Field Init shorthand. When there is a variable and a field of the same /// name, the assignment can be simplified from `field: field` into simply `field`. The following /// example of a hypothetical constructor demonstrates this: /// /// ```rust /// struct User { /// name: String, /// admin: bool, /// } /// /// impl User { /// pub fn new(name: String) -> Self { /// Self { /// name, /// admin: false, /// } /// } /// } /// ``` /// /// Another shortcut for struct instantiation is available, used when you need to make a new /// struct that has the same values as most of a previous struct of the same type, called struct /// update syntax: /// /// ```rust /// # struct Foo { field1: String, field2: () } /// # let thing = Foo { field1: "".to_string(), field2: () }; /// let updated_thing = Foo { /// field1: "a new value".to_string(), /// ..thing /// }; /// ``` /// /// Tuple structs are instantiated in the same way as tuples themselves, except with the struct's /// name as a prefix: `Foo(123, false, 0.1)`. /// /// Empty structs are instantiated with just their name, and don't need anything else. `let thing = /// EmptyStruct;` /// /// # Style conventions /// /// Structs are always written in CamelCase, with few exceptions. While the trailing comma on a /// struct's list of fields can be omitted, it's usually kept for convenience in adding and /// removing fields down the line. /// /// For more information on structs, take a look at the [Rust Book][book] or the /// [Reference][reference]. /// /// [`PhantomData`]: marker/struct.PhantomData.html /// [book]: ../book/ch05-01-defining-structs.html /// [reference]: ../reference/items/structs.html mod struct_keyword { } #[doc(keyword = "super")] // /// The parent of the current [module]. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [module]: ../reference/items/modules.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod super_keyword { } #[doc(keyword = "trait")] // /// A common interface for a class of types. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod trait_keyword { } #[doc(keyword = "true")] // /// A value of type [`bool`] representing logical **true**. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`bool`]: primitive.bool.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod true_keyword { } #[doc(keyword = "type")] // /// Define an alias for an existing type. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod type_keyword { } #[doc(keyword = "unsafe")] // /// Code or interfaces whose [memory safety] cannot be verified by the type system. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [memory safety]: ../book/ch19-01-unsafe-rust.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod unsafe_keyword { } #[doc(keyword = "use")] // /// Import or rename items from other crates or modules. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod use_keyword { } #[doc(keyword = "where")] // /// Add constraints that must be upheld to use an item. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod where_keyword { } #[doc(keyword = "while")] // /// Loop while a condition is upheld. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod while_keyword { } // 2018 Edition keywords #[unstable(feature = "async_await", issue = "50547")] #[doc(keyword = "async")] // /// Return a [`Future`] instead of blocking the current thread. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`Future`]: ./future/trait.Future.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod async_keyword { } #[unstable(feature = "async_await", issue = "50547")] #[doc(keyword = "await")] // /// Suspend execution until the result of a [`Future`] is ready. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [`Future`]: ./future/trait.Future.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod await_keyword { } #[doc(keyword = "dyn")] // /// Name the type of a [trait object]. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [trait object]: ../book/ch17-02-trait-objects.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod dyn_keyword { } #[doc(keyword = "union")] // /// The [Rust equivalent of a C-style union][union]. /// /// The documentation for this keyword is [not yet complete]. Pull requests welcome! /// /// [union]: ../reference/items/unions.html /// [not yet complete]: https://github.com/rust-lang/rust/issues/34601 mod union_keyword { }