The Rusticon

This is currently a work in progress - feel free to alter or add definitions as necessary.

term	definition
algebraic data type	A type with a set of possible variants. These are declared in Rust using the enum keyword. More information can be found on the Wikipedia article.
attribute	A way of adding metadata to an item. Written as #[attribute_name] (other examples being #[doc="Foo"], #[doc(hidden="true")]).
bikeshed	A highly important discussion about some non-fundamental part of the language (such as syntax or identifier names).
bors	The name of our continuous integration bot, a Python script that checks for reviewed pull requests and runs the test on it, merging it if they pass.
box	(noun) An allocated chunk of memory, (verb) To place a value in such a box
built-in trait	A compiler-defined trait that is implicitly implemented for each eligible type. They are Send, Share, Copy, and 'static.
cargo	The official package manager for Rust programs and libraries.
closure	Refers both to the type (∣ ∣, proc()) and the literal notation: ∣args∣ expression (where expression can be a block, ie ∣x∣ { println(x.to_str()); 5}). It is said to "close over" its environment; it can "capture" values from surrounding code. (Note: This is using a non-pipe unicode character because github doesn't like using that character in tables.)
crate	Rust's compilation unit, a single library or executable. Is the root of a namespace.
DST	Dynamically sized type
FFI	See foreign function interface.
foreign function interface	Calling code written in another language. Rust has a native C FFI, using extern "C" fn.
heap allocation	A dynamic allocation not on the stack.
HRTB	Higher-ranked trait bound. See RFC 387.
ICE	Internal compiler error: an internal assertion failure in the compiler, which always indicates a bug in the compiler. There should never be any user input that causes an ICE to happen, so if you see one, it's always a bug and reporting it is helpful (see HOWTO submit a RUST bug report).
inlining	Inlining is removal of a function call by including the function body directly into the callsite, enabling further optimizations. Controlled with the inline attribute: #[inline(never)], #[inline] for a standard (though very strong) inline hint, and #[inline(always)]. Note that #[inline] is required for any cross-crate inlining.
Intermediate Representation	LLVM IR Code. It can be seen in text form by passing--emit=ir to rustc.
IR	See Intermediate Representation.
IRFY	Is Rust Fast Yet. Graphs tracking how long the buildbots take to build + test. Also see its companion, Is Rust Slim Yet.
lifetime	A piece of metadata that all references have. They represent the scope that the pointer is valid for. For more information, consult the lifetime guide.
link-time optimization	A type of optimization performed by a compiler at link time. In rustlang, link-time optimization can only be performed on executables.
LTO	See link-time optimization.
macro	A type of syntax extension, defined with macro_rules! name_of_macro. Are a way of declaratively generating Rust from arbitrary tokens. For example, assert!, debug!, and fail! are macros. The standard macros can be found in the documentation.
monomorphise	The act of generating specialized versions of generic constructs at compile time to improve run time performance. See Whole-Program Compilation in MLton and Niko Matsakis's answer on Stackoverflow.
newtype struct	A tuple structure with a single unnamed field. For example struct NodeIndex(int). Useful to create wrapper types.
owning pointer	Box<T>, a pointer to an owned box.
plain old data (Pod)	Any value that can be safely copied by moving bits, including scalars, references, and structs containing only Pod. Types which are pod implement the Copy trait.
raw pointer	*const T or *mut T, a pointer to anything. Requires unsafe code to dereference, no static verification is done on them.
record structure	A struct declared with named fields, for example struct Point { x: f32, y: f32 }
reference	A non-owning pointer to an object. Has an associated lifetime, to assert that what it points to is always valid data.
rust	Rust is named after a fungus that is robust, distributed, and parallel. And, Graydon is a biology nerd. See TL;DR
rustdoc	The Rust documentation generator.
rustc	The Rust source code compiler.
sigil	(Obsolete) A character placed in front of a type, identifier or literal. In the context of Rust, this usually refered to the pointer symbols: &, ~, @, and *.
stack allocation	All local variables are a stack allocation.
syntax extension	Code generation at compiletime, broken into three groups: declarative macros, which are described above as macros; procedural macros, which are written as Rust code that processes a token tree and produce an AST, and attributes.
task	Rust's fundamental unit of computation. Similar to a thread.
TLS	Task/Thread-Local Storage. See these meeting minutes
trait	Rust's approach to ad-hoc polymorphism, and used for generics and dynamic dispatch. Also known as type classes.
tuple structure	A struct declared without named fields, for example struct Point(f32, f32)
TWiR	This Week in Rust. cmr's weekly summary of Rust's development.
type hint	Syntax like foo::<int>() to give an explicit type for a generic function, method or struct constructor. Usually redundant due to type inference.
unbox	To get the value out of a box, usually destroying the box in the process.
unit type	The unit type, denoted (), permits only one value, also denoted (). Functions without return value have return type (). Sometimes called nil.
uninhabited type	An enum with no variants. This cannot be constructed in safe code.
unit structure	A struct that only has one value, for example struct Foo; where Foo becomes the name of both the type and its only value. Works just the same as the unit type (), except it is a distinct type.
variant	One of the set of possible values that can be represented by an enum.
zero-variant enum	See phantom type.

Syntaxicon

What is this syntax called?

Note: these names represent the current consensus on desired naming by #rust-internals and brson. Ask there before changing them.

syntax	name
()	The unit type.
'static, 'a	A lifetime. May also be used to name a loop or a for clause (a label).
Box<T>	If T is a type, an owning pointer to T, and the pointer is to an owned box.
&T, &'a T	If T is a type, a reference to T, possibly with a lifetime ('a).
∣ ∣, ∣T∣ -> U	A closure.
&[T], &'a [T]	A slice with element type T and possibly with a lifetime.
&mut [T], &'a mut [T]	A mutable slice with element type T and possibly with a lifetime. One can borrow a &mut to the elements of the slice.
[T, ..n]	An array of length n.
[T]	An array whose length is unknown (a dynamically-sized type).
Box<Trait>:Send, &'a Trait:Send	A trait object where :Send are the kind bounds.
foo!()	Either a macro or syntax extension.
#[xyz], #![xyz]	An attribute.
::<int>, : int (in let x: int ...)	A type hint.

Taking Arguments

AKA: "Help, where do I put the mut?"

There are a few combinations:

fn A(x: T) { }
fn B(x: &T) { }
fn C(x: &mut T) { }
fn D(mut x: T) { }
fn E(mut x: &T) { }
fn F(mut x: &mut T) { }

The mut before the x refers to the binding, whereas the mut after the & refers to aliasability. Only one &mut may exist to a given value at a given time, which means you are free to mutate it as you please. When a binding a mutable, you may reassign, so in D through F, in the body of the function you could write x = foo();. In A and D, the type is passed by-value, and if the type is "affine", it will be moved. The opposite of "affine" is "Copy", or "POD" (plain-old-data, jacked from C++), and these types will be copied rather than moved. That is, A and D would get a fresh copy that, if they mutated, the caller would not see the mutations. Additionally, D would be able to mutate x willy-nilly, as opposed to A, which would need a let mut y = x; or similar.

B and E take shared references. These are "aliasable" references, and multiple shared references can point at the same data at the same time. Any mutations that happen through a &T need to be safe in the face of this! Doing so is called "internal mutability", and is how the RefCell type works.