4.5 impl and methods

Declaration in `impl`	Receiver
`fn m()`	`&self`
`var fn m()`	`&var self`
`move fn m()`	`self` by value (move)
`static fn m()`	none, called as `T.m()`
`init m()`	constructor (§4.3)
`op +(…)`	operator (§5.3)

Inside a method self and Self are available. Fields and methods are available without self. unless the name is shadowed by a local variable.
impl T { … } MUST be located in the package that declared T.
impl I for T { … } is an explicit implementation of an interface. Allowed if I or T is declared in the current package.

Associated constants. const NAME: T = e inside impl T or interface declares a constant of the type, available as T.NAME:

oxl

impl Money {
  pub const ZERO: Money = Money{ minor: 0 }
  pub const MAX_TRANSFER: Money = Money.rub(1_000_000)
}

interface Codec<T> { const NAME: str }          // the implementation must supply a value
impl Codec<Point> for GeoHashCodec { const NAME: str = "geohash" }

e MUST be a comptime expression; calls are allowed only to comptime functions and to constructors without effects.
An interface constant without a value is mandatory for an implementation; with a value — it is the default.
Associated constants are allowed in attribute arguments (@timeout(Limits.CHECKOUT)).

impl-foreign-type, unknown-method

4.5 impl and methods

Related diagnostics

See also