Default methods and bounds

An interface method may include a default body. An impl inherits it unless it provides an override. Defaults may call other methods from the same contract.

T: Interface constrains a generic parameter and makes those methods available in the body. Join several required interfaces with +.

interface Greet {
  fn name(self: string) -> string
  fn greeting(self: string) -> string { "Hello, ${self.name()}!" }
}

struct Person { value: string }

impl Greet for Person {
  fn name(self: Person) -> string { self.value }
}

fn welcome<T: Greet>(value: T) -> string { value.greeting() }

fn main() { println(welcome(Person { value: "Ada" })) }

Detailed reference →

Interfaces and impls

Associated interface types

Examples use the moon toolchain version shown beside each result.

Output & diagnostics

Expected:
Hello, Ada!

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