Instance functions

Instance functions are functions that are associated to a specific type of variable. When called they take the form value.foo(), where the instance is the first part value. And the instance function is foo().

These are a bit special in Rune. Since Rune is a dynamic programming language we can't tell at compile time which instance any specific value can be. So instance functions must be looked up at runtime.

struct Foo;

impl Foo {
    fn new() {
        Foo
    }
}

pub fn main() {
    let foo = Foo::new();
    foo.bar();
}

$> cargo run --bin rune -- run scripts/book/instance_functions/missing_instance_fn.rn
error: virtual machine error
   ┌─ scripts/book/instance_functions/missing_instance_fn.rn:11:5
   │
11 │     foo.bar();
   │     ^^^^^^^^^ missing instance function `0xfb67fa086988a22d` for `type(0xc153807c3ddc98d7)``

The error is currently a bit nondescript. But in the future we will be able to provide better diagnostics by adding debug information.

What you're seeing above are type and function hashes. These uniquely identify the item in the virtual machine and is the result of a deterministic computation based on its item. So the hash for the item Foo::new will always be the same.