Struct wasmtime::NoFunc

pub struct NoFunc { /* private fields */ }

A reference to the abstract nofunc heap value.

The are no instances of (ref nofunc): it is an uninhabited type.

There is precisely one instance of (ref null nofunc), aka nullfuncref: the null reference.

This NoFunc Rust type’s sole purpose is for use with Func::wrap- and Func::typed-style APIs for statically typing a function as taking or returning a (ref null nofunc) (aka Option<NoFunc>) which is always None.

Example

let mut config = Config::new();
config.wasm_function_references(true);
let engine = Engine::new(&config)?;

let module = Module::new(
    &engine,
    r#"
        (module
            (func (export "f") (param (ref null nofunc))
                ;; If the reference is null, return.
                local.get 0
                ref.is_null nofunc
                br_if 0

                ;; If the reference was not null (which is impossible)
                ;; then raise a trap.
                unreachable
            )
        )
    "#,
)?;

let mut store = Store::new(&engine, ());
let instance = Instance::new(&mut store, &module, &[])?;
let f = instance.get_func(&mut store, "f").unwrap();

// We can cast a `(ref null nofunc)`-taking function into a typed function that
// takes an `Option<NoFunc>` via the `Func::typed` method.
let f = f.typed::<Option<NoFunc>, ()>(&store)?;

// We can call the typed function, passing the null `nofunc` reference.
let result = f.call(&mut store, NoFunc::null());

// The function should not have trapped, because the reference we gave it was
// null (as it had to be, since `NoFunc` is uninhabited).
assert!(result.is_ok());

Implementations

impl NoFunc

pub fn null() -> Option<NoFunc>

Get the null (ref null nofunc) (aka nullfuncref) reference.

pub fn null_ref() -> Ref

Get the null (ref null nofunc) (aka nullfuncref) reference as a Ref.

pub fn null_val() -> Val

Get the null (ref null nofunc) (aka nullfuncref) reference as a Val.

Trait Implementations

impl Clone for NoFunc

fn clone(&self) -> NoFunc

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NoFunc

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for NoFunc

fn eq(&self, other: &NoFunc) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for NoFunc

impl Eq for NoFunc

impl StructuralPartialEq for NoFunc

impl WasmTy for NoFunc