Struct wasmtime::NoExtern

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pub struct NoExtern { /* private fields */ }
Expand description

A reference to the abstract noextern heap value.

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

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

This NoExtern 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 noextern) (aka Option<NoExtern>) which is always None.

§Example

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

let module = Module::new(
    &engine,
    r#"
        (module
            (func (export "f") (param (ref null noextern))
                ;; If the reference is null, return.
                local.get 0
                ref.is_null noextern
                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 noextern)`-taking function into a typed function that
// takes an `Option<NoExtern>` via the `Func::typed` method.
let f = f.typed::<Option<NoExtern>, ()>(&store)?;

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

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

Implementations§

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impl NoExtern

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pub fn null() -> Option<Self>

Get the null (ref null noextern) (aka nullexternref) reference.

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pub fn null_ref() -> Ref

Get the null (ref null noextern) (aka nullexternref) reference as a Ref.

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pub fn null_val() -> Val

Get the null (ref null noextern) (aka nullexternref) reference as a Val.

Trait Implementations§

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impl Clone for NoExtern

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fn clone(&self) -> NoExtern

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for NoExtern

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

Formats the value using the given formatter. Read more
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impl PartialEq for NoExtern

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

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

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

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impl Eq for NoExtern

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impl StructuralPartialEq for NoExtern

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impl WasmTy for NoExtern

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<T> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> WasmParams for T
where T: WasmTy,

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type ValRawStorage = <(T,) as WasmParams>::ValRawStorage

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fn typecheck( engine: &Engine, params: impl ExactSizeIterator<Item = ValType>, position: TypeCheckPosition, ) -> Result<(), Error>

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fn vmgcref_pointing_to_object_count(&self) -> usize

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fn store( self, store: &mut AutoAssertNoGc<'_>, func_ty: &FuncType, dst: &mut MaybeUninit<<T as WasmParams>::ValRawStorage>, ) -> Result<(), Error>

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impl<T> WasmResults for T
where T: WasmTy,

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unsafe fn load( store: &mut AutoAssertNoGc<'_>, abi: &<T as WasmParams>::ValRawStorage, ) -> T

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impl<T> WasmRet for T
where T: WasmTy,

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type Fallible = Result<T, Error>

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fn compatible_with_store(&self, store: &StoreOpaque) -> bool

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unsafe fn store( self, store: &mut AutoAssertNoGc<'_>, ptr: &mut [MaybeUninit<ValRaw>], ) -> Result<(), Error>

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fn may_gc() -> bool

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fn func_type(engine: &Engine, params: impl Iterator<Item = ValType>) -> FuncType

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fn into_fallible(self) -> Result<T, Error>

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fn fallible_from_error(error: Error) -> Result<T, Error>