Trait wasmtime_wiggle::bitflags::_core::ops::IndexMut

pub trait IndexMut<Idx>: Index<Idx> where
    Idx: ?Sized, {
    fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
}

Used for indexing operations (container[index]) in mutable contexts.

container[index] is actually syntactic sugar for *container.index_mut(index), but only when used as a mutable value. If an immutable value is requested, the Index trait is used instead. This allows nice things such as v[index] = value.

Examples

A very simple implementation of a Balance struct that has two sides, where each can be indexed mutably and immutably.

use std::ops::{Index, IndexMut};

#[derive(Debug)]
enum Side {
    Left,
    Right,
}

#[derive(Debug, PartialEq)]
enum Weight {
    Kilogram(f32),
    Pound(f32),
}

struct Balance {
    pub left: Weight,
    pub right: Weight,
}

impl Index<Side> for Balance {
    type Output = Weight;

    fn index(&self, index: Side) -> &Self::Output {
        println!("Accessing {:?}-side of balance immutably", index);
        match index {
            Side::Left => &self.left,
            Side::Right => &self.right,
        }
    }
}

impl IndexMut<Side> for Balance {
    fn index_mut(&mut self, index: Side) -> &mut Self::Output {
        println!("Accessing {:?}-side of balance mutably", index);
        match index {
            Side::Left => &mut self.left,
            Side::Right => &mut self.right,
        }
    }
}

let mut balance = Balance {
    right: Weight::Kilogram(2.5),
    left: Weight::Pound(1.5),
};

// In this case, `balance[Side::Right]` is sugar for
// `*balance.index(Side::Right)`, since we are only *reading*
// `balance[Side::Right]`, not writing it.
assert_eq!(balance[Side::Right], Weight::Kilogram(2.5));

// However, in this case `balance[Side::Left]` is sugar for
// `*balance.index_mut(Side::Left)`, since we are writing
// `balance[Side::Left]`.
balance[Side::Left] = Weight::Kilogram(3.0);

Required methods

fn index_mut(&mut self, index: Idx) -> &mut Self::Output

Performs the mutable indexing (container[index]) operation.

Panics

May panic if the index is out of bounds.

Implementations on Foreign Types

impl IndexMut<RangeFull> for OsString

pub fn index_mut(&mut self, _index: RangeFull) -> &mut OsStr

impl<T, I, const N: usize> IndexMut<I> for [T; N] where
    [T]: IndexMut<I>, 

pub fn index_mut(&mut self, index: I) -> &mut <[T; N] as Index<I>>::Output

impl<T, I> IndexMut<I> for [T] where
    I: SliceIndex<[T]>, 

pub fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<[T]>>::Output

impl<I> IndexMut<I> for str where
    I: SliceIndex<str>, 

pub fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<str>>::Output

impl IndexMut<RangeInclusive<usize>> for String

pub fn index_mut(&mut self, index: RangeInclusive<usize>) -> &mut str

impl IndexMut<RangeTo<usize>> for String

pub fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str

impl IndexMut<RangeToInclusive<usize>> for String

pub fn index_mut(&mut self, index: RangeToInclusive<usize>) -> &mut str

impl IndexMut<RangeFrom<usize>> for String

pub fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut str

impl IndexMut<Range<usize>> for String

pub fn index_mut(&mut self, index: Range<usize>) -> &mut str

impl<A> IndexMut<usize> for VecDeque<A>

pub fn index_mut(&mut self, index: usize) -> &mut A

impl<T, I, A> IndexMut<I> for Vec<T, A> where
    A: Allocator,
    I: SliceIndex<[T]>, 

pub fn index_mut(&mut self, index: I) -> &mut <Vec<T, A> as Index<I>>::Output

impl IndexMut<RangeFull> for String

pub fn index_mut(&mut self, _index: RangeFull) -> &mut str

impl<A, I> IndexMut<I> for SmallVec<A> where
    A: Array,
    I: SliceIndex<[<A as Array>::Item]>, 

pub fn index_mut(
    &mut self,
    index: I
) -> &mut <I as SliceIndex<[<A as Array>::Item]>>::Output

impl IndexMut<StackSlot> for StackSlots

pub fn index_mut(&mut self, ss: StackSlot) -> &mut StackSlotData

impl IndexMut<Inst> for DataFlowGraph

Allow mutable access to instructions via indexing.

pub fn index_mut(&mut self, inst: Inst) -> &mut InstructionData

impl<K, V> IndexMut<K> for SecondaryMap<K, V> where
    K: EntityRef,
    V: Clone, 

Mutable indexing into an SecondaryMap.

The map grows as needed to accommodate new keys.

pub fn index_mut(&mut self, k: K) -> &mut V

impl<K, V> IndexMut<K> for BoxedSlice<K, V> where
    K: EntityRef, 

Mutable indexing into a BoxedSlice.

pub fn index_mut(&mut self, k: K) -> &mut V

impl<K, V> IndexMut<K> for PrimaryMap<K, V> where
    K: EntityRef, 

Mutable indexing into an PrimaryMap.

pub fn index_mut(&mut self, k: K) -> &mut V

impl<'_, K, V, Q, S> IndexMut<&'_ Q> for IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher,
    Q: Hash + Equivalent<K> + ?Sized, 

Access IndexMap values corresponding to a key.

Mutable indexing allows changing / updating values of key-value pairs that are already present.

You can not insert new pairs with index syntax, use .insert().

Examples

use indexmap::IndexMap;

let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    map.insert(word.to_lowercase(), word.to_string());
}
let lorem = &mut map["lorem"];
assert_eq!(lorem, "Lorem");
lorem.retain(char::is_lowercase);
assert_eq!(map["lorem"], "orem");

use indexmap::IndexMap;

let mut map = IndexMap::new();
map.insert("foo", 1);
map["bar"] = 1; // panics!

pub fn index_mut(&mut self, key: &Q) -> &mut V

Returns a mutable reference to the value corresponding to the supplied key.

Panics if key is not present in the map.

impl<K, V, S> IndexMut<usize> for IndexMap<K, V, S>

Access IndexMap values at indexed positions.

Mutable indexing allows changing / updating indexed values that are already present.

You can not insert new values with index syntax, use .insert().

Examples

use indexmap::IndexMap;

let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    map.insert(word.to_lowercase(), word.to_string());
}
let lorem = &mut map[0];
assert_eq!(lorem, "Lorem");
lorem.retain(char::is_lowercase);
assert_eq!(map["lorem"], "orem");

use indexmap::IndexMap;

let mut map = IndexMap::new();
map.insert("foo", 1);
map[10] = 1; // panics!

pub fn index_mut(&mut self, index: usize) -> &mut V

Returns a mutable reference to the value at the supplied index.

Panics if index is out of bounds.

impl<TyIx, Ty> IndexMut<TyIx> for TypedIxVec<TyIx, Ty> where
    TyIx: Into<u32>, 

pub fn index_mut(&mut self, ix: TyIx) -> &mut Ty

Implementors