## QueryCache

# Trait QueryCache

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    pub trait QueryCache: Sized {
        type Key: Hash + Eq + Copy + Debug;
        type Value: Copy;

        // Required methods
        fn lookup(&self, key: &Self::Key) -> Option<(Self::Value, DepNodeIndex)>;
        fn complete(&self, key: Self::Key, value: Self::Value, index: DepNodeIndex);
        fn iter(&self, f: &mut dyn FnMut(&Self::Key, &Self::Value, DepNodeIndex));
    }

Expand description

Trait for types that serve as an in-memory cache for query results, for a given key (argument) type and value (return) type.

Types implementing this trait are associated with actual key/value types by the `Cache` associated type of the `rustc_middle::query::Key` trait.

## Required Associated Types§

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#### type Key: Hash + Eq + Copy + Debug

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#### type Value: Copy

## Required Methods§

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#### fn lookup(&self, key: &Self::Key) -> Option<(Self::Value, DepNodeIndex)>

Returns the cached value (and other information) associated with the given key, if it is present in the cache.

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#### fn complete(&self, key: Self::Key, value: Self::Value, index: DepNodeIndex)

Adds a key/value entry to this cache.

Called by some part of the query system, after having obtained the value by executing the query or loading a cached value from disk.

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#### fn iter(&self, f: &mut dyn FnMut(&Self::Key, &Self::Value, DepNodeIndex))

## Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

## Implementors§

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### impl<K, V> QueryCache for DefaultCache<K, V>
where K: Eq + Hash + Copy + Debug, V: Copy,

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#### type Key = K

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#### type Value = V

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### impl<K, V> QueryCache for VecCache<K, V, DepNodeIndex>
where K: Idx + Eq + Hash + Copy + Debug, V: Copy,

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#### type Key = K

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#### type Value = V

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### impl<V> QueryCache for DefIdCache<V>
where V: Copy,

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#### type Key = DefId

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#### type Value = V

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### impl<V> QueryCache for SingleCache<V>
where V: Copy,

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#### type Key = ()

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#### type Value = V